Car Body Construction Research Articles

Process time distribution simulation in robotic assembly line balancing

Feedback control systems utilised in car body construction cause process time variance when compensating for external disturbances. By considering these in robotic assembly line balancing, the risk of cycle time violations can be controlled. This requires knowledge of the underlying process time distributions, which are not known in advance. Therefore, a simulation method is proposed to assess the impact of varying process time distributions on the balancing of robotic assembly lines. The initial step involves acquiring the process times of existing production processes. In the subsequent simulation, these are randomly and repeatedly selected as substitutes for the process times in the balancing of a new robotic assembly line. The impact of process time distribution variations on the result is investigated, and a single solution can be selected. The proposed method is evaluated based on the balancing of a robotic assembly line for a body-in-white rear compartment. Results are compared to normally distributed process times, which is a common assumption for modelling uncertain process times. Both approaches are evaluated utilising actual process time distributions. It is demonstrated that the proposed method yields fewer and less severe underestimations of cycle times, thereby reducing the number of uncontrolled violations of cycle times.

Expanding Lightweight Design Potential by Hybrid Joining of Aluminum Sheets with Aluminum Casting Through Compound Sand Casting and Induction Heating

Combining light metals like aluminum to produce lightweight structures offers a high weight‐saving and contributes to a circular economy in automotive car body construction. Compound casting is a promising process for producing car body parts. Difficulties arise in creating metallic continuity between insert and casting. Insert coatings are used to remove the oxide layer and thereby improve the wettability of the melt. This study uses a hybrid joining method to improve the metallic bond between insert and casting. Induction heating differently influences the strength properties of age‐ and nonage‐hardenable inserts. Compression shear tests characterize the metallic bond strength. Microscopic images show the influence of the process variables on the compound quality. Reproducible sound metallic bonding with low scattering is achieved by enhancing the compound casting process through induction and no insert coating. Cast wall thicknesses down to 4 mm contribute to further lightweight potential as they have the same strength level as the reference sample. A decisive factor is the insert temperature in the compound zone. Thereby, insert preheating conditions play a crucial role. Additional heat treatment of hardenable compounds leads to a further increase in metallic bond strength.

Material substitution to reduce the environmental impacts in construction of car body manufacturing plants

The efficient use of resources is a key driver for reconciling nature and technology in the automotive manufacturing process. Resource efficiency not only considering the final product but also the construction of the manufacturing system is therefore essential for achieving the sustainability goals pursued by global automotive manufacturers. In this context, the substitution of energy-intensive primary materials with renewable raw materials represents a significant potential for reducing the environmental impacts of automotive plant engineering. However, the use of new materials often leads to conflicting objectives in terms of environmental and economic aspects as well as technical feasibility. To ensure an effective contribution to sustainability, it is necessary to evaluate the entire product life cycle of the substitute material, to localize the resulting secondary effects and to develop target-oriented solution concepts. Against this background, an approach is presented for the implementation of material substitution. The feasibility is demonstrated with a case-study on the substitution of energy-intensive steel with renewable wood material for the structural elements of a vertical conveyor pallet in the car body construction. The technical development and series testing is described and subsequently a comparative environmental and economic evaluation is carried out to analyze the potential benefits compared with the status quo while considering the resulting secondary effects. Finally, a potential assessment is made based on a reference body shop.

Behaviour of aluminium/steel hybrid RSW joints under high cycle fatigue loading

The lightweight construction of automotive car bodies is the more important to reduce the fuel consumption and costs. High-strength steels and aluminium alloys are suitable for achieving these aims. Recent car bodies contain both materials, therefore necessary to make reliable joints between them. The resistance spot welding (RSW) can be used for joining of car bodies and it is applicable for aluminium/steel hybrid joints, too. High cycle fatigue (HCF) test results can be rarely found in the literature while HCF loading basically determines the lifetime of hybrid joints. 5754-H22, 6082-T6, and DP600 base materials were used for similar and hybrid RSW joints and HCF tests were performed. Number of cycles to failure values, failure modes, furthermore brittle intermetallic compound (IMC) layers were studied and analysed. In both aluminium/steel hybrid joints, the HCF test results showed better endurance limit like concerning aluminium/aluminium similar joints, but worse than steel/steel joints. For 5754-H22 alloy the endurance limit values are 648 N, 939 N, and 1285.5 N, for similar aluminium, hybrid, and similar steel joints, respectively. For 6082-T6 alloy these values are 513 N, 625.5 N, and 1285.5 N, respectively. In case of similar joints only base material fracture happens, but hybrid joint specimens show different failure modes. Base material fracture and shearing after partial base material fracture were typical failure modes in case of 5754-H22/DP600 and 6082-T6/DP600 hybrid joints, respectively. The full and partial plugging as a failure modes appeared for hybrid joints, too. The IMC layer characteristics showed opposite results in cases of hybrid joints, both the layer thicknesses of the shared and plugged joints and the thickness differences between the inner and outer parts of the joints were different.

