LSCAE LAB

The joining process for glass reinforced plastic (GRP) pipes is external and internal. Currently, internal and external connections are performed manually, and there are frequent delays in the process, excessive labor costs, and safety problems. An automated process using robots has advantages such as rapid processing, reduction of manpower, and safety. In this study, we developed a pipe root with an automated tape layered machine (ATL) to improve the bonding process inside the GRP pipe. A safety assessment was performed when the load generated during the development of the pipe root and the operation of the robot was applied to the GRP pipe. From the results of the configuration and performance tests of the developed robot, it was shown that the developed robot was sufficiently safe to operate inside the GRP pipe and that the required automation process capability was satisfactory.

In this study, a three-dimensional flow analysis of underground subway station was conducted by applying ventilation mode in operation and platform screen door (PSD) opening and closing conditions on fire in underground platform. In order to analyze optimal smoke control and heat removal conditions, the whole underground subway station was set as a model, and a total of eight cases were analyzed by changing the operating conditions of fans for each area under the opening and closing conditions of the PSDs. The analysis results confirmed that the operation mode of supply fan in platform E and I areas located at the third floor underground is more effective than that of exhaust fan in the event of a fire in underground subway station when the PSD is closed. The amount of CO entering a waiting room increased, and the overall CO distribution in the underground subway station was also increased when the PSD is opened. In addition, the CO distributions due to the opening and closing of the PSD were similar to one another when a fire occurred on the platform, which suggests that the operating conditions of the fan affects the formation of CO distribution in the underground subway station rather than the discharge of CO.

The fatigue strength and life of a GFRP composite bogie frame for urban subway trains were evaluated in this study. The GEP224 glass fabric/epoxy was selected as the structural material of a composite bogie frame to save its weight. In order to obtain the fatigue characteristics of the GEP224 glass/epoxy composite material, the tension–compression fatigue test was done with three different stacking sequences of warp direction, fill direction, and warp/fill direction, respectively. A fatigue test was conducted with a stress ratio, R of 0.1 and −1, and up to endurance limit of 107 with frequency of 5 Hz. The fatigue strength of the GFRP composite bogie frame was evaluated on the basis of the S-N curve and Goodman diagrams obtained from GEP224 glass/epoxy composites according to the JIS E 4207 and UIC 515/615-4. The result shows that fatigue strength of the GFRP composite bogie has satisfied the design requirements. Also, the GFRP composite bogie frame had a good fatigue performance in comparison with conventional metal bogie frame, considering its weight.

In this study, the crush behaviors of square sandwich composite tubes with woven fabric carbon/epoxy skins and aluminum honeycomb cores with the different honeycomb cell sizes and tube sizes were evaluated. For the evaluation, four different kinds of tubes were fabricated and crushed under quasi-static and dynamic impact loads. The impact tests were carried out using heavy wagons. From the test results, the crushing mode under the dynamic load was changed into more stable collapse than the corresponding static tests. Additionally, the increased bond strength between the honeycomb core and the composite face leaded to a higher energy absorption capability.

In this study, the failure modes and energy absorption capabilities of different kinds of circular tubes made of carbon, Kevlar, and carbon–Kevlar hybrid fibers composites with epoxy resin have been evaluated. The relationship between the crushing parameters (specific energy absorption, maximum peak load, mean crushing load) and the material properties for different fibers and patterns was also investigated. The fabric carbon/epoxy tubes had the best energy absorption capability (specific energy absorption of 81.7%). In contrast, the tubes made of Kevlar showed the worst energy absorption capability. Based on the linear regression analysis results, the crushing parameters generally showed good correlation with the compressive strength and shear modulus. In particular, the specific energy absorption of the tubes with the brittle fracture mode revealed the strongest correlation with the compressive strength (R-square value = 0.90).

In this study, we evaluated the structural integrity and weight of a rocket motor with a torispherical dome by size optimal design. Size optimal design was achieved by first-order and sub-problem methods, using the Ansys Parametric Design Language (APDL). For rapid design verification, a modified 2D axisymmetric finite-element model was used, and the bolt pre-tension load was expressed as function of the ratio of the cross-sectional area. The thickness of the dome and the cylindrical part of the rocket motor were selected as the design parameters. Our results showed that the weight and structural integrity of the rocket motor at the initial design stage could be determined more rapidly and accurately with the modified 2D axisymmetric finite-element model than with the 3D finite-element model. Further, the weight of the rocket motor could be saved to maximum of 17.6% within safety limit.

This paper describes the results of experiments and numerical simulation studies on the impact and indentation damage created by low-velocity impact subjected onto honeycomb sandwich panels for application to the BIMODAL tram. The test panels were subjected to low-velocity impact loading using an instrumented testing machine at six energy levels. Contact force histories as a function of time were evaluated and compared. The extent of the damage and depth of the permanent indentation was measured quantitatively using a 3-dimensional scanner. An explicit finite element analysis based on LS-DYNA3D was focused on the introduction of a material damage model and numerical simulation of low-velocity impact responses on honeycomb sandwich panels. Extensive material testing was conducted to determine the input parameters for the metallic and composite face-sheet materials and the effective equivalent damage model for the orthotropic honeycomb core material. Good agreement was obtained between numerical and experimental results; in particular, the numerical simulation was able to predict impact damage area and the depth of indentation of honeycomb sandwich composite panels created by the impact loading.

This paper describes the results of an experimental investigation on the low-velocity impact response of four different types of sandwich structures considered as the structural materials of the Korean low floor bus. The test panels were subjected to low-velocity impact loading using an instrumented testing machine at six energy levels. Impact parameters like maximum contact force, contact time, deflection at peak load and absorbed energy were evaluated and compared for different types of sandwich panels. The extent of the damage and depth of the permanent indentation was measured quantitatively using 3-dimensional scanner. Failure modes were studied by sectioning the specimens and observed under optical microscope. The impact test results show that sandwich panels with woven glass fabric/epoxy facesheet could not observe permanent visible impact damage and has a good impact damage resistance in comparison with sandwich panel with metal aluminum facesheet.

This paper explains the manufacturing process of a composite train carbody with a sandwich composite structure for bodyshell and a stainless steel structure for the under frame. In addition, the structural behavior and safety of the composite carbody of the Korean tilting train was investigated by the static load tests. From the test results, the stiffness of the composite carbody met the specified design. In the aspect of strength, the maximum stress of the composite bodyshell was of 12.2% of strength of CF1263 carbon/epoxy.

This paper deals with the active vibration control of a simply-supported beam traversed by a moving mass using fuzzy control. Governing equations for dynamic responses of a beam under a moving mass are derived by Galerkin’s mode summation method, and the effect of forces (gravity force, Coliolis force, inertia force caused by the slope of the beam, transverse inertia force of the beam) due to the moving mass on the dynamic response of a beam is discussed. For the active control of dynamic deflection and vibration of a beam under the moving mass, the controller based on fuzzy logic is used and the experiments are conducted by VCM (voice coil motor) actuator to suppress the vibration of a beam. Through the numerical and experimental studies, the following conclusions were obtained. With increasing mass ratioy at a fixed velocity of the moving mass under the critical velocity, the position of moving mass at the maximum dynamic deflection moves to the right end of the beam. With increasing velocity of the moving mass at a fixed mass ratioy, the position of moving mass at the maximum dynamic deflection moves to the right end of the beam too. The numerical predictions of dynamic deflection of the beam have a good agreement with the experimental results. With the fuzzy control, more than 50% reductions of dynamic deflection and residual vibration of the tested beam under the moving mass are obtained.

In order to examine the structural integrity of hybrid railway carriage structures of Korean Tilting Train eXpress due to the degraded properties of composite materials under ground environments, T300/AD6005 graphite/epoxy composite specimens were exposed to accelerated ageing conditions including ultraviolet radiation, temperature and moisture for 2000 h. It was found that the mechanical properties of composite specimens after exposure to accelerated ageing environments were lower than those of unexposed specimens, and decreased as the ageing time increases. The values of the degraded properties were used in the structural analysis to check the design requirements of hybrid railway carriage structures caused by environmental degradation of composite materials. The results show that the structural integrity of hybrid railway carriage structures is affected by the degradation of composite materials during its mission life under ground environments.

In order to evaluate the changes in the mechanical properties, mass and coefficient of thermal expansion of composites in space, graphite/epoxy composite specimens were exposed to simulated low earth orbit (LEO) environmental conditions including ultraviolet radiation, thermal cycling and high vacuum. Surface morphology was investigated by using a scanning electron microscope, and outgassed products were analyzed with a quadrupole mass spectrometer. The failure cycle of composite laminates exposed to the attack of LEO environmental factors was predicted by using four modified failure criteria. The modified failure criteria were expressed as a function of stresses as well as thermal cycles.

In this study, a Cohesive Zone Model (CZM) was used to predict the progressive failure behavior of adhesive joining of a domeseparated composite pressure vessel according to variation in the temperatures. A set of cohesive zone parameters for the adhesive material were obtained through Mode I, Mode II, and Mixed Mode I/II interfacial fracture toughness tests. In order to evaluate the effect of temperature on the interfacial fracture toughness, in situ temperature environments were simulated in the range -30 to 60oC, using an environmental chamber and furnace. The double-lap joint test was suggested as a way to verify the proposed CZM and simulation procedure. It was found that good accuracy in the prediction of debonding loads, and the damage onset and growth of adhesive joining, was obtained between the numerical predictions and the experimental results. The results of progressive failure analysis of the adhesive joining of the dome-separated composite pressure vessel showed that the maximum debonded length was predicted to be about 6.0% of the total adhesive length and that the damage onset and propagation behavior of the adhesive joining showed a similar tendency under room and low-temperature environments. However, in the high-temperature environment (60oC), the debonding of the adhesive joining tended to propagate early and quickly compared to the same action under room and low-temperature conditions.

In order to evaluate the effect of structural degradation of a GFRP composite bogie frame due to ballast-flying phenomena, the impact test and residual compression test after impact was conducted for glass fiber/epoxy 4-harness satin woven laminate composites applied to skin part of a bogie frame. The impact test was performed using a instrumented impact testing system with energy levels of 5J, 10J, and 20J, and the impactor was designed to have various ballast shapes such as sphere, cube, and cone to consider the ballasted track environments. The residual compression strength was tested to evaluate the degradation of mechanical properties of impact-damaged laminate composites. The results showed that the damage area and the degradation of residual compressive strength after impact for laminate composites was increased with increase of impact energy for all ballast shapes, and was particularly most influenced by ballast shape of cone.

This paper describes an experimental investigation on low-velocity impact responses and damage modes of sandwich composites due to the changes of impact loading location and wall partition angle of honeycomb core. The sandwich panels were composed of a glass/epoxy laminated facesheet and an aluminum honeycomb core. Square samples of 100mm by 100mm sides were subjected to a low-velocity impact load using an instrumented testing machine at three different energy levels. Impact parameters such as maximum force, time to maximum force, deflection at maximum force, and absorbed energy were evaluated and compared. Sandwich specimens were cut to analyze damage modes after impact. The experimental results showed that low-velocity impact responses and damage mechanism of sandwich panels were affected significantly by the changes of wall partition angle of honeycomb core, and the energy absorption capacity of sandwich panels with wall partition angle of 45o was improved by about 25%.

In the current study, the static structural safety and durability of two composite bogie frame models were evaluated using a finite element analysis. Prior to evaluation, the in-plane and out-of-plane mechanical properties of the base material were measured. The fatigue property was also measured to evaluate the durability of two composite bogie frames. Based on material data, the static structural safety was examined using the Tsai-Wu failure criterion under ten different loading conditions. Stress combination data were used to evaluate durability of two composite bogie frames. Analysis results indicate that the maximum Tsai-Wu failure indices of the two composite bogie frames under a twisting load were 0.48 and 0.57. Based on the durability evaluation using Goodman diagrams, all combined stress data of the two models were within the endurance limit. In the bogie frames with a side beam height of 50 mm, the side beam bottom area was the most affected region. The joint center area revealed higher mean stress and stress amplitude values in the bogie frames with a side beam height of 150 mm.

