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利用扫描电镜对两种高强钢的疲劳断口进行了观察,并参照裂纹扩展速率曲线(log da/dN-log△K)进行了分析,其结果如下: (1)在对应低速率区的断口表面存在三个特征形貌区,这表明在该区的裂纹扩展过程具有三个阶段:裂纹形成,微裂纹扩展,和一个受沿晶开裂机制和穿晶疲劳条纹生长机制所控制的过渡阶段. (2)在中速率区,疲劳裂纹扩展的发生主要是受疲劳条纹生长机制作用.但是,发现疲劳条纹间距S并不与宏观裂纹扩展速率dα/dN相一致. (3)在高速率区,裂纹扩展速率行为是由疲劳条纹生长机制和韧窝机制所控制.有关这两种机制的相互作用和韧窝生长规律都进行了定量研究.
The fatigue fracture of the two high strength steels was observed by scanning electron microscopy and analyzed with reference to the log da / dN-logΔK. The results are as follows: (1) At the fracture surface corresponding to the low rate region There are three characteristic topography zones, indicating that there are three stages of crack propagation in this zone: crack formation, micro-crack propagation, and a transitional phase controlled by the mechanism of intergranular cracking and the mechanism of the growth of transgranular fatigue strands. 2) In the medium rate region, the fatigue crack growth is mainly affected by the fatigue striation growth mechanism. However, it is found that the fatigue stripe spacing S is not consistent with the macroscopic crack growth rate dα / dN. (3) In the high rate region, the crack The rate-expansion behavior is governed by the fatigue-stripe growth mechanism and the dimple mechanism, and both the interaction of these two mechanisms and the growth of dimples are studied quantitatively.