锻压技术

2524铝合金不同应力比下的疲劳裂纹扩展行为

英文标题：Fatigue crack growth of aluminum alloy 2524 under different stress ratios

作者：刘义伦何军刘驰赵先琼李松柏王卿

单位：中南大学

分类号：TG146.2

出版年,卷(期):页码：2018,43(6):134-141

摘要：

研究了不同应力比（R=0.1，0.2，0.3，0.5）对2524-T3铝合金的疲劳裂纹扩展速率的影响，并结合扫描电镜（SEM）下裂纹的断口形貌特征进行了分析。结果表明：应力比R对疲劳裂纹扩展寿命和速率存在明显影响，在恒定最大载荷条件下，应力比越小则裂纹扩展寿命越短；当应力强度因子范围ΔK相同时，应力比越大，裂纹扩展速率da/dN越快。利用Paris公式对数据进行回归分析，da/dN-ΔK曲线呈收敛趋势，进一步采用Elber模型进行拟合，从裂纹闭合的角度解释了应力比R对裂纹扩展速率的影响，结果表明该模型能够较好地描述2524-T3铝合金在不同应力比下的疲劳特性。疲劳断口呈现出早期裂纹扩展、稳定扩展和快速扩展3个阶段，不同应力比下，疲劳辉纹间距和二次裂纹数量存在明显差异。

The influences of different stress ratios (R=0.1, 0.2, 0.3, 0.5) on the fatigue crack growth rate of aluminum alloy 2524-T3 were studied, and the fracture morphology characteristic of crack was analyzed by scanning electron microscope (SEM). The results show that the stress ratio R has a significant effect on the life and rate of fatigue crack growth. Under constant maximum load conditions, the smaller the stress ratio is, the shorter the crack growth life is. When the stress intensity factor range ΔK is the same, the bigger the stress ratio is, the faster the crack growth rate da/dN grows. Then, the data were subjected to regression analysis by Paris formula, and the trend of da/dN-ΔK curve was convergent. Furthermore, data fitting was conducted by Elber model, and the influence of stress ratio R on crack growth rate was explained by crack closure theory. The results show that the model can better describe the fatigue properties of aluminum alloy 2524-T3 under different stress ratios, and the fatigue fracture presents three stages of early crack growth, steady state expansion and rapid expansion. Thus, for different stress ratios, there are obvious differences for the spacing of fatigue striations and the number of secondary cracks.

基金项目：

国家自然科学基金资助项目(51375500)；中南大学中央高校基本科研业务费专项资金资助（2018zzts472）：湖南省科技计划项目(2016GK2005)；湖南省教育厅科技计划项目(17C0638)

刘义伦(1955-)，男，博士，教授；Email：yilunliu@csu.edu.cn；通讯作者：何军（1992-）,男，硕士研究生；Email：163712116@csu.edu.cn

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