In order to optimize bolt locations for suspension joint parts of a GFRP composite bogie frame, the optimum design was done. The structural integrity of a composite bogie frame was evaluated under three main in-service loads according to JIS E 4207. The optimum design was conducted using a sub-modeling technique, a sub-problem approximation method, and batch processing codes programmed by ANSYS Parametric Design Language (APDL). The results showed that the optimum design using the sub-modeling technique was able to obtain more accurate results by the control of mesh density for the interesting parts, and reduce maximum Von-Mises stress in comparison with initial model.

A glass-fiber-reinforced plastic (GFRP) composite bogie frame was designed and manufactured in this study. The lightweight GFRP bogie frame was designed to not only sustain heavy static and dynamic loads but also have a suspension function. Therefore, its dynamic characteristics are an important factor. In this study, its natural frequency was evaluated by means of a modal test and the test results were validated using a finite element analysis. Given these experimentally obtained dynamic characteristics, the running performance of a railway vehicle equipped with the GFRP bogie frame was assessed. The first bending natural frequency of the composite bogie frame was 22.8 Hz, which corresponds to 27.7% of the steel frame. The vehicle dynamic analysis results showed that the derailment index, dynamic wheel unloading, wheel wear index, and ride comfort satisfied the design requirements.

In this study, the fatigue characteristics and life of two types of woven fabric glass /epoxy laminate composites with WR580glass fiber for carbody structures and GEP224 glass fiber for bogie frames were evaluated and compared with those of conventional metallic materials. Additionally, the laminate composite for carbody structures was reinforced with carbon plies to investigate the improvement of fatigue life. A fatigue test was conducted for tension-tension and tension-compression load with a stress ratio, R of 0.1 and -1, and up to endurance limit of 107 with frequency of 5Hz. In tension-compression fatigue test, the anti-buckling jig was designed to prevent buckling of specimen induced by compressive load. The Goodman diagrams were introduced to evaluate the fatigue life of laminate composites. The test results showed that the fatigue life of the GEP224 woven fabric glass/epoxy laminate composite with the stacking sequence of warp direction had a good performance in comparison with that of SM490A used to existing metal bogie frame. Also, the fatigue performance of WR580 woven fabric glass/epoxy laminate composite with the reinforcement of woven fabric carbon /epoxy ply had shown a significant improvement than that of a bare specimen without reinforcement.

In this study, a standardized finite element model for the carbody structures of various railway vehicles made of sandwich composites was suggested. The standardized finite element model for composite carbody structures was introduced and proposed by comparing the results of real structural tests under vertical, compressive, twisting load and natural frequency tests of various railway vehicles. The results showed that the quadratic shell element was suitable to model the reinforced metal frame used to improve the flexural stiffness of sandwich panels compared to beam elements, and layered shells and solid elements were recommended to model the skin and honeycomb core of sandwich panels compared to sandwich shell elements. Also, the proposed standard finite element model has the merit of being applied to crashworthiness analysis just by minor modifications, such as contact conditions and constraint equations.

This paper describes the results of the numerical evaluation on crashworthiness and rollover characteristics of a lowfloor bus vehicle made of sandwich composites. The sandwich composite used for the vehicle structures was composed of aluminum honeycomb core and WR580/NF4000 glass-fabric/epoxy laminate facesheets. Material tests were conducted to determine the input parameters of the composite laminate facesheet model and the effective equivalent damage model for the orthotropic honeycomb core material. Crashworthiness and rollover analysis of the low-floor bus was conducted using the explicit finite element method (FEM) analysis code LS-DYNA3D with the lapse of time. The crash condition of the low-floor bus was a frontal accident with a speed of 60 km/h. Rollover analysis was done according to the safety rules of the European standards (ECE-R66). The angular and translation velocity and its angle with the ground just before impact for rollover were calculated using the dynamic analysis program. The results showed that the survival spaces for the driver and passengers were secured against frontal crashworthiness and rollover of the low-floor bus. In addition, the modified Chang-Chang failure criterion is recommended to predict the failure modes of the composite structures for crashworthiness and rollover analysis. This paper describes the results of the numerical evaluation on crashworthiness and rollover characteristics of a lowfloor bus vehicle made of sandwich composites. The sandwich composite used for the vehicle structures was composed of aluminum honeycomb core and WR580/NF4000 glass-fabric/epoxy laminate facesheets. Material tests were conducted to determine the input parameters of the composite laminate facesheet model and the effective equivalent damage model for the orthotropic honeycomb core material. Crashworthiness and rollover analysis of the low-floor bus was conducted using the explicit finite element method (FEM) analysis code LS-DYNA3D with the lapse of time. The crash condition of the low-floor bus was a frontal accident with a speed of 60 km/h. Rollover analysis was done according to the safety rules of the European standards (ECE-R66). The angular and translation velocity and its angle with the ground just before impact for rollover were calculated using the dynamic analysis program. The results showed that the survival spaces for the driver and passengers were secured against frontal crashworthiness and rollover of the low-floor bus. In addition, the modified Chang-Chang failure criterion is recommended to predict the failure modes of the composite structures for crashworthiness and rollover analysis.

This paper presents the dynamic stability of a cantilevered Timoshenko beam with a concentrated mass, partially attached to elastic foundations, and subjected to a follower force. Governing equations are derived from the extended Hamilton's principle, and FEM is applied to solve the discretized equation. The influence of some parameters such as the elastic foundation parameter, the positions of partial elastic foundations, shear deformations, the rotary inertia of the beam, and the mass and the rotary inertia of the concentrated mass on the critical flutter load is investigated. Finally, the optimal attachment ratio of partial elastic foundation that maximizes the critical flutter load is presented.

In order to evaluate the degradation of the mechanical and physical properties of composites under ground environments, T300/AD6005 graphite-epoxy composite specimens were exposed to natural environments for 5 years and accelerated environmental conditions including ultraviolet radiation, temperature and moisture for 2000 h. It was found that transverse flexural properties were more sensitive to environmental damage in a composite than other properties. Matrix cracking and matrix loss were observed at the surface of aged specimens by using scanning electron microscope. In order to achieve the same effect on the material in a shorter time period, the accelerated factor, a, was introduced and determined for several mechanical properties by using proposed degradation equations of material properties and linear relationship between the natural and accelerated aging time.

In this study, transient analyzes were conducted to predict the thermal distortion of the Korea Multi-Purpose Satellite (KOMPSAT) solar array during its orbital motion. The solar array consists of five honeycomb sandwich panels with aluminum facesheets. To enable future improvements, the solar arrays were also analyzed with composite facesheets for the temperature distribution and thermal distortion. In order to evaluate the degradation effects of the material properties of the composite facesheets in low earth orbit environment, the composite materials were exposed to simulate low earth orbit environmental conditions including ultraviolet (UV) radiation, high vacuum and thermal cycling. The values of the degraded properties were used in the thermal distortion analysis. The results show that the solar arrays with composite facesheets are beneficial with regard to weight savings, temperature distribution and thermal distortion during the mission when compared to those with aluminum facesheets, even though the composite materials are degraded due to low earth orbit environmental factors.

This paper presents a study of a lightweight structural design technology that replaces the existing metal carbody with carbon/epoxy laminate composites and sandwich composites to increase the energy efficiency of the EMU(Electric Multiple Unit) carbody. Carbon/epoxy laminate composites were designed in consideration of various stacking sequences because it is necessary to keep the bending and twisting rigidity and strength levels the same or higher compared to the existing metal carbody. A stacking sequence of [0°/45°/90°/-45°] 2s was finally selected through a prediction of the material properties and a structural analysis according to the stacking sequences. The selected composite stacking sequence was applied to the roof, cantrail, and cap module in consideration of simplification of the manufacturing process and flexibility of the modular design. The EMU carbody, which was replaced with carbon/epoxy laminate composites and sandwich composites, was evaluated in terms of structural integrity in accordance with the EN12663-1 specification. The structural integrity was confirmed to be equal to or higher than that of the existing metal carbody. In addition, it was found that a weight reduction effect of approximately 40.34% for the roof and cantrail structures and approximately 64% for the cap module structure could be obtained by a lightweight structural design through material substitution.

This study investigated the reinforcement design of an existing modular bridge taking into consideration the polar environment where it will be used. The design requirements for the modular bridge reinforcement design to retain the functions of the modular bridge, including modular installation and ease of transport were determined. For a reinforced modular bridge that satisfies these design requirements, a superstructure reinforcement that combines aluminum extrusions and sandwich composites was presented based on a conventional modular bridge. Moreover, in the reinforced structure evaluation results, it was found that the allowable strength and stiffness were satisfied under the maximum wind load in the polar environment.

This study aims to predict the mode I and II fracture behaviors of a composite adhesion interface by considering the effects of temperature. The fracture behaviors in environments at –30 °C, 24 °C, and 60 °C degrees were predicted. The parameters required for ABAQUS CZM were determined based on basic material properties and interlaminar fracture toughness tests with respect to temperature. The obtained parameter values were applied to conduct progressive failure analyses. The DCB and ENF models, which exhibit mode I and II fracture behaviors, respectively, were used for these progressive failure analyses. Furthermore, the analysis and test results were compared, indicating a maximum difference of 14.25 %.

The munitions industry uses high-strength carbon fiber composites imported from other countries because of the lack of the information about the properties that should be satisfied by the domestic high-strength carbon fiber composites. Verification of the applicability of domestic high-strength carbon fiber composites to the munitions industry requires comparison of the fiber strength transition rate between the carbon fiber composites imported from other countries and domestically. A strand test was performed to evaluate in the unit of a fiber the mechanical properties of the imported high-strength carbon fiber composites and domestically. Additionally, a composite pressure vessel was prepared using the filament winding method to perform a hydrostatic pressure test and calculate the fiber strength in the unit of a structure. Comparison of the fiber strength results showed that the fiber strength transition rates of the domestic carbon fiber composites H2550 and H3055, were 86.35 and 74.19%, respectively. Domestic carbon fiber composite material H2550 is expected to be replaceable in the munitions industry.

Because of its good mechanical properties epoxy is used as matrix material of Carbon Fiber ReinforcedPlastic (CFRP) for lightweight railway vehicles. However, when exposed to fire, CFRP is easily pyrolyzed. In thisstudy, carbon fiber/phenol composite, which has pyrolysis temperature higher than that of epoxy, was used to improvethis situation. To make carbon fiber/multi-resin composite, carbon fiber/epoxy and carbon fiber/phenol prepregs werelaminated separately to form layers of each resin. After the lamination, it was co-cured by hot-press process. The resultsof fire safety test using a cone-calorimeter showed that the case, which consists of 10 layers of carbon fiber/epoxy and5 layers of carbon fiber/phenol, secures better fire safety performance than that of the carbon fiber/epoxy composite,including such factors as ignition time, maximum HRR (Heat Release Rate), and MARHE (Maximum Average Rate ofHeat Emission), while minimizing the amount of carbon fiber/phenol prepreg usage

In this paper, study was conducted of laminate composite frames to reduce the weight of rolling stock. Aunidirectional carbon fiber/epoxy composite and a woven carbon fiber/epoxy composite were applied to the body frameof rolling stock. In order to verify the method for the numerical analysis applied to the laminate composite frame, theresults from a structural test and a numerical analysis were compared. The error was below 7.78%, verifying the reliabilityof the method for numerical analysis. The verified numerical analysis method was applied to compare the specificstiffness of the conventional aluminum body frame with that of the laminate composite frame. For this, laminatecomposite frames having a specific stiffness similar to that of the aluminum frame were designed. The results show thatthe frame made of the woven carbon fiber/epoxy composite provided the greatest weight reduction (54.05%) in comparisonwith the conventional aluminum frame.