Laser weld quality: it's in the process!

AbstractLaser‐welded seams are state‐of‐the‐art in car body construction, where the strength of a weld seam is the most important criterion – but hardly detectable from the outside. The latest technology for inline process monitoring enables reliable and effective quality monitoring. It combines robot‐assisted welding and inline quality control.

Researching the influence of various factors on the superficial layer materials used in car body construction and protection

To carry out the restoration of the car body, in addition to modern equipment for body repair and painting, it is necessary the use of high-quality consumables for body repair and painting, which are selected for each brand of car, strict following the technology of repair car body, painting work and qualified specialists in body repair and painting, as well as knowledge of the factors affecting the degradation and condition of the body and its elements to improve the quality of final results. In average value, the thickness of the protective layer varies from manufacturer to manufacturer in the range of values 80-170 \\im. The use of different materials for the manufacture of vehicle components and materials for protection against external factors of the body is a major interest for the vehicle industry and is the subject of this article.

Modelling of the temperature distribution of spot-weldable composite/metal joints

Resistance spot welding is the most economical joining method for the production of automotive steel bodies. In modern car body construction, however, its future applicability is limited due to the growing mix of materials in multi-material design. In response to increasing weight reduction requirements to protect the environment and natural resources, lightweight materials, and fibre-reinforced plastics (FRP) in particular, are more and more used in modern vehicle bodies. To facilitate the future joining of FRP/steel structures with resistance spot welding, spot-weldable force-introduction elements may be embedded in the laminate as a joining interface. When welding the so-called inserts, thermal damage to the surrounding polymer should be avoided, as this is the only way to calculate the strength of the joint correctly. For this purpose, the paper presents a numerical model that allows the prediction of the temperature propagation during spot welding of FRP/steel joints with embedded inserts. The simulative approach is subsequently validated by comparison with experimentally determined temperature curves and in doing so, an excellent model prediction can be noted.

Compensating the springback of ultra-high-strength steel parts by specific stress superposition during sheet metal forming

Ultra-high-strength steel sheets offer considerable advantages in car body construction regarding the permanent requirements for vehicle weight reduction as well as the increase in crashworthiness of sheet metal parts. However, when forming such sheet metal materials, the main problem relates to their distinctive springback behaviour, which occurs after the formed part has been released. This paper shows a methodology for springback compensation based on the superposition of stresses acting in the meridian direction of the formed sheet metal part. These stress superposition effects are induced via the tool radii by alternating blank draw-in during deep drawing. As a result, the workpiece areas contacting the punch radii during the deep drawing process are subjected to repeated bending and unbending. In order to analyse occurring stress superposition effects and their influence on springback appearance, simulation was performed using the FE-code LS-Dyna. Furthermore, an optimal blank draw-in kinematic could be defined using the forming simulation, which significantly reduced springback of a double-curved hat-shaped component made of DP 980 steel sheet after forming. Finally, this numerically determined methodology for springback compensation has been experimentally proved using tool that enables alternating blank draw-in during sheet metal forming.

