外物损伤对不锈钢疲劳强度的影响

基于空气炮法，针对不锈钢平板试样开展了外物损伤（FOD）模拟试验，使用三维体式显微镜观测了损伤的宏观特征，并用扫描电子显微镜观测了损伤的微观特征，模拟外物损伤具有挤压变形、材料的剪切丢失、塑性变形等宏观特征和微小裂纹、塑性变形、微小缺口、片层结构等微观特征.采用步进法对FOD试样进行了高周疲劳试验，试验结果表明FOD使试样的疲劳强度相对未损伤试样下降超过14%，并且随损伤尺寸的增大，试样的疲劳强度基本呈降低的趋势.疲劳源区多为损伤处的微小缺口或微小裂纹，说明FOD为疲劳裂纹的萌生和扩展提供了有利条件. 

Effect of foreign object damage on fatigue strength of stainless steel

Based on air gun method, the foreign object damage (FOD) simulation test of stainless steel plate specimen was carried out. The macroscopic characteristics of damage were observed by three-dimensional numerical microscope,whilst the microscopic characteristics of damage were observed by scanning electron microscope. It was found that, the macro damage characteristics include compressional deformation, material shear loss, plastic deformation, etc., and the micro damage characteristics of damaged specimens involve micro cracks, plastic deformation,micro notches and lamellar structure,etc. By step loading test method, the high cycle fatigue test was made on FOD specimen. The test results show that the fatigue strength of FOD specimen deceases over 14% compared with non-damaged specimen. Fatigue strength decreases with the increasing damage size. The origin of the fatigue cracks lies in micro cracks or micro notches, indicating that FOD provides favorable conditions for fatigue crack initiation and growth.