Investigation of Temperature Impact on Friction Conditions in Running Production of Automotive Body ComponentsBarlo, A; Sigvant, M; Pilthammar, J
doi: 10.1088/1757-899x/1307/1/012004pmid: N/A
During the running production of automotive body components drifts in the process window is seen causing problems with non-conforming parts. Up until now, these drifts have been counter-acted based on the knowledge and experience of the press line operators. This experience-based process control will however become more troublesome in the future as recycled material grades will undoubtedly present larger in-coil variations in material parameters and effect also the friction conditions from component to component.The following study will present two cases from production of the Volvo XC60. For the two cases, the initial simulations made for the components showed a safe part, but during running production failure occurred suspected to be due to temperature effects in the tribology system. The study will furthermore present updated simulations considering developing thermal effects to replicate the failures, as well as present both standard and thermal simulations of the adjustments made in production.
Investigation on the limp properties of formed foils for hydrogen applicationsWituschek, S; Römisch, D; Lechner, M; Merklein, M
doi: 10.1088/1757-899x/1307/1/012031pmid: N/A
The mass production of bipolar plates for electrolyzers and fuel cells is a central step towards the realization of efficient and cost-effective energy systems of the future. However, current production processes are reaching their limits and can hardly realize the quantities that will soon be demanded, nor can they scale up to the required volumes. Particularly for the handling of half-plates and bipolar plates, major challenges are to be expected, especially with regard to production rates. Existing handling systems have restricted scalability and precision. Therefore, new stacking technologies are necessary, which have to be adaptable to the mechanical properties of the components and maintain tight tolerances during stacking to ensure hydrogen sealing for safety and efficiency. An important property in the handling of the plates is their limpness, which is distinguished by instability of the components as well as plastic deformation at low forces and moments. Therefore, the limp behavior of the components must be analyzed. To investigate the limpness of foil components, a flowfield is first formed using a 1.4404 stainless steel foil with a sheet thickness of 0.075 mm. Subsequently, the workpieces are analyzed in terms of their limp properties by means of a 3-point bending test.
Holistic springback compensation procedureZimmermann, P; Birkert, A; Saup, P; Marner, F; Häussermann, M
doi: 10.1088/1757-899x/1307/1/012034pmid: N/A
The elastic springback during the manufacturing process of stamped car body components causes dimensional deviations. To compensate these deviations, the common approach is to modify the tool surfaces in the opposite direction of the deviations – this is called springback compensation. In the procedure of springback compensation various issues must be solved. To achieve the main goal of a dimensionally accurate part, it must be ensured that, on the one hand the distance normal to the sheet surface between the springback part and the target geometry is within a specified dimensional tolerance. On the other hand, it must be ensured that the surface areas and characteristic lengths of the springback part and that of the target geometry match as closely as possible. In the past, approaches/methods, such as the physical compensation method and the physical scaling approach, have been presented which can successfully counteract these problems. Furthermore, in a multi-stage process in subsequent operations a stable part position must be achieved and unwanted plastic deformations must be avoided during blankholder closing. Therefore, different compensation strategies have been presented, which can fulfil these requirements. However, in the publication of these methods, the problems were always considered individually. This paper shows how all the named requirements can be achieved by combining the individual methods in springback compensation.
Biaxial Tensile Testing of Cruciform Samples to Determine the Impact of Pre-Strain on the Forming Limit Diagram of Aluminum Alloy 5052 through Finite Element SimulationPawar, Shrutee Pradeep; Kumar, Pavan; Narasimhan, K.
doi: 10.1088/1757-899x/1307/1/012013pmid: N/A
The present work focuses on the effect of pre-strain on the forming limit curves (FLCs) of aluminium alloy 5052 sheet of 2.5 mm thickness using cruciform samples. To identify the effect of pre-strain on the FLC, the finite element simulations are performed on cruciform samples. The cruciform samples are deformed to a small level of pre-strain in different strain paths. Thereafter, the further deformation under the various strain paths to measure the effect of pre-strain on the forming limits are carried out. Pre-strain in uniaxial, plane strain and biaxial loading conditions are considered in this work. For each case, i.e., uniaxial, plane strain and biaxial conditions two pre-strain conditions are considered. The cruciform samples are carefully thinned in the central region to promote development of large plastic strains there and eventually to neck and fail. The output obtained through simulations are presented in terms of forming limit curves for various strain paths.
