Car Body Structure Research Articles

Cold metal transfer spot welding of 1 mm thick AA6061-T6

In order to meet the upcoming regulations on greenhouse gas emissions, aluminum use in the automotive industry is increasing especially in car body structure and closure applications. To address the shift from steel to aluminum, there needs to be a corresponding shift of joining technologies which consequently drives the development of an effective single sided joining process for aluminum alloys. In this paper, a variant of gas metal arc welding, i.e. cold metal transfer, CMT, which is unique in its approach to reduce the overall heat input, has been introduced to address that concern. Three welding arc modes: Standard, Pulsed and CMT are investigated to identify the advantages of CMT mode and the CMT mode was further investigated by four CMT spot welding modes: direct welding (DW) mode, plug welding (PW) mode, direct welding on a chill block (DWB) mode and plug welding on a chill block (PWB) mode. The resultant welds were investigated by macro and micro metallographic examination, microhardness testing and mechanical property testing. The results showed that the CMT arc mode could obtain the strongest welds understandably with the fewest welding defects. Under CMT arc mode, the direct welding with chill block mode (DWB) produced the largest weld faying interface. These welds also exhibited fewest partial tearing defects which led to the highest strength and ductility among the four welding modes for single sided spot welding of 1mm+1mm AA6061-T6 sheet combination.

Active Vibration Control of a Railway Vehicle Carbody Using Piezoelectric Elements

In recent years and according to modern transportation development, rail vehicles are manufactured lighter to achieve higher speed and lower transportation costs. On the other hand, weight reduction of rail vehicles leads to increase the structural vibration. In this study, Active Vibration Control of a rail vehicle using piezoelectric elements is investigated. The optimal control employed as the control approach regard to the first two modes of vibration. A simplified Car body structure is modeled in Matlab using the finite element theory by considering six DOF beam element and then the Eigen functions and mode shapes are derived. The surface roughness of different classes of rail tracks have been obtained using random vibration theory and applied to the secondary suspension as the excitation of the structure; Then piezoelectric mounted where the greatest moments were captured. The effectiveness of Piezoelectric in structural vibrations attenuation of car body is demonstrated through the state space equations and its effect on modal coefficient.

Self-locking self-pierce riveting: a new self-pierce riveting technology for multi-material applications in lightweight car body structures

Due to the fact that car attributes like the dynamic drive ability, CO2 emissions and efficiency are factors which are massively influenced by the total vehicle mass; lightweight becomes a key issue in modern car body design. Nowadays, most cost-effective lightweight solutions can be achieved by multi-material design. This restricts conventional thermal joining technologies and shows the demand for cost-effective and efficient mechanical and adhesive joining technologies. This paper shows the development of a new type of a self-pierce riveting system with solid rivets for joining lightweight materials such as ultra-high-strength steels or aluminium in multi-material structures. Compared to the conventional solid self-pierce riveting, the embossing ring is not located at the die but just below the protruding head of the joining element. While processing, the die-sided material is deformed by the stamp-sided material, which is deformed by the embossing ring. A modified die with an enlarged surface area is used to significantly reduce the deformations of the die-sided material. Besides experimental studies, the process simulation (FEM) is used to achieve an optimum geometry of the rivet. This paper presents detailed information about the development of the new riveting technology and the characteristics of the new joining technology compared to the conventional solid self-pierce riveting. Joints with the new solid self-locking self-piercing rivet show slight deformations of die-sided sheets, high process stability and flexibility.

Process characteristics and load-bearing capacities of joints welded with elements for the application in multi-material design

In the global market of the engineering sector, products can only be economically successful when they are extraordinarily light, safe, environment-friendly, and favorable compared to the competitors’ products. Because of new regulations for the reduction of CO2 emissions, especially the automotive industry is increasingly focusing on weight reduction in the car body structure through multi-material design with high-strength steels and aluminum. Conventional joining technologies for the body shop are often not applicable for these dissimilar material joints, for which reason new technologies must be invented. The hybrid thermal-mechanical joining technologies “resistance element welding” and “friction element welding” have been invented in recent years and are suitable for the high-volume production of multi-material structures with ultra-high-strength steels. Multi-material joints require effective corrosion protection measures. This paper presents how suitable process parameters can be determined for these two innovative technologies. Moreover, it shows the influence of a zinc-based anticorrosive fastener coating on the process parameters, the load-bearing capacity, and the corrosion behavior of the joints.

