疲劳断口形貌与材料性能的关系

EFFECT OF MATERIAL PROPERTY ON FRACTURE SURFACE PATTERN

1.疲劳断口分析概述 当金属材料承受循环载荷时,随材料的初始状态以及应力-应变水平不同,将在整个体积内发生循环硬化或循环软化现象。开始时,这些变化是在受载金属中均匀发生的。当循环周次达到一定的数值时,某些变化将集中在局部区域进行。

Fracture surface analysis is an important means for judging failure mode, finding failure reason and preventing failure. Under constant amplitude cyclic loading, the pattern of a fatigue fracture surface and the crack numbers depend on the loading type as well as the stress level, while the problem is much complex under variable amplitude cyclic loading because of the cyclic dependent property of the material. According to principle of microstructure stability in metallic systems as well as cyclic dependent property, the author studied systematically the effect of cyclic dependent property on accumulative damage and fracture surfaces of the fatigue specimens. The conclusions are that under the same loading history. There are different fracture surface characteristics for cyclic hardening material and cyclic softening ones, and that in the case of high-low stress levels the number of crack at the fracture surface depends not only on the level of the first high stress but also on its cyclic number and the cyclic dependent property of material.