关键词: 喷丸, 单边缺口拉伸试样, 残余应力, 应力强度因子, 疲劳寿命预测

Abstract:

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.

Key words: shot peening, single-edge-notch tension specimen, residual stresses, stress intensity factors, fatigue life prediction