Simultaneous topology and size optimization of locomotive structure using multinary genetic algorithms

Structural optimization of a typical locomotive carbody subjected to various operational loads is investigated using a simultaneous topology and size optimization approach. The proposed approach builds on a string representation of the structure in which the presence or absence of a structural element between specific nodes, as well as its cross-section, are represented by integers. Strings representing various structure topologies are then evolved according to a modified Genetic algorithm with improved genetic operators. The efficiency of the proposed model is verified through applying it to optimize the carbody structure of ER24PC locomotive. Operational load cases and performance criteria are adopted from the European standard EN12663. It is shown that the results based on the present optimal design have higher safety factors compared to the original design without a significant increase in weight. Besides, the computational cost of the optimization process is shown to be considerably less than that of the classical binary Genetic algorithm.

Experimental Investigation on Forming of Tailor Welded Blanks

One of the main aims of automotive developers is vehicle weight reduction. There are many well known ways related to weight reduction, for example using thinner and higher strength sheet materials, or using of formed tubes as load-bearing elements in car body structures. In the field of modern automotive industry we must not forget that the heavy loaded, and in passenger-safety aspect relevant elements frequently consist of tailor welded blanks (TWBs). The components could have different strength or thickness or coatings too. Therefore, certain segments of the welded elements could behave differently during forming. Generally the higher strength coupled with less formability, but in the case of welded blanks, the interaction of each parts are unknown in many aspects.This paper presents the results of the experimental work, carried out to evaluate the drawability of tailor welded blanks. The welded blanks were prepared by laser beam welding technology. The blanks consisted of a well drawing component, marked DC04, and a high strength steel component. The applied high strength steels are DP600, DP800 and DP1000 types. Our current object was to determine some basic parameters of deep-drawability as a typical sheet metal forming operation. It can be stated that as the strength ratio (SR) is increasing between the segments, the limiting drawing ratio is decreasing.

State of the Art on Basic Methodologies for Crashworthy Design of Automotive Body Components Considering Axial Collapse Mode

The body structure of a passenger vehicle is one of the important functional groups of a vehicle. A crashworthy car body structure is so conceptualised as to absorb considerable amount of the impact energy by deforming in definite areas, and thereby reduce the deceleration experienced by its passengers to survivable levels. The non-deforming areas of the car body structure are designed as stiff survivable space for the passengers. Various criteria, such as deformation pattern, deceleration pulse of the vehicle, different bio-mechanical criteria defined for the passengers etc., can be used for assessing the crashworthiness of vehicles. Various methods have been developed and used over the years to analyse and optimise the crashworthiness of vehicles. This paper presents an overview of simplified design approaches for analysing car body components for their behaviour in crash events. This includes a brief summary of various collapse modes. Main characteristics of the axial collapse mode and simplified design approaches available for this mode, relevant for our research work, are also presented.

State of the Art on Basic Methodologies for Crashworthy Design of Automotive Body Components Considering Bending Collapse Mode

The body structure of a passenger vehicle is one of the important functional groups of a vehicle. A crashworthy car body structure is so conceptualised as to absorb considerable amount of the impact energy by deforming in definite areas, and thereby reduce the deceleration experienced by its passengers to survivable levels. The non-deforming areas of the car body structure are designed as stiff survivable space for the passengers. Various criteria, such as deformation pattern, deceleration pulse of the vehicle, different bio-mechanical criteria defined for the passengers etc., can be used for assessing the crashworthiness of vehicles. Various methods have been developed and used over the years to analyse and optimise the crashworthiness of vehicles. This paper presents an overview of simplified design approaches for analysing car body components for their behaviour in crash events. This includes a brief summary of various collapse modes. Main characteristics of the bending collapse mode and simplified design approaches available for this mode, relevant for our research work, are also presented.

