本报告是在PVRC的资助下对316不锈钢等工程材料进行的蠕变疲劳损伤研究项目的结果。该项目的主要目标是分析、评估和开发高温下单轴和双轴应力/应变循环下的蠕变-疲劳相互作用模型。双向加载是扭转与轴向加载的耦合，保持时间为30分钟，以产生蠕变效应。数据来自1150°F（620°C）下进行的疲劳蠕变试验。 基于试验数据和深入的宏微观分析，基于延性耗尽概念，建立了单轴蠕变损伤模型。将提出的延性耗竭模型与时间分数规则进行了比较。与时间分数规则相比，该模型具有更好、更全面的预测能力，能够区分失效是由蠕变还是由低周疲劳引起的。对于双轴应变/应力循环状态下的蠕变疲劳损伤，对提出的单轴延性损伤概念进行了修改，以考虑双轴应变/应力效应。

This report is the result of a research program on creep-fatigue damage conducted under a Grant from PVRC on engineering materials such as 316 stainless steel. The main objective of the program is to analyze, evaluate and develop a model for creep-fatigue interaction under uniaxial and biaxial stress/strain cycling at elevated temperature. The biaxial loading was torsion coupled with axial loading with 30 minutes hold-time to generate the creep effect. Data was obtained from fatigue-creep tests conducted at 1150°F (620°C). Based on test data and in-depth macro-micro analysis, a model which accounts for uniaxial creep damage is developed on the basis of ductility-exhaustion concept. A comparison is made between the proposed ductility-exhaustion model and the time fraction rule. The proposed model shows a better and more comprehensive prediction capability than the time fraction rule and was able to distinguish whether the failure is by creep or by low cycle fatigue.For creep-fatigue damage under biaxial state of strain/stress cycling, the uniaxial proposed ductility damage concept was modified to account for the biaxial strain/stress effect.