复杂应力状态下典型材料全载荷过程中的力学行为

Mechanical Behavior of Typical Material in Whole Load Processes Under Complex Stress State

针对材料在复杂应力状态下全载荷过程中的力学行为问题,应用实心圆轴试件进行拉扭联合试验,重点解决试验中拉伸扭转应力时时按固定比例C(σ/τ)加载的难题.以304不锈钢和16Mn R碳钢为研究对象,进行24组不同C值的拉扭试验.在此基础上,研究了实心圆轴试件在全寿命过程中等效真应力应变的处理方法,探索了不同应力状态对塑性极限承载能力的影响,并引入三轴应力度(TS)概念对其进行表征.结果表明:两种材料的极限应力(σ_(max))随着不同TS值变化均存在应力驻点,此处材料的σ_(max)最小;两种材料的极限应变(ε_(max))与TS值呈现反比函数关系;利用本文所提出的工程计算公式,可以在确定结构某点的应力状态情况下,推测结构在此时所能承受的极限应力与极限应变.但是不同材料的σ_(max)-TS、ε_(max)-TS呈现不同的函数关系,需分别进行试验标定.

To investigate the material＇ s mechanical appearance under complex stresses in the whole load processes, solid cylindrical specimens are used for the tension-torsion tests. Meanwhile, how to realize the fixed proportional （C（σ/τ） ） tension-torsion loading test in the life cycle of solid cylindrical shaft is derived. 24 series of experiments of 16MnR carbon steel and 304 stainless steel specimens have been done under different C values. Based on test results, the calculation method of equivalent true stress and strain of solid cylindrical specimen is derived. Hence, the influence of different stress state on the plastic limit strain is described by triaxial stress coefficient （TS）. Results show that：the plastic limit stress of the two materials has a minimum value through the change of TS values,which defined as stress stationary point. The plastic limit strain of the two materials is in inverse proportion to TS. When the stress state of a point is determined, the plastic limit stress and strain can be calculated by the formula presented in this paper. Difference of material make the limit stress-TS and limit strain-TS mathematical models different, so that the model should be calibrated respectively.