Experiment and constitutive modeling on cyclic plasticity behavior of LYP100 under large strain range

Low yield point (LYP) steel is a promising material for energy dissipation device resisting seismic actions, and is expected to experience large strain when subjected to strong earthquakes. In order to offer a better understanding of the cyclic behavior of LYP steel under large strain range, cyclic tests of eight (8) coupons made of LYP100 under the strain amplitude ranging from −10% to +12% are performed. Evident work-hardening, early re-yielding, and strain range dependence are characterized in the cyclic loading tests. To illustrate these characteristics, the peak stress of every cyclic loop and the elastic region of the unloading process are examined. Based on the analysis results of the peak stress and the elastic region, a modified Yoshida-Uemori model is proposed to quantify the cyclic behavior of LYP100, and the corresponding numerical algorithm is developed. In addition, a practical method based on the derivative-free optimization theory is proposed to calibrate the material parameters of the novel model. The proposed constitutive model shows a satisfactory accuracy for describing the cyclic behavior of LYP100 under large strain range.