Papers by Author: Ke Chen

Abstract: The finite element method is widely used to numerically simulate sheet forming processes. The increasing use of advanced high strength steel (AHSS) sheet places an increased demand on accuracy of forming simulation and springback prediction. Appropriate identification and characterization of material behavior are of vital importance to improve the simulation accuracy. An overview of yield criteria and hardening laws of material constitutive models are presented in this work. Because of the anisotropic yield behavior and Bauschinger effect of AHSS sheet materials, suitable anisotropic yield model in combination with anisotropic hardening law is one essential component for successful AHSS sheet forming simulation and springback prediction. Necessary mechanical tests for determination of parameters of material constitutive models are given in this paper, the advantages and already known limitations of different test procedures are also discussed. Recommendations on choose or further improve the constitutive models are given for enhance the efficiency and accuracy of AHSS sheet forming simulation.

Abstract: With the increasing use of finite element analysis method in sheet forming simulations, springback predictions of advanced high strength steel (AHSS) sheet are still far from satisfactory precision. The main purpose of this paper was to provide a method for accurate springback prediction of AHSS sheet. Material model with Hill’48 anisotropic yield criterion and nonlinear isotropic/kinematic hardening rule were applied to take account the anisotropic yield behavior and the Bauschinger effect during forming processes. U-channel forming and springback simulation was performed using ABAQUS software. High strength DP600 sheet was investigated in this work. The simulation results obtained with the proposed material model agree well with the experimental results, which show a remarkable improvement of springback prediction compared with the commonly used isotropic hardening model.

Abstract: The uneven deformation can decrease formability of Tailor Welded Blanks (TWB).The integrated strength is a key factor that determines the uneven deformation besides the technological conditions. In this paper, the influences of integrated strength on cracking trend and cracking type are investigated through bulging simulation and experiments. It is proposed that the integrated strength should be considered as a crucial factor during the TWB designing. Reasonable integrated strengths matching of base metals can improve the formability of the tailor welded blanks and reduce the trend of cracking. In the case that the integrated strengths of base metals are significantly different, the cracking occurs in the weaker side and is parallel to the welded seam; while the cracking appears in the welded seam and is vertical to it under the condition that the integrated strengths match well. The corresponding technological measures can be adopted as the guidance for materials selection and reasonable matching in the designing.