Car Body Parts Research Articles

Friction Stir Welding between 6082 and 7075 Aluminum Alloys Thermal Treated for Automotive Applications

The automotive industry demands ecofriendly manufacturing processes and lightweight structures and materials to reduce CO2 emissions and decrease weight and fuel consumption while optimizing overall performance. Aluminum alloys in the 7xxx and 6xxx series offer high potential for weight reduction in automotive and other transportation industries. 7xxx aluminum alloys have the best strength performance among all commercial aluminum alloys. Alloys in the 6xxx series generally have medium-to-high strength, high corrosion resistance, and good formability. Alloys in both the 7xxx and 6xxx series are strengthened by heat treatment. The increased strength-to-weight ratio and the thermal treatment processing open the possibility to use these alloys as possible alternative materials instead of steel in the automotive industry for the fabrication of car body parts. However, their poor formability and weldability are the main drawbacks when these alloys are considered as substitutes of steel and other dissimilar joints during the fabrication of car body parts and the production chain. Recently, Hot Forming and in-die Quenching (HFQ), a patented hot stamping process, has been introduced to manufacture complex-shaped high-strength heat-treatable aluminum alloys. The work described in this article is an experimental investigation of the weldability between AA6082 and AA7075 by Friction Stir Welding (FSW) that considers thermal treatments used during HFQ for automotive applications. The aforementioned FSW base metals, 6082 and 7075, are heat treated according to the solution heat treatment adopted during HFQ to evaluate the effect of the HFQ thermal cycle on the quality of the produced joints. Optical microscopy has been used to characterize the microstructure of the produced joints. The defect-free welded joints are characterized by good mechanical mixing between the joined materials as well as by grain refinement. The mechanical behavior of the produced welded joints was studied and compared with the parent materials, whereas the measured mechanical properties are correlated with the microstructure.

곡면 병합을 이용한 금형 수정 가공의 단차 최소화

Die and mold are the most effective method for manufacturing parts. After a die or mold is used for a long time, it can be deformed or worn down or partly damaged. For the cases, it is welded with additional materials to be machined in repairing area with the original NC data for initial machining. However, this repairing process may cause microdrops at the boundary of repair machining area, since the used die might be deformed due to various reasons including residual stress or heat stress by welding, in addition to the error from the setup for the repair machining. This study is to develop a method to generate adapted NC data for repairing a deformed die, which can reduce the microdrops at the border of repair machining area. As a result, it cannot only negate or minimize the time and cost for removing the microdrops on repaired die surface but also can improve quality of the final products. Even though the proposed method was applied to dies for car body parts, it is not limited to the auto industry but can be extended to the other die and mold industries.

Flexible Hot Rolling of Extruded Shapes of Aluminum Alloy EN AW-6082

One of the strategies employed to lower weight and to decrease material consumption is reducing part thickness itself. Thus, functionally graded materials in which structural reinforcement is adjusted locally, are of great interest. With regard to conventional industrial processes, such as extrusion or flexible cold rolling, thickness variations can only be achieved either longitudinally or through the cross-section of the semi-finished products. Hence, a combined thickness variation (along both axes) is difficult to generate solely by extrusion or rolling. A simultaneous thickness variation in both directions, however, would enable further weight savings in structural components such as car body parts. In this study, a promising approach with extruded shapes, serving as a billet for a flexible hot rolling process, is elaborated upon. By employing the described process modification, shapes with simultaneous thickness variations in longitudinal as well as in transverse direction are feasible. Initial numerical analysis reveals the weight-saving potential of using these semi-finished products for structural parts in a car body. A demonstration of the production process for the semi-finished parts and the occurring challenges are discussed. To verify and adjust the new technology, a numerical model of the flexible hot rolling process has been created based on the finite element software QForm VX. This model is also employed for tool design optimization to produce semi-finished components with the required geometrical quality. Finally, the results of hot rolling experiments conducted using the adjusted roll design are presented.

