Effect of Prefabricated Crack Arrest Line on Fatigue Crack Growth Behavior of Industrial Pure Iron DT4C
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摘要: 借助ANSYS仿真结果，确定在疲劳裂纹扩展路径上预制“直线-圆”形止裂线的尺寸；在DT4C工业纯铁上加工出标准扩展紧凑拉伸试样，在距其U型切口根部不同距离（La分别为6.4，7.0，7.6 mm）处预制止裂线，通过疲劳裂纹扩展试验及疲劳断口分析，研究了La对试样疲劳裂纹扩展行为的影响。结果表明：当La为7.6 mm时，止裂线的引入降低了裂纹尖端的应力，延长了试样的疲劳寿命；在裂纹尖端到达止裂线位置之前，当La为6.4 mm时，止裂线的引入提高了裂纹扩展速率，而当La为7.6 mm时则降低了试样的裂纹扩展速率；在裂纹尖端穿过止裂线位置之后，含止裂线试样的裂纹扩展速率均明显降低；不含止裂线和含止裂线试样的裂纹扩展区呈现疲劳辉纹特征，瞬断区呈现韧窝断裂特征。Abstract: According to the ANSYS simulation, the size of the prefabricated "straight-circle" shaped crack arrest line on the fatigue crack growth path was determined. Standard extended compact tensile specimens were sampled from industrial pure iron DT4C, and then crack arrest lines were prefabricated at different distances from the root of the U-shaped notch (La was 6.4, 7.0, 7.6 mm, respectively). The effect of La on the fatigue crack growth behavior of specimens was studied by fatigue crack growth tests and fatigue fracture surface analysis. The results show that when La was 7.6 mm, the introduction of crack arrest line reduced the stress at the crack tip and prolonged the fatigue life of the specimen. Before the crack tip reached the arrest crack line position, the introduction of the crack arrest line at La of 6.4 mm improved the crack growth rate, while that at La of 7.6 mm reduced the crack growth rate. After the fatigue crack tip passed through the crack arrest line position, the crack growth rates of all the specimens with crack arrest line decreased significantly. The crack growth zone of specimens without and with crack arrest lines showed fatigue striation characteristics and the instantaneous fracture zone showed dimple fracture characteristics.
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Keywords:
- fatigue fracture /
- fatigue crack growth /
- crack arrest line /
- stress distribution
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