Car Body Structure Research Articles

Study on the Dynamic Response of the Carbody–Anti-Bending Bars System

Ride comfort is an important requirement that passenger rail vehicles must meet. Carbody–anti-bending system is a relatively new passive method to enhance the ride comfort in passenger rail vehicles with long and light carbody. The resonance frequency of the first bending mode (FBM) of such vehicle is within the most sensitive frequency range that affects ride comfort. Anti-bending bars consist of two bars that are mounted under the longitudinal beams of the carbody chassis using vertical supports. When the carbody bends, the anti-bending bars develop moments in the neutral axis of the carbody opposing the bending of the carbody. In this way, the carbody structure becomes stiffer and the resonance frequency of the FBM can be increased beyond the upper limit of the discomfort range of frequency, improving the ride comfort. The theoretical principle of this method has been demonstrated employing a passenger rail vehicle model that includes the carbody as a free–free Euler–Bernoulli beam and the anti-bending bars as longitudinal springs jointed to the vertical supports. Also, the method feasibility has been verified in the past using an experimental scale demonstrator system. In this paper, a new model of the carbody–anti-bending bar system is proposed by including three-directional elastic elements (vertical and longitudinal direction and rotation in the vertical–longitudinal plane) to model the fastening of the anti-bending bars to the supports and the vertical motion of the anti-bending bars modelled as free–free Euler–Bernoulli beams connected to the elastic elements of the fastening. In the longitudinal direction, the anti-bending bars work as springs connected to the longitudinal elastic elements of the fastening. The modal analysis method is applied to point out the basic properties of the frequency response functions (FRFs) of the carbody–anti-bending bars system, considering the bounce and FBMs of both the carbody and the anti-bending bars. A parametric study of the FRF of the carbody shows that the vertical stiffness of the fastening should be sufficiently high enough to eliminate the influence of the modes of the anti-bending bars upon the carbody response and to reduce the anti-bending bars vibration in the frequency range of interest. Longitudinal stiffness of the elastic elements of the fastening is critical to increase the bending resonance frequency of the carbody out of the sensitive range. Longer anti-bending bars can improve the capability of the anti-bending bars to increase the bending resonance without the risk of interference effects caused by the bounce and bending modes of the anti-bending bars.

Weight Optimization of the Electric Bus Carbody Structure

Car body is a lightweight construction unit in the form of welded steel construction, has high strength and rigidity against dynamic loading without a fixed change in shape. In this study, the design of the car body bus frame consisted of roof, mascara, side wall, end wall, front part, and underframe. All of these components are designed using Autodesk Inventor Professional 2020 software. The frame material used is SS201. For data retrieval purposes, weight calculations are used in Autodesk Inventor. In the study, we succeeded in making the car body design according to regulations, measuring the weight of the car body, and optimizing the car body. The results showed that with a little optimization on the side wall frame, the weight of the car body bus can be reduced by 11.7% from the initial weight of 461.5 kg to 407.4 kg without changing its characteristics.

Применение высокопрочной стали для создания полувагонов повышенной грузоподъемности

Purpose: substantiation of the possibility to increase the load capacity of gondola cars using high-strength steel in the car body structure. Methods: gondola cars load capacity changing analysis. Numerical research of the effect of the steel yield strength value on the mass of the beam structure according to the criteria of strength and stiffness for a beam on two hinged supports operating in bending, and also according to the buckling criteria of a compressed beam. Gondola car body structure finite element analysis in order to confirm the strength and buckling parameters with the normative requirements. Results: the analysis of load capacity of universal fouraxle gondola cars built in the period from the beginning of production of the first Russian cars up to the present time was performed. Results of the analysis of the effect of steel yield strength on the mass of the structure according to the strength criteria and stiffness for a beam on two hinged supports operating in bending, and also according to the buckling criteria of a compressed beam was presented. High-strength steel technical requirements for welded structures of freight wagons is considered. Parameters for evaluating the suitability of rolled high-strength steel for freight wagon construction are given. The results of strength and stability analysis of the gondola car model 12-6744 with high-strength steel, which confirm the design compliance of the car in terms of normative parameters of strength and stability with the requirements of the existing standards are given. The gondola car model 12-6744 advantages are described, as well as the economic effect of its operation for the consignor. Practical importance: the possibility of using high-strength steel to increase the load capacity of gondola cars is substantiated. The gondola car model 12-6744 with high-strength steel was designed. Its advantages are given, and the economic effect of operating such a wagon for the consignor is shown.

