深海超高压环境模拟容器裂纹评定

深海超高压环境模拟容器用于模拟水下压力环境,其容器壁上承受反复载荷,容易产生疲劳裂纹.疲劳裂纹扩展是影响其断裂的主要因素.本文旨在分析半椭圆裂纹在老化的深海超高压环境模拟容器中的扩展行为,评估容器的安全性,因此对材料20MnMoNb钢的裂纹扩展特性进行了试验研究,首先考虑三角形和梯形加载情况,通过比较两组实验结果,考察了其材料对保载时间的敏感性.采用基于统一的裂纹扩展率模型的三维有限元方法进行了疲劳裂纹扩展计算,并通过CT试样的一组数值和实验结果进行了验证,最后建立了不同初始尺寸、展弦比和倾角的裂纹有限元模型,并根据裂纹在容器内壁的容许深度准则,计算了容器的剩余寿命.其分析结果可为深海超高压环境模拟容器可靠性评估提供参考.

Crack Evaluation of an Ultra-High-Pressure Chamber Used for Deep-Sea Environment Simulation

Ultra-high-pressure (UHP) thick chamber for simulating the underwater pressure environ?ment bears high cyclic load and is prone to cracks caused by fatigue. Fatigue crack growth is an impor?tant factor affecting their fracture. The objective of this paper is to analyze the behavior of semi-ellipti?cal crack growth in an aged UHP chamber and to estimate the safety margin of the chamber. For this purpose, crack growth properties of the material 20MnMoNb steel were experimentally investigated first considering triangular and trapezoidal load history respectively. Two series of results were com?pared to examine the sensitivity of the material on holding time. A three-dimensional finite element (FE) model was used for fatigue crack growth calculation based on the unified crack growth rate model and verified by comparing groups of numerical and experimental results on CT specimen. A series of FE models for cracks with different initial size, aspect ratio and inclination level are presented and re?sidual life of the chamber is obtained based on the allowable criterion depth of surface cracks on the inner wall of the chamber. The analysis results will be used as a reference to evaluate the reliability of the UHP chamber.