Experimental and modeling study of uniaxial cyclic behaviors of structural steel under ascending/descending strain amplitude-controlled loading

Abstract

The cyclic tests are referred to as the basis of the investigation of the hysteretic behaviors in various loading histories. Regardless of the conventional loading protocols mainly on the ascending strain amplitude loading, there are still limited studies focusing on the metallic cyclic behaviors under the descending strain amplitude loading. In this study, total 14 ascending/descending and 3 random cyclic loading tests are performed to acquire better understanding of the cyclic behaviors of the low alloy structural steel (with Chinese steel grade Q345). Through the analysis of the evolution rule of the elastic region and back-stresses, it is concluded that the size of elastic region is rapidly reduced and the change of the size of hysteresis loop is mainly attributed to the evolution of stagnation value of back-stresses. Two hardening phenomena, referred to as the irreversible and reversible hardening, lead to the contraction of hysteresis loops during the descending loading. A novel multi-surface model, encompassing the notion of irreversible and reversible hardening, is proposed and used to simulate the cyclic loading tests by virtue of a newly developed adaptive strain-controlled algorithm. This model, determined by 14 material parameters, has been validated by the remarkable agreement with the experimental results and low relative error indices under regular as well as random loading protocols (i.e. avg 6.8% for regular loading and avg 7.6% for random loading).