The purpose of this paper is to suggest a lightweight design for the aluminum extrusion carbody structure of a double deck high-speed train using material substitution and size optimization method. In order to conduct material substitution, the topology optimization was used to determine the application parts of sandwich composites at the carbody structures. The results of analysis showed that sandwich composites could be applied at roof and 2nd underframe. The size optimization was used to determine thickness of the aluminum extruded and carbon/epoxy composite. The design variable, state constraint and objective function were formulated to solve the size optimization, and then, the feasible design was presented by these conditions. The results of the lightweight design showed that the weight of double deck high-speed train hybrid carbody could be reduced by 2.18(17.70%) tons.

In this paper, the topology optimization method was used to describe the lightweight design of link structures for an amphibious boat. Topology optimization was used to determine the optimum density distribution of the structure. The analysis revealed that the link structures for amphibious boat can be reduced up to 31 percent by weight without altering the design of the connected and supported parts. The structural integrity of the proposed lightweight link structures was evaluated via topology optimization and verified by finite element analysis and static test. The structural integrity of lightweight link structures was found to meet the design requirements. The running stability of amphibious boat with lightweight link structures was verified via ground and water driving tests.

In this paper, the design application for the lightweight and insulation of the manipulator of the mobile welding robot for the closed/narrow space is presented. A variety of robotic platforms have been developed for weldworker using a welding robot outside a workpiece for welding work in a complex and narrow space such as a ship or an offshore plant. Normally, The development process of robots consists of machine development, electronic device development, control algorithm development and integration verification considering application environment and requirements. In order to develop the robustness of the welding robot, the lightweight design of the robot manipulator considering the environmental conditions was performed in the basic design of the robot platform. Also, The results of the robot selection and validation, analysis and testing for the insulation performance and cooling performance and the results of the research are shown.

In this paper, evaluation method of structural integrity for cone-type composite lattice structures with hexagonal cell was conducted. A finite element analysis was used to evaluate the structural integrity of cone-type composite lattice structure. The finite element model for evaluation of structural integrity was generated using solid element. In order to consider the difference in mechanical properties between intersection and non-intersection part, the mechanical properties were applied considering the fiber volume fraction of each part. Compression test of conetype composite lattice structure were conducted for verification of evaluation method of structural integrity. The analysis result showed 2% errors in displacement and good agreement with test result.

In this paper, finite element modeling methods for cylindrical composite lattice structures were verified through natural frequency test. Finite element models for cylindrical composite lattice structure were developed using beam, shell and solid elements. Natural frequency test was measured using impact test method under free-boundary condition. The analysis result of the beam element model showed up to 23% errors because the beam element could not consider the degradation of mechanical properties of non-intersection parts of the composite lattice structures. On the other hand, the natural frequencies of finite element analysis for shell and solid element models showed good results with natural frequencies test. From the analysis of the experiment, finite element model for composite lattice structures should use shell or solid element which takes into consideration the intersection and non-intersection parts.

In this paper, evaluation method of structural integrity of cylindrical composite lattice structures was conducted. A finite element analysis was used to evaluate the structural integrity of composite lattice structures. In order to verify the optimal finite element in the evaluation of the structural integrity, finite element models for cylindrical composite lattice structure were generated using beam, shell and solid elements. The results of the finite element analyses with the shell and solid element models showed a good agreement. However, considerable differences were found between the beam element model and the shell and solid models. This occurred because the beam element does not take into account the degradation of the mechanical properties of the non-intersection parts of cylindrical composite lattice structures. It was found that the finite element analysis of evaluation of structural integrity for cylindrical composite lattice structures have to use solid element.

The purpose of this study is to design and implement an automatic resin impregnation equipment for composite strand specimens. Composite strand specimens were fabricated using this resin impregnation equipment with the filament winding method. The disadvantages of existing equipment include resin-induced pollution, poor tension control, and inefficient use of space. These problems lead to unnecessary processes and maintenance issues when fabricating the strand specimens. This study overcame these problems by installing a container in the resin recovery part, connecting the bobbin and rotating axis using a coupler and key, and moving the fiber impregnating part horizontally. Experiments were conducted on the strand specimens to evaluate the reliability of the proposed equipment. The experimental results showed an error within 1% compared to the mechanical properties provided by the material manufacturer, thereby demonstrating the reliability of the device.

This study evaluated the design and structural integrity of a three-axle bogie frame in a railway freight car through a numerical analysis and an experimental evaluation. A three-axle bogie frame, which supports the weight of the car body and load, is required to transport heavier cargo because two-axle vehicles have structural limitations. Therefore, this study performed a structural analysis and static load tests to evaluate the design and structural integrity of a three-axle bogie frame. The results obtained from the numerical analysis were compared to those of the experiments. For the bogie frame used in the experiments, a failure evaluation was performed using non-destructive methods. The numerical analysis and experimental evaluation were satisfactory for the structural integrity evaluation.

This paper describes a method to design a lightweight modular bridge for a railway infrastructure system. A lightweight design was achieved using the material selection method. Aluminum extrusions and honeycomb sandwich composites were selected as the best materials to reduce the weight of the upper structure of a conventional modular bridge made of carbon-steel material. The structural integrity of the lightweight modular bridge was evaluated under vertical and wind loads. The twisting and bending natural frequencies were also evaluated to investigate its dynamic characteristics. The results showed that the structural integrity and natural frequencies of the lightweight modular bridge, made of aluminum extrusion and sandwich composites, satisfied the design requirements. Moreover, it was found that the weight of the conventional modular bridge made of carbon steel could be reduced by a maximum of 47% using lightweight materials.

In this paper, The concept of a wheel with carbon fiber composite is to replace the conventional material used for a wheel hub, such as plastic, with a disk-type hub made of carbon fabric and epoxy resin. The impact load from the ground under real conditions was considered; a low-velocity impact test was conducted to evaluate the impact performance of the carbon wheel and compare it with that of a conventional plastic wheel. This study applied a 70 J impact load as a test condition. The impact energy was controlled in the test by adjustment of height and weight of impactor. The use of a carbon disk wheel hub was confirmed to reduce weight and generate an excellent repulsive force at low energy under conditions similar to real driving conditions. The results showed that the maximum load increased proportionally depending on the impact load, but the growth of the maximum load was reduced at a 20 J impact load and tended to decrease at a 45 J impact load. The carbon wheel showed excellent properties ; the level of rebounding was 35.3% and 19.1% of the total impact energy at impact loads of 5 J and 10 J, respectively. On the other hand, the carbon disk wheel rebounded less than 5% of the total energy due to crack generation of the thin carbon hub for impact loads of more than 20 J.

In this paper, we evaluate structural integrity of the wearable robot by using finite element analysis, which is made of CFRP(Carbon Fiber Reinforced Plastic) composite materials to be lightened. On the basis of the ASTM(American Standard Test Method), mechanical tests of the material are carried out in tensile, compressive and shear test for analytical evaluation. With the tested composite material, the main frame and two femoral frames of the robot is redesigned to satisfy the lightening design requirements. It is verified with the structural analysis that the redesigned frames are good for the part of the wearable robot.

This paper aims to evaluate the variation in the mechanical properties of carbon/epoxy composites under in situ low- and high-temperature environments. In situ low- and high-temperature environments were simulated with temperature ranging from -40℃ to 220℃ using an environmental chamber and furnace. The variation in the mechanical properties of the composites was measured for longitudinal and transverse tensile properties, in-plane shear properties and interlaminar shear strength. Under the low temperature of -40℃, all mechanical properties increased moderately compared to the baseline properties measured at room temperature. The changes in the longitudinal tensile properties decreased moderately with increasing temperature. However, transverse tensile properties, in-plane shear properties and interlaminar shear strength each showed a significant drop due to the glass transition behavior of the matrix after 140℃. Notably, the tensile property value near 100℃ increased compared to baseline property value, which was an unusual occurrence. This behavior was a direct result of post-curing of the epoxy resin due to its exposure to high temperature.

This paper reports an experimental study for evaluating the effect of temperature on the mode I, mode II and mixed-mode interlaminar fracture toughness of adhesive joints with a curved cross-section of filament-wound dome-separated composite pressure vessel. Mode I and mixed-mode interlaminar fracture toughness were evaluated using DCB specimens, while mode II interlaminar fracture toughness was determined using ENF specimens. [±10°]6, [±27°]6 and ([±10°]3/FM73/[±27°]3) winding specimens with the curved cross-section were considered. In-situ temperature environments were simulated with a range of -30℃ -60℃ using an environmental chamber and furnace. Experimental results on the effect of temperature indicate that interlaminar fracture toughness tends to be high at low temperature and is degraded with increase in temperature. For specimen types, it was found that interlaminar fracture toughness of [±10°]3/FM73/[±27°]3 winding specimens considered as adhesive joints of dome and helical part was higher than other specimens.

The purpose of this paper is to suggest the effective equivalent finite element model for the impact limiter of a nuclear spent fuel shipping cask made of sandwich composite panels. The sandwich composite panels were composed of a metallic facesheet and a core material made of urethane foam, balsa wood and red wood, respectively. The effective equivalent finite element model for the impact limiter was proposed by comparing the results of lowvelocity impact test of sandwich panels. An explicit finite element analysis based on LS-DYNA 3D was done in this study. The results showed that the solid elements were recommended to model the facesheet and core of sandwich panels for impact limiter compared to combination modeling method, in which the layered shell element for facesheet and solid element for core material are used. In particular, the solid element for balsa and red wood core materials should be modeled by the element elimination approach.

This paper describes a weight-reduction design method for the car bodies of a double deck high-speed train (service speed of 300 km/h). The method uses lightweight materials and a topology optimization technique. In this study, aluminum extrusions and sandwich composites were selected as the best materials to reduce the weight of the car body. The topology optimization technique was used to determine which car body parts could be made of the sandwich composites to achieve additional weight savings. The results of the topology optimization analysis showed that sandwich composites could be used for secondary car body members such as the roof and the second underframe. Also, it was found that a car body composed of aluminum extruded parts and sandwich composites could weigh up to 14% less than a car body made of only aluminum extrusions.

This study performed the progressive failure analysis of adhesive joints of a composite pressure vessel with a separated dome by using a cohesive zone model. In order to determine the input parameters of a cohesive element for numerical analysis, the interlaminar fracture toughness values in modes I and II and in the mixed mode for the adhesive joints of the composite pressure vessel were obtained by a material test. All specimens were manufactured by the filament winding method. A mechanical test was performed on adhesively bonded double-lap joints to determine the shear strength of the adhesive joints and verify the reliability of the cohesive zone model for progressive failure analysis. The test results showed that the shear strength of the adhesive joints was 32MPa; the experiment and analysis results had an error of about 4.4%, indicating their relatively good agreement. The progressive failure analysis of a composite pressure vessel with an adhesively bonded dome performed using the cohesive zone model showed that only 5.8% of the total adhesive length was debonded and this debonded length did not affect the structural integrity of the vessel.

This study aims to develop a Flywheel Energy Storage System (FESS) that uses wind power produced when an urban train is in motion, by utilizing a mounted turbine. This system was designed to generate and store electric power from wind power of a travelling urban train. The flywheel was designed to continue rotation using a one-way clutch bearing installed in the turbine shaft pulley, even in cases where the urban train decelerates or stops. This FESS can generate an additional 44% of electric power in comparison to a system not equipped with a flywheel. The generated power and operational features of the FESS were evaluated and verified through a wind tunnel test. The results show that the electric power stored in the FESS could supply auxiliary power for urban train components or service equipment, such as charging mobiles, Wi-Fi modules, and electric lights.

