含埋藏球形缺陷管道蠕变裂纹萌生寿命的预测

文中利用有限元方法，实现了高温条件下对含埋藏球形缺陷管道蠕变裂纹萌生时间的计算和预测，建立了108个有限元模型，涵盖了广泛的尺寸因素和载荷因素:3种径厚比（R_i/T），3种缺陷尺寸（a/T），3种缺陷位置（e/T）和4种内压（p）.提出一个新的参量——平均等效应力，它不仅能够表征整个蠕变过程的应力状态，也能表征整个蠕变过程的损伤发展.通过非线性回归分别得到蠕变裂纹萌生时间与平均等效应力的函数关系以及径厚比（R_i/T），缺陷尺寸（a/T），缺陷位置（e/T）和内压（p）与平均等效应力的函数关系，从而得到各尺寸因素（R_i/T，a/T，e/T）和载荷因素（p）与裂纹萌生时间的函数关系，即蠕变裂纹萌生时间预测公式.

Prediction of creep crack initiation time in steel pipes with embedded spherical defects

Creep crack initiation time (t_i) of P92 pipes with embedded spherical defects was investigated by using finite element (FE) method. 108 models were built and they covered a wide variety of geometry factors such as inner radius to the wall thickness ratio (R_i/T), defect depth over the wall thickness ratio (a/T), ratio of the distance from the center of the defect to the inner surface of the pipe over the wall thickness (e/T) and loading factors (internal pressure (p)). A new parameter-Average Equivalent Stress (AES) was proposed to characterize the stress level and damage evolution throughout the whole creep process. The mathematic relationship between ti and AES and that between R_i/T, a/T, e/T and AES were obtained by nonlinear regression. Finally, the proposed prediction functions for creep crack initiation time was deduced from the above functions.