Car Body Structure Research Articles

Floor Frame Structure Conceptual Design of Car Body by Multi-level Optimization Method

To optimize the floor structure of car body in conceptual design phase, a discrete topo optimization method is implemented. First of all, by several body beam section parameters are collected and simplified as rectangular beam cross section. The parameterized simulation model of concept car body structure is modeled with simplified beams. The floor general structure is determined and redefined the discrete topology domain of car body floor, solves the coupling relations between two kinds of design variables which are topology of the floor beam and connection position of floor beam, through the construct platform and conversion of optimization goals and design constraints between different levels, the multi-island genetic algorithm (MIGA) algorithm was used to seek the optimal solution and fully verifies its accuracy by examples.

Study on impact test and numerical simulation of an aluminum alloy car body structure for railway vehicle.

Study on impact test and numerical simulation of an aluminum alloy car body structure for railway vehicle.

Investigation of diffusion behavior of carburized sheet metal in hot stamping

Today, manufacturing of structural car body parts faces several challenges, like forming accuracy, passenger safety and lightweight design. One possibility to fulfill these partially rivalling demands is the application of hot stamped components. The combination of hot forming and in-die quenching reduces not only springback, but also results in tensile strengths of more than 1500 MPa. Besides conventional hot stamping, the process can be adapted to manufacture parts with tailored properties. One of the biggest issues of these state-of-the-art processes is the formation of extensive transition zones due to heat transfer. A promising approach to adjust the mechanical properties with a minimized transition zone is tailored carburization of sheet metal. Therefore, the parts are locally coated with graphite, heat treated and subsequently quenched. In this work, the time variant process of carbon diffusion is investigated. Sheets with two different thicknesses are carburized and quenched. The resulting mechanical properties are analyzed using uniaxial tensile tests and microhardness measurements. On this basis, a process window is identified. Furthermore, the applicability of EDX and WDX analysis for the measurement of carbon concentration is investigated within this work.

A Practical Structural Health Monitoring System for High-Speed Train Car-Body

A practical structural health monitoring (SHM) system based on Lamb wave for high-speed train car-body structures is presented. The system can detect the occurrence and report the location and probabilistic size of structural damage in real-time. Based on the theory of Lamb wave, a piezoelectric transducer array network is implemented to generate and acquire the detection signal by mounting on the surface of the structure to be monitored. An algorithm, that can locate, quantify and image the damage based on the damage index that indicates the differential between baseline signal and current acquired signal, is proposed to develop the system. Furthermore, a system framework of three-layer architecture and a diagnosis strategy are designed to build the SHM system. Finally, the system is implemented on China's latest high-speed train (CRH380A) operated along the Chengdu-Chongqing High-Speed Railway after well tuning then demonstrates the feasibility and reliable in practical application.

Collision test of actual railway carbody structure made of stainless-steel

Collision test of actual railway carbody structure made of stainless-steel

Study on the Design of Container Highway and Railway Automatic Transfer Vehicle in Ocean Port

Abstract To realize “seamless” connection of ocean port container multimodal transport, efficiently carry out “door-to-door” transport of ocean port containers and overcome the shortcomings of existing highway and railway vehicles, this study takes the standard for heavy-duty container vehicles in TB1335-1996 Railway Vehicle Strength Design and Test Identification Code as the design basis and designs a new ocean port container transport vehicle in combination with automatic guidance technology. This study innovatively designs the automatic lifting system of the bogie and the docking part of the vehicle, introduces the automatic guidance technology and the remote-control technology to optimize the car body structure, and uses the SAP software to carry out the finite element analysis of the car body load capacity and Flexsim software to carry out the simulation analysis on the operation of vehicles. The designed transfer vehicle can improve the transfer efficiency of ocean port containers, reduce the transit time of field and station equipment and container transport links, and improve the level of multimodal transport and comprehensive economic benefits.

Thermo‐mechanical modelling and finite element analysis of self‐piercing riveting processes

AbstractIn this contribution, a thermo‐mechanical finite element analysis of the self‐piercing riveting process of two steel sheets is carried out taking into account the conversion of plastic work into heat. Thereby, a user defined constitutive model recently proposed by BRÖCKER and MATZENMILLER is applied considering the highly temperature and rate dependent characteristics of metals. All constitutive parameters are identified with test data of the microalloyed steel HX340LAD typically used for car body structures. The numerical results of the self‐piercing riveting process are compared to the according test data for model validation by means of the final joint geometry and the setting force.