ANALYSIS OF THE DEVELOPMENT OF GONDOLA CAR BODY STRUCTURES

The article is devoted to the analysis of promising directions for the development of gondola car body structures. It considers the history of the emergence of gondola cars as a separate type of railway rolling stock. The authors systemise the design of gondola cars and discuss the advantages and disadvantages of various designs. The study has shown that the manufacture of the two-axle gondola cars began in the second half of the 19th century. They were designed mainly for transporting coal and iron ore, with their bodies made of wood. Further design improvement led to the appearance of four-axle gondola cars with increased load capacity. Rolled metal began to be used in body structures to improve strength. Particular attention in the article goes to analysing the results of innovative design and technological solutions intended to enhance the efficiency and reliability of body structures. The research indicates that attempts to replace steel with aluminium alloys in manufacturing bodies did not yield results. The reason is the high cost of aluminium and the labour-intensive manufacturing. A promising direction is the use of low-alloy steels 10KhSND and 10KhNDP. For many years, there has been a trend in the railcar-building industry toward producing higher-load gondola cars. It requires increasing the axle load to 25 tons. However, implementing such cars necessitates a substantial restructuring of the railway infrastructure. We consider the design features of innovative domestic gondola cars in detail. The latest technical solutions for the body frame, efficient materials, and components with improved performance have doubled the overhaul mileage. The article analyses the North American experience of gondola car construction and operation. It shows that some models of American gondola cars use longitudinal cylindrical boxes to increase the body volume and reduce the car’s centre of mass. They are on both sides of the girder beam and occupy the space between the carts. Aluminium alloys are also widely used: the frame and lower part of the body are steel, and the side and end walls are aluminium alloy. Keywords: gondola car, body, girder beam, pivot beam, side walls, hatch cover, reliability.

High potential: lightweight optimised structural design of car bodies for railway vehicles with alternative drive systems

Climate change and related goals and measures require a shift away from fossil fuels as an energy source. One solution for non-electrified lines for rail transport is the use of alternative drive technologies such as battery or hydrogen drive instead of diesel units. In order to use these efficiently in rail vehicles, it is imperative to make adjustments to the body structure. Existing car body structures must be adapted to integrate the space-intensive and heavy additional equipment components. Within the framework of the project AnoWaAS those with the highest lightweight construction potential are methodically identified from a large number of different derivatives of car body designs. The high influence of a force flow-compliant design on the lightweight potential is analysed in depth. Possible adapted construction methods for further exploitation of the lightweight potential are shown and analysed with regard to their potential. With the help of trapezoidal windows and the structural integration of equipment enclosures, it is possible to reduce the structural mass of a car body by more than 20%.

ОЦЕНКА УСТОЙЧИВОСТИ ОБШИВКИ БОКОВЫХ СТЕН И КРЫШИ КУЗОВА ПАССАЖИРСКОГО ВАГОНА ПРИ ВЫПОЛНЕНИИ РЕМОНТНЫХ РАБОТ

The lining stability of the side walls and roof of the passenger car body is assessed during repair work related to its asymmetric lifting with a jack at one end of the body. Using mathematical modeling, the lifting height is determined which is necessary to ensure the possibility to dismantle the springs of the spring set of the central suspension. The stability of the reinforced lining of the car body was assessed using the developed problem-oriented elastic-dissipative finite element model of the supporting structure of the passenger car body. The calculations are performed in a static non-linear formulation, taking into account the geometric nonlinearity and non-conservativeness of the operating loads. The stability of the reinforced load-bearing lining of the car was assessed both for the initial structure and for a structure with geometric imperfections such as technological loss. The analysis of the research results allows to conclude that during the technological operation associated with lifting the passenger car body with a jack under one support, it can lead to a loss of stability of the sill belt lining of the side wall and the smooth sheathing of the roof slope. The results obtained agree with the results of the inspection of full-scale cars in operation.

