大型储罐大角焊缝裂纹的可靠性分析

以100 000立方米浮顶式大型储罐为例，采用基于应力强度干涉模型的一次二阶矩法和基于ANSYS含裂纹平板的可靠性分析方法对大型储罐角焊缝裂纹进行了可靠性分析.首先基于应力强度干涉模型，根据应力强度因子断裂判据，采用一次二阶矩法计算储罐角焊缝裂纹动态扩展的可靠度，计算得到的应力强度因子为354.4 MPa·mm，可靠度为93.32%.然后运用ANSYS软件计算含裂纹平板的可靠度，先是采用1/4节点奇异单元法，计算出裂纹尖端应力强度因子为376.46 MPa·mm，再通过蒙特卡罗法来计算裂纹扩展的可靠性，得到可靠度为82.36%.通过比较两种方法得到的结果，采用ANSYS有限元分析所得的可靠度低于基于应力强度干涉理论计算得到的可靠度.从安全性角度出发，应选择可靠度低的分析结果来提供决策支撑.

Reliability analysis of large fillet-weld crack of large-scale storage tank

Taking the large storage tank of 100,000 cubic meters with floating roof as a case,the first order second moment （FOSM） method on the model of stress-strength interference and the reliability analysis method of the crack plate on ANSYS were respectively used to analyze the reliability of the large fillet-weld crack of the large-scale storage tank.First,using the fracture criterion of the stress intensity factor based on the model of stress-strength interference,the reliability degree of dynamic growth of the large fillet-weld crack of the large-scale tank was calculated through the FOSM method.In this way,the values of the stress intensity factor and the reliability degree are 354.4 MPa · √mm and 93.32％.Then,ANSYS software was used to calculate the reliability degree of the crack plate.The value of the stress intensity factor of the crack tip is 376.46 MPa · √mm using 1/4-point displacement method.The Monte-Carlo method is used to calculate the reliability of crack growth,and the value of the reliability degree is 82.36％.Bying comparing the results from the two methods,the value of the reliability by ANSYS analysis is lower than that by the stress-strength interference theory.As far as safety is concerned,the result of lower reliability degree should be selected as decision support.