Analysis of the aerodynamic pressure effect on the fatigue strength of the carbody of high-speed trains passing by each other in a tunnel

When two high-speed trains pass through a tunnel, the aerodynamic changes are more complex and drastic than in open air owing to the interference of the tunnel wall and the entry effect. The impact on the carbody fatigue strength is very significant in the fatigue reliability design of the carbody. In this paper, the sequential coupling method was used for the first time to study the effect of pressure waves on the fatigue strength in a large-scale and complex carbody structure. The computational fluid dynamics method was used to calculate and analyze the aerodynamic pressure wave of the intersection of the trains in a long and short tunnel. A full-scale finite element shell model of the carbody structure was established. Then, the time integration method was used to convert the transient pressure wave into the aerodynamic loads bearing by the side wall of the carbody. The inhomogeneous stress concentrations at the restraint points were eliminated by the inertial release method; moreover, a finite element analysis of the carbody was carried out under the combined aerodynamic and mechanical loads. The Goodman fatigue strength curve of the aluminum alloy carbody was drawn. The influence of the aerodynamic load on the fatigue strength of the vehicle body was analyzed and compared under the entry effect of the short tunnel. The results show that the aerodynamic load of the short tunnel has a significant impact on the fatigue strength of the carbody owing to the train's entry effect. The safety factor of the fatigue strength is 15% less than that of the long tunnel aerodynamic load. In this paper, computational fluid dynamics and finite element method were used to analyze and evaluate the impact of the pressure wave on the fatigue strength of the carbody, which is of great reference value in the structural design of the carbody subjected to complex aerodynamic loads.

Uncertainty Optimization Design of a Vehicle Body Structure Considering Random Deviations

In vehicle body manufacturing, there are small differences between the actual value and design value of, for example, plate thickness and material characteristics. This is caused by the processing technology, environment and other uncertain factors. Therefore, the performance of the vehicle body processed according to the deterministic optimization solution fluctuates. The fluctuations may make structural performance fail to meet the design requirements. Thus, in this study, an optimization design is executed with 6 $$ \sigma $$ robustness criteria and a Monte Carlo simulation single-loop optimization strategy based on the radial basis function neural network approximate model considering deviations in plate thickness, elastic modulus, and welding spot diameter, which is called the uncertainty optimization design method. As an example, considering the bending stiffness, torsion stiffness, and first-order frequency as constraints, the method is applied to the lightweight design of a car body structure, and the reliability of deterministic optimization design and uncertainty optimization design is compared. The results demonstrate that the uncertainty optimization design solution is effective and feasible without lowering the static stiffness and modal performance, and the weight is reduced.

Innovative joining technology for multi-material applications with high manganese steels in lightweight car body structures

Due to restrictions imposed by legal requirements, automotive manufacturers are forced to reduce the pollutants emission of new models. A promising approach is the reduction of the vehicle weight, whereby the body in white offers great potential. This weight reduction is realized by new car body constructions, which contain the increasing usage of different materials. Furthermore, new lightweight materials like TWIP steels become more important. The successful and economic implementation of multi-material design with TWIP steels requires the availability of suitable joining technologies. Conventional thermal joining technologies can be used in consideration of specific characteristics related to welding austenitic steels. Within the project, challenging material combinations related to dissimilar materials are investigated. In this paper, high-speed joining is investigated as an innovative and promising joining technology for multi-material applications. This mechanical joining technology contains an auxiliary joining part, called tack, which is driven with high speed into the joining partners. The challenges as well as the optimization of the auxiliary joining part is shown. The investigations are attended by metallographic analysis, whereby mechanical properties are determined through destructive tests. The characteristics are compared to the results of current used standard tacks.

Mechanical properties of repair welded joints for automobile body structures

The purpose of this study is to evaluate the mechanical properties of repair spot welding and plug welding for automobile body structures. The lifecycle of a modern car includes different phases. From research and development to production and assembly and finally to the use of the car by the customers. These are the most examined phases, whereas the after-sales sector is a nonetheless important part of the lifecycle. After sales includes the repair of damaged automobile structures after road accidents. Increasing demands for safety and comfort lead to the request for feasible repair methods which create equal mechanical characteristics of the body structures such as the original set up. The joining technologies for modern press-hardened high-strength steels are essential in this context. Testing of lap shear and cross-tensile specimens is used to show mechanical properties of two repair welding technologies. The results show a major loss of strength in the tested joints when using plug welding instead of state of the art repair spot welding. Various analytical methods are moreover used to get a detailed understanding of the influence of both repair welding technologies on the material structure.

Stiffness Analysis of Car Body of Metro Head Car

Aiming at the head car body of a subway car in China, the finite element analysis model of car body structure of metro vehicle is established by using Hypermesh and ANSYS software, Draw lessons from domestic metro vehicle technical standards, according to the stress analysis and risk degree of the head body of metro vehicle, The stiffness analysis of the body of the subway head car is carried out, the analysis result meets the design requirement.

