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对7475-T7351铝合金进行了喷丸强化和未喷丸(机械加工后抛光)单边缺口拉伸(SENT)试样的小裂纹扩展行为试验研究,利用权函数法(WFM)和叠加原理分析计算了三维表面小裂纹在外加载荷和残余应力场联合作用下的应力强度因子(SIF),并将其加入到基于裂纹闭合的小裂纹扩展分析程序FASTRAN3.9中,采用该程序预测了均布外载荷σmax=160MPa、R=0.06下,喷丸强化和未喷丸SENT试样自然萌生裂纹扩展的a-N曲线。研究发现喷丸强化残余压应力对疲劳小裂纹扩展速率的降低是疲劳寿命延长最主要的原因,采用基于裂纹闭合的小裂纹扩展分析方法能够较好地定量描述喷丸强化的疲劳延寿作用。
The small crack propagation behavior of shot peening and shot peening (machined and polished) single-edge notched (SENT) specimens of 7475-T7351 aluminum alloy were investigated by using the weight function method (WFM) and superposition principle The stress intensity factor (SIF) of three-dimensional small surface crack under the combined action of applied load and residual stress field was calculated and added to the crack growth analysis program FASTRAN3.9 based on crack closure. The program was used to predict the uniform distribution AN curves of spontaneous crack propagation in the shot peening and shot peening of SENT specimens under external load σmax = 160 MPa and R = 0.06. It is found that the decrease of the fatigue crack growth rate by shot peening residual compressive stress is the most important reason for the fatigue life extension. The fatigue crack extension by shot peening can be described quantitatively well by the crack propagation analysis based on crack closure.