A component-oriented material design to improve crashworthiness of safety-relevant car body structures made out of lean medium manganese steel

A component-oriented material design to improve crashworthiness of safety-relevant car body structures made out of lean medium manganese steel

Rate-dependent damage sequence interaction model for predicting the mechanical property of in-service aluminum alloy 6005A-T6

Engineering structures and materials will undergo fatigue, aging, and other degradation behaviors during long-term service under the combined influence of complex boundary conditions. These service damages make the materials and structures no longer meet the initial design requirements and pose a potential risk to the service system. This study proposes a material mesoscopic model to decouple the microstructure into a system composed of matrix and void phases. The matrix phase has an invariant constitutive relationship as an ideally undamaged material, and the different evolutionary behaviors of the void phase are described as damage evolution functions and lead to different stress–strain behaviors of the actual material. First, the damage described by different definitions is proposed, and a nonlinear function of damage evolution consistent with the Weibull distribution characteristic of microstructural continuity is derived. Then, an experimental–numerical method is improved to accurately identify the accelerated damage evolution behavior under various strain rates. Finally, the ideally undamaged constitutive of the matrix phase and the damage evolution function of the void phase are established, which can cover the void nucleation, growth, and aggregation process. Besides, the damage sequence interaction model is established in conjunction with the mesoscopic physical mechanism, and the total damage evolution function for materials containing prior service damage in subsequent ductile deformation is achieved by measuring the apparent elastic modulus of the material only. Finally, the ideally undamaged constitutive and damage evolution function are calibrated for aluminum alloy 6005A-T6, commonly used in the car body structure of rail vehicles, and verified with damaged specimens that experienced certain service loads. The material's damage sequence interaction mode is determined, and the rate-dependent residual strength is predicted.

A New Car-Body Structure Design for High-Speed EMUs Based on the Topology Optimization Method

In recent years, the research and development of high-speed trains has advanced rapidly. The main development trends of high-speed trains are higher speeds, lower energy consumption, higher safety, and better environmental protection. The realization of a lightweight high-speed car body is one of the key features in the development trend of high-speed trains. Firstly, the basic dimensions of the car body’s geometric model are determined according to the external dimensions of the body of a CRH EMU, and the specific topology optimization design domain is selected to establish the finite element analysis model; secondly, the strength and modal analyses of the topology optimization design domain are carried out to check the accuracy of the design domain and provide a comparative analysis for subsequent design. Then, the variables, constraints, and objective functions of the topology optimization design are determined to establish the mathematical model of topology optimization, and the design domain is calculated for topology optimization under single and multiple conditions, respectively. Finally, based on the topology optimization calculation results, truss-type reconstruction modeling is carried out for the car body’s side walls, roof, underframe, end walls, and other parts. Compared with the conventional EMU body structure, the weight of the reconstructed body structure is reduced by about 18%. The results of the finite element analysis of the reconstructed car-body structure prove the reliability and safety of the structure, indicating that the reconstructed car-body scheme meets the corresponding performance indicators.

ОБОСНОВАНИЕ ПРОЧНОСТИ НЕСУЩЕЙ КОНСТРУКЦИИ КУЗОВА ВАГОНА С УЧЕТОМ КРИТИЧЕСКИХ НАПРЯЖЕНИЙ В ГОФРАХ

The issues are considered that are connected with substantiating the strength and stability of the metal structure of a double-deck passenger car body under the influence of both compressive loads and the effects of excessive solar radiation and other external factors. 
 A computational and experimental method is proposed for assessing the stability of corrugated sections of the roof slopes of passenger car bodies. Five variants of the structural design of the double-deck car roof covering are proposed. The stability of the covering for the accepted variants was evaluated by an analytical method using a tabular and rod finite element model. Based on the results of the calculation, a rational variant of the structural design of the car roof was determined. 
 The results of theoretical studies are confirmed by the data of full-scale bench tests of the metal structure of a new double-deck car body.