Tolerance analysis of compliant, feature-based sheet metal structures for fixtureless assembly

Products made of compliant sheet metals are widely used in automotive, aerospace, appliance and electronics industries. One of the most important challenges for the assembly process with compliant parts is dimensional quality, which affects product functionality and cost. Joining fixtures serve to position and secure the parts in the assembly process and thus significantly contribute to product quality. However, these fixtures are costly and inflexible. Feature-based fixturing is an approach to reduce fixtures in the assembly process. The approach relies on part-inherent fastening features that ensure the fixture functions. This paper presents an approach to calculate assembly variations for feature-based fixturing in the automotive body shop. The mathematical fundamentals are described and the approach was implemented using a numerical model. The model was validated and applied to car body structures. The validation shows a high quality of the model and the suitability to predict assembly variations. Finally, an assembly that is built with conventional fixtures is compared to an assembly that is set up with feature-based fixturing. This comparison shows that the approach of feature-based fixturing has a high potential to meet the requirements and thus being applied in the future.

Numerical and experimental investigation for formability of friction stir welded dissimilar aluminum alloys

Automotive manufacturers have been trying to improve fuel efficiency without compromising the structural integrity and one of the ways to resolve the issue is to expand usage of tailor welded blanks (TWBs) in car body structure. Friction stir welding (FSW) is a joining process, which can be well fitted to obtaining aluminum tailored blanks when compared to other conventional joining processes. This paper presents an experimental and numerical study on TWBs produced by FSW with dissimilar aluminum 5083-H32 and 6061-T6 alloy sheets. The quality of the friction stir welded dissimilar joints was evaluated in terms of metallographic observations, hardness studies and tensile tests. Moreover, the local property changes in the weld regions were observed through digital image correlation (DIC) method. Formability of friction stir welded blanks was evaluated in the biaxial stretch forming mode using the limiting dome height (LDH) test. The failure location and the LDH values of the formed blanks were correlated to the hardness and local properties across the welds. The FE simulation of the LDH tests was also conducted incorporating Yld2000-2d anisotropy constitutive properties of the parent metal and further considering the properties of the non-homogeneous welded zone. The Marciniak-Kuczynski model was applied to predict the failure successfully in the FE model, and the results were validated with experimental data.

Optimization of the process robustness of the stamping of complex body parts with regard to dimensional accuracy

The need for car body structures of higher strength and at the same time lower weight results in serious challenges for the stamping process. In order to produce design conform parts the stamping dies must be adjusted by the amount of the springback in the opposite direction. This approach can only be successful, if the springback only ranges in a certain bandwidth in series production. To do so, it must be fulfilled that for a common spread of input process parameters first of all the draw-in of the flange edge of the drawshell may not reach the drawbeads, secondly material failure by locally increasing strain may not occur at any possible parameter set and last but not least the location of the part in the respective follow-up operation may not vary in such a way that the springback is being affected considerably. After the three basic requirements have been fulfilled the effect of the integral of the elastic strain energy in bending areas has to be minimized by increasing the tensile stress to a maximum. As a result of that the scatter of the bending springback is being reduced.

Modeling of Forming Limit Bands for Strain-Based Failure-Analysis of Ultra-High-Strength Steels

Increased passenger safety and emission control are two of the main driving forces in the automotive industry for the development of light weight constructions. For increased strength to weight ratio, ultra-high-strength steels (UHSSs) are used in car body structures. Prediction of failure in such sheet metals is of high significance in the simulation of car crashes to avoid additional costs and fatalities. However, a disadvantage of this class of metals is a pronounced scatter in their material properties due to e.g., the manufacturing processes. In this work, a robust numerical model is developed in order to take the scatter into account in the prediction of the failure in manganese boron steel (22MnB5). To this end, the underlying material properties which determine the shapes of forming limit curves (FLCs) are obtained from experiments. A modified Marciniak–Kuczynski model is applied to determine the failure limits. By using a statistical approach, the material scatter is quantified in terms of two limiting hardening relations. Finally, the numerical solution obtained from simulations is verified experimentally. By generation of the so called forming limit bands (FLBs), the dispersion of limit strains is captured within the bounds of forming limits instead of a single FLC. In this way, the FLBs separate the whole region into safe, necking and failed zones.

