Car Body Structure Research Articles

Multi-Objective Optimization of a Car Body Structure

Multi-Objective Optimization of a Car Body Structure

Research of High Speed Train Carbody Structure Vibration Behaviors and Structure Fatigue Strength Characteristic Technology

The hybrid simulation method based on Multibody Simulation (MBS) and finite element method (FEM) were proposed here and applied to study the relation between carbody structure vibration behaviors and structure fatigue strength characteristic. The detailed steps include: Firstly, rigid-flexible couple vehicle multibody system dynamic model was created and performed to obtain the load time histories corresponded to the typical load cases. Secondly, the carbody structure stresses was calculated through Finite Element (FE) quasi-static stress method. Finally, with the material fatigue property and some uncertainty factors, carbody fatigue damage distribution and life was calculated and evaluated. And the conclusions can be understood that the mechanism between the full vehicle dynamic property and structure damage distribution. The results are also shown that the hybrid simulation technology could be applied into the carbody structure fatigue design.

Research on Two Ends Energy-Absorbing Structure of High-Speed Railway Passenger Car Body

Based on characteristics of high-speed trains, a special passive protective structure was designed and simulated by the non-linear FEA code LS-DYNA. The two-step energy-absorbing structure fixed on the cab side and the similar function structure on the other end were studied. It was proved that the two-step structure deformed orderly and had an energy absorbing capacity of 3.4MJ which could protect the cab effectively and that the rear end low stiffness zone had an energy absorbing capacity of 6.5MJ which also could protect the integrity of the passenger areas. Three typical train-to-train collision scenarios were studied by full-scale FEA method.

Significant Alloy Elements in Welded Steel Structures of Car Body

Significant Alloy Elements in Welded Steel Structures of Car Body Structure, safety and exploitation conditions of welding steel in car body depend on many factors. The main role of that conditions is connected with car body material, welding technology, state of stress and temperature. Because of that, a good selection of steel and welding method is very important for proper steel structure. Low alloy steel is used for car body structure, very often with small amount of carbon and the amount of alloy elements such as Ni, Mn, Mo, Cr and V in car body and welded joints. Depending on the kind of steel which is used, a proper welding method and adequate filler materials should be applied. The present paper describes the influence of Mn, Ni, Mo, Cr, V in WMD (Weld Metal Deposit) on the behaviour of steel structure especially for low temperature service.

Conceptual Design for the Structure of Electric Car Body

In this paper, ANSYS software is applied to determine the material distribution, load transfer path and equivalent sectional dimensions of the conceptual car body model based on the original body shape of engine cars. In terms of the finite element model of the body, the topology optimization is carried out according to the maximum bending and torsion stiffness, respectively. Through comparing the material distribution under different volume fractions and considering at the same time the manufacture feasibility, the initial style of body frame is achieved. Then, as the sectional dimensions of beams is optimized in both size and dimension, parameter matching scheme of the body frame in minimized weight is brought forward under constraints of the strength and stiffness at maximum frontal impact loads that improves the utilization rate of the material. The results suggest that both the design efficiency and quality can be improved greatly by combining topology and size optimization technology at the concept design phase of car body structure.

Numerical Analysis for the Characteristics of Stress Distribution on Lap Laser Welding Joint of Stainless Sheet Steel

It gave a better strength that taking lap laser welding (llw) instead of resistant spot welding (rsw) to assemble the framework and the flankwall of stainless steel car body structure, and the fracture situations of fatigue test were different in the two welding methods. That was chiefly connected to the stress distribution and concentration of welding joint. The analyses on stress distributions and concentration factors of the two joints in different external loadings were made in this paper. The results indicate that the stress concentration factor of llw joint on the flankwall is 73.4% lower than that of rsw and the value on the framework is 81.6%. The crack initiation site of fatigue test appears at the place with the highest stress concentration, which is agreed well with the theoretical analysis.

Assessment of Nugget Size of Spot Weld using Neutron Radiography

Resistance spot welding (RSW) has been widely used for many years in the fabrication of car body structures, mainly due to the cost and time considerations. The weld quality as well as the nugget size is an issue in various manufacturing and processes due to the strong link between the weld quality and safety. It has led to the development of various destructive and non-destructive tests for spot welding such as peel testing, ultrasonic inspections, digital shearography, and infrared thermography. However, such methods cannot show spot weld nugget visually and the results are very operator’s skill dependent. The present work proposes a method to visualize the nugget size of spot welds using neutron radiography. Water, oil and various concentrations of gadolinium oxide-alcohol mixture were evaluated as a contrast media to obtain the best quality of radiography. Results show that mixture of 5 g gadolinium oxide (Gd 2 O 3 ) in 25 ml alcohol produces the best contrast. It provides the possibility to visualize the shape and size of the nugget spot weld. Furthermore, it can discriminate between nugget and corona bond. The result of neutron radiography evaluation shows reasonable agreement with that of destructive test. Received: 13 October 2010; Revised: 25 August 2011; Accepted 26 August 2011

