Orthotropic damage in high-strength steel sheets. An elasto-viscoplastic material model with mixed hardening

2003 ◽  
Vol 110 ◽  
pp. 177-182 ◽  
Author(s):  
E. Omerspahic ◽  
K. Mattiasson
Keyword(s):  
High Strength Steel ◽  
High Strength ◽  
Material Model ◽  
Viscoplastic Material ◽  
Mixed Hardening ◽  
Steel Sheets

Investigation on Effect of Slide Motion Control on Stamping of High Strength Steel Sheets

2013 ◽  
Vol 554-557 ◽  
pp. 1331-1337 ◽  
Author(s):  
Masato Takamura ◽  
Shigeru Nishimura ◽  
Hideyuki Sunaga
Keyword(s):  
Stress Relaxation ◽  
Motion Control ◽  
High Strength Steel ◽  
High Strength ◽  
Material Model ◽  
Relaxation Behavior ◽  
Stress Relaxation Behavior ◽  
Automotive Body ◽  
Steel Sheets ◽  
Servo Press

High strength steel sheets are increasingly used in automotive body parts with the aim of weight reduction, but their use urgently requires further improvement in sheet forming technology to overcome difficulties such as poor formability, dimensional inaccuracy, etc. On the other hand, servo press facilities are becoming increasingly used in industry and many attempts are being made to bring out their characteristic features for enhancing the formability of high strength steel sheets. Although some of these attempts have been successful in finding the advantages of servo presses for improving formability and dimensional accuracy, the mechanisms of such improvements have yet to be clarified in conjunction with the mechanical properties of the materials used. One of the most remarkable features of the servo press lies in its flexibility in slide motion control. It is thus effective to investigate the relevance of strain rate sensitivity of a material to the mechanism of improvement in formability enabled by the flexible slide motion of the servo press. However, very few studies have been carried out with material testing, material modeling, and numerical analyses combined with experimental verifications. In this study, Norton’s creep model was implemented in the FEM solver in order to take into account visco-elasto-plastic deformation including stress relaxation behavior. Parameters for the visco-elasto-plastic material model were identified through physical measurements and FEM simulations of uniaxial tension and crosshead displacement dwell tests, as shown in Fig. 1. The identified material model was applied to sheet forming simulations of an automotive body part and validity of the model was examined by comparing with stamping experiments using a servo press with a variety of slide motions. Numerical results with the identified material model showed the same tendency with respect to the slide motions as the experimental results. Stress relaxation behavior was found to be an important factor for improving formability enabled by modifying the slide motion.

Finite Element Analysis of Reinforcement Rocker Part Made from JAC780Y Steel Sheets

2021 ◽  
Vol 877 ◽  
pp. 83-89
Author(s):  
Aeksuwat Nakwattanaset ◽  
Surasak Suranuntchai
Keyword(s):  
Finite Element ◽  
Sheet Metal ◽  
High Strength Steel ◽  
High Strength ◽  
Material Model ◽  
Advanced High Strength Steel ◽  
Forming Process ◽  
Element Analysis ◽  
Steel Sheets ◽  
Springback Prediction

The manufacturing industries for automotive parts aim to develop technologies for reducing vehicle weight in order to decrease fuel consumption. However, passive safety function for drivers and passengers must not be impaired or should be even improved. Therefore, advanced high strength steel sheet plays more and more important role in designing automotive components. Nowadays, prediction of formability for sheet metal stamping has high capability more than the past. The major challenge is springback prediction. Moreover, it assists in the tooling design to correctly compensate for springback. Especially in automotive production, springback effects have been generally exhibited distinct after forming process of the high strength steel sheets. The springback effect occurred in the deformed state of metal parts must be taken into account by designing any sheet metal panels. Then, the purpose of the present research is to investigate the springback phenomenon of an automotive part named Reinforcement Rocker RL made from an advanced high strength steel grade JAC780Y, after stamping. In addition, the tools design has been carried out. Finite Element (FE) program known as DYNAFORM (based on LS-DYNA solver), has been applied to analyze and improve the springback effect on such forming part. An anisotropic material model according to type 36 (MAT_036 3-PARAMETER_BARAT) was applied. The results obtained from simulations were compared with required parts in each section. Then, the die surface from compensation in 2nd step forming was modified to use. Finally, the simulation part was verified with the real stamping part. It was found that the finite element simulation showed high capability for prediction and compensation of springback in high strength steel sheets forming.

scholarly journals Mechanical clinching and self-pierce riveting for sheet combination of 780-MPa high-strength steel and aluminium alloy A5052 sheets and durability on salt spray test of joints

2021 ◽  
Vol 113 (1-2) ◽  
pp. 59-72
Author(s):  
Yohei Abe ◽  
Ken-ichiro Mori
Keyword(s):  
Aluminium Alloy ◽  
High Strength Steel ◽  
Salt Spray ◽  
High Strength ◽  
Alloy Sheet ◽  
Galvanized Steel ◽  
Load Reduction ◽  
Minimum Thickness ◽  
Steel Sheets ◽  
Mechanical Clinching

AbstractTo increase the usage of high-strength steel and aluminium alloy sheets for lightweight automobile body panels, the joinability of sheet combinations including a 780-MPa high-strength steel and an aluminium alloy A5052 sheets by mechanical clinching and self-pierce riveting was investigated for different tool shapes in an experiment. All the sheet combinations except for the two steel sheets by self-pierce riveting, i.e., the two steel sheets, the two aluminium alloy sheets, and the steel-aluminium alloy sheets, were successfully joined by both the joining methods without the gaps among the rivet and the sheets. Then, to show the durability of the joined sheets, the corrosion behaviour and the joint strength of the aged sheets by a salt spray test were measured. The corrosion and the load reduction of the clinched and the riveted two aluminium alloy sheets were little. The corrosion of the clinched two steel sheets without the galvanized layer progressed, and then the load after 1176 h decreased by 85%. In the clinched two galvanized steel sheets, the corrosion progress slowed down by 24%. In the clinched steel and aluminium alloy sheets, the thickness reduction occurred near the minimum thickness of the upper sheet and in the upper surface on the edge of the lower aluminium alloy sheet, whereas the top surface of the upper sheet and the upper surface of the lower sheet were mainly corroded in the riveted joint. The load reduction was caused by the two thickness reductions, i.e., the reduction in the minimum thickness of the upper sheet and the reduction in the flange of the aluminium alloy sheet. Although the load of the clinched steel without the galvanized coating layer and aluminium alloy sheets decreased by about 20%, the use of the galvanized steel sheet brought the decrease by about 11%. It was found that the use of the galvanized steel sheets is effective for the decrease of strength reduction due to corrosion.

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