Calibration and validation of fatigue design models for railway car bodies considering uncertainty

AbstractThe fatigue design of railway vehicles is a requirement for resource‐ and energy‐efficient lightweight design. A simulation‐based design process makes high demands on the reliability of results. Therefore, this work focuses on the calibration of weld quality parameters for the simulation‐based fatigue design of railway car bodies. Since the direct measurement of weld parameters is costly, an indirect Bayesian calibration approach is implemented, effectively combining limited testing with numerical simulations. Fatigue tests have been performed on the probe, component, and structure level for the load‐bearing section of the Next Generation Train (NGT) car body within the SimbaCon (Simulation‐based Conception) project at DLR. Based on the distribution of the measured life spans for component tests, the corresponding weld seam quality factors are calibrated using Bayesian calibration. The resulting weld seam qualities are used for the fatigue assessment of the complex car body structure.

Discussion on Fatigue Reliability Evaluation Method of Welded Structure of Carbody Based on Digital Twin

Abstract Taking the key welds of the heavy-duty gondola carbody as the research object, first, the fatigue assessment of the carbody is carried out based on the quasi-static the main S–N curve method, and the quasi-static evaluation method is discussed; second, the typical welds are selected. Based on the full-size bench physical test and virtual test of railway freight carbody, the quasi-static method is discussed; finally, the line test is used to verify the results. The results show that: (1) among all the load conditions in the quasi-static analysis of railway freight cars, the damage of the core plate needs to be considered according to different parts of the carbody, and this condition is effective for the evaluation of the bearing area of the linear load transfer of the carbody for the welds with nonlinear load transfer such as floor, the stress response caused by core plate load has the problem of over-estimation of damage. (2) The lap weld of floor and beam is less damaged under heavy load, but the stress response is larger in empty state, which indicates that the vibration effect should be considered in the design. (3) The virtual test can make up for the problem of traditional quasi-static analysis. The combination of the two can better realize the fatigue reliability evaluation of carbody.

A damage sequence interaction model for predicting the mechanical property of in-service aluminium alloy 6005A-T6

In the long-term service process, materials and structures will bear fatigue, ageing, and other degradation behaviours under environmental factors such as temperature, vibration, and radiation. Service damage makes materials and structures gradually deviate from the original design expectations. In this study, the material is decoupled into a two-phase system consisting of matrix and void phases. The different mechanical behaviours of material by the evolution of the void phase are analysed under the premise of the constitutive uniqueness of the matrix phase. Different characterisation methods of damage are discussed, and a finite element analysis–test combination method is proposed to identify the damage evolution function and the undamaged hardening, avoiding the influence of the necking effect and the accuracy of the test apparatus. A damage interaction model associated with the physical mechanism of microstructure evolution is constructed based on the ductile damage evolution function, discussing the influence of different damage definitions on the sequence interaction. The aluminium alloy 6005A-T6 commonly used in car body structures of rail vehicles is studied. The damage evolution function and undamaged hardening are established by testing undamaged specimens and verified by testing service-damaged specimens that bore a certain service loading. Then the damage interaction mode was determined. The proposed damage sequence interaction model provides an effective non-destructive testing method to obtain the hardening behaviour of in-service engineering materials. It can also extend to various existing constitutive equations.

