应力–应变曲线初始屈服的一个新定义及其应用

A NEW DEFINITION FOR INITIAL YIELD OF STRESS-STRAIN CURVES AND ITS APPLICATION

将弹塑性理论中塑性应变路径相关硬化参量的计算和材料初始屈服的概念结合起来,提出一个确定应力–应变曲线初始屈服的新方法。该方法的思想是利用破坏点的确定性给出确定的初始屈服点,其关键是如何计算每条应力–应变曲线的路径相关硬化参量。作为上述新定义的一个应用,选择广义塑性偏剪应变作为塑性应变路径相关的硬化参量,利用一组较高围压下煤岩加卸载应力–应变全曲线数据,确定其初始屈服点,并绘制不同硬化状态的q-p应力与破坏轨迹。分析表明,q-p应力空间中煤岩后继屈服轨迹的斜率呈逐渐递增的非定值性。这是煤岩一个重要的斜率非等值硬化现象,值得深入研究。

Through combining the path dependent hardening parameter and the definition of initial yield,a new definition method of initial yield is proposed. The key idea of this method is to apply the failure point to define the initial yield point on each stress-strain curve,in which the calculation of path dependent hardening parameter is prime. As an application of this new definition,a group of loading-unloading stress-strain curves of coal samples under confining pressures of 15–50 MPa are used to determine their initial yield points;and then the subsequent yield loci in q-p space are drawn,which reveal a new phenomenon that the slope of each q-p locus increases with hardening parameter. This is an important phenomenon for coal hardening plasticity;and it needs further studies.