On the Compressive Stress Relaxation Behavior and Storage Life Prediction of 60Si2Mn Helical Springs
60Si2Mn螺旋弹簧的压缩应力松弛行为与贮存寿命预测

In order to evaluate the stress relaxation properties of 60Si2Mn helical springs at room temperature, the compressive accelerated stress relaxation tests at different high temperatures and under different initial stress conditions were carried out on a small Instron E3000K8953 electronic static and dynamic fatigue testing machine. The effect of ambient temperature and initial stress on the relaxation behavior was investigated. The characteristics of the transition from elastic strain to plastic strain and the variation of plastic strain along with the stress during relaxation are demonstrated based on viscoelastic model. Microscopic mechanism of stress relaxation is explored based on metallographic analysis and TEM microstructure observation for spring specimens before and after relaxation. Results show that the environmental temperature and initial stress level exerted significant effect on stress relaxation behavior. Temperature-dependent constitutive equations are established for thermal-activated stress relaxation processes, and storage life prediction of spring subjected to different stresses and at room temperature and high temperature is performed, respectively.