喷丸强化7475-T7351铝合金的小裂纹行为和寿命预测

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。

Small Crack Behavior and Fatigue Life Prediction for Shot Peening Aluminum Alloy 7475-T7351

Experimental study of small crack behavior is made on shot peening and un-shot peening single-edge-notch tension (SENT) specimens for aluminum alloy 7475-T7351. The weight function method (WFM) is used to calculate the stress intensity factors (SIF) for 3D small surface cracks under the combined action of external uniform load and residual stresses. The calculated SIF results are added to the small crack growth calculation program, FASTRAN3.9. This program is used to predict the fatigue life of naturally occurring small crack growth a-N data of shot peening and un-shot peening SENT specimens under an external load of σ_max=160 MPa and R=0.06. It is found that the reduction of small crack growth rate by shot peening residual stresses is the main cause for prolonging the fatigue life of the specimens, and the fatigue life prediction method based on small crack theory and crack closure concept can be well used to quantitatively predict the effect of prolonging fatigue life by shot peening.