The purpose of this paper is to suggest a weight-reduction design method for the hybrid carbody of a high-speed maglev train that uses aluminum extrusion profiles and sandwich composites. A sandwich composite was used on the roof as a secondary member to minimize the weight. In order to assemble the sandwich composite roof and aluminum extrusion side frame of the carbody using welding, a guide aluminum frame located at the four sides of the sandwich composite roof was introduced in this study. The clamping force of this guide aluminum frame was verified by three-point bending test. The structural integrity and crashworthiness of the hybrid carbody of a high-speed maglev train were evaluated and verified according to the Korean Railway Safety Law using a commercial finite element analysis program. The results showed that the hybrid carbody composed of aluminum extrusion frames and a sandwich composite roof was lighter in weight than a carbody made only of aluminum extrusion profiles and had better structural performance.

본 논문에서는 복합재 대차프레임 볼트 체결부의 내구성 향상 방안에 대한 연구를 다루고 있다. 이를 위해, 인서트와 나사산 유무에 따른 3가지 경우를 고려하여 볼트 체결부에 대한 시험 및 해석을 통해 인서트 형태 및 유무에 미치는 영향을 평가하였다. 제안된 볼트 체결부의 구조 성능은 ASTM D5961에 의거한 시험을 통해 비교 평가하였다. 시험결과, 나사산이 없는 인서트를 갖는 볼트 체결부가 가장 적합한 것으로 확인되었다. 또한, 볼트 체결부를 고려한 복합재 대차프레임에 대한 구조 안전성 평가를 JIS E 4207에 의거하여 유한요소해석을 통해 평가하였다. 복합재 구조물은 Tsai-Wu 파손기준식에 의해 파손평가를 적용하였고, 볼트 체결부와 같은 금속재 구조물은 Von-Mises 파손기준식에 의해 평가하였다. 이때, 볼트 체결부의 경우에는 상세한 구조해석 결과 검토를 위해 서브 모델링 기법을 적용하였다. 구조해석결과, 나사산이 없는 인서트가 적용된 볼트 체결부의 경우에는 볼트 체결부 주위의 복합재 구조물에 발생하는 Tsai-Wu 파손지수가 다른 경우에 비해 약 50% 감소하는 경향을 보였는데, 이는 나사선이 없는 인서트 형상이 복합재 대차프레임 볼트 체결부의 내구성을 향상시킬 수 있을 것으로 판단된다. This paper describes the study on a method for improving the structural durability of bolted joints applied to a composite bogie frame. In this study, three bolted joints with and without inserts and screw threads were selected for determining the effect of the inserts, using experiment and analysis. The structural performances of the proposed bolted joints were compared and evaluated using the test method prescribed by the ASTM D5961 standard. The results revealed that the bolted joint having an insert shape without the screw thread offered improved durability for application to a composite bogie frame. Furthermore, the structural integrity of the frame comprising the bolted joints was evaluated using finite element analysis according to the JIS E 4207 standard. The Tasi-Wu and Von-Mises failure criteria were used for determining the failure of the composite structure and bolted joints, respectively. A sub-modeling technique was introduced for investigating the performance of the bolted joints in greater detail. The analysis results demonstrated that the Tasi-Wu failure index of the composite structure near the bolted joints was reduced by approximately one-half after applying an insert without the screw thread. This implies that the structural durability of the bolted joints of a composite bogie frame could be improved by using a metal insert without the screw thread.

본 논문은 KTX 안티롤바 너클부의 동특성 및 구조 안전성 평가를 위해 시험 및 수치적 방법을 사용하였다. 시험적 방법에서는 KTX와 KTX-산천 안티롤바 너클부의 동특성을 비교 평가하기 위해 호남선의 운행환경을 고려한 가속도 및 변형률 데이터를 각각 측정하였으며, 수치적 방법에서는 너클부에 대해 LS-DYNA 3D를 사용하여 구조 안전성 평가를 수행하였다. 이때 해석에 사용된 유한요소모델은 시험과 비교평가를 통해 신뢰성을 검증하였다. 수치해석 결과, 얇은 금속판 및 고무의 적층구조로 이루어진 너클부의 응력 및 속도장이 너클과 커넥팅로드 사이의 상대적 접촉 감소로 인해 두꺼운 강재로만 이루어진 너클부에 비해 좀 더 완화된 경향을 보였다. 그 결과 얇은 금속판과 고무로 구성된 너클 구조가 반복적인 외력 하중하에서 KTX 안티롤바의 탄성거동을 허용하여 동적 거동하의 구조적 안전성을 향상시키기 위한 최선의 방법임을 확인하였다. To evaluate the structural integrity and dynamic characteristic of the knuckle part of a KTX anti-roll bar, an experimental and a numerical approach were used in this study. In the experimental approach, the acceleration and strain data for the knuckle parts of the KTX and KTX-SANCHUN anti-roll bar were respectively measured to evaluate and compare its structural dynamic characteristics under the operating environments of the Honam line. In the numerical approach, the evaluation of its structural integrity was conducted using LS-DYNA 3D, and then, the reliability of the finite element model used was ensured by a comparative evaluation with the experiment. The numerical results showed that the stress and velocity field of the knuckle part composed of a layered structure of a thin steel plate and rubber were more moderate than those of the knuckle part made of only a thick steel block owing to the reduction of relative contact between the knuckle and the connecting rod. It was found that the knuckle part made of a thin steel plate and rubber was recommended as the best solution to improve its structural integrity resulting from the elastic behavior of the KTX anti-roll bar being enabled under a repeating external force.

본 연구의 목적은 최적화 해석 기법을 이용하여 복합재 압력용기의 스커트 치수를 도출하는 것이다. 복합재 압력용기 스커트 최적화 해석은 부분문제 근사법을 사용하였으며, APDL(ANSYS Parametric Design Language)을 이용하여 해석의 모든 과정을 일괄처리하였다. 설계변수로는 압력용기 스커트 부위의 두께와 길이를 선정하였으며, 내압에 의해 발생하는 변위와 무게를 각각 목적함수로 하여 최적화 해석을 통해 최적의 스커트 치수를 도출하였다. 그 결과 복합재 압력용기의 스커트 무게를 최대 4.38% 절감할 수 있었다. This study aims to find the optimal skirt dimensions for a composite pressure vessel with a separated dome part. The size optimization for the skirt structure of the composite pressure vessel was conducted using a sub-problem approximation method and batch processing codes programmed using ANSYS Parametric Design Language (APDL). The thickness and length of the skirt part were selected as design variables for the optimum analysis. The objective function and constraints were chosen as the weight and the displacement of the skirt part, respectively. The numerical results showed that the weight of the skirt of a composite pressure vessel with a separated dome part could be reduced by a maximum of 4.38% through size optimization analysis of the skirt structure.

본 연구의 목적은 설계자 전용 알루미늄 압출재 철도차량 차체 구조물의 자동화 구조해석 지원프로그램을 개발하는 것이다. 본 연구에서 개발된 프로그램 명칭은 “AUTO-RAP”이며, 알루미늄 압출재 철도차량 설계 및 구조해석에 대해 전문적인 지식과 경험이 없는 엔지니어도 설계와 검증이 동시에 가능하도록 하였다. 설계자는 기존의 알루미늄 압출재의 데이터베이스를 활용하거나 사용자 정의에 의한 지식기반설계가 가능하도록 하였으며, 설계검증은 철도안전법과 도시철도차량 안전기준에 관한 규칙에 의거하여 철도차량 차체 구조 안전성을 자동으로 평가하도록 프로그래밍 하였다. 또한, 본 프로그램은 MFC(Microsoft Foundation Classes)를 사용하여 GUI 환경을 구축하였으며, ANSYS와 ABAQUS 같은 다양한 상용 유한요소해석 프로그램 및 CAD 프로그램과의 호환성을 위해 .stp, .iges 등의 파일 생성을 지원한다. 결론적으로, 본 프로그램을 통하여 알루미늄 압출재 철도차량 차체 구조물의 제품 설계 비용과 시간 단축에 기여할 것으로 판단된다. The purpose of this study is to develop automated structural design and analysis aided-program of aluminum extrusion carbody structures for railway vehicle. This developed program is called “AUTO-RAP” and could perform simultaneously structural design and verification for railway carbody structures made of aluminum extrusion independent of expertise and experience of design engineers. Design engineers are able to conduct the knowledge-based design by providing database of existing aluminum extrusion or user-defined function. The design verification is automatically programmed to evaluate its structural integrity according to Korean Railway Safety Law or Urban Transit Safety Law. In addition, this program could automatically generate an executable file of various commercial finite element programs such as ANSYS and ABAQUS and CAD files such as .stp and .iges by GUI environment applications using MFC(Microsoft Foundation Classes). In conclusion, it is expected to contribute to reduce product design cost and time of carbody structures aluminum extrusions in railway industry.

복합재 연소관의 접합 체결부 최적의 설계 길이를 결정하기 위해 접합부 길이변화에 따른 구조해석을 수행하였다. 이때, 접착 체결부의 길이는 50 mm에서 300 mm의 범위를 갖는다. 무응력 상태의 초기 접합부 길이대비 응력구배가 발생하는 않는 구간의 길이를 “응력구배 길이 비”로 정의하고 이를 접착 체결부 길이선정을 위한 평가기준으로 정의하였다. 구조해석 결과 접착 체결부의 길이가 200 mm 이상으로 증가할 경우 응력구배 길이 비의 증가가 서서히 나타남을 확인하였다. 이는, 접착 체결부에 적용되는 2,500 psi 내압에서 구조적 안전성을 확보하는 최적화된 접착 체결부의 길이가 200 mm임을 의미한다. In order to determine optimal design length of adhesive joint of a composite rocket motor case, stress analysis of joint part according to changes of adhesive length was done. Adhesive length has a range of 50 mm to 300 mm as design variables. The ratio of adhesive length without any stress gradient to initial non-stressed adhesive length was determined as evaluation criteria for selection of adhesive length, which called "stress gradient length ratio". The numerical result showed that stress gradient length ratio of joint part with adhesive length of more than 200 mm was increased very slowly with increase of adhesive length. It means that adhesive length of about 200 mm could be the optimal dimension to ensure the structural safety of joint part against internal pressure of 2,500 psi.

허본 논문에서는 도상자갈 비산에 의한 GFRP 복합재 대차프레임의 구조안전성을 평가하기 위해 대차프레임의 스킨부를 구성하는 유리섬유/에폭시 적층 복합재의 충격시험과 충격 후 잔류압축시험을 수행하였다. 충격시험은 충격시험장비를 사용하여 5J, 10J, 그리고 20J의 충격에너지에 대해 수행하였고, 선로상의 도상자갈 비산을 모사하기 위해 구형, 육면체형, 그리고 원뿔형의 충격체를 설계하여 충격시험을 수행하였다. 충격손상을 갖는 적층 복합재의 잔류압축강도를 평가하기 위해 충격 후 압축시험을 수행하여 충격에 의한 재료의 물성저하여부를 판단하였다. 본 연구를 통하여 충격에너지가 증가함에 따라 적층 복합재의 충격손상영역과 압축강도저하가 증가하는 것을 확인하였으며, 원뿔형 형상의 도상자갈이 다른 형상에 비해 재료의 손상을 가중시키는 것을 확인하였다. In order to evaluate the effect of structural degradation of a GFRP composite bogie frame due to ballast-flying phenomena, the impact test and residual compression test after impact was conducted for glass fiber/epoxy 4-harness satin woven laminate composites applied to skin part of a bogie frame. The impact test was performed using a instrumented impact testing system with energy levels of 5J, 10J, and 20J, and the impactor was designed to have various ballast shapes such as sphere, cube, and cone to consider the ballasted track environments. The residual compression strength was tested to evaluate the degradation of mechanical properties of impact-damaged laminate composites. The results showed that the damage area and the degradation of residual compressive strength after impact for laminate composites was increased with increase of impact energy for all ballast shapes, and was particularly most influenced by ballast shape of cone.