Multi Objective Knowledgebase Concept Design Methodology of Automotive Space Frame Structures for Crashworthiness by Numerical Methods

Crashworthiness of an automotive can be well-defined as its capability to defend its occupants and other accomplices, like pedestrians and other automobiles, complicated in an incident of impact. The multi objective knowledgebase methodology facilitates the performance oriented design of a crashworthy profile based car body structure with regular cross-sections in its concept design stage.Crashworthy design of a car body is realised by designing its components to absorb sufficient amount of energy in an event of impact, so that the integrity of the passenger compartment is maintained. The multi objectiveknowledgebase aims at pre-defining the targets for the structural performance of these car body components during a crash scenario, and choosing appropriate cross-sectional geometry and materials for these components, matching the targets. In this work, information extracted from FE simulations of full vehicles and profiles with regular cross sections is extensively used for developing this knowledgebase. Due to the performance oriented design concept employed here, the optimisation time required during the detailed design phase can be considerably reduced.

Research of Typical Fatigue Load Spectrum Simulation of Carbody Structure Based on Non-stationary Aerodynamic Load

Research of Typical Fatigue Load Spectrum Simulation of Carbody Structure Based on Non-stationary Aerodynamic Load

Experiment and finite element simulation of high strength steel adhesive joint reinforced by rivet for automotive applications

Vehicle lightweight drives the adoption of new materials on automobile body structures. As a prerequisite for designing safe and reliable new material vehicle body, knowledge of testing and simulating new joining methods is of critical importance. In this study, a high strength steel adhesive joint reinforced by rivet is investigated first using mechanical tests to account for the effect of joint type and loading conditions, then numerically characterized using finite element simulation with simplified joint models. Results show that (1) adhesive and rivet conditionally enhance each other in the hybrid joint and (2) the calibrated adhesive/rivet model is validated in the hybrid joint, proving to be an effective and efficient tool for full vehicle simulation.

End-of-Life in the railway sector: Analysis of recyclability and recoverability for different vehicle case studies

The railway system represents one of the most resource-efficient answer to our ever-growing demand for transport service and the development trends for the following years forecast a substantial increase in this sector. Considering the European Union, rolling stock realizes a significant share of both goods and passengers carriage while it is responsible for a derisory quota of environmental impact and energy consumption involved by transportation. Contrary to the low environmental impact, the amount of End-of-Life (EoL) waste generated by rolling stocks in relation to the number of vehicles is notable, much greater than in the case of road vehicles. As railway vehicles are constituted by many heterogeneous components, the EoL rolling stock is a precious source of materials, whose recycling brings measurable economic benefits and needs to be appropriately debated. The paper presents calculation of recoverability/recyclability rate for different typologies of vehicles representative of railway transport; calculation is performed on the basis of primary data and according to the recyclability and recoverability calculation method issued by UNIFE in the context of Product Category Rules (PCR). The typologies of railway vehicles taken into account are electric metro, diesel commuter train and high-speed electric train. The analysis envisages also to replicate the calculation in case innovative materials and manufacturing technologies are adopted in the construction of car-body structure. Results show that recyclability/recoverability rates are abundantly over the quota of 90% for each one of the three trains, these latter being made in major part of metals that benefit from very efficient recovery processes. The adoption of innovative materials and manufacturing technologies for car-body structure involves a scarce reduction of recyclability and recoverability rates (about 2% and 0.2% respectively) due to the introduction of components and materials characterized by critical dismantlability and low efficiency recovery processes; recoverability results less affected by lightweighting because post-shredding thermal recovery treatments are roughly independent with respect to dismantlability. A sensitivity analysis based on different dismantling scenarios reveals that the effectiveness of dismantling has a moderate influence on recyclability/recoverability rate (the variation does not exceed 3%). The low variability of recyclability/recoverability rate can be explained by the following reasons: predominance of metals in trains material composition, efficiency of metals separation processes close to 100%, post-shredding recycling processes of metals characterized by recovery factors equal to the ones of post-dismantling recycling processes.

Effect of Fine Grained Dual Phase Steel on Bake Hardening Properties

High strength dual phase (DP) steels have been increasingly used in car body structure for reducing weight and increasing safety performance. Bake hardening process is widely applied for improving final mechanical properties of formed components by means of carbide precipitation and occurred Cottrell cloud. In this work, effects of bake hardening on mechanical behavior of coarse and fine grain DP steels are investigated. Initially, fine grain ferritic–pearlitic structure is produced from a low carbon steel by constrained groove pressing (CGP) based on severe plastic deformation. Ferrite grains with a submicro size of 470 nm can be hereby achieved. DP microstructures are generated afterward by intercritical annealing. Finally, bake hardening at the temperature of 160 °C for 20 min is performed under consideration of various pre-strains between 0 and 10%. It is found that bake hardenability of the DP steels can be significantly increased due to the fine grain structure induced by the CGP, which provide enhanced heterogeneous nucleation sites for precipitates and accelerated carbon diffusion.