PERANCANGAN DAN ANALISIS CARBODY LOKOMOTIF DENGAN METODE ELEMEN HINGGA

A locomotive is one of critical part in train set, because a locomotive had to bear a big load and has operational time which long enough. So in a locomotive design required more in depth analysis compared to the other means of transportation. The purpose of this research is to make a design locomotive carbody according to those standards applied and analyze stress happened to carbody locomotive designed. In the design of this to analyze carbody locomotive construction strength, the analysis are done using finite element methode(FEM) with help of Ansys software. The simulation of loads working on the structure was made approaching the real loading. Structure of locomotive carbody should be able to hold the loads working on carbody construction. From the design results locomotive carbody that have been made, this locomotive carbody sized length 19000 mm, width 2790 mm, and high 3700 mm. Materials that used for the locomotive carbody design isSS 400 and SM 490A with Yield stress of 245 MPa dan 325 MPa. The analysis results received a value of von mises stress maximum of 195,429 MPa that occurs at the part of the end of underframe (end center sill), where the sress value are still below of Yield stress materials which are in the form of SM 490 at 325 MPa. From the analysis result suggests that overall locomotive carbody structure can be expressed as safe and able to hold the loads operational.

Spot weld bonding − process behavior of three-sheet steel stack‑ups and analysis strategies with online measuring methods

Due to the increased demands for reducing CO2emissions, improving fuel efficiency of modern vehicles has been continuously monitored. The body of a typical compact car design has a weight share of approx. 40%. In addition to increasing torsional stiffness and crash safety of the body, the aim is also to reduce the overall weight at the same time. In order to achieve these individual requirements, the use of three-sheet steel stack-ups with adhesive applications for car body construction is one of the current strategies used in automobile manufacturing. Adhesive applications lead to a change in process behavior of resistance spot welding. The effective weldability lobe is reduced and an adjusted preheat current is necessary to reconstitute the weldability of a component. Depending on squeeze time and electrode force the adhesive will be displaced. For an asymmetric sheet stack-up, the electrical resistance for every faying surface is highly differentiated. During welding, a specific characteristic of the electrical resistance is created for each individual material combination. These characteristics can be analyzed by using an online measurement device. In this manuscript, different sheet stack-ups are examined with regard to their weldability lobes and their process behavior. The individual three-sheet steel stack-ups used are made of low carbon steel (DX51), HSLA-steel (HX340) and UHS-steel (22MnB5). The corresponding characteristics of electrical resistance will be recorded by using an online measurement device. In addition, the process of adhesive displacement during the squeeze time and the initial welding current are discussed on the basis of the electrical energy generated in the component to be welded. The obtained results contribute to a direct verification of the welding process and an automatic detection of possible imperfect welds.

Functional optimization of hot-stamped components by local carburization

One of the major challenges in modern car body construction is the reduction of component weight while still maintaining passenger safety. In terms of these requirements, the substitution of conventional steel grades by ultra-high strength materials is the most promising approach. Hot stamping of these steels has developed to a state of the art process for manufacturing safety-relevant car body parts such as B-pillars or front bumpers. By locally adjusting the mechanical properties, for example, increasing the ductility, passive safety can be further improved. For this purpose, the hot stamping process is adapted in different ways. Varying from these established methods, tailored carburization is an alternative approach for manufacturing functional optimized components by combining hot stamping with prior local carburization. Within this work, the potential of local carburization is analyzed by a fundamental investigation of the influence of the process parameters on the mechanical properties as well as the transition zones between carburized and non-carburized areas. Besides the mechanical properties, the heat transfer between carburized sheets and tools is studied. The process suitability is validated by a demonstrator.

Friction Stir Spot Welding with Additional Bonding of Thick Sheet Aluminum Joints

The high-strength aluminum alloys offer great potential for realizing lightweight constructions in car body construction. However, the use of aluminum alloys increases the overall thickness of the material, which poses new challenges for potential joining processes. This paper examines a process combination of friction stir spot welding (FSSW) and bonding for 4 mm EN AW 6082-T6 sheets. For the investigations, adhesive or glass beads were applied between the joining components and then the sheets were welded using FSSW. The analysis shows that the adhesive and the glass beads have a very small influence on the joint formation. The use of glass beads in FSSW with bonding is recommended because less adhesive is displaced from the joint area, which increases the joint strength. The target of obtaining high weld spot strengths without strength-reducing adhesive burn-off could not be achieved because a certain residence time is necessary to form a weld spot with high strength at this sheet thickness in order to sufficiently plasticize the material. Adhesive burn-up cannot be completely avoided. For this reason, it is necessary to weigh up which characteristics are required for the specific application and adjust the welding parameters accordingly.

