混合型裂纹的疲劳扩展

Fatigue Crack Propagation under Mixed Mode Loading

Department of Mechanical Engineering, East China Jnstitute of Chemical Technology, Shanghai

摘要: 本文对受单向拉伸疲劳载荷的中心斜裂纹L₃铝试板进行了研究。根据Erdogan和Sih的最大拉应力理论,推导出以△K作为参变量,以裂纹角β₀进行修正的Paris形式的扩展速率表达式。并且进一步论证以更简单的用裂纹长度在x轴上投影的Paris方程来表示。初始裂纹角β₀有20°、30°、45°、60°、80°、90°等各种角度,裂纹尖端有经预制疲劳裂纹尖端与未经预制疲劳裂纹尖端两种情况,比较了这两种情况下疲劳扩展轨迹及疲劳扩展速率。

Abstract: Mixed mode fatigue crack propagation is analyzed in this paper, using a center cracked plate geometry, loaded under uni-axial cyclic tension.Based on maximun principal stress criterion, a modified Paris expression of fatigue crack growth rate is derived in terms of △K and crack angle β₀ for an inclined crack.It is also shown that it is more convenient to express the Paris equation by means of crack length projected on the x-axis, a_x rather than the actual length, a, itself.The crack trajectory due to cyclic loading is predicted. β₀ is varied from 20°to 90°. Experimental data on Type L₃ aluminium agree fairly well with predicted values when β₀ exceeds 30°.

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