实心圆轴拉扭组合全寿命实验中应力按比例加载的控制方法

针对实心圆轴拉、扭组合实验全寿命过程中拉(σ)、扭(τ)应力按固定比例加载的难题,基于拉扭试验机控制的核心问题,从弹性应力比C(σ/τ)的概念出发,推导出载荷比F/T(轴力/扭矩)控制参数,同时考虑全寿命中的拉扭真应力关系,给出载荷程序控制路线,应用PID方式实现试验机控制。以304不锈钢及16MnR碳钢为研究对象,进行了24组不同C的拉扭实验。在此基础上,以塑性过程中的真应力比槇C(σ/τ)为依据,提出了比例修正系数C'的概念,解决了试验机在全过程的控制问题。结果表明:以C为基础的控制模式可对弹性阶段精确控制;材料进入塑性后,C的差异与材料无关,仅与控制方法有关;将提出的C引入控制程序后,可有效提高全寿命过程中应力按比例加载的准确性。

Control methods of cylindrical shaft tension-torsion test under fixed proportional loading in life cycle

This study is to investigate how to realize the fixed proportional tension-torsion loading test in the life cycle of solid cylindrical shaft. The route of loading control is based on the theory of elastic stress ratio (C(?/?)) with the consideration of true stress and strain. The PID control method is used in the tension-torsional testing machine. 24 series of experiment has been done in different C with 24 specimens of 16MnR and 304 stainless steel. A ratio correction coefficient (C?) is put forward depend on the true stress strain ratio ( / ) and experiment results. The results show that: the control route based on C is accurate when the specimen in elastic phase. The difference of between 16MnR and 304SS is related to control method, but not related to specimen when the material gets to large plastic deformation. The accuracy of the fixed proportional tension-torsion loading test in the life cycle was increased when the C? was applied to control procedure.