预应变对含裂纹钛制压力容器失效评定的影响

Effect of Pre-strain on Failure Assessment of Titanium Pressure Vessel with Crack

为了分析预应变对含裂纹钛制结构完整性的影响,研究了预应变对工业纯钛拉伸力学性能、断裂韧性及失效评定图的影响。拉伸试验结果表明:工业纯钛的屈服应力和屈强比均随预应变增大而增大,而塑性变形能力随预应变增大而减小,同时断裂韧性随预应变增大而降低。对紧凑拉伸(CT)试样和含裂纹钛制压力容器进行断裂有限元分析,结果表明:裂纹尖端的塑性区随预应变增大而减小,从而导致J积分值随预应变增大而减小。基于BS 7910:2013的失效评定曲线分析发现:选择1曲线和选择3曲线会随着材料预应变而变化,安全区域逐渐减小。因此,随着预应变的增加,失效评定图中屈服应力的储备系数增加,而断裂韧性的储备系数降低。由本研究可知:预应变会对失效评定产生显著影响,需要将其考虑到含裂纹钛压力容器的完整性评定中。

To understand the effect of pre-strain on the integrity assessment of titanium structure with crack,the dependence of tensile mechanical parameters,fracture toughness,failure assessment diagram(FAD)on pre-strain was focused.Firstly,tensile tests reveal that with increasing the pre-strain value,the yield stress and the yield-ultimate strength ratio increase,but the ductility decreases,and the fracture toughness decreases.Then,based on finite element(FE)analyses of compact tension(CT)specimen and titanium pressure vessel with crack,the plastic zone near the crack tip decreases with increase of pre-strain,resulting in the decrease of J-integral.Moreover,the BS 7910:2013 failure assessment curves(FAC)of Options 1 and 3 vary with pre-strain,and the acceptable area decreases.Therefore,with increase of pre-strain,the reserve factor of yield stress increases but that of fracture toughness decreases significantly.In brief,the pre-strain affects the failure assessment of titanium pressure vessel with crack,and needs to be considered in the integrity assessment.