Investigation on effect of high-efficiency solid solution and hot stamping process on microstructure evolution and mechanical properties of high-strength aluminum alloyWang, Y.L.; Geng, H.C.; Zhu, B.; Zhang, Y.S.; Ren, X.Q.; Ren, X.P.
doi: 10.1088/1757-899x/1307/1/012049pmid: N/A
Aluminum alloy has become an important lightweight material in the automotive industry due to its excellent performance. The development of hot stamping technology has effectively promoted the application of high-strength aluminum alloys in auto parts. However, aluminum alloy hot stamping requires a long time for solid solution and aging heat treatment, which hinders its mass production application in the existing mature hot stamping production line. Therefore, this paper studies the effect of a high-efficiency solid solution and hot stamping process on the microstructure and mechanical property strengthening mechanism of high-strength aluminum alloy. The contact heating and hot stamping experiment device was designed. It was found that the temperature rise rate of the sheet during the contact heating process could reach 44.51 °C/s. The experiment results show that contact heating treatment with a solution temperature of 480 °C and a solution time of 20s can achieve the high-efficient solution treatment of the sheet metal. The high-temperature deformation behavior of 7075-T6 at different temperatures (300-450 °C) and different strain rates (0.01∼1/s) under the condition of high-efficiency solid solution rapid heating was studied.
Study on electric pulse effect on steel DP780 during roll formingYu, Zhichao; Chen, Jiahui; Li, Han; Zhou, Jie; Pan, Libo
doi: 10.1088/1757-899x/1307/1/012050pmid: N/A
The electrophysical impact on metals introduces a novel optimization avenue for roll forming. This study explores the influence of different electric pulse parameters (peak current and frequency) on the roll forming behavior of DP780 high-strength steel. Through electric pulse-assisted tensile, bending, and roll forming experiments, coupled with microstructure and fracture morphology analyses, the study comprehensively assesses the impact of electric pulses on the mechanical properties and springback mechanism of DP780 sheets. Results indicate that electric pulses reduce deformation resistance and enhance the plasticity of DP780 sheets by repairing defects, promoting dislocation slip, and changing the fracture form of the material. Moreover, electric pulses effectively inhibit springback in roll forming, particularly at larger bending angles and under specific E-pulsing parameters. This is attributed to the promotion of residual stress release by electric pulses, leading to a reduction in springback. In conclusion, electric pulse assistance optimizes the roll forming process of DP780 high-strength steel, evidenced by decreased deformation resistance, improved material plasticity, and effective suppression of springback. These findings open up a new optimization pathway for sheet metal forming.
Tribological investigations of water-based lubricants for application in the deep drawing processBehrens, B-A; Hübner, S; Wehmeyer, J; Müller, P.; Yarcu, S
doi: 10.1088/1757-899x/1307/1/012001pmid: N/A
This paper describes the tribological investigation of water-based lubricants in the context of a deep drawing process. Therefore, different methods were conducted in order to determinate the suitability of these lubricants for a deep drawing process. Three lubricant manufacturers each provided their lubricants as part of this work. The sheet materials investigated are an aluminum material (AA6014) and two steel materials (DC04, DP800), each with a thickness of 1.5 mm. All sheet materials were examined in the as-delivered condition as part of this work. The hypothesis for this research proposal is that it is possible to achieve comparable tribological properties in sheet metal forming using water-based lubricants as when using mineral oil-based lubricants. The aim is to optimize a tribological system for water-based lubricants when used as additional lubrication in order to replace mineral oil-based lubricants and, as a result, to shorten the representative process chain by one process step (cleaning). In the course of this work, topographical measurements of the sheet materials were carried out in order to investigate the lubricant holding capacity of the sheet materials. Furthermore, strip drawing tests were performed to determine the friction coefficients of the different lubricant-sheet combinations. The final step was to conduct deep-drawing tests to determine the limits of use of the water-based lubricants by continuously increasing the holding-down force.
