弹簧应力松弛反常载荷损失及原因分析

Abnormal Load Loss and Cause Analysis of Spring Stress Relaxation

揭示弹簧应力松弛性能与材料组织之间的联系,对研究开发弹簧新材料、提升弹簧性能等具有重要的意义。本工作以圆柱螺旋压缩弹簧为例,采用周期试验法研究了试验温度和初始载荷对弹簧载荷损失和微观组织的影响。结果表明,温度和初始载荷耦合作用会引起载荷损失的反常变化——施加较低的初始载荷条件下温度较低时载荷损失较大,应力松弛后弹簧材料内形成了由位错富集区与位错贫瘠区组成的条带状组织。根据材料的组织特征,通过引入可激活位错与不可激活位错、可激活应力与不可激活应力的概念,导出了应力松弛的对数方程,明确了该方程的物理含义,解释了载荷损失的反常变化现象。由此认为应力松弛是可激活位错在可激活应力和热激活共同作用下运动引起的。

It is of great significance to reveal the relationship between spring stress relaxation performance and the microstructure of spring material for the development of new spring materials and the improvement of spring performance.In this work,effects of test temperature and initial load on the load loss and microstructure of the cylindrical helical compression spring were studied by periodic test method.The results show that the coupling effect of temperature and initial load can cause the abnormal load loss-the slight initial load will cause larger load loss at lower temperature than that at higher temperature,after stress relaxation,a strip structure composed of dislocation rich and dislocation poor regions was formed in the spring material.Due to the structural characteristics of materials,and by introducing the concepts of activable dislocation and inactive dislocation,activable stress and inactive stress,the logarithmic equation of stress relaxation is derived,the physical meaning of the equation is clarified,and the abnormal change phenomenon of load is explained.It is considered that the stress relaxation is caused by the movement of activable dislocations since the combined action of activable stress and thermal activation.