Effect of Different Intercritical Annealing Treatments without and with Overaging on the Mechanical Material Behavior

In the last decade, press‐hardening of manganese‐boron steels for the manufacturing of safety‐relevant components has become a well‐established industrial process. Thereby, very high strengths are achieved with pure martensitic microstructures. However, in certain areas of the car body structure more ductile components are necessary to absorb crash energy. For tailoring the material properties, two‐ or multiphase microstructures can be induced by rolling and heat treatment processes. The press‐hardening steel 22MnB5 which is employed in the present study, is used to manufacture three different ferritic‐martensitic microstructures. These different materials are characterized by classical mechanical models, based on experimental results. For the mechanical description of the initial yield stress depending on the stress state of different multiphase steels, the Hill model is calibrated. The elastic limit and the kinematic hardening of three various heat treatment conditions are determined using conventional tensile tests and the Galimel test, respectively. Therefore, the applied mathematical relations are derived and adapted for the performed investigations. The relationship between the load conditions and the proper application of the equations are explained. The resulting microstructures are characterized and the ramifications with respect to their energy absorption capability are discussed.

Guideline to optimize the convergence behaviour of the geometrical springback compensation

The need for car body structures of higher strength and at the same time lower weight results in serious challenges for the stamping process. To produce accurate parts at the end the stamping dies must be adjusted more or less by the amount of the springback in the opposite direction. Which stamping dies out of a multistage die set need to be adjusted, and how great the respective adjustment needs to be, is still quite often defined by practical experience and trial-and-error. Normally a certain number of compensation iterations based on the same compensation strategy must be realized and in addition to that, even the compensation strategy itself must be modified in some iterations in order to achieve accurate parts within tolerance. In contrast to the today still convenient trial-and-error optimization approach, a compensation guideline has been developed. Key content is the influence of the relevant compensation parameters, such as the measuring reference system (measurement system) including clamping of the parts (orientation of the springback part relative to the target part) and the amount of the compensation in the different stages (compensation factor and compensation strategy).

Application of energy derivative method to determine the structural components' contribution to deceleration in crashes

ABSTRACTObjective: For occupant protection, it is important to understand how a car's deceleration time history in crashes can be designed using efficient of energy absorption by a car body's structure. In a previous paper, the authors proposed an energy derivative method to determine each structural component's contribution to the longitudinal deceleration of a car passenger compartment in crashes. In this study, this method was extended to 2 dimensions in order to analyze various crash test conditions. The contribution of each structure estimated from the energy derivative method was compared to that from a conventional finite element (FE) analysis method using cross-sectional forces.Method: A 2-dimensional energy derivative method was established. A simple FE model with a structural column connected to a rigid body was used to confirm the validity of this method and to compare with the result of cross-sectional forces determined using conventional analysis. Applying this method to a full-width frontal impact simulation of a car FE model, the contribution and the cross-sectional forces of the front rails were compared. In addition, this method was applied to a pedestrian headform FE simulation in order to determine the influence of the structural and inertia forces of the hood structures on the deceleration of the headform undergoing planar motion.Result: In an oblique impact of the simple column and rigid body model, the sum of the contributions of each part agrees with the rigid body deceleration, which indicates the validity of the 2-dimensional energy derivative method. Using the energy derivative method, it was observed that each part of the column contributes to the deceleration of the rigid body by collapsing in the sequence from front to rear, whereas the cross-sectional force at the rear of the column cannot detect the continuous collapse. In the full-width impact of a car, the contributions of the front rails estimated in the energy derivative method was smaller than that using the cross-sectional forces at the rear end of the front rails due to the deformation of the passenger compartment. For a pedestrian headform impact, the inertial and structural forces of the hood contributed to peaks of the headform deceleration in the initial and latter phases, respectively.Conclusions: Using the 2-dimensional energy derivative method, it is possible to analyze an oblique impact or a pedestrian headform impact with large rotations. This method has advantages compared to the conventional approach using cross-sectional forces because the contribution of each component to system deceleration can be determined.

Strain Effect on the Microstructure, Mechanical Properties and Fracture Characteristics of a TWIP Steel Sheet

Twinning-induced plasticity (TWIP) steels are a highly promising group of steels for the production of complex structural components in cold forming operations for car body manufacturing. In this work, the effect of cold rolling strain on the microstructure, mechanical properties and fracture characteristics of a TWIP steel sheet used for automobile body structure was studied by means of optical microscopy, scanning electron microscopy, electron back-scattered diffraction technique, microhardness measurement, tensile test and fractography. TWIP steel sheets were cold rolled with reductions of 0, 15 and 30%. An increase of the cold rolling strain led to an increase of deformation twinning activity in certain favourably oriented grains and resulted in significant increase in ultimate tensile strength and hardness of TWIP steel. However, the ductility of TWIP steel significantly decreased with increasing degree of cold rolling strain. The increase in the ultimate tensile strength was almost linear with the increase in cold rolling strain. After cold rolling reduction of 30%, the ultimate tensile strength increased by approximately 50%, whereas the elongation decreased by approximately 85%. The size and depth of the dimples in the fracture surface decreased with the increase of the twin boundaries at 30% cold rolling strain, leading to highly limited plasticity through the tensile testing.