Sound transmission loss of windows on high speed trains

The window is one of the main components of the high speed train car body structure through which noise can be transmitted. To study the windows’ acoustic properties, the vibration of one window of a high speed train has been measured for a running speed of 250 km/h. The corresponding interior noise and the noise in the wheel-rail area have been measured simultaneously. The experimental results show that the window vibration velocity has a similar spectral shape to the interior noise. Interior noise source identification further indicates that the window makes a contribution to the interior noise. Improvement of the window's Sound Transmission Loss (STL) can reduce the interior noise from this transmission path. An STL model of the window is built based on wave propagation and modal superposition methods. From the theoretical results, the window's STL property is studied and several factors affecting it are investigated, which provide indications for future low noise design of high speed train windows.

TO THE ISSUE OF EXTENDING THE SERVICE LIFE OF CARS FOR TRANSPORTATION OF PELLETS

Purpose. Freight rolling stock of «Ukrzaliznytsia» primarily has cars that are overaged. The same situation is observed in the park of specialized cars. So the car fleet for the transport of pellets consists of about 50% of cars that served one-and-a-half and more lifetimes. However, the volume of shipments of iron ore is constant for a number of years. In this regard, there is a need to find methods to justify continuing useful life of cars and to assess the conformity of residual life of the car body structure to operating load for an extended period of use. Methodology. When selecting the cars for the test their condition underwent technical diagnosis in order to identify the level of corrosion and mechanical damage. The next stages of the tests included the experimental determination of the loading level and the stress state of car body carcass based on strength and endurance tests and the evaluation of the possible values of the extended period of operation. Findings. Pre-test diagnosing of cars showed that the technical condition of cars for transportation of pellets, as a whole, is in satisfactory condition. Carried out static and impact strength tests with subsequent evaluation of strength of the car structural elements showed that the strength of the latter is provided in accordance with regulations and such cars do not threaten the traffic safety. Shock endurance tests have shown that all the cars have passed endurance tests with no damage that would impede testing and could not be removed during scheduled repairs. The cars had lifelength that allows prolong their useful life after one-and-a-half lifetime. Originality. The work presents the estimate of the residual life of bodies of pellet transportation cars, which spent one-and-a-half of the set lifetime. Practical value. The experimental results confirm the possibility of extending the service life of cars after one-and-a-half life of their lifetime. The results of the work can be used to extend the service life of cars for transportation of pellets. Part of the rolling stock, which had to be written off in connection with the expiration of the set one-and-a-half lifetime without additional measures can continue its lifetime.

Influence of short-term heat treatment on the microstructure and mechanical properties of EN AW-6060 T4 extrusion profiles—Part B

In the automotive industry aluminium and its corresponding semi-finished products contribute an essential part to the aim of weight reduction in car body structures. Aluminium alloys of the 6000 series with Mg and Si contents are preferred because of the possibility to increase strength by ageing processes. However, the cold formability in comparison to other materials like mild steels is quite low and due to this, complex parts are only producible at higher temperatures. Therefore, the so called Tailor Heat Treatment was developed to improve the cold formability of aluminium alloys. In this approach, a short-term heat treatment is conducted to achieve a local softening of the material due to dissolution of Mg and Si clusters (retrogression). This effect is used to improve the material flow, relief critical forming zones and enhance the overall formability of the material. Afterwards, strength can be increased again by ageing processes. However, up till now a holistic process understanding, taking into account all process parameters as well as a microstructural explanation is missing. Therefore, the focus of the fundamental investigations lies on connections between the mechanical properties and short-term heat treatment with industry-relevant heating rates as well as natural and artificial ageing process. Conclusively, the evolution of the mechanical properties with regard to the natural ageing process is compared with findings of DSC analysis, which were discussed in Part A. Based on these results, a process window is derived for the subsequent forming process and the final mechanical properties of the final part in dependency of the forming history as well as the artificial ageing process, are identified.

