Burning underground will change the surface of microstructure of BHA, and accelerate corrosion and fatigue crack initiation and propagation;
③井下发生燃爆，会改变下部钻具表面的金相组织，加速了腐蚀和疲劳裂纹萌生、扩展；
The result shows: the local residual tensile stress and cyclic compressive loading thrust fatigue crack initiation and propagation in the size of compressive plastic zone.
结果表明，疲劳裂纹是在残余拉应力和循环压应力作用下萌生和扩展的，压塑性变形是裂纹萌生和扩展的必要条件。
The primary failure model is fatigue fracture that is always resulted by the crack initiation and propagation.
疲劳断裂是气门弹簧失效的主要模式，它是疲劳裂纹萌生及其扩展的结果。
On constant frequency ratio, loading ratio has an importance influence on the initiation and propagation of fatigue crack under double frequency complex loading.
在频率比确定的条件下，载荷比是影响双频疲劳裂纹萌生及扩展的一个重要因素。
The study work is focused on the effect of temperature upon mechanical properties, creep, initiation and propagation of fatigue crack for the valve material.
着重温度对气门材料的力学性能、蠕变和疲劳裂纹形成与扩张的影响等问题进行分析和研究。
The fatigue fractography consists of several different zones, including fatigue crack initiation, slow, fast propagation and final fracture.
疲劳断口上存在典型的疲劳裂纹萌生区、缓慢扩展区、快速扩展区和最后瞬断区。
It is indicated that retained austenite in microstructure can inhibit the initiation and propagation of fatigue crack, improve the resistance to impact fatigue and decrease impact fatigue wear.
试验得出，残余奥氏体可阻止疲劳裂纹的萌生和扩展，提高冲击疲劳抗力，降低冲击疲劳磨损。
The results showed that manufacturing defects of the bolt resulted in initiation and propagation of fatigue crack, and uneven loading of the bolt speeded up failure process of fatigue fracture.
确认螺栓机加工不当引起疲劳裂纹的萌生及扩展，加之螺栓受力不均匀加速了疲劳断裂过程。
The process of crack initiation and propagation was observed through replication, and the effect of grain size on the behaviour of short fatigue cracks was studied.
对两种晶粒尺寸的中碳钢光滑试样进行了旋转弯曲疲劳试验；应用复型技术监测了短裂纹形成与扩展过程，研究了晶粒尺寸对短裂纹行为的影响。
The fatigue crack initiation life for pipeline connection assemblies is also predicted. The fatigue crack propagation path is analyzed and the fatigue crack propagation life is predicted.
进一步，预估了管路连接件裂纹萌生寿命，预测了裂纹扩展路径并预估了疲劳裂纹扩展寿命。
The main course of fatigue fracture is due to existence of the inclusion in the material. The inclusion induce crack initiation, the crack propagation and the axe fracture in the circle stress.
疲劳断裂的主要原因是在材料中存在的夹杂物诱发裂纹源，在循环应力的作用下裂纹扩展导致断裂。
The initiation and propagation of fatigue cracks at the notch roots were also observed by using SEM method. It was indicated that the crack firstly initiated from the surface of notch tip.
采用SEM对缺口试样疲劳裂纹形成与扩展特征进行了初步分析，发现裂纹最先在缺口尖端表面形成。
The initiation and propagation of fatigue cracks at the notch roots were also observed by using SEM method. It was indicated that the crack firstly initiated from the surface of notch tip.
采用SEM对缺口试样疲劳裂纹形成与扩展特征进行了初步分析，发现裂纹最先在缺口尖端表面形成。
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