This paper presents the initial development of a high temperature life prediction method that accounts for the variability in the material properties of Grade 91 steel. The method accounts for material variability by fitting a variable 3-parameter Weibull distribution to experimental rupture data and accounts for the variability of creep deformation on the steady-state stresses via a Monte Carlo approach. To ensure reasonable computational times, the model represents the material as an extremely viscous Stokes fluid with a non-Newtonian viscosity, therefore solving the stress relaxation problem with a steady, static, instead of transient, analysis. The complete statistical analysis combines this model for creep deformation with a probabilistic model for creep rupture to evaluate the probability of premature failure for a set of sample problems, comparing the predicted failure statistics to the design life predicted by the ASME Boiler and Pressure Vessel Code rules.

本文介绍了一种高温寿命预测方法的初步开发，该方法考虑了91级钢材料性能的变化。该方法通过将可变的3参数Weibull分布拟合到实验破裂数据来解决材料的可变性，并通过蒙特卡洛方法解决稳态应力下蠕变变形的可变性。为了确保合理的计算时间，该模型将材料表示为具有非牛顿粘度的极粘斯托克斯流体，因此可以通过稳定，静态而非瞬态分析来解决应力松弛问题。完整的统计分析将这个蠕变变形模型与一个蠕变破裂概率模型相结合，以评估一系列样本问题的过早失效概率，