In the present work, a new concept for the prediction of fatigue life under variable structural and thermal loads is presented based on the modeling of short crack propagation by the effective cyclic J‐integral. Stresses in the range below the initial endurance limit up to plastic deformations can be considered. The development and validation of the concept is based on the large database of constant and variable amplitude loading tests for the austenitic stainless steel X6CrNiNb18‐10 (1.4550, AISI 347). Taking into account the influence of notches and welding process, tests were performed for specimens with different stress concentration factors and even with specimens of nonhomogeneous microstructure due to welding or its physical simulation (Gleeble). The input for the developed model is based on local stress–strain hysteresis in the order of their occurrence. This is the basis for considering load sequence effects; the new J‐based model considers several types of them. The model as well as the identification of the parameters will be presented in detail. Validation to experimental results is also shown against the background of common fatigue concepts. Basic aspects of the model are discussed.

中文翻译：

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模拟可变结构和热载荷下的短裂纹扩展

在目前的工作中，基于有效循环J对短裂纹扩展的建模，提出了一种在可变结构和热载荷下预测疲劳寿命的新概念。-不可缺少的。可以考虑在初始耐力极限以下直至塑性变形的范围内的应力。该概念的开发和验证基于奥氏体不锈钢X6CrNiNb18-10（1.4550，AISI 347）的恒定和可变振幅载荷测试的大型数据库。考虑到缺口和焊接工艺的影响，对具有不同应力集中因子的试样进行了测试，甚至对由于焊接或其物理模拟（Gleeble）而导致的非均匀显微组织试样进行了测试。所开发模型的输入基于局部应力-应变滞后，以它们的出现顺序为基础。这是考虑荷载顺序影响的基础；新的J基于模型考虑了其中几种类型。该模型以及参数的识别将详细介绍。还以常见的疲劳概念为背景对实验结果进行了验证。讨论了模型的基本方面。