Nano-scale characterization of intermetallic compounds in dissimilar aluminum-steel resistance element welded joints

To achieve the goal of lightweight vehicle and energy-saving, the joining of dissimilar materials, specifically aluminum (Al) alloy and steel, is gaining increasing attention in car body structure. In the present study, 6061 Al alloy and DP780 steel sheet were joined using the resistance element welding (REW) technique with a flat Q235 rivet. The intermetallic compounds (IMCs) in the welded joints were thoroughly analyzed using various characterization techniques such as scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), electron backscatter diffraction (EBSD), focused ion beam (FIB), high-resolution transmission electron microscopy (HRTEM) and selected area electron diffraction (SAED). The results showed that the IMC in the REWed joints consists of a tongue-shaped Fe2Al5 towards the steel side and a finger-shaped Fe4Al13 towards the Al side. Dislocations were observed at the grain boundaries of Fe2Al5 grains for the first time. Nanotwins and stacking faults inside the Fe4Al13 grains were observed indicating that the formation of planar defects was mainly by rapid cooling. The (100) twining was considered to be the main twining type during the solid/liquid interfacial reaction in dissimilar REW welding between Al alloys and steel.

ИССЛЕДОВАНИЕ ВЛИЯНИЯ ИЗБЫТОЧНОЙ СОЛНЕЧНОЙ РАДИАЦИИ И БОКОВОЙ ВЕТРОВОЙ НАГРУЗКИ НА ОЦЕНКУ ПРОЧНОСТИ КУЗОВА ДВУХЭТАЖНОГО ВАГОНА

Approaches to the analysis of the load-bearing systems of the bodies of double-deck cars, as well as the experience of their operation on domestic railways are analyzed. It is found out that for modern load-bearing structures of bodies with minimum permissible safety margin and stability of elements, it is advisable to pay more attention to specific loads, such as wind and loads associated with excessive solar radiation.
 The method of studying the influence of these factors on the load-bearing capacity of the elements of car body pressure shell is proposed. The method provides for both experimental simulation of exposure of the double-deck car roof with excessive solar radiation in combination with subsequent exposure to repair loads, and carrying out a complex of calculations based on the application of the finite element method (FEM).
 The conducted studies indicate the need for a more precise account of the influence of lateral wind load and excessive solar radiation when assessing the strength of the load-bearing structures of the double-deck car bodies.
 It is shown that the proposed technique makes it possible to take into account these specific loads on the basis of mathematical modeling with confirmation of the results obtained by the data of field experiments.

A strategy for lightweight designing of a railway vehicle car body including composite material and dynamic structural optimization

AbstractRolling stock manufacturers are finding structural solutions to reduce power required by the vehicles, and the lightweight design of the car body represents a possible solution. Optimization processes and innovative materials can be combined in order to achieve this goal. In this framework, we propose the redesign and optimization process of the car body roof for a light rail vehicle, introducing a sandwich structure. Bonded joint was used as a fastening system. The project was carried out on a single car of a modern tram platform. This preliminary numerical work was developed in two main steps: redesign of the car body structure and optimization of the innovated system. Objective of the process was the mass reduction of the whole metallic structure, while the constraint condition was imposed on the first frequency of vibration of the system. The effect of introducing a sandwich panel within the roof assembly was evaluated, focusing on the mechanical and dynamic performances of the whole car body. A mass saving of 63% on the optimized components was achieved, corresponding to a 7.6% if compared to the complete car body shell. In addition, a positive increasing of 17.7% on the first frequency of vibration was observed. Encouraging results have been achieved in terms of weight reduction and mechanical behaviour of the innovated car body.

Application of Digital Image Processing Techniques to Detect Through-Thickness Crack in Hole Expansion Test

Advanced high-strength steels (AHSS) have become increasingly popular in the automotive industry due to their high yield and ultimate tensile strengths, enabling the production of lighter car body structures while meeting safety standards. However, they have some setbacks compared to conventional steels, such as edge cracking through sheet thickness caused by forming components with shear-cut edges. When characterizing the formability of sheet metal materials, the hole expansion test is an industry-standard method used to evaluate the stretch-flangeability of their edges. However, accurately visualizing the first cracking is usually tricky and may be subjective, often leading to inconsistent results and low reproducibility with some impact of the operator on both direct and post-processing measurements. To address these issues, a novel digital image processing method is presented to reduce operator reliance and enhance the accuracy and efficiency of the hole expansion test results. By leveraging advanced image processing algorithms, the proposed approach detects the appearance of the first edge cracks, enabling a more precise determination of the hole expansion ratio (HER). Furthermore, it provides valuable insights into the evolution of the hole diameter, allowing for a comprehensive understanding of the material behavior during the test. The proposed method was evaluated for different materials, and the corresponding HER values were compared with the traditional method.

