压力容器疲劳裂纹扩展的超载迟滞效应及其估算

本文通过ST45钢轴向穿透裂纹模拟容器的内压疲劳裂纹扩展试验,探讨了在压力容器上推广、应用超载迟滞效应的问题。文中考虑常规压力容器水压试验的加载规定,着重研究了1.5倍小超载比情况下的迟滞特性,并讨论了超载点裂纹长度、基本循环内压大小及超载后停歇对迟滞效应的影响。最后选用 Wheeler、Will-enborg、广义Willcuborg、松冈(Matsuaka)、Maarse等五个较有名的数学模型计算试验容器的迟滞效应大小。研究表明:压力容器1.5倍的小超载,迟滞效应也是相当明显的,可使带有20mm左右裂纹的试验容器寿命提高约80％,Willenborg模型是估算压力容器上小超载迟滞效应较为理想的模型。

THE RETARDATION PHENOMENON OF FATIGUE CRACK GROWTH IN PRESSURE VESSELS AND ITS ESTIMATION

This paper studies the application of overload retardation effects to simulated pressure vessels with an axial crack pass through by fatigue crack growth tests.In consideration of the practical proof hydro-test ing procedures, a single overpressure with small overpressure ratio (1,5 times the baseline pressure) is particularly investigated. The influences of crack length at overpressure point, baseline cyclic pressure and the holding time after overpressure on the retardation are examined. The retardation effect on the pressure vessels was calculated, and the calculation restlts were compared with that of tests.The results show that the retardation effect of 1.5 times the baseline overpressure is considerable and should be taken into account, when evaluating the fatigue lives of pressure vessels. The Willenborg model is good for estimating retardation effects in pressure vessels,when the overpressure ratios are low.