应变强化对压力容器安全裕度的影响

Effects of Strain Hardening on Safety Margin of Pressure Vessels

通过试件拉伸试验和圆筒容器的有限元模拟,分析了加载路径和预应变量对应变强化容器塑性失稳压力的影响.拉伸试验和有限元模拟结果表明:加载路径对试件和容器的极限承载能力影响较小;不同预应变量虽使容器产生不同程度的塑性变形,但材料的强化效应在一定程度上弥补了容器尺寸变化的影响,仅使圆筒容器的塑性失稳载荷略有下降;在径比为1.02～1.10的薄壁容器范围内,壁厚对应变强化后容器塑性失稳压力的下降影响很小.在同时考虑预应变后容器几何形状改变和材料应力应变曲线改变的情况下,4%～12%预应变后,最小安全裕度由按常规设计的4.76降至2.21,与国内外标准中的最低安全裕度要求相当,表明应变强化后容器仍有较高的强度裕度.

Through the tensile tests of specimens and the finite element simulations of cylinder vessels,the effects of loading path and pre-strain quantity on the plastic instability pressure of strain-strengthening vessels were analyzed.The results indicate that the loading path has no obvious effect on the ultimate bearing capacity of the specimens and the pressure vessels,and that,though different pre-strain quantities make vessels produce plastic defor-mations to variable degrees,the material reinforcing effect may make up for the impact of vessel size change to a certain extent.Thus,only a slightly-decreased plastic instability load of the cylinder vessels is observed.Moreover,it is found that,at a diameter ratio of 1.02~1.10 for thin-wall vessels,the wall thickness has little influence on the decrease of plastic instability pressure.Considering the change of both the geometric shape of vessels and the stress-strain curve after the hardening,the strain hardening ranging from 4% to 12% may result in a decrease of the minimum safety margin from conventional 4.76 to 2.21,which meets the demand for the minimum safety margin set by international standards,thus concluding that the vessels after strain hardening are still of relatively high strength margin.