Analysis of C80B Wagon’s Load-Stress Transfer Relation

In this paper, C80B car body is the research object to study the load-stress transfer relationship that has great influence on the car body structure. First of all, through the test data of line DaTong to Qin Huangdao, the load-time history of C80B car body’s load on center plate, load on draw gear, roll load and torsional load have been obtained, as well as the stress-time history of the body fatigue key parts have been obtained. And the load spectrum and stress spectrum have been made up. Then the finite element analysis of the car body is made. The load-stress transfer coefficient of fatigue key parts on car body could be obtained. Last the load and stress transfer relationship in detail considering the measured data has been analyzed.

틸팅열차의 샌드위치 복합재 차체 구조물에 대한 충돌안전도 평가 및 향상방안 연구

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 외연유한 요소 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.

Evaluation of tension-compression and tension-tension fatigue life of woven fabric glass/epoxy laminate composites used in railway vehicle

In this study, the fatigue characteristics and life of two types of woven fabric glass /epoxy laminate composites with WR580 glass 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.

The suggestion of the standardized finite element model through the experimental verifications of various railway vehicle structures made of sandwich composites

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.

Development of Estimation Procedure of Contact Heat Transfer Coefficient at the Part–Tool Interface in Hot Stamping Process

Energy efficiency, a high level of passenger safety, and weight reduction of the vehicles still constitute the main functional elements for the design of modern car body structures. Toward this objective, the usage of advanced sheet-metal forming technologies like hot stamping of quenchable boron manganese steel is developing nowadays. Hot stamping is a combination of hot forming and simultaneously quenching and hardening of the blank. In this article, an experimental procedure developed to estimate the thermal conductance at the part–tool interface during a hot stamping procedure is presented. The tools set (punch and die) has been designed to form omega-shaped samples. This work represents the first stage of the procedure development where the standard experiment is a simple compressive load of sample in the bottom of the omega-shape die, considering the real hot-stamping conditions. Tests are carried out under different contact pressure values for two different blank materials (Usibor 1500P and a material B). The results show that the thermal conductivity increase contributes to the reduction of the thermal contact resistance and therefore to a more rapid cooling of the part.

The Investigation of Laser Lap Welding Process on High-Strength Galvanized Steel Sheets

The development of automobile steel was analyzed in this paper; it is pointed out that high-strength galvanized steel will be widely used in the car body structure. By analyzing welding problems about the dual phase (DP) series of high-strength galvanized steel, the importance of laser welding was concerned. Finally, laser lap welding process technology of high-strength galvanized steel was studied; the results show that the lap weld with welding process smooth and spatter-free as well as beautiful welding bead surface appearance and good mechanical properties can be made by using the dual-beam laser welding technology and interlayer for welding high-strength galvanized steel.

Incremental Sheet Metal Forming: Numerical Simulation and Rapid Prototyping Process to make an Automobile White‐Body

AbstractIn order to make an automobile body structure, incremental sheet metal forming is introduced as a rapid prototyping process. Numerical modeling of the process is initially used to predict the deformation of the sheet metal to avoid failure during the incremental forming process using ABAQUS/Explicit finite element code and OYANE's ductile fracture criterion via a VUMAT user material. An automobile CAD model is then designed, and segmented into several parts in order to accommodate the working space of the CNC machine and formability of sheet metal. After that, CAM software is used to generate a tool‐path for making wooden‐dies and all small parts. Finally, a welding process is applied to join all parts which were cut by laser cutting after incremental sheet forming process.

Local Laser Strengthening of Steel Sheets for Load Adapted Component Design in Car Body Structures

The current trend in car body construction concerning light weight design and car safety improvement increasingly requires an adaption of the local material properties on the component load. Martensitic hardenable steels, which are typically used in car body components, show a significant hardening effect, for instance in laser welded seams. This effect can be purposefully used as a local strengthening method. For several steel grades the local strengthening, resulting from a laser remelting process was investigated. The strength in the treated zone was determined at crash relevant strain rates. A load adapted design of complex reinforcement structures was developed for compression and bending loaded tube samples, using numerical simulation of the deformation behavior. Especially for bending loaded parts, the crash energy absorption can be increased significantly by local laser strengthening.

