棘轮安定曲线在不锈钢压力容器应变强化技术中的应用

应变强化是不锈钢压力容器结构实现轻型化的重要途径,而应变强化内压的确定则是应变强化技术的核心。为了能够更准确有效地达到结构应变强化的目的,对循环加载的应变强化方式进行了研究。通过304不锈钢材料的室温单轴棘轮试验,建立了应力比R0条件下的棘轮安定曲线。根据Mises等效原理,利用该曲线通过一次弹塑性有限元分析直接获得结构在循环载荷作用下的强化内压和产生的塑性应变,与试验结果吻合较好,说明运用循环加载的应变强化方式可以有效地达到应变强化的目的。在达到相同的应变强化程度要求下,该方法降低了强化内压,因此可以减小过载加压的风险。

Application of Ratcheting and Shakedown Curve in Stainless Steel Pressure Vessel Strain-Hardening

Strain-hardening is an important way to achieve stainless steel pressure vessel light-weight trend, while how to work out the internal pressure for strain-hardening is the key problem. In order to accurately and effectively achieve structure strain hardening, cyclic loading methods were studied. Ratcheting and shakedown curve (RSC) under stress ratio condition was established through 304 stainless steel uniaxial ratcheting experiment at room temperature. According to Mises equivalent stress and strain principle, the strengthened internal pressure for strain-hardening due to cyclic loading and the final accumulated strain of pressure vessel were determined directly through only once elastic-plastic finite element analysis of RSC. Simulation results agree well with the experimental data. Above results indicate that this new method for strain-hardening by cyclic loading is reasonable and feasible. Furthermore, the strengthened internal pressure for strain-hardening used in this new method is lower than that of traditional method, therefore, the overloading risk can be reduced.