Numerical simulation of high-speed joining of sheet metal structures

Abstract The increasing trend of multi-material and space-frame design in automotive car body constructions consolidates the need for mechanical joining technologies with one-sided accessibility. The high-speed joining process (also called “RIVTAC®” or “Impact”) is an innovative and flexible technology. In this process, a tack having a profiled shank and an ogival shaped tip is pushed into the joining partners with a speed of 20 to 40 m/s without any pre-punching. The plastic and friction work is converted into heat, which causes an abrupt rise of temperature in the joining zone. This improves the flowability of the material which leads to filling the annular grooves existing on the shank of the tack. Simultaneously, a force-fit is created between the sheet metal and the tack. Furthermore, the effects of inertia are used so that the thin-walled structures can be joined without any additional tools (e.g. a die). The joining process causes the deformation of the structure, which must be taken into account with regard to tolerances. The numerical simulation is a powerful tool to predict the deformation and the joinability of a complex structure as well as the mechanical properties of the connection. The paper is about the detailed process- and load-simulation of high-speed joining as well as the required experimental data basis, such as temperature and strain rate dependent flow curves. Furthermore, the friction parameters are very important for the physical consideration of the force-fit connection. Coupled structural-thermal simulations of an axisymmetric 2D-model are performed using explicit and implicit codes.

Increasing flexibility of self-pierce riveting using numerical and statistical methods

Abstract Self-pierce riveting with semi-tubular rivets (SPR-ST) is currently the most important joining technology for modern mixed-material car body constructions. In these body designs a multitude of material and thickness combinations occurs and for many of these combinations individual parameters of the SPR-ST process like the rivet length and die geometry have to be determined. This paper shows an approach to increase the flexibility of the SPR-ST process by the determination of the process parameters using FEM simulations in combination with statistical methods. In the described investigations one parameter set is derived for the SPR-ST process from seven different material combinations with steel and aluminum materials. For each material combination a simulation model is validated by the comparison of the joint geometry and force-stroke diagram from the experimental reference joints with the results from the process simulation. On the basis of the validated simulation models, numerical sensitivity analyses are carried out for each material combination to investigate the correlations between the process parameters die geometry and rivet length with important quality characteristics of the joint like interlock, minimal thickness of the die-sided sheet and joining force. With the knowledge of these studies computed process optimizations are carried out, in order to define one die geometry to join all seven material combinations in good quality, so a tool changing is no longer required. The reduction from seven to only one optimized SPR-ST tool saves costs as well as processing time and production space.

Stress-strain state analysis of the leading car body of DPKr-2 diesel train under action of design and operational loads

Purpose.Provision of strength and durability of the main structural element of DPKr-2 diesel train -the leading car body. Methodology. A spatial solid-state 3-D model of the body is built and durability calculations are carried out concerning action of loads stipulated by regulatory documents operating in Ukraine. In particular, the following main estimated modes are considered: mode 1 – a notional safety mode which takes into account the possibility of considerable longitudinal forces arising during shunting movements, transportation and accidental collision; mode 2 – an operational mode which takes into account forces acting on a train during acceleration to constructional speed, coasting or braking from this speed while passing a curve. Results. Based on the results of theoretical and experimental studies a conclusion has been made that the leading car body construction of DPKr-2 diesel train meets the requirements of regulatory documents regarding strength and durability. Practical relevance. A complex of calculation and experimental work concerning assessment of stress-strain state of the leading car body of DPKr-2 diesel train under action of design and operational loads allowed the creation of construction which meets not only operational requirements but also strength and durability ones.

Modelling and Characterisation of a Servo Self-Piercing Riveting (SPR) System

SPR is a cold mechanical joining process in which multiple sheets of material are riveted together without the need for a predrilled hole. It works by pushing a typically semi-tubular rivet into a target stack of material, during which the plastic deformation of the material and rivet are such that a mechanical lock is formed within the material stack. The process is used extensively in the automotive industry in car body construction, and is a competing technology to more established joining techniques such as resistance spot welding. As part of the ongoing development of the technique, there is a strong need to understand and simulate the dynamics of the process. In this work, a lumped parameter model of the SPR system with a non-parametric model of the joint is presented. Simulated results are compared with experimental data for a given joint configuration. Furthermore, the model is used to highlight the significance of the compliances within the system. It is shown that during rivet insertion, the stiffness of the C-frame structure is an influential factor in determining the dynamic response of the system. The results provide the basis for a more comprehensive sensitivity analysis into the factors which affect the quality of the resulting joint.