A rigid–flexible coupling finite element model of coupler for analyzing train instability behavior during collision

AbstractRail vehicles generate huge longitudinal impact loads in collisions. If unreasonable matching exists between the compressive strength of the intermediate coupler and the structural strength of the car body, the risk of car body structure damage and train derailment will increase. Herein, a four-stage rigid–flexible coupling finite element model of the coupler is established considering the coupler buckling load. The influence of the coupler buckling load on the train longitudinal–vertical–horizontal buckling behavior was studied, and the mechanism of the train horizontal buckling instability in train collisions was revealed. Analysis results show that an intermediate coupler should be designed to ensure that the actual buckling load is less than the compressive load when the car body structure begins to deform plastically. The actual buckling load of the coupler and the asymmetry of the structural strength of the car body in the lateral direction are two important influencing factors for the lateral buckling of a train collision. If the strength of the two sides of the car body structure in the lateral direction is asymmetrical, the deformation on the weaker side will be larger, and the end of the car body will begin to deflect under the action of the coupler force, which in turn causes the train to undergo sawtooth buckling.

Dynamic size optimization approach to support railway carbody lightweight design process

The transition to a globalised electrical power supply pushes rolling stock manufacturers to find structural solutions for reducing the power required by the vehicles. Within a market where details can make the difference in economic terms, the concept of design optimization is becoming established. However, current industrial procedure for the evaluation of carbody structural strength, in static field and according to EN 12663-1:2015 standard, does not include any optimization process. More in general, optimization processes, and especially dynamic optimization, are not widely used for designing of railway vehicles. In this framework, the present paper proposes a new dynamic optimization approach to support the design of railway vehicle carbodies subjected to static loads. Proposed methodology aims to minimize the mass of the metallic structure, working on the thicknesses of the optimized components, maintaining the baseline geometry. The constraint function was imposed on the first natural vibration frequency of the system. The optimization strategy is based on a dynamic size optimization process in conjunction with modal analysis techniques, applied on the single carbody shell. The procedure has involved the roof assembly of a single tram vehicle body. The proposed approach is resulted numerically efficient in terms of calculation times. Encouraging results have been achieved in terms of mass saving and mechanical behaviour of the carbody shell. Optimized components were 21% lighter than the original, that corresponds to 3% if evaluated on the total mass of the single carbody metallic structure. The methodology turns out to be a useful tool for supporting designers to reduce the mass of the carbody structures, reducing overdimensioning condition that could affect the carbody structure.

Research on Load Reverse Engineering and Vibration Fatigue Analysis Technology of Rapid Box Wagon

The overall stiffness and modal frequency of the car body of a rapid box car are reduced by the design of the full-side open movable side door structure. The vibration fatigue performance of the welded structure in this car body needs to be verified. The rigid-flexible coupling model of the rapid box wagon was established first, and the model was verified by modal test data. By the application of the virtual iteration method on this model, the displacement excitation loads of this vehicle were acquired. The effectiveness of the load reverse obtaining technology was verified through the comparison between calculated data and the experimental data. Based on the rigid-flexible coupling model and the load obtained by reverse engineering, the fatigue life of the welded structure in the car body was evaluated through the modal structural stress method. The calculated results show that the car body structure obtains obvious modal vibration, which leads to short fatigue life in several weld lines. According to the application requirements of this wagon, the local improvement scheme was proposed, and the effect of the improvement program was evaluated. In this paper, a new fatigue evaluation technology based on the load reverse method of test data was proposed, which provides a theoretical basis for the structural design and program improvement of railway vehicles.