表面纳米化对工业纯锆四点弯曲疲劳性能的影响

Effect of Surface Nanocrystalline on Four-point Bending Fatigue Properties of Commercial Pure Zirconium

摘要:

采用表面机械研磨工艺对工业纯锆进行处理,利用四点弯曲疲劳试验对试样的疲劳性能进行测试。通过对试样微观组织观察、显微硬度和残余应力表征,并结合有限元方法对四点弯曲试样应力分布的模拟,分析表面纳米化对工业纯锆四点弯曲疲劳性能的影响机理。研究表明,表面纳米化工业纯锆相对于原始试样疲劳极限提高约23%。这是由于原始工业纯锆在加载时最大拉应力位于试样表层,导致疲劳裂纹在表层萌生,而表面纳米化工业纯锆由于组织强化及残余压应力作用,使疲劳强度得到提高,并且使裂纹在次表层萌生,从而获得较好的疲劳性能。

Abstract:

The surface mechanical attrition treatment was used to process the commercial pure zirconium and the fatigue properties of the samples were examined by four-point bending fatigue test. By observing the microstructure, characterizing the microhardness and residual stress, and combining the finite element method simulation of the stress distribution in the four-point bending specimen, the effect of surface nanocrystalline on the fatigue property was analyzed. The results show that the fatigue limit of the surface nanostructured commercial pure zirconium increases by about 23% compared with the original sample. This is due to the fact that the maximum tensile stress of the original sample under loading is located at the surface region, which leads to the initiation of fatigue cracks in the surface layer. For the surface nanostructured sample, the microstructure strengthening effect and residual compressive stress are beneficail for the fatigue performance. In addition, crack source was shifted to the subsurface layer because of the high strength of the surface layer. Therefore, the surface nanostructured commercial pure zirconium samples possess better fatigue properties.