본 논문은 샌드위치 복합재 틸팅열차의 충돌안전도 평가 및 성능 향상방안에 대해 서술하고 있다. 차체 구조물에 적용된 샌드위치 복합재는 알루미늄 하니컴 심재와 유리섬유 및 카본/에폭시 적층 복합재 면재로 이루어져있다. 충돌해석은 외연유한요소 해석 프로그램인 LS-DYNA3D를 이용하였다. 이때, 유한요소모델링과 충돌해석 계산시간의 절약을 위하여 3차원 유한요소모델과 1차원 등가 모델을 적용하였다. 틸팅열차의 충돌 조건은 철도안전법에 명시하고 있는 4가지 충돌사고 시나리오를 고려하여 해석을 수행하였다. 충돌해석 결과 시나리오-2를 제외한 나머지 충돌 시나리오에서 성능 요구조건을 만족하였다. 충돌 시나리오-2의 충돌안전도 요구조건을 충족하기 위하여 전두부의 적층복합재 커버와 금속프레임의 강성 향상방안을 제안하였으며, 결과적으로 충돌 시나리오-2의 요구조건을 만족하였다. This paper describes the crashworthiness evaluation and performance improvement of tilting train made of sandwich composites. The applied sandwich composite of carbody structure was composed of aluminum honeycomb core and glass/epoxy & carbon/epoxy laminate composite facesheet. Crashworthiness analysis of tilting train was carried out using explicit finite element analysis code LS-DYNA 3D. The 3D finite element model and 1D equivalent model were applied to save the finite element modeling and calculation time for crash analysis. The crash conditions of tilting train were conducted according to four crash scenarios of the Korean railway safety law. It found that the crashworthiness analysis results were satisfied with the performance requirements except the crash scenario-2. In order to meet the crashworthiness requirements for crash scenario-2, the stiffness reinforcement for the laminate composite cover and metal frames of cabmask structure was proposed. Consequentially, it has satisfied the requirement for crash scenario-2.

본 논문은 4-매 주자직 유리섬유/에폭시 적층 복합재가 적용된 철도차량 경량 대차프레임의 피로 수명 및 강도 평가에 대해 기술한다. 대차프레임 경량화 재질로 적용된 유리섬유/에폭시 4-매 주자직 적층 복합재료의 피로특성 평가를 위하여 경사, 위사 그리고 0°/90° 방향으로 적층된 시험편에 대하여 인장-압축 피로시험을 수행하였다. 유리섬유/에폭시 4-매 주자직 적층 복합재료의 피로시험은 5Hz의 주파수, -1의 응력비(R), 107의 피로수명을 갖도록 하였다. 또한, JIS E 4207의 하중조건에 따른 대차프레임의 피로강도 평가를 Goodman 선도를 통하여 수행하였다. 유리섬유/에폭시 적층 복합재 경량 대차프레임의 피로수명 및 강도 평가기준을 만족하였으며, 무게를 고려할 경우 기존 대차프레임 재질인 SM490A 금속재에 비하여 우수한 피로특성을 갖는다. We describe the evaluation of the fatigue life and strength of a lightweight railway bogie frame made of glass fiber/epoxy 4-harness satin-woven composites. To obtain the S-N curve for the evaluation of the fatigue characteristics of the composite bogie frame, we performed a tension-compression fatigue test for composite specimens with different stacking sequences of the warp direction, fill direction, and 0°/90° direction. We used a stress ratio (R) of -1, a frequency of 5 Hz, and an endurance limit of 107. The fatigue strength of the composite bogie frame was evaluated by a Goodman diagram according to JIS E 4207. The results show that the fatigue life and strength of the lightweight composite bogie satisfy the requirements of JIS E 4207. Given its weight, its performance was better than that of a conventional metal bogie frame based on an SM490A steel material.

본 논문은 유리섬유/에폭시 4-매 주자직 적층 복합재와 PVC 폼 코어로 제작된 철도차량용 복합재 대차프레임의 금속재 체결부 볼트 위치 최적화 연구에 대해 서술했다. 최적화 해석은 APDL(Ansys Parameter Design Language)을 이용한 서브모델링 기법을 적용하였으며 부분문제 근사방법에 의한 최적화를 수행하였다. 이때, 최적화 해석에 적용된 서브모델링 기법은 관심영역을 포함한 부분모델에 대한 계산을 재수행 함으로써 해석에 소요되는 시간을 절약하고 상세한 결과를 도출 할 수 있다. 복합재 대차프레임의 구조해석은 JIS E 4207에 의거하여 수행하였다. 서브모델링 기법을 적용한 복합재 대차프레임의 최적화 해석은 전체모델에 대한 결과에 비해 요소망 밀도의 조절을 통한 해석시간 절약과 상세한 결과를 얻을 수 있으며, 또한 볼트위치의 최적화로 인해 보다 낮은 Von-Mises 응력값이 나타남을 확인하였다. This paper describes the optimum design of bolt locations for metal joint parts of railway bogie frame made of glass fiber/epoxy 4-harness satin woven laminate composite and PVC foam core. The optimum design analysis was done by sub-problem approximation method using Ansys Parameter Design Language(APDL). The sub-modeling method was introduced to conduct the detailed recalculation for the only target parts and reduce calculating time. The structural analysis for composite bogie frame was performed according to JIS E 4207. The results showed that the optimum design analysis using sub-modeling method was able to obtain faster and more precise results than that of the entire model by the control of mesh size for the target parts, and the maximum Von-Mises stress has been reduced in comparison with its original dimensions due to the optimum design of bolt locations.

본 논문은 철도차량 경량화 재질로 적용된 유리섬유/에폭시 4-매 주자직 적층 복합재료의 인장-압축 피로특성을 평가하였다. 유리섬유/에폭시 4-매 주자직 적층 복합재료의 인장-압축 피로시험은 경사, 위사 그리고 ±45° 방향으로 적층된 시험편에 대하여 수행하였다. 인장-압축 피로시험은 5Hz의 주파수를 갖으며, 응력비(R)는 -1로 수행하였다. 인장-압축 피로시험 수행 시 압축하중에 의한 시험편의 좌굴을 방지하기 위하여 좌굴방지지그를 설계하고 이를 시험에 적용하였다. 또한, Goodman 선도는 유리섬유/에폭시 4-매 주자직 적층 복합재의 피로특성과 수명을 평가하기 위해 사용하였다. 유리섬유/에폭시 4-매 주자직 적층 복합재료의 인장-압축 피로시험결과 경사방향 적층 복합재의 피로특성이 기존 금속재 대차에 적용되는 SM490에 비하여 우수한 것으로 나타났다. This paper describes the evaluations of tension-compression fatigue characteristics and life for glass fiber/epoxy laminate composite applied to railway bogie to reduce weight. Test samples of tension-compression fatigue were composed of glass fiber/epoxy 4-harness woven laminate composites with different stacking sequence of warp-direction, fill-direction and ±45°-direction. The tension-compression fatigue test was conducted with stress ratio (R) of -1 and frequency of 5Hz. Goodman diagram were used to evaluate the fatigue characteristics and life of glass fiber/epoxy 4-harness satin woven laminate composite. Anti-buckling jig was designed to prevent buckling of specimen under compression load. The test results showed that the fatigue characteristics of glass fiber/epoxy 4-harness satin woven laminate composite with stacking sequence of warp-direction had a good performance in comparison with that of SM490 used to conventional metal railway bogie.

본 논문은 국내에서 개발중인 모노레일 대차 프레임에 대해 구조 안전성 및 피로강도를 평가하였다. 현재 모노레일 대차 프레임에 대한 평가기준은 없는 실정이며, 이에 구조 안전성 및 피로강도 평가는 유럽규격인 UIC 615-4 기준을 적용하여 수행하였다. 이때, 설계된 대차 프레임에 대해 각 하중조건에서의 변위 및 Von-Mises 응력 결과를 통해 구조 안전성을 평가하였다. 그리고 피로강도는 UIC 615-4 기준의 규정에 따라 조합 주운용하중조건에 의해 평가되고, 일괄처리 기능을 갖는 winLIFE v3.1을 이용한 피로해석 결과와 비교 검증하였다. 본 연구를 통하여 설계된 대차 프레임은 구조적 안전성 및 피로강도를 만족하였으며, 일괄처리 기능을 갖는 피로해석은 조합하중을 이용한 기존 피로해석보다 더 효율적임을 확인하였다. In this paper, the structural integrity and fatigue strength for the bogie frame of Monorail being developed in domestic was evaluated. Presently, the standard of evaluation for the bogie frame of monorail was not regulated. Therefore, the evaluation of the structural integrity and fatigue strength for the bogie frame was performed on the basis of the UIC 615-4 standard. The structural integrity of the designed bogie frame was evaluated by displacement and Von-Mises stress under each load conditions. And the fatigue strength was evaluated by combined main in-service load conditions specified at UIC 615-4 standard and it was compared with result of fatigue analysis using winLIFE v3.1 with the function of batch processing. The results shows that the structural integrity and fatigue strength of the designed bogie frame was satisfied, and the fatigue analysis using batch processing was more effective than conventional fatigue analysis using combined load conditions.

본 논문은 철도차량용 추진제어장치의 성능평가를 위한 관성부하 시험설비의 구조안전성 및 동특성 평가를 연구하였다. 추진제어장치는 철도차량의 핵심 부품으로서 차량에 적용하기 전에 안정성 및 신뢰성 검증이 충분히 이루어 져야 한다. 따라서 추진제어장치의 성능시험을 위한 관성부하 시험설비를 이론식을 바탕으로 하여 설계하였다. 설계된 관성부하 시험설비에 대해 Ansys v11.0을 이용하여 구조해석을 수행하였으며, ADAMS를 통해 동특성을 평가하였다. 관성부하 시험설비의 구조안전성은 조합하중하의 베어링에서 안전계수가 10.2로 만족하였다. 또한, 동적 시뮬레이션에 따른 플라이휠은 0.83mm이내의 최대진폭변위로 구조적 안정성이 확보되었다. Abstract This paper describes the evaluation of structural integrity and dynamic characteristic of inertial load test equipments for performance test of railway vehicle propulsion control system. The propulsion control system of railway vehicle has to be confirmed of safety and reliability prior to its application. Therefore, inertial load test equipments were designed through theoretical equation for performance test of propulsion control system. The structural analysis of inertial load test equipments was conducted using Ansys v11.0 and the dynamic characteristic was evaluated using Adams. The results showed that the structural integrity of inertial load test equipment was satisfied with a safety factor of 10.2 on the bearing part under combined load. Also, the structural stability of flywheel according to dynamic simulation was secured by the maximum oscillation displacement within 0.83mm.