An attempt to detect anomalies in CT-data of car body parts using machine learning algorithms

Industries, which produce hundreds of terabyte of CT data per year, demand automated evaluation approaches. This work provides a first glance of an attempt to automatically detect and characterize possible defects and/or anomalies which formed during common joining processes. We investigated a standard riveting process with respect to the resulting final head height of steel selfpiercing half-hollow rivets. The methods include conventional image processing algorithms, like edge-detection, thresholding and principle component analysis (PCA) which were used to pre-process the CT data. In order to automatically evaluate the reconstructed volumes, which contained several of the aforementioned rivets, we compared the performance of different, publicly available, convolutional neural network (CNN) architectures. Furthermore, we investigated the impact of data augmentation and showed by means of a k-fold cross-validation that the training data causes no overfitting of the network. The obtained results suggest that an automated evaluation of the generated computed tomography scans, with regard to a rivet’s final head height, is feasible. However, in order to increase the network’s reliability and accuracy, the amount of training data needs to be further enlarged and diversified.

Hybrid laser arc welding of dissimilar TWIP and DP high strength steel weld

High manganese TWIP steels have a remarkable potential to produce impact resistant car body parts in the automotive industry. Hybrid laser arc welding (HLAW), i.e. simultaneous action of an arc and laser source, can be regarded as the most promising joining technique for such components due to, among other factors, the possibility to use filler metals to avoid improper microstructures and Mn chemical segregations in dissimilar welds of TWIP with other steel grades. In this regard, this work studies the influence of the main welding settings during HLAW of 1.4 mm thick TWIP and Dual Phase (DP) steel sheets used in the automotive industry, which were joined with the use of an austenitic steel filler. Quality of TWIP-DP welds was investigated based on welding parameters, tensile and hardness properties, and microstructures.TWIP and DP steel sheets can be properly joined with a linear heat input in the 50–75 kJ/m range. Welded samples exhibit an average tensile strength and elongation at fracture roughly of 650 MPa and 13%, respectively. These values are similar to those of DP steel, but significantly lower than TWIP steel. The tensile welded samples failed within the heat affected zone of DP steel, being weldments and TWIP steel more resistant. This work confirms that HLAW can be considered a promising solution to join vehicle components made of TWIP and DP sheets when fillers are needed.

A Recurrent Neural Network Architecture for Failure Prediction in Deep Drawing Sensory Time Series Data

In the course of the fourth industrial revolution and the coherent phenomenon of industrial big data, production lines and, more specifically, single production processes are complemented by sensor systems to facilitate the acquisition of sensory data on the shop floor level, providing a number of possibilities for data driven optimization applications. One possible application is to support manual quality control at the end of a production line by an automated quality control system based on data driven predictive analysis of the acquired shop floor data. In this paper, we demonstrate the application of such a predictive quality system for a deep drawing manufacturing process of car body parts. As a first step, we formalized the experience and expertise of the domain experts to enable automated a-posteriori quality assessment of the deep drawing process data. As a second step, we trained a combination of two long short-term memory neural networks with the auto-labeled data to predict the occurrence of process failures, i.e. cracks within the manufactured car body part, enabling automated a-priori quality assessment of the deep drawing process. We show that our model correctly predicts the occurrence of more than 94% of the process failures, facilitating the possibility to react to failures pre-emptively before they actually occur. We argue that our approach can be transferred to many other production processes whose quality control can be supported by the acquisition of time series data from the involved production machines.

Automatic bead position calculation for hem flange bonding

Abstract This article deals with improving the planning of hem flange bonding in the car body manufacturing process. Particularly during the ramp-up of the plant, great effort is put into ensuring that the generated adhesive bond meets the quality requirements. Here, several challenges occur in parallel. This ranges from the specific adhesive design, a result of multi-dimensional and individually curved car body parts, to the multi-stage process chain, where the associated manufacturing equipment is complex. This intricacy is countered by a discrete analysis of the adhesive continuum. Based on an established method, the location where the adhesive must be applied is computed under consideration of contiguous contours, disturbance variables and applicability by the projected dispensing system. For this reason the performance of the involved machines is examined. The results of this new method comprise a robot path along which an application system is guided, and control commands for the latter. Finally, a validation proves that this way, the adhesive application can be designed in a shorter period of time and in high quality at an early stage of plant design.

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.