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.

High strength aluminum alloys in car manufacturing

In recent decades, there are many requirements stated against car manufacturing both from the customers’ side and also as legal requirements to reduce harmful emissions to provide increased environment protection, as well as to achieve increased safety, higher comfort and more economical vehicles. To meet these often contradictory requirements, application of light weight design principles is one of the most widely applied solutions. There are two main trends for producing lightweight automotive structures with low cost manufacturing which are particularly valid for car body elements produced by sheet metal forming. Application of high strength steels is one of the main possibilities. Various generations of high strength steels (e.g. DP-steels, TRIP steels, XHSS and UHSS advanced high strength steels) were developed in the last decades which are already successfully applied in the automotive industry. The application of lightweight alloy materials – particularly various aluminum alloys – is regarded as the other possible solution to meet the requirements of lightweight car body constructions. Aluminum has even higher weight reduction potential than steel materials, but aluminium has lower formability than steel; replacing steel with lighter materials such as aluminum can be costly and is not simply straightforward. Aluminum sheet, in particular, has lower formability at room temperature than typical sheet steels. This is one of the main reasons that recently the hot forming of aluminum alloys came to the forefront of research activities. In this paper, some recent results obtained within a joint European project entitled Low Cost Materials Processing Technologies for Mass Production of Lightweight Vehicles will be introduced.

Joining methods in car body construction

Growing requirements from customers for quality and safety, also strictive emissions limits caused for automobile manufacturers researching for new solutions and materials. The development of the automotive market is associated with the enrichment of societies and, consequently, increased demands. Modern production systems meet needs of corporations. However, automation and robotization of traditional production methods or assembly are not always sufficient [4]. In order to improve the quality of products and reduce costs at the same time, it is very important to carefully analyze each stage of production. The key step in designing a new car model to enter the market is choosing the right method to join the elements into a whole body. The random car body consists of 4,000 spot welds, 13 meters of welds, 90 meters of glue [9]. Most of the car body elements are sheet metal with a thickness of less than three millimeters. The aim of the study to present various methods of joining car body parts and to compare their strength in an analytical way and using the finite element method. Particular attention has been given to the clinching, which becomes a cheaper and more flexible alternative to resistance spot welding.

Numerical Investigation of the Tool Load in Joining by Forming of Dissimilar Materials Using Shear-Clinching Technology

Modern developments in the automotive sector are motivated by the objective of lowering the emission of pollutants. In contrast, growing demands for safety and comfort lead to a potential increase of the weight of vehicles. Thus, the consequent use of lightweight design is indispensable. This includes the use of different materials for the construction of car bodies. Because of various material properties, joining of dissimilar materials is challenging and requires often the application of non-thermic processes like riveting or clinching. These processes are limited by the mechanical properties of the joining partners. Especially the increasing use of ultra-high strength alloys, like the hot stamped steel 22MnB5, makes the development of new joining technologies necessary. One of these innovative technologies is shear-clinching. By combining shear-cutting and clinching in one process, this technology produces durable and tight connections of dissimilar materials with high differences regarding strength and formability. In contrast to shear-cutting the die-sided material has no contact with the punch. Since the process of shear-clinching is a combination of cutting and joining using the same tool, the tool loads differ from common shear-cutting. Especially cutting hot stamped steels is a challenge due to their high ultimate strength which leads to high tool loads. Thus, the analysis of the load condition is essential for the dimensioning of durable and wear resistant tools. Hence, the scope of this paper is a numerical investigation of the tool loads during the indirect cutting process and the subsequent step of joining by forming during shear-clinching. Since an experimental investigation of the occurring tool loads in the closed process is not practicable, the finite element method has to be used. Therefore, a damage-based numerical model is set up to enable the coupled simulation of the combined cutting and joining process and the resulting tool loads. This allows the analysis of the loads during the whole process, identifying the influences of materials and sheet thicknesses.