본 논문은 샌드위치 복합재가 적용된 철도차량 차체 구조물을 위한 표준유한요소모델을 제시하였다. 최근 샌드위치 복합재는 높은 굽힘 강성 및 강도를 가지며 차체의 경량화와 공간 확보를 통해 에너지 효율을 향상시킬 수 있어 국내의 많은 분야에서 널리 사용되고 있다. 그러므로 복합재 철도 차량의 제작 전에 유한요소법 등을 통해 구조안전성을 검증해야 한다. 본 연구에서는 다양한 철도차량의 실제 구조시험과 같은 수직, 압축, 비틀림 하중 및 고유진동수 해석을 통해 철도차량 구조물의 표준유한요소모델을 검증 제시하였다. 그 결과, 샌드위치 패널의 굽힘 강성을 향상시키기 위한 보강 금속 프레임에는 빔 요소보다는 사각 쉘 요소가 적절하였으며, 샌드위치 패널의 허니콤 코어와 적층복합재의 경우 적층 쉘 요소와 비교하여 적층 쉘 요소와 솔리드 요소를 사용하는 것이 적절하다. 또한, 제안된 표준유한요소모델은 유한요소모델의 수정 없이 충돌모델에 적용할 수 있는 장점을 가지고 있다. This paper describes the standardized finite element model for carbody structures of railway vehicle made of sandwich composites. Recently, sandwich composites were widely used to railway vehicle due to the improvement of energy efficiency, high specific stiffness and strength, weight reduction and space saving in korea. Therefore, structural integrity should be verified using finite element analysis prior to the manufacture of composite railway vehicle. The standardized finite element model for composite carbody structures was introduced through comparing the results of real structural test under vertical, compressive, twisting load and natural frequency test of various railway vehicles in this study. The results show that the quadratic shell element is suitable to model the reinforced metal frame used to improve the flexural stiffness of sandwich panel compared to beam element, and layered shell and solid element are recommended to model the skin and honeycomb core of sandwich panel compared to sandwich shell element. Also, the proposed standard finite element model has the merit of being applied to crashworthiness problem without modifications of finite element

본 연구에서는 토리구형 돔 형상을 갖는 연소관의 치수 최적화를 통한 경량화와 구조 안전성을 평가하였다. 치수최적화 설계는 빠른 설계 검증을 위하여 볼트의 단면적 비가 고려된 2차원 축대칭 유한요소 모델을 이용하여 수행하였다. 이때, 해석 프로그램은 ANSYS APDL(Ansys Parameter Design Language)을 이용하였고, 해석법은 sub-problem법과 first-order법을 선택하여 수행하였다. 설계 변수로는 연소관의 돔과 실린더 부위의 두께를 선정하였다. 수정된 2차원 축대칭 유한요소 모델은 3차원 유한요소 모델과의 결과 비교를 통하여 신뢰성을 확인하였고, 초기설계 단계에서 수정된 2차원 축대칭 유한요소 모델을 이용하여 연소관의 구조 안전성 평가와 빠르고 정확한 경량화 설계를 수행할 수 있었다. 연소관의 안전계수에 따른 최적화 해석 결과 최대 17.6%의 무게 절감 효과를 확인하였다. In this study, we evaluated the structural integrity and weight of a rocket motor with a torispherical dome by size optimization. Size optimization was achieved by first-order and sub-problem methods, using the Ansys Parametric Design Language (APDL). For rapid design verification, a modified 2D axisymmetric finite-element model was used, and the bolt pre-tension load was expressed as function of the ratio of the cross-sectional area. The thickness of the dome and the cylindrical part of the rocket motor were selected as the design parameters. Our results showed that the weight and structural integrity of the rocket motor at the initial design stage could be determined more rapidly and accurately with the modified 2D axisymmetric finite-element model than with the 3D finite-element model; further, the weight of the rocket motor could be saved to maximum of 17.6% within safety limit.

본 연구는 철도차량에 적용되는 직물 유리섬유/에폭시 적층 복합재의 피로특성 및 피로수명에 대해 평가하였다. 이때, 피로시험은 0.1의 응력비(R)와 5Hz의 주파수에서 인장-인장 하중 조건이 고려되었으며, 시험편은 카본/에폭시 플라이가 보강된 시험편과 보강되지 않은 시험편 두 가지 타입을 고려하였다. 또한, 직물 유리섬유/에폭시 적층 복합재의 피로수명을 평가하기 위해 철도차량 차체와 언더프레임에 주로 사용되는 알루미늄 6005와 비교하였다. 본 연구를 통하여 3장의 카본/에폭시 플라이가 보강된 직물 유리섬유/에폭시 적층 복합재 시험편이 보강되지 않은 기본 시험편보다 피로강도 및 피로수명이 크게 향상됨을 확인하였다. In this study, the fatigue characteristics and life of a woven glass fabric/epoxy laminate composite applied to railway vehicles was evaluated. The fatigue test was conducted using a tension-tension load with a stress ratio R of 0.1 and frequency of 5 Hz. Two types of woven glass fabric/epoxy laminate composite was used in the fatigue test: with and without carbon/epoxy ply reinforcement. In addition, the fatigue life of the woven glass fabric/epoxy laminate composite was compared with that of aluminum 6005, which is used in the car body and underframe structures of railway vehicles. The test results showed that the failure strength and life of the woven glass fabric/epoxy laminate composite reinforced with three carbon/epoxy plies had a remarkable improvement compared with that of the bare specimen without reinforcement.

WR580/NF4000 유리섬유 에폭시 면재를 갖는 알루미늄 하니컴 샌드위치 복합재가 적용된 자동무인경전철 차체 구조물은 구조 시험과 유한요소 해석에 의해 평가되었다. 구조 시험은 JIS E 7105 규정에 따라 수행되었다. 차체 구조물의 구조 안전성은 다이얼 게이지와 가속도 센서를 통해 얻어진 처짐 및 고유진동수 결과에 의해 평가되었다. 그리고 제안된 유한요소 모델은 구조 시험 결과와 비교 되었으며, 유한요소 해석은 구조 시험과 잘 일치함을 보였다. 또한, 차체 구조물의 강성을 높이기 위해 언더프레임에 보강재가 적용된 모델은 설계단계에서 제안되었다. 보강된 언더프레임 모델을 갖는 복합재 차체 구조물은 구조 강성이 약 44%가 향상되었다. The vehicle structure of Automated People Mover(APM) made of aluminum honeycomb sandwich with WR580/NF4000 glass-fabric epoxy laminate facesheets was evaluated by structural test and finite element analysis. The test of the vehicle structure was conducted according to JIS E 7105. The structural integrity of vehicle structure was evaluated by stress, deflection and natural frequency obtained from dial-gauge and acceleration sensor. And the proposed finite element models were compared with the results of structural test. The results of finite element analysis showed good agreement with those of structural test. Also, in order to improve the stiffness of vehicle structure, the modified underframe model with reinforced side sill was proposed in design stage. The composite vehicle structures with modified underframe model had the mproved structural stiffness about 44%.

논문은 샌드위치 복합재가 적용된 바이모달 트램의 설계검증을 위한 구조 성능 시험과 유한요소 해석에 대해 기술하였다. 차체 구조물에 적용된 샌드위치 복합재는 알루미늄 하니컴 심재와 WR580/NF4000 유리섬유/에폭시 면재로 구성되었다. 이때, 차체 구조물의 구조 시험은 JIS E 7105 규정에 따라 수직하중, 압축하중, 비틀림 및 고유진동수 시험이 각각 수행되었다. 그리고 다이얼게이지, 스트레인게이지, 가속도 센서를 통해 얻어진 처짐, 응력, 고유진동수 결과에 따른 구조 안전성을 평가하였다. 그리고 Ansys v11.0을 이용하여 유한요소해석을 수행하였고, 구조 시험 결과와 비교하였다. 구조 시험 결과는 제안된 유한요소 모델을 사용한 구조 해석 결과와 처짐, 응력, 고유진동수가 비교적 잘 일치함을 확인하였다. This paper describes the evaluation of structural performance test and finite element analysis to verify the design of Bimodal Tram made of sandwich composites. The sandwich composite applied to vehicle structure was composed of a aluminum honeycomb core and WR580/NF4000 glass fabric/epoxy laminate composite facesheet. The load tests of vehicle structure were conducted for vertical load, compressive load, torsion and modal analysis according to JIS E 7105. The structural integrity of vehicle was evaluated by the measurement of displacement, stress and natural frequency obtained from dial gauge, strain gauge and gravity sensor, respectively. And finite element analysis using ANSYS v11.0 was done to compare with structural test. The results showed that the displacement, stress and natural frequency were in an good agreement with those of structural analysis using the proposed finite element models.

In this paper, a study on low-velocity impact response of honeycomb sandwich panels was done for the changes of impact location and core fabrication angles. The test specimens were made of glass/epoxy laminate facesheet and aluminum honeycomb core. Square samples of 100mm and 100mm sides were subjected under low-velocity impact loading using instrumented testing machine at three energy levels. Impact parameters like maximum force, time to maximum force, deflection at maximum force and absorbed energy were evaluated and compared for the changes of impact location and core fabrication angle. The impact damage size were measured at facesheet surface by 3-Dimensional scanner. Also, sandwich specimens after impact test were cut to analyse the failure mode.

This paper describes the results of structural integrity and crashworthiness of Automatic Guideway Transit(AGT) vehicle made of sandwich composites. The applied sandwich composite of vehicle structure was composed of aluminum honeycomb core and WR580/NF4000 glass fabric/epoxy laminate composite facesheet. Material testing was conducted to determine the input parameters for the composite facesheet model, and the effective equivalent damage model for the orthotropic honeycomb core material. The finite element analysis using ANSYS v11.0 was done to evaluate structural integrity of AGT vehicle according to JIS E 7105 and ASCE 21-98. Crashworthiness analysis was carried out using explicit finite element code LS-DYNA3D with the lapse of time. The crash condition was frontal accident with speed of 10km/h at rigid wall. The results showed that the structural integrity and crashworthiness of AGT vehicle were proven under the specified loading and crash conditions. Also, the modified Chang-Chang failure criterion was recommended to evaluate the failure modes of composite structures after crashworthiness event. 본 논문은 샌드위치 복합재가 적용된 자동무인경전철 차체 구조물의 구조 안전성 및 충돌 안전성 결과에 대해 서술하고 있다. 차체 구조물에 적용된 샌드위치 복합재는 알루미늄 하니컴 심재와 WR580/NF4000 유리섬유/에폭시 적층 복합재 면재로 이루어져 있다. 차체 구조물에 적용되는 적층 복합재 면재에 대해 기계적 시험을 통하여 물성을 획득하였고, 직교 이방성 특성을 갖는 하니컴 심재의 물성은 유효등가손상모델을 적용하였다. ANSYS v11.0을 이용한 유한요소 해석은 JIS E 7105 기준과 ASCE 21-98 기준에 따라서 자동무인경전철 차체의 구조 안전성을 평가하였다. 충돌해석은 외연유한요소 해석 프로그램인 LS-DYNA3D를 이용하였다. 충돌 조건은 강체벽에 10km/h의 속도로 정면충돌 사고를 모사하였다. 또한, 수정된 Chang-Chang 파손기준식은 충돌 후 복합재 구조물의 파손 모드를 평가하는데 추천된다.

The objective of this research is to design the roller rig for the maintenances of high-speed train bogies operated on the tracks. Roller rigs have been studied and researched to develop the faster, safer and more efficient railway system. It is to reduce the time of testing vehicles and to make as wide a range of tests available as possible. Therefore, it is very important issue to check and evaluate the dynamic responses of high-speed train after several years of operation. This paper presents a study on the conceptual design and dynamic model to develop the roller rig for the routine maintenances of high-speed trains bogies with maximum speed of 350km/h. ANSYS was used to analyze the wheel/roller's contact behavior of driving axle and ADAMS was used to verify and analyze the dynamic behaviors of roller rig.

In this study, unsteady wind pressure analyses on platform screen door (PSD) have been conducted considering the flow intereference effects between the moving train and the configuration of subway station. The major role of PSD prevents passenger accidents, wind pressure, polluted dust and noise when the train is entering the station platform. Computational fluid dynamic method with moving gird algorithm has been adopted to accurately predict unsteady pressure levels exerted on the PSD. Closed and open type station configuration are considered. Also, wind pressure levels for passing and stopping drive motion of the entering train are presented and practically compared each other.