Investigation of the tribological behavior of car body parts in series production

Abstract The tribological behavior in the series production of car body parts plays a key role for part quality. However, there are still unresolved issues concerning the tribological system. Fluctuating material properties as well as further influencing variables have an impact on the friction behavior during the forming process and therefore influence on the material flow. A rather new method reveals the potential of material flow measurement on numerous formed parts, which is used for investigations of the tribological system. In this work a method of investigating the tribological system is presented, using a part-specific data acquisition system, which has been developed in context of a digitalization project to gather detailed information on the entire production process. This method includes several inline-measurement systems for recording material properties as well as a camera-based system for measuring material flow. Hence, this method provides an opportunity to analyze the friction behavior in series production. In this contribution the setup of a camera-based system is described and the first results of successful material flow measurements are provided. Furthermore, the material properties and process factors are contrasted with the measurement results of the material flow to analyze the interrelationship. The investigations have shown the functionality of the method, which can therefore be used for further investigations and a specific process adaptation.

Potentials of single stage induction heating for press hardening of steel blanks

Due to growing challenges regarding crash-performance, CO2 emission as well as increasing demand for lightweight construction, hot metal forming of car body parts has risen to one of the most important technologies for saving weight of a car body. During hot forming shaped blanks of steel are heated and austenitized at around 950°C and subsequently quenched for martensitic formation. Currently the heating is realized in roller hearth furnaces which allow only a slow heating and, therefore, a limited production rate. Induction heating of the blanks offers a big potential to increase the production rate dramatically and also to improve the energy efficiency. Only due to the fact, that the heated blanks typically are already pre-shaped with holes and cut-outs induction heating becomes a very complex task. The paper compares different possible induction heating methods (longitudinal heating, transverse flux heating, single stage induction heating, hybrid heating by induction and conventional heating). For the case of single stage induction heating a detailed numerical and experimental investigation in the frame of a recently completed research project is presented.

Mass production-line and process route to enable the use of high strength aluminium alloy materials in car body engineering

Hot stamping of sheet metal materials provides advantages such as application for mass production lines and net shape manufacturing at economical cost. Recent regulations by governments world-wide on environment, emission controls and safety determine the need to provide complete lightweight solutions in the transport industry particularly for the automotive sector. These regulations are influencing multi-material-design concepts in automotive body engineering and the use of high strength aluminium alloy materials: 6xxx and 7xxx series in the development of electric and non-electric vehicles. The use of high strength aluminium alloy materials to manufacture car body parts is increasing in the lightweight solutions mainly due to weight-strength ratio advantage. Due to different material behaviours such as formability and strengthening mechanism, compared with high strength steel alloys, an industrial proven redefined hot forming process route, HForm™ will be needed to ensure high productivity and return on investment in the manufacture of parts using the aluminium alloys sheets. The produced parts will also satisfy functional requirements in the automotive industry such as surface quality, tight tolerances, strength, crashworthiness, corrosion resistance as well as ease-to join in the body-in-white (BiW) structure and e-coat. However to implement the HForm™ process and manufacture functional automotive body parts requires dedicated furnace for aluminium alloy materials, intermediate cooling station, handling/transport systems, a servo hydraulic press, and coated dies with integrated lubricant metering system. Presented in this paper is a complete solution to enable paradigm-shift in the car body engineering.

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.

Galvanic Corrosion between AA5052 Aluminum-Magnesium Alloy and SS400 Carbon Steel in Aqueous NaCl Solutions

Aluminum alloys (AAs) such as 5000 and 6000 series have relatively good corrosion resistance and plastic workability. The use of these alloys for automobile body parts have been increased significantly because of reducing the weight of the body and improvement of fuel consumption. Although aluminum alloys themselves have relatively good corrosion resistance in atmospheric environments, galvanic corrosion between aluminum alloys and other materials should be taken into consideration in automotive application. This is because the body parts made of Al alloys should be jointed with other materials such as steel parts by welding or other methods and because the jointed parts can be exposed to atmospheric corrosion environments. In this study, galvanic corrosion between AA5052 aluminum-magnesium alloy and SS400 carbon steel is investigated in aqueous NaCl solutions. A galvanic couple used in this study was made of AA5052 Al-Mg alloy (Mg: 2.65, Si: 0. 08, Fe: 0.27, Cu: 0.01, Cr: 0.17, Zn: 0.01, Al: bal. (mass%)) and carbon steel (JIS SS400). The plate of both materials was 10-mm width and 15-mm length and 3-mm thickness. After lead wire was connected on the surface of the plates, they were embedded in an epoxy resin. At this time, both materials were separated with a 500-um gap. The surface of the galvanic couple was polished with SiC papers up to JIS 2000 grit and rinsed in EtOH. Galvanic corrosion experiments were performed for 2 hours in aqueous NaCl solutions at various concentrations ranging from 5 mM to 500 mM. Galvanic current and corrosion potential of the couple were measured during the immersion in the solutions. Corrosion potentials measured during the immersion in various concentrations of NaCl were almost constant for 2 h. The corrosion potentials changed in the less noble direction with increasing NaCl concentrations. Galvanic currents between AA5052 and SS400 showed positive values during the immersion in the solutions, indicating that aluminum-alloy side was basically an anode. However, the galvanic currents were almost the same independent of NaCl concentrations. From the results of polarization behaviors for AA5052 and SS400, a significant anodic current increase due to the propagation of localized corrosion on aluminum alloy and a diffusion-limiting current for the reduction of dissolved oxygen on steel were observed at the corrosion potentials of the galvanic corrosion tests. These results indicated that galvanic corrosion between AA5052 and SS400 in the early stage of immersion progressed under a diffusion-limiting condition for the reduction of dissolved oxygen on steel.

