Satoshi Shirakami

Development of measurement method of work hardeningbehavior in large plastic strain for sheet metal forging

For the purpose of accuracy improvement of sheet metal forging FE analysis, we have developed a new measurement method of work hardening behavior in large plastic strain by repeatedly performing simple shear test using pre-strained steel sheet. In this method, it is possible to measure work hardening behavior more than equivalent plastic strain 2.0. In addition, it was carried out a comparison between developed method and compression test in order to verify the validity of the results by the developed method. As a result, both results were in good agreement. The validity of developed method has been verified.

Work-Hardening Behavior of Cold Rolled Interstitial-Free Steel Sheet and Dual Phase High Strength Steel Sheets Subjected to Two-Stage, Coaxial and Non-Coaxial Tension/Compression

In-plane tension/compression tests of a cold rolled interstitial-free (IF) steel and sheet a 980MPa dual phase high strength steel sheet (980DP) were carried out to investigate the work-hardening behavior under two-stage loading paths. The two-stage loading paths consist of the uniaxial tension/compression for the rolling direction (RD) followed by unloading and subsequent uniaxial tension/compression in the 0°, 45° and 90° directions from the first loading direction (0°-, 45°- and 90°-loading). The work hardening behavior in the second loading was different between the 980DP and the IF steel. It was found that the work hardening behaviors were significantly affected by the inner product of the strain rate mode tensors for the first and second loading and that the effect of the deformation mode (tension/compression) was small.

Development of measurement method of draw bead parameters for CAE analysis

In this study, a new identification procedure for the simulation parameters of the equivalent draw bead model was proposed. In this method, the blank holding force was gradually reduced during the draw bead test and the variations in the draw bead restraining force and die clearance were measured continuously. The lifting force at which the die clearance started to increase was also obtained from the variation in die clearance. As an application example, a square cup drawing process was simulated using the parameters identified by this procedure. The results of wrinkles on a flange were in good agreement with experimental results. Moreover, we proposed an alternative method to identify the parameters solely using the CAE analysis.