Chaoyang Sun

INVESTIGATION OF PLASTIC DEFORMATION BEHAVIOR ON COUPLING TWINNING OF POLYCRYSTAL TWIP STEEL

Twinning induced plasticity (TWIP) steel exhibits high strength and exceptional plasticity due to the formation of extensive twin under mechanical load and its ultimate tensile strength and elongation to failure ductility-value can be as high as 5×10 MPa·%, which provide a new choice for automobile in developing the lightweight and improving safety. Generally, due to the texture was formed during process of plastic deformation, metal material appear anisotropic behavior. The deformation mechanisms, responsible for this high strain hardening, are related to the strain-induced microstructural changes, which was dominated by slip and twinning. Different deformation mechanisms, which can be activated at different stages of deformation, will strongly influence the stress strain response and the evolution of the microstructure. In this work, to predict the texture evolution under different *国家自然科学基金项目51105029和51575039,国家自然科学基金委员会与中国工程物理研究院联合基金项目U1330121及非线性力学国家 重点实验室开放基金项目LNM201512资助 收到初稿日期: 2015-03-19,收到修改稿日期: 2015-09-29 作者简介:孙朝阳,男, 1976年生,副教授,博士 DOI: 10.11900/0412.1961.2015.00156 第1507-1515页 pp.1507-1515

The Effect of Process and Model Parameters in Temperature Prediction for Hot Stamping of Boron Steel

Finite element models of the hot stamping and cold die quenching process for boron steel sheet were developed using either rigid or elastic tools. The effect of tool elasticity and process parameters on workpiece temperature was investigated. Heat transfer coefficient between blank and tools was modelled as a function of gap and contact pressure. Temperature distribution and thermal history in the blank were predicted, and thickness distribution of the blank was obtained. Tests were carried out and the test results are used for the validation of numerical predictions. The effect of holding load and the size of cooling ducts on temperature distribution during the forming and the cool die quenching process was also studied by using two models. The results show that higher accuracy predictions of blank thickness and temperature distribution during deformation were obtained using the elastic tool model. However, temperature results obtained using the rigid tool model were close to those using the elastic tool model for a range of holding load.