Numerical Prediction of Forming Car Body Parts with Emphasis on Springback

Numerical simulation is an important tool which can be used for designing parts and production processes. Springback prediction, with the use of numerical simulation, is essential for the reduction of tool try-outs through the design of the forming tools with die compensation, therefore, increasing the dimensional accuracy of stamped parts and reducing manufacturing costs. In this work, numerical simulation was used for performing the springback analysis of car body stamping made of aluminium alloy AA6451-T4. The finite element analysis (FEM) based software PAM-STAMP 2G was used for performing the forming and springback simulations. These predictions were conducted with various combinations of material models to achieve accurate springback prediction results. Six types of yield functions (Barlat89, Barlat2000, Vegter-Lite, Hill90, Hill48 isotropic, and Hill48 orthotropic) were used in combination with the Voce hardening model. Springback analysis was conducted in three sections of the formed part; the numerical results were compared with the experimental values. It was found that the combinations of Barlat’s yield functions and the Voce hardening law were most accurate in terms of springback prediction. Additionally, it was found that the phenomena that were investigated, which are required for the determination of the kinematic hardening model, such as the change of Young’s modulus E, the transient behaviour, work-hardening stagnation, and permanent softening, were not observed in the aluminium alloy studied.

Finite element simulation and Experimental verification of Incremental Sheet metal Forming

Incremental sheet metal forming is now a proven manufacturing technique that can be employed to obtain application specific, customized, symmetric or asymmetric shapes that are required by automobile or biomedical industries for specific purposes like car body parts, dental implants or knee implants. Finite element simulation of metal forming process is being performed successfully using explicit dynamics analysis of commercial FE software. The simulation is mainly useful in optimization of the process as well design of the final product.This paper focuses on simulating the incremental sheet metal forming process in ABAQUS, and validating the results using experimental methods. The shapes generated for testing are of trapezoid, dome and elliptical shapes whose G codes are written and fed into the CNC milling machine with an attached forming tool with a hemispherical bottom. The same pre-generated coordinates are used to simulate a similar machining conditions in ABAQUS and the tool forces, stresses and strains in the workpiece while machining are obtained as the output data. The forces experimentally were recorded using a dynamometer. The experimental and simulated results were then compared and thus conclusions were drawn.

Smart Process Combination for Aluminum/Plastic Hybrid Components

The research on lightweight construction increasingly gains in importance, especially for the automotive industry. New lightweight components ensure the necessary stability of car body parts on the one hand. On the other hand they are supposed to allow a low priced production. Hence, aluminum or magnesium alloys have quite a large share in production engineering. During the last years, research mainly addressed metal/plastic compounds. Weight reduction as well as the capability of producing complex structures are only some of the benefits of this technology. Furthermore, additional functionality can be integrated or functional tasks can be distributed: The metal ensures stiffness and realizes the technical connection to the car body by means of welding, while the plastic enables the insertion of special elements for the joining or assembly process. This paper presents two approaches of realizing a combined process to produce aluminum/plastic-hybrid structures. In a first approach, an active tool is presented to realize the sheet based process. The second approach focusses on the tube-based process and presents the topical state of research within the Federal Cluster of Excellence EXC 1075 “Merge Technologies for Multifunctional Lightweight Structures”.

