時新紅，張建宇，肖青山，費斌軍

 

北京航空航天大學  固體力學研究所，北京 100191

 

　　摘要：對航空常用鋁合金不同軸向平均應力下拉扭比例加載疲勞失效典型斷口進行了宏觀及微觀分析。通過對典型斷口的宏觀分析，得到比例加載下多軸疲勞裂紋萌生與擴展的平面和方向；通過對典型斷口的微觀分析，得到疲勞源區、擴展區及瞬斷區的微觀特征。宏觀分析的結果表明，拉扭比例加載下，最大剪應力幅和法向平均應力對裂紋萌生和擴展的方向有一定的影響，疲勞裂紋的萌生和擴展平面均接近最大剪應力幅值所在的平面，隨著平均應力值的增大，較多的裂紋傾向于在有著較大法向平均應力的最大剪應力幅平面內萌生和擴展，并且偏離最大剪應力幅平面的角度值在增加。微觀分析的結果表明，隨著軸向平均應力值的增加，疲勞源區裂紋源數目增加，臺階特征也變得不明顯，擴展區的疲勞條帶特征越來越不明顯，瞬斷區的等軸韌窩越來越多。

 

　　關鍵詞：多軸疲勞，軸向平均應力，鋁合金

 

　　Studies On Crack Initiation And Growth Of Mutiaxial Fatigue Under Different Axial Mean Stress

 

　　Shihongxin,Zhangjianyu,Xiaoqingshan,Feibinjun

 

　　Beijing University of Aeronautics & AstronauticsResearch Institute of solid mechanics Beijing 100191

 

　　Abstract:Macro-analysis and micro-analysis of aluminum alloy fracture appearance were conducted for different mean tensile stress under in-phase axial-torsional loadings. Macro-analysis of fracture appearance was carried out in order to obtain the planes and orientations of crack initiation and propagation, and micro-analysis of fracture appearance was carried out in order to obtain the micro features of origin region, extension region and final rupture region under in-phase axial-torsional loadings. The results of macro-analysis show that both the maximum shear stress amplitude and normal mean stress have effects on the orientations of crack initiation and propagation, and the orientations of fatigue crack initiation and propagation are close to the plane of the maximum shear stress amplitude plane. More cracks are inclined to initial and propagate on or near the maximum shear stress amplitude plane that had the larger normal mean stress with increasing the mean tensile stress, and the angle of deviation from the plane of maximum shear stress amplitude increases. The results of micro-analysis show that with increasing the mean tensile stress, the step-like characteristic become not evident in the origin region, fatigue fringe become not remarkable in the extension region and equiaxed dimples become more significant in the final rupture region.

 

　　Key words:multiaxial fatigue, axial mean stress, aluminum alloy

 

　　聯系方式

 

　　時新紅：shixinhong@buaa.edu.cn 

責任編輯：趙澤南

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