This paper presents the evaluation of crashworthiness and rollover characteristics of low-floor bus vehicles made of aluminum honeycomb sandwich composites with glass-fabric epoxy laminate facesheets. Crashworthiness and rollover analysis of low-floor bus was carried out using explicit finite element analysis code LS-DYNA3D with the lapse of time. Material testing was conducted to determine the input parameters for the composite laminate facesheet model, and the effective equivalent damage model for the orthotropic honeycomb core material. The crash conditions of low-floor bus were frontal accident with speed of 60km/h. Rollover analysis were conducted according to the safety rules of European standard (ECE-R66). The results showed that the survival space for driver and passengers was secured against frontal crashworthiness and rollover of low-floor bus. Also, The modified Chang-Chang failure criterion is recommended to predict the failure mode of composite structures for crashworthiness and rollover analysis. This paper presents the evaluation of crashworthiness and rollover characteristics of low-floor bus vehicles made of aluminum honeycomb sandwich composites with glass-fabric epoxy laminate facesheets. Crashworthiness and rollover analysis of low-floor bus was carried out using explicit finite element analysis code LS-DYNA3D with the lapse of time. Material testing was conducted to determine the input parameters for the composite laminate facesheet model, and the effective equivalent damage model for the orthotropic honeycomb core material. The crash conditions of low-floor bus were frontal accident with speed of 60km/h. Rollover analysis were conducted according to the safety rules of European standard (ECE-R66). The results showed that the survival space for driver and passengers was secured against frontal crashworthiness and rollover of low-floor bus. Also, The modified Chang-Chang failure criterion is recommended to predict the failure mode of composite structures for crashworthiness and rollover analysis.

The structural stiffness, strength and stability on the bodyshell and floor structures of the Korean Low Floor Bus composed of laminate, sandwich panels and metal reinforced frame were evaluated. The laminate composite panel and facesheet of sandwich panel were made of WR580/NF4000 glass fabric/epoxy laminate, while aluminum honeycomb or balsa was applied to the core materials of the sandwich panel. A finite element analysis was used to verify the basic design requirements of the bodyshell and the floor structure. The use of aluminum reinforced frame and honeycomb core was beneficial for weight saving and structural performance. The symmetry of the outer and inner facesheet thickness of sandwich panels did not affect the structural integrity. The structural strength of the panels was evaluated using Von-Mises criterion for metal structures and total laminate approach criterion for composite structures. All stress component of the bodyshell and floor structures were safely located below the failure stresses. The total laminate approach is recommended to predict the failure of hybrid sandwich composite structures at the stage of the basic design.

본 논문에서는 바이모달 트램의 차체와 바닥재 구조 재료로 적용되는 2종류의 샌드위치 패널에 대한 충격 손상을 시험과 수치해석을 통해 상호 비교하였다. 적용된 시편은 100mm×100mm의 크기를 가지며 저속충격시험기를 사용하여 4가지 경우의 충격에너지에 대해 시험하였다. 또한, 저속충격 조건에 따라 차체 적용 샌드위치 구조물의 저속 충격 특성을 유한요소해석으 로 분석하기 위해 범용 외연유한요소해석 프로그램인 LS-DYNA3D를 이용하여 특성을 분석하였다. 이때 금속재와 복합재 재 료의 손상모델, 그리고 직교이방성 특성을 갖는 하니컴 재료의 유효손상모델을 제시하기 위하여 기계적 특성 시험을 수행하 여 물성 파라메터를 획득하였고, 시험과 해석결과 충격 하중에 대한 샌드위치 패널의 손상 영역과 깊이를 비교적 잘 예측할 수 있음을 증명하였다. This paper describes the results of experiments and numerical simulation studies on the low-velocity impact damage of two different sandwich composite panels for application to bodyshell and floor structure of the BIMODAL tram vehicle. Square test samples of 100mm sides were subjected to low-velocity impact loading using an instrumented testing machine at four impact energy levels. Part of this work presented is focused on the finite element analysis of low-velocity impact response onto a sandwich composite panels. It is based on the application of explicit finite element (FE) analysis codes LS-DYNA 3D to study the impact response of sandwich structures under low-velocity impact conditions. Material testing was conducted to determine the input parameters for the metallic and composite material model, and the effective equivalent damage model for the orthotropic honeycomb materials. Numerical and experimental results showed a good agreement for damage area and the depth of indentation of sandwich composite panels created by the impact loading. This paper describes the results of experiments and numerical simulation studies on the low-velocity impact damage of two different sandwich composite panels for application to bodyshell and floor structure of the BIMODAL tram vehicle. Square test samples of 100mm sides were subjected to low-velocity impact loading using an instrumented testing machine at four impact energy levels. Part of this work presented is focused on the finite element analysis of low-velocity impact response onto a sandwich composite panels. It is based on the application of explicit finite element (FE) analysis codes LS-DYNA 3D to study the impact response of sandwich structures under low-velocity impact conditions. Material testing was conducted to determine the input parameters for the metallic and composite material model, and the effective equivalent damage model for the orthotropic honeycomb materials. Numerical and experimental results showed a good agreement for damage area and the depth of indentation of sandwich composite panels created by the impact loading.

In this paper, a study on low-velocity impact response of four different sandwich panels for the hybrid bodyshell and floor structure application of the Korean low floor bus vehicle was done. Square samples of 100mm sides were subjected low-velocity impact loading using an instrumented testing machine at six energy levels. Impact parameters like maximum force, time to maximum force, deflection at maximum force and absorbed energy were evaluated and compared for four different types of sandwich panels. The impact damage size and depth of the permanent indentation were measured by 3-Dimensional Scanner. Failure modes were studied by sectioning the specimens and observed under optical microscope. The impact test results show that sandwich panel with composite laminate facesheet could not observe damage mode of a permanent visible indentation after impact and has a good impact damage resistance in comparison with sandwich panel with metal aluminum facesheet.

Sandwich composites made of glass fabric epoxy facesheets with aluminum honeycomb core or balsa core is considered for the structural design of bodyshell of a Korean Low Floor Bus. Initially, in order to select the optimal facesheet and core materials in design stage, the flexural response of a sandwich composite is a critical importance. In this study, theoretical formula which could easily and quickly evaluate and obtain the flexural responses such as deflection and flexural stiffness of a sandwich composite subjected to external load was established. This theory could calculate the flexural responses of sandwich composites with narrow as well as wide width and with facesheets of unequal thickness, and also distinguish between the bending and shear effects of deflection. Finite element analysis using ANSYS V10.0 was used to offer the best elements for real sandwich composites, and flexural test according to ASTM C393 was conducted to compare with the results of theoretical formula and finite element analysis. The results show that the flexural responses of sandwich composites using proposed theoretical formula is in good agreement with those of experiment and finite element method.

In this study, transient and quasi-static analysis were done for the evaluation of structural integrity of the platform screen door due to train wind pressure. Fluent 6.0 was used to calculate the train wind pressure, and Ansys 10.0 was used to evaluate the structural stability of platform screen door due to train wind pressure. Transient analysis was used to check the design requirements of platform screen door, and quasi-static analysis was introduced to save the calculating time and check quickly structural performances when compared to those of transient analysis. The results show that structural stability of the platform screen door under train wind pressure is proven and quasi-static analysis can quickly check the structural integrity of platform screen door.

The paper presents gravitational effect on eigenvalue branches and flutter modes of a vertical cantilevered pipe conveying fluid. The eigenvalue branches and modes associated with flutter of cantilevered pipes conveying fluid are fully investigated. Governing equations of motion are derived by extended Hamilton's principle, and the related numerical solutions are sought by Galerkin's method. Root locus diagrams are plotted for different values of mass ratios of the pipe, and the order of branch in root locus diagrams is defined. The flutter modes of the pipe at the critical flow velocities are drawn at every one of the twelfth period. The transference of flutter-type instability from one eigenvalue branches to another is investigated thoroughly.

We have evaluated the structural integrity of a sandwich composite train roof structure that can be a lightweight, cost saving solution to large structural components for rail vehicles in design stages. The sandwich composite train roof structure was 11.45 meters long and 1.76 meters wide. The finite element analysis was used to calculate the stresses, deflections and natural frequencies of the sandwich composite train roof against the weight of air-conditioned system. The 3D sandwich finite element model was introduced to examine the structural behavior of the hollow aluminum extrusion frames joined to both sides of the sandwich composite train roof. The results shown that the structural performance of the sandwich composite train roof under loading conditions specified is satisfaction and the use of aluminum reinforced frame and aluminum honeycomb core is beneficial with regard to weight saving and structural performance in comparison with steel reinforced frame and polyurethane foam core. Also, we have manufactured prototype of sandwich composite train roof structure on the basis of analysis results.

This paper presents the dynamic stability of a cantilevered Timoshenko beam on partial elastic foundations subjected to a follower force. The beam with a tip concentrated mass is assumed to be a Timoshenko beam taking into account its rotary inertia and shear deformation. Governing equations are derived by extended Hamilton's principle, and finite element method is applied to solve the discretized equation. Critical follower force depending on the attachment ratios of partial elastic foundations, rotary inertia of the beam and magnitude and rotary inertia of the tip mass is fully investigated.

Mode II interlaminar fracture behaviors of carbon fabric/epoxy composites, which are applicable to tilting traincarbodies, was investigated by the ENF (End notched flexure) test. The specimens were made of CF3327 plain wovenfabric with epoxy and a starter delamination at one end was made by inserting Teflon film with the thickness of 12.5㎛or 25.0㎛. The equation for mode II interlaminar fracture toughness was suggested based on the effective crack lengthfrom the compliance of load-displacement curve. Mode II interlaminar fracture toughness was evaluated for severaltypes of the specimens. Also crack propagating behaviors and fracture surfaces were examined through an opticaltravelling scope and a scanning electron microscope.

Aging characteristics of glass fabric/phenolic composites for tilting train subjected to combined environmental aging factors were invertigated. A 2.5KW accelerated aging tester with a xenon-arc lamp was used to provide environmental aging factors such as temperature, moisture, and ultraviolet. A series of aging tests were conducted up to 3000 hours and several types of specimens were prepared along the warp direction and the fill direction. Mechanical degradations for tensile, flexural, and shear properties were evaluated as a function of exposure times through a meterial testing system. Thermal analysis properties such as storage shear modulus, loss shear modulus, and tan δ were measured through a dynamic mechanical analyzer. Finally exposed surfaces of the composites were examined using a scanning electron microscope. According to the experimental results, mechanical properties and thermal analysis properties of glass fabric/phenolic composites were found to be slightly degraded as a function of exposure times due to combined environmental effects.

철도차량에서 복합재료에 대한 활용은 날로 증대되고 있는 추세이다. 현저한 기술적 진보를 얻기 위해 철도차량은 더 가볍고, 강하고, 안전하며 전통적인 소재와는 차별화된 소재를 요구하고 있다. 복합재료의 철도차량에의 응용은 무게 감소, 이로 인한 속도 증가, 에너지 소비량 감소, 낮은 관성, 적은 트랙 마모 그리고 큰 유효 탑재량 등의 장점을 지니고 있으며 철도차량 디자인에 여러 다양함을 제공하고 낮은 무게 중심 설계에 의한 안전성 확보, 단순화된 구조 설계에 의한 좌석수의 증가 등의 장점을 지니고 있다. 또한, 모듈화 설계를 가능케 함으로서 제작공정의 감소 및 유지보수 효율화를 얻을 수 있게 된다. (중략)

In order to determine the most suitable material system for achieving the lightweight design while fulfilling the design requirements of carbody structures of Korean Tilting Train eXpress(TTX), aluminum carbody, composite carbody, and hybrid carbody combined with aluminum and composite structures were considered in the present study. The finite-element analysis was used to verify the design requirements of the TTX carbody structures with the material system considered in the design stages. The stresses in the carbody structures and deflections of underframe against static load cases were used as design criteria. The results show that the hybrid carbody structures are beneficial with regard to weight saving and structural integrity in comparison to aluminum and composite carbody structures.

