基于滞回环数据的 42CrMo 高强度钢低周扭转疲劳性能分析

The hysteresis loop is a stress-strain data loop continuously monitored during low-cycle plastic loading,which contains rich accumulated information on material fatigue damage. However,due to the difficulties in hysteresis loop data collection, feature extraction and analysis, there are few relevant research reports. In order to deeply evaluate the low-cycle torsional fatigue properties of 42CrMo high-strength steel,a fatigue test analysis method based on hysteresis loop data is proposed. A torsional fatigue testing machine is used to obtain the hysteretic loop data of the material,and a feature extraction algorithm is designed to obtain the rules of evolution of cyclic stress,shear modulus,residual stress and plastic strain with the loading cycle as well as the cyclic softening characteristics of the material. Through experimental design and analysis,it is confirmed that the 42CrMo material does not meet the Masing characteristics,and as the strain amplitude increases,the non-Masing characteristics become more significant. The low-cycle torsional fatigue test data is used to analyze the cyclic stress-strain relationship characteristics and strain-life relationship characteristics of the material,and calculate shear modulus G,cyclic strength coefficient K′, cyclic strain hardening inde xn′, fatigue strength index b, fatigue strength coefficient τ′_f, fatigue ductility index c,and fatigue ductility coefficient γ′_f,etc. The proposed method makes full use of a large amount of loading hysteresis loop data in the torsional fatigue test to extract the hysteresis loop characteristics of each cycle,and uses rich analysis data to describe the fatigue properties of the material.