飞机结构材料疲劳裂纹的扩展机制及其工程应用

 本文简要地评述了铝合金、钛合金和高强度钢的疲劳裂纹扩展机制及其工程应用;提出了预测疲劳裂纹扩展门槛值的一个普遍关系式;评价了现有四种超载模型对Ti-6A1-4V合金在拉伸超载下的延缓效应和预测寿命能力。对Willenborg和Maarse模型作了改进,并应用于A1和Ti合金的寿命预测。改进后的Maarse模型明显地提高了预测拉伸超载下和谱载下寿命的精度。文中还讨论了显微组织、应力比和表面状态等对材料疲劳裂纹扩展行为的影响。

MECHANISMS OF FATIGUE CRACK PROPAGATION AND THEIR ENGINEERING APPLICATIONS TO SOME STRUCTURAL MATERIALS

A brief review of recent works on the mechanisms of fatigue crack propagation behavior and their applications to some aircraft Al-alloys, Ti-alloys and high-strength steels in the Institute of Aeronautical Materials is presented.The change of microscopic morphology and mechanisms of FCP at different propagation stages, especially in the initiation stage, are described. A general analytical expression for calculating fatigue threshold values of common metals and alloys is proposed.The ability of each of four current retardation models to predict fatigue life of Ti-6Al-4V alloy under tensile overloading is evaluated. Some modifications of the Willenborg and Maarse models and their applications to the life prediction of Al-and Ti-alloys are investigated. The presented modified Maarse model is recognized to be improved obviously in the life prediction under tensile overloading and spectrum loadings.The effects of microstructures, stress ratios, surface conditions and environments on the fatigue crack propagation behaviors of some aircraft structural materials are discussed.