WITHDRAWN: Mechanical Strength Behaviour of Silane treated E-glass Fibre, Al-6061 and SS-304 Wire Mesh Reinforced Epoxy resin Hybrid Composites

Abstract In this research work the mechanical strength behaviour of silane treated e-glass fibre, Aluminium 6061 and stainless steel 304 metal wire mesh reinforced epoxy resin Hybrid composites were analyzed. The principal objective of this research work is to unveil the importance of silane treatment on metal surface in adhesion and delamination resistance in composites. The reinforcements were acid etched then silanated by 3-Aminopropyletrimethoxylane via aqueous solution method. The mechanical properties were found increase for surface modified reinforcements rather than as-received reinforcement epoxy composites. Maximum tensile strength, flexural strength and Izod impact energy of 134 MPa, 241 MPa and 5.4 J were observed for composite consist of surface modified SS-304 wire mesh and e-glass fibre. The surface treated SS-304 steel mesh reinforced epoxy composite gives ¾ of penetration depth from the impacting side while the other composites gives maximum penetration. Scanning electron microscopy results revealed the improved bonding of e-glass fibre and metal wire meshes with epoxy resin. These mechanically strengthened composites could be used as working material where sudden load prone zones are available. Similarly defence safety equipments, automobile body parts and construction devices manufacturing industries the requirements of these materials are highly welcome one.

Fracture toughness of structural adhesives for the automotive industry

Adhesive bonding is currently employed by automotive manufacturers to complement (or replace) welding in joining dissimilar materials. In order to reduce the impact on the existing manufacturing infrastructures, structural adhesives are deployed in the body shop but hardening is accomplished in the paint cure oven. Various adhesive formulations have been specifically developed for the implementation in the automotive manufacturing chain. However, it is very important to assess the mechanical behaviour of the joints which results from the peculiar curing strategy. In the present work, automotive grade single component epoxy and two component epoxy modified acrylic adhesives were evaluated. T-joints were fabricated using a cold rolled galvanized steel (FeP04) employed in the production of car body parts. The fracture toughness of the joints was determined using the test protocol proposed by the European Structural Integrity Society (ESIS). Optical microscopy was employed to ascertain the mechanisms of failure. The results indicated that both adhesives were able to provide a fairly good mechanical response with minimum preparation of the mating substrates. Moreover, the obtained values of fracture toughness were shown to be essentially independent of the adhesive layer thickness.

Theoretical and experimental investigation on deformation modes in cylindrical cup drawing with central pre-hole

Compound deformation always occurs in a sheet metal forming process, especially for manufacturing car body parts. In the present work, a theoretical analysis on cylindrical cup drawing with a central pre-hole are investigated based on slab method. The theoretical maximum radial stress in both pure deep drawing and pure hole flanging are chosen as compared factor. Five deformation modes named, pure deep drawing, deep drawing dominated mode, drawing-flanging compound mode, flanging dominated mode and pure hole flanging are divided according to their maximum radial stresses. Moreover, the theoretical results are verified by cylindrical cup drawing experiments.

Recycle-Friendly Aluminum Alloy Sheets for Automotive Applications Based on Hemming

Unavoidably, Fe impurities are mixed into Al alloys during recycling of aluminum automotive parts. High Fe content recycle-friendly aluminum alloy sheets (RASs) are discussed in terms of their applications to car body parts and closures. RASs have advantages, such as they are low cost and light weight, they require less energy to process, and they reduce emissions when used in vehicles. The hemming ability of RASs was investigated through various quenching rates and hot-rolling reduction rates. The hemming factor (HF) values of low Fe content samples (0.1 and 0.3 wt% Fe content) were 2 and 3. The hemming ability of samples with an Fe content of 0.5 wt% was unacceptable for applications to automotive outer closures (i.e., HF values of 4 and 5). The HF values changed from 3 to 5 for even higher Fe content samples (0.8 wt% Fe), depending on the quenching and hot-rolling reduction rates. Lower quenching (air quenching) and lower hot-rolling reduction rates (6-pass hot rolling) both improved the hemming ability of the high Fe content samples. A low-cost and recycle-friendly aluminum alloy automotive sheet from end-of-life vehicles is presented, and its hemming properties are characterized.