On fatigue Crack Growth Mechanisms in the Near-Threshold Range

本研究对近阈值范围内平面应力和平面应变循环加载下疲劳裂纹扩展机制进行了为期三年的研究。本研究利用最先进的力学测试和显微结构表征技术（包括断裂表面位错结构的透射电镜分析），通过实验研究了四种材料（铁和有色、低合金和高合金）的疲劳行为。实验数据用于测试和开发模型，以描述疲劳行为作为应力状态，环境和材料性能的函数。

This research consists of a three-year period study of the mechanism(s) of fatigue crack growth during plane stress and plane strain cyclic loading in the near-threshold range. This investigation examines experimentally the fatigue behavior of four materials (ferrous and non-ferrous, low alloy and high alloy) using state-of-the-art mechanical testing and microstructural characterization techniques (including transmission electron microscopy analyses of dislocation structures at fracture surfaces). The experimental data are used to test and develop models to describe fatigue behavior as a function of stress state, environment, and material properties.