In order to evaluate the static stability of hybrid carbody structures of Korean Tilting Train eXpress(TTX) caused by degradation of composites under ground environments, T300/AD6005 graphite/epoxy composite specimens were exposed to accelerated environmental conditions including ultraviolet radiation, temperature and moisture for 2000 hours. It was found that the stiffness and strength of composites after aging were lower than those of unexposed specimens, and decreased as the aging time increases. The values of the degraded properties were used in the static analysis to check the static stability of hybrid carbody structures caused by environmental degradation of composites. The results shown that the structural stability of hybrid carbody structures was affected by the degradation of composites after exposure to accelerated aging environments.

In order to ecaluate the strength of carbody structures of railway rolling stock made of laminated fiber-reinforced composite meterials, total laminate approach was introduced. Structural analyses were conducted to check the basic design of the hybrid composite carbody structure of the Korean Tilting Train eXpress(TTX) with the service speed of 180km/h. The mechanical tests were also conducted to obtain strengths of composite laminates. The results shown that all stress components of composite carbody structures were inside of failure envelopes and total laminate approach was recommended to predict the failure of composite carbody structures at the stage of the basic design

The study on the user-centered interior design of trains consists of the practice of sensitive technology for the management of customer's emotions ans its harmonical use on design and it aims on the embodiment of new ergonomics design. In the center, it has analyzed the criteria and characteristics for the 'User First Design' and has concluded the design direction and components to a concrete idea and proposed prototypes, which may becomes a good example for train interior design later on. And not at least it proposes a direction which may become a guideline of ergonomic design to secure competition cpacity

To make railway carbody light in weight has advantages at some aspects of both manufacturing and maintenance. Recently, railway carbodys of steel structure have been lightened their weight by using aluminum extrusion plate. for the additional lightening of railway carbody, an optimal design which maintains proper strength and minimizes weight must be achieved. Optimization which is used with finite element analysis for aluminum extrusion plate has the disadvantage of consuming much time. In this paper, the method of equivalent material property which is available to FEA code is established using the method of equivalent stiffness. This method for plate is expanded into the method for railway carbody structure with plates and shells. An objective function is established for maximum stiffness of unit aluminum extrusion plate using established method of equivalent material property. We performed an multi-objective optimization using the penalty function method. As a result, recommendable shapes and sizes of unit extrusion plate for under-frame of high speed train is presented.

기존선 속도향상, 안전성 확보, 수송서비스 개선을 목표로 하는 철도기술연구개발사업은 고객에게 고품질의 서비스를 제공하고 타 교통시스템과의 경쟁력을 확보하기 위하여 주관행정부처인 철도청과 전문기관인 한국철도기술연구원에서 추진하고 있다. 이 사업은 1999년 12월 철도기술연구개발사업기본 계획을 수립하여 2001년 8월 한국철도기술연구원을 사업자로 선정하고 총 450억의 정부지원예산을 투입하여 2004년까지 4차년도에 걸쳐 기존선 속도향상을 위한 실용화 기술개발, 철도유지보수시스템개발, 고속 철도운영시스템개발을 목표로 하고 있다.

본 연구에서 다목적 실용위성의 태양전지판에 대한 임무수행 기간동안 열적 뒤틀림 해석을 수행하였다. 태양전지판의 모델링은 MSC/PATRAN을 사용하였으며 온도분포 및 열적 뒤틀림 해석은 상용프로그램인 ABAQUS를 사용하였다. 다목적 실용위성의 태양전지판은 알루미늄을 면재로 갖는 5개의 하니컴 샌드위치 패널로 이루어져있다. 온도분포 및 열적 뒤틀림 해석은 면재로 알루미늄을 사용한 경우와 준등방성 복합재료를 사용한 경우로 나누어 해석하였다. 그리고, 진공, 자외선, 열환경등과 같은 저궤도 우주환경인자들에 의해 야기되는 물성저하에 따른 준등방성 복합재료를 면재로 사용한 태양전지판의 열적 뒤틀림 거동을 평가하기 위해, 복합재료를 저궤도 우주환경 모사장비에서 노화시험을 수행하였다. 본 연구의 결과 태양전지판의 임무수행 기간동안 무게, 온도분포, 그리고 열적 뒤틀림을 고려하였을 때 알루미늄을 면재로 사용하는 경우보다는 준등방성 복합재료를 사용하는 경우가 유리함을 알았다.

본 연구에서 그라파이트/에폭시 복합재료 시편을 모사된 저궤도 환경하에서 노화시험을 수행하였다. 저궤도 환경은 자외선환경을 포함한 열-진공챔버의 제작으로 모사하였다. 복합재료의 질량변화, 기계적 물성변화 그리고 열팽창계수 변화측정은 고진공(10^-ㄴㅁ~10^-6 Torr), 자외선(<200nm의 파장) 그리고 열적 사이클 환경(+100℃ ~ -100℃)에 노출하여 평가하였다. 복합재료 시편의 질량손실은 열적 사이클이 진행함에 따라 선형적인 증가를 보였다. 그러나, 열적 사이클의 수가 진행될수록 질량감소 경향은 서서히 사라지고 있음을 알 수 있었다. 강성과 강도는 사이클이 진행됨에 따라 뚜렷한 감소를 보였으며 특히 모재지배물성이 큰 감소를 나타내었다. 또한, 열팽창계수는 사이클이 증가할수록 모두 감소하는 경향을 보였다. 주사전자현미경으로 노회된 시편의 표면을 관찰한 결과 모재균열과 모재손실이 발생함을 알았다.

본 연구에서 그라파이트/에폭시 복합재료 시편을 모사된 저궤도 환경하에서 노화시험을 수행하였다. 저궤도 환경은 자외선 환경을 포함한 열-진공 챔버의 제작으로 모사하였다. 복합재료의 질량변화, 기계적 물성변화 그리고 열팽창계수 변화측정은 고진공(10^-5 ~ 10^-6 Torr), 자외선(<200nm의 파장) 그리고 열적 사이클 환경 (+100℃ ~ -100℃)에 노출하여 평가하였다. 복합재료 시편의 질량손실은 열적 사이클이 진행함에 따라 선형적인 증가를 보였다. 그러나, 열적 사이클의 수가 진행될수록 질량감소 경향은 서서히 사라지고 있음을 알 수 있었다. 강성과 강도는 사이클이 진행됨에 따라 뚜렷한 감소를 ㅂ였으며 특히 모재지배물성이 큰 감소를 나타내었다. 또한, 열 팽창계수는 사이클이 증가할수록 모두 감소하는 경향을 보였다. 주사전자현미경으로 노화된 시편의 표면을 관찰한 결과 모재균열과 모재손실이 발생함을 알았다.

The disk/blade assembly of a turbine engine is made in the shape of a dovetail type or a fir-tree type. Since disk fillet regions or contact surface undergo high stress concentration. fatigue cracks frequently occur in the disk/blade assembly. Therefore, it is necessary to analyze the stress distributions in the fir-free type disk/blade assembly and predict the region of fatigue failure. The stress distributions of the disk/blade assembly were investigated by using the photoelastic method and the finite element method. Two dimensional photoelastic techniques were used to investigate the stress distributions of contact surface and fillet regions. The stress distributions were obtained by the shear-difference method and were compared to the finite element results. It was found that maximum tensile stresses were higher in the fillet region than in the contact surfaces of the fir-tree models. The finite element results showed good agreement with the experimental results.

본 논문에서는 영상처리기법을 이용해서 광탄성 정보를 처리하는 기법에 관하여 연구하였다. 등경선으로부터 얻은 각 화소의 빛의 세기에 대한 연사을 통해 주응력 방향을 계산하고, 등색선에서 프린지 증식과 세선화과정으로 프린지 차수를 추출해 내는 기법을 사용하여 광탄성 정보를 처리하였다. 이와 같은 방법으로 육안으로 하던 기존의 처리 방법에 비해 빠르고 정확하게 결과를 얻을 수 있었고, 처리해야 하는 정보량도 감소하였다. 이결과를 터빈 엔진의 블레이드/디스크 어셈블리에 적용하여 접촉점 부위에 대해 응력 해석을 수행하였고, 유한요소법과 비교하여 잘 일치함을 확인할 수 있었다.

In this study evaluated the mechanical properties of randomly oriented composite materials used as reinforcement in railway facilities, and proposed equations to predict the changes in mechanical properties with varying curing temperature. The curing temperature is an important factor for reducing the time of FRP reinforcement work and prior to changing curing temperature, evaluation of mechanical properties for randomly oriented composite materials with varying curing temperature is essential. Thus, tensile specimens of chopped strand mat and glass fiber combination mat as randomly oriented composite material were manufactured by varying curing temperature and mechanical properties were evaluated. As a results of the test, it is considered that the glass fiber combination mat showed changes in tensile strength and elastic modulus of up to 8% with varying curing temperature. So that it is able to reinforce the railway facilities in the high temperature. The mechanical properties of chopped strand mat changed by more than 24%. To predict mechanical properties in relation to curing temperature, equations were derived using the method of least squares.

본 논문의 목적은 소재대체법과 치수최적화 기법을 이용한 2층 고속열차 알루미늄 압출재 차체의 경량 설계를 제시하는 것이다. 소재대체법을 수행하기 위해 위상최적화 기법을 이용하여 차체 구조물의 샌드위치 복합재 적용 부위를 결정하였다. 해석결과, 루프와 2층 언더프레임에 샌드위치 복합재가 적용 가능함을 보여주었다. 치수최적화는 알루미늄 압출재와 카본/에폭시 복합재의 두께를 결정하는데 사용되었다. 치수최적화를 수행하기위해, 설계변수, 제약조건, 목적함수를 정식화 하였으며 이러한 조건에 의해 유효설계를 도출하였다. 경량 설계의 결과로 2층 고속열차 하이브리드 차체의 무게를 2.18 ton(17.70%)까지 줄일 수 있음을 보여주었다.

철도차량 경량화에 사용되는 탄소섬유 강화 플라스틱은 주로 기계적 성질이 우수한 에폭시를 기지재로 사용한다. 그러나 에폭시는 화재에 노출 시, 쉽게 열분해 되어 화재 안전성에 취약한 단점이 있다. 본 연구에서는 이를 개선하기 위하여 에폭시 대비 열분해 온도가 높아 화재 안전성이 우수한 탄소섬유/페놀 복합재를 이용하였다. 탄소섬유/다종수지 복합재는 에폭시 수지 층과 페놀 수지 층이 별도로 형성될 수 있도록 각각의 프리프레그(Prepreg)를 분리하여 적층 하였으며, 핫-프레스 공법을 이용해 동시경화 시키는 방법으로 제작하였다. 콘 칼로리미터 화재 안전성 시험결과 에폭시 수지 프리프레그만 사용했을 경우와 비교해 페놀 수지 프리프레그를 5층 적층한 경우 페놀 프리프레그를 최소로 사용하면서 점화시점 및 최대 열 방출률(HRR), 최대 평균 열 방출률(MARHE) 등 화재 안전성에 대한 주요지표가 개선됨을 확인하였다.Because of its good mechanical properties epoxy is used as matrix material of Carbon Fiber Reinforced Plastic (CFRP) for lightweight railway vehicles. However, when exposed to fire, CFRP is easily pyrolyzed. In this study, carbon fiber/phenol composite, which has pyrolysis temperature higher than that of epoxy, was used to improve this situation. To make carbon fiber/multi-resin composite, carbon fiber/epoxy and carbon fiber/phenol prepregs were laminated separately to form layers of each resin. After the lamination, it was co-cured by hot-press process. The results of fire safety test using a cone-calorimeter showed that the case, which consists of 10 layers of carbon fiber/epoxy and 5 layers of carbon fiber/phenol, secures better fire safety performance than that of the carbon fiber/epoxy composite, including such factors as ignition time, maximum HRR (Heat Release Rate), and MARHE (Maximum Average Rate of Heat Emission), while minimizing the amount of carbon fiber/phenol prepreg usage