Influence of Hole Preparation Technique on Stretch Flangeability of Aluminium AlloysKumar, Vinay; Kumar, D Ravi
doi: 10.1088/1757-899x/1307/1/012044pmid: N/A
Application of aluminium alloys has increased for light-weighting the sheet metal parts in manufacturing of automobiles. Formability is important in sheet metal forming of aluminium alloys. In the assessment of formability of sheet metals, stretch flangeability or edge formability is an important aspect in application such as flanges or plunged rims. The stretch flangeability refers to the ability to avoid cracking during hole expansion and it is evaluated by performing the hole expansion test. Besides material properties, hole making process also influences the stretch flangeability of aluminium alloys. In this work, the stretch flangeability of two Al-Mg alloys has been investigated through hole expansion tests by using three different hole making techniques namely punching, water jet cutting and laser cutting. The stretch flangeability of aluminium alloys has been compared with that of a high strength steel (Dual phase steel of grade DP600) which is more commonly used steel for stretch flanging applications.
High speed impact cutting (HSIC) of advanced high strength steel 42SiCr under exploitation of adiabatic shear bandsBirnbaum, P.; Kunke, A.; Kräusel, V.
doi: 10.1088/1757-899x/1307/1/012012pmid: N/A
Shear Cutting of Advanced High-Strength Steels poses technological challenges due to the substantial mechanical loads imposed on cutting tools, leading to elevated wear rates. A strategy for cutting high-strength materials involves the utilization of high-speed impact cutting (HSIC), wherein component separation occurs along a locally adiabatically heated shear band, resulting in reduced cutting forces. The steel alloy 42SiCr undergoes heat treatments involving Quenching+Tempering (Q+T) as well as Quenching+Partitioning (Q+P) for two sheet thicknesses. This results in the formation of martensitic microstructures with varying retained austenite content, as determined through X-ray Diffraction (XRD). Subsequently, the heat-treated steel samples are subjected to tensile testing for mechanical property evaluation, revealing ultimate tensile strengths exceeding 1500 MPa and fracture elongations ranging from 2 % to 12 %. Following this, the material is subjected to HSIC using the AdiaPress Adia 7 machine, employing predefined cutting energies. It is observed that both Q+T and Q+P-treated materials can be successfully cut using HSIC, although distinct cutting edge morphologies are evident. Optical examinations of the cut edges, conducted through top-view and cross-sectional analysis using Scanning Electron Microscopy and 3D laser scanning microscopy, confirm the presence of adiabatic shear bands and discrete zones.
Applicability of the formability evaluation method for advanced high strength steelsLian, Changwei; Niu, Chao; Han, Fei
doi: 10.1088/1757-899x/1307/1/012014pmid: N/A
The use of high strength and ultra-high strength steels has become the main technical solution for reducing vehicle weight and improving safety. It is more complicated to evaluate the formability of advanced high strength steels with different microstructure and deformation characteristics. In this paper, the applicability of existing formability evaluation methods for advanced high strength steels has been verified by experiment and theoretical analysis. The experiment and data analysis of conventional formability evaluation methods, such as strain hardening index, forming limit curve and hole expansion ratio, were carried out on advanced high strength steels, such as dual-phase steel, complex-phase steel, quenched and tempered steel and dual-phase steel with high formability, which are widely used in automotive industry. It is found that due to the complex work hardening characteristics of advanced high strength steels, the work hardening homogenization and forming limit cannot be characterized by a single work hardening index or forming limit diagram, and the standard hole expansion method cannot reflect the quality sensitivity of the formed edge. A new formability evaluation index is proposed and discussed, which can be used to more accurately compare the formability of advanced high strength steels and provide a reference for material evaluation and part selection.