Investigation of the Failure of Advanced High Strength Steels Heterogeneous Spot Welds

Nowadays, environmental regulation encourages carmakers to reduce the global vehicle weight. Steelmakers develop grades with high performance (Advanced High Strength Steels, AHSS) and fine steel sheet assemblies are used in car body structures, with an optimized thickness in each part. However, unusual fracture modes are sometimes observed during the mechanical tests of heterogeneous AHSS welds, made of dissimilar steel grades and sheet thicknesses. Weld fractures can occur with a strength lower than expected. This study aims at understanding these fracture mechanisms and focuses on two common steel grades joined by Resistance Spot Welding (RSW): DP600 (a dual phase steel) and Usibor®1500 (a martensitic steel). The parameters affecting the failure modes and load bearing capacity are investigated during two common types of tests: the Cross Tension and Tensile Shear tests. The positive effects of heterogeneous welding with respect to the corresponding homogeneous configurations are discussed, as well as the consequences of a so-called Dome failure occurring at the weld nugget boundary.

Representative surrogate problems as test functions for expensive simulators in multidisciplinary design optimization of vehicle structures

A large variety of algorithms for multidisciplinary optimization is available, but for various industrial problem types that involve expensive function evaluations, there is still few guidance available to select efficient optimization algorithms. This is also the case for multidisciplinary vehicle design optimization problems involving, e.g., weight, crashworthiness, and vibrational comfort responses. In this paper, an approach for the development of Representative Surrogate Problems (RSPs) as synthetic test functions for a relatively complex industrial problem is presented. The work builds on existing sensitivity analysis and surrogate data generation methods to establish a novel approach to generate surrogate function sets, which are accessible (i.e. not resource demanding) and aim to generate statistically representative instances of specific classes of industrial problems. The approach is demonstrated through the construction of RSPs for multidisciplinary optimization problems that occur in the context of structural car body design. As a proof of concept the RSP approach is applied for the selection of suitable optimization algorithms, for several problem formulations and for a meta-optimization (i.e. an optimization of the optimization algorithm parameters) to increase optimization efficiency. The potential of the approach is demonstrated by comparing the efficiency of several optimization algorithms on an RSP and an independent simulation-based vehicle model. The results corroborate the potential of the proposed approach and significant performance gains in optimization efficiency are achieved. Although the approach is developed for the particular application presented, the approach is described in a general way, to encourage readers to use the gist of the concept.

The next generation material for lightweight railway car body structures: Magnesium alloys

While magnesium alloys have the attractive attributes of low density, the application of the metal in transportation industries has been restricted by its low stiffness and strength. The aim of this study was to examine the possibility of lightweight railway car body construction using magnesium alloys from the structural and manufacturing perspectives. Extruded members, making up a car body, were designed employing a gradient-based optimization algorithm. And then, numerical simulations were conducted to confirm the structural performance of the newly designed car body. In addition, one of the designed members was extruded and joined with another via friction stir welding in order to verify its fabrication potential. The work demonstrated that, with just 85% of the weight of an aluminium car body currently in operation, a magnesium-based railway car body can be potentially constructed by extrusion followed by friction stir welding for the next generation rolling stocks; that is to say, the weight saving amount is 10% of the total bare frame weight, or 2% of its total rolling stock weight.

Pressing Technologies for ELVs

This article explains the physical features of various methods of compaction, primarily for end of life vehicle (ELV) bodies coming from ELV processors. By EU directive 2000/53/EC it is mandatory for all EU members to meet the reuse of 95 % of the old vehicle weight. It means that the vehicles have to be decomposed completely – metal shells freed from all the components like interior trim, rubber sealing, glass, all the liquids, seats tanks and other hard metal components like drive-train, engine etc. It follows that pressing machines used for compressing whole vehicles today, are overpowered, with high energy demand, robust structures and heavy weight. Hence it makes sense to concentrate on comparison of pressing methods and choosing the most energy efficient one and the designing a new device, if necessary. This device is aimed for operation in Slovak Republic but also usable in other countries with same or similar requirements such as optimized system for processing of car bodies, mobile concept and modularity of the whole mobile modular disintegration complex consisting of a pressing machine, shears and shredder. Car body structure