Multi-objective Optimization Method in Car-body Structure Light-weight Design with Reliability Requirement

Lightweight design of car body structure is in demand to meet performance requirements of modes,stiffness,collision safety,etc.In order to improve the robustness of design,the uncertainty factors in the design process must be considered.In a variety of optimization designs,non-dominated sorting genetic algorithm NSGA-Ⅱis more and more widely used in the multi-objective and reliability engineering design.After application of high strength steel to the body structure in attempt for lightweight,the investigative procedures are carried out as follows to determine the effective thickness values of the key structure components in the front body structure: first,the finite element models of both the body in white and the 40% offset frontal collision are established;second,the property indexes including the torsional stiffness of entire body in white,the maximum collision force and the mean acting force,the collision energy absorption and the minimum mass etc.are considered throughout in the multi-optimization model,and then the NSGA-Ⅱ algorithm is used to perform 6σ reliability optimization based on the high-precision response surface approximation model;at last,Monte Carlo simulation technique is used to evaluate the robustness performance of the optimization scheme.The optimization results show that the vehicle collision safety performance is improved and the body torsional stiffness and structural component weight are well controlled.

Research on the Effect of Traction Tonnage on Train Longitudinal Impact

The traction tonnage has important effect on train longitudinal impact. An integrated model of train longitudinal dynamics was established based on simulation and test results. The effect of the traction tonnage on train longitudinal dynamics was investigated through modeling different types of heavy-haul trains. The model was validated by using measured longitudinal force time histories from on-track tests. Case study shows that the traction tonnage has significant influence on train longitudinal impact; Train longitudinal force increases with traction tonnage. The relationships between the maximum coupler forces (including tensile and compressive forces) and traction tonnage were obtained with the least square method for cases of train under emergency baking and release condition. The established train longitudinal dynamics model provides a platform for car body and coupler structure optimization and train control.

Active media-based form hardening of tubes and profiles

New requirements from the automotive industry regarding light weight design request the realization of structural parts with maximum strength over 1,000 MPa. On the other hand, demands concerning part complexity, function integration and part quality become higher and higher. The press hardening technology of boron-manganese alloyed steel for blank based part applications represent the state of the art. Typical applications are reinforcement parts in crash relevant car body structures. The consequently using of such parts allows to fulfil the requests of current and future cars regarding crash performance at acceptable structural weights. Beside press hardening parts also hydroformed profiles enable a high potential for applications in structural car body elements with high loads. By this, hydroforming of tubes and blanks at room temperature represents also the state of the art for several applications in car body structures or exhaust systems, but also for special applications outside the car industry. These parts are mainly made from materials such as steel, high-strength steel, stainless steel and aluminium. Originating from increased demands for hydroformed parts regarding maximum strength and complexity the limits of conventional hydroforming processes are reached. The use of temperature as a process parameter in hydroforming offers the chance to increase the application field of this innovative technology. The potential of this strategy was proven; complex car body parts of aluminium and magnesium were realized at elevated temperatures. However, today available fluids can only be used up to 300°C because of the limited thermal resistance of the available fluids. Gaseous media (e.g. nitrogen) offer the chance to use the potential of temperature-supported hydroforming also in steel forming. Consequently, temperatures up to 1,000°C can be provided. In analogy to hot stamping processes for blanks, it is also possible to combine the gas forming process with a special heat treatment and to realize closed structural parts with highest strength in anthology to applications of hydroformed car body structures, such as A-pillars (BMW, Volvo, Opel), roof rails (Audi), cross members (BMW), crash cans (Volvo) or sill reinforcement parts (Audi, Volvo), in serial production.

A Study on Improvement of Fatigue Life for Woven Glass Fabric/Epoxy Laminate Composite Applied to Railway Vehicle

In this study, the fatigue characteristics and life of woven glass fabric/epoxy laminate composites applied to railway vehicle were evaluated. The fatigue test was conducted by tension-tension load with stress ratio R of 0.1 and frequency of 5Hz. The material used to fatigue test was two types of woven glass fabric/epoxy laminate composite with and without the reinforcement of carbon/epoxy ply. Also, the fatigue life of woven glass fabric/epoxy laminate composite was compared with that of aluminum 6005 used to the car-body and under-frame structures of railway vehicle. The test results showed that the failure strength and life of woven glass fabric/epoxy laminate composite with the reinforcement of three carbon/epoxy plies had a remarkable improvement in comparison with that of bare specimen without reinforcement.

Research of Modern Railway Vehicle Structure Fatigue Design Method Based on Multibody Dynamic Simulation

For high-speed railway carbody structure durability analysis problems in China, one integrated method based on MBS (multibody simulation) is proposed here. Firstly, one EMU (Electricity Multiple Unit) full vehicle was performed to dynamic modeling and simulation. The numerical simulation results were applied to illustrate the vehicle dynamic characteristics. And the relationships between structural strength, stiffness, and frequency characteristics were also studied. Secondly, the multidisciplinary design technique was used to solve multi-mode coupled vibration of carbody structure on the cumulative effects of local vibration and damage effects, as well as structure light-weighting and other parallel optimization problems. Finally, the effective measures were proposed to control carbody structure’s physical failure.