Liu Fang Born in 1984, she received B.S. degree from Wuhan University of Technology in 2006. Now she is aPh.D. candidate of Institute of Mechanics, Chinese Academy of Sciences. Her main research interest is the elasto-plastic damage constitutive relation of materials. E-mail: liufang@lnm.imech.ac.cn Fu Qiang Born in 1983, he received Ph.D. degree from Institute of Mechanics, Chinese Academy of Sciences in 2010. His main research interest is the crystal plasticity. E-mail: fuq@lnm.imech.ac.cn Chen Cen Born in 1986, she is a Ph.D. candidate of Insti- tute of Mechanics, Chinese Academy of Sciences. Her main research interest is the constitutive relation of composite material. E-mail: chencen@lnm.imech.ac.cn Corresponding author. Tel.: +86-10-82543912. E-mail address. lng@lnm.imech.ac.cnLiang Naigang Born in 1944, he is a professor in Institute of Mechanics, Chinese Academy of Sciences. His main re- search interest is the constitutive relation of materials. E-mail: lng@lnm.imech.ac.cn