应力比对A7N01铝合金焊接接头裂纹近门槛值区拐点的影响
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摘要
以A7N01铝合金焊接接头为研究对象,借助有限元法及有限元软件先进行A7N01铝合金板对接焊模拟,得到接头处残余应力分布情况,再对接头裂纹进行扩展模拟,最后应用最小二乘法对提取的仿真数据进行处理,重点分析了应力比对疲劳裂纹近门槛值区拐点的影响。结果表明:在接头裂纹扩展速率曲线的近门槛值区存在一个拐点,且应力比对其有影响。拐点对应的应力强度因子幅值ΔK_t随应力比R的增大而减小,且当R>0.5时,ΔK_t变化不大。拐点前后拟合直线斜率k随应力比R的变化为:在L_1区(低速扩展区),拟合直线斜率k_1随应力比R的变化更为明显,且随应力比R的增大而减小;在L_2区(Paris的延续),拟合直线斜率k_2随应力比R变化不大。
Taking A7 N01 aluminum alloy welded joints as object, it simulates the fatigue cracks in finite element method, analyzes the effect of stress ratio on fatigue cracks in the near threshold region inflection point. And then it simulates the crack propagation of joint. Using the least square method, it discusses the extracted simulation data. The results show that there is an inflection point near threshold region of A7 N01 aluminum alloy welded joint fatigue crack growth rate curve, and the stress ratio has an influence on it. The amplitude of stress intensity factor ΔK_t corresponding to inflection point decreases with the increase of stress ratio R,but when R>0.5,the change of the amplitude of stress intensity factor is not big, and the relation between ΔK_t and R is obtained at the same time. The change of the line slope k is variational with the stress ratio R before and after the inflection point: in the zone L_1,the change of the line slope k_1 with the stress ratio R is more obvious, and decreases with the increase of the stress ratio, while in the zone L_2,the k_2 varies little with the stress ratio R.
Taking A7 N01 aluminum alloy welded joints as object, it simulates the fatigue cracks in finite element method, analyzes the effect of stress ratio on fatigue cracks in the near threshold region inflection point. And then it simulates the crack propagation of joint. Using the least square method, it discusses the extracted simulation data. The results show that there is an inflection point near threshold region of A7 N01 aluminum alloy welded joint fatigue crack growth rate curve, and the stress ratio has an influence on it. The amplitude of stress intensity factor ΔK_t corresponding to inflection point decreases with the increase of stress ratio R,but when R>0.5,the change of the amplitude of stress intensity factor is not big, and the relation between ΔK_t and R is obtained at the same time. The change of the line slope k is variational with the stress ratio R before and after the inflection point: in the zone L_1,the change of the line slope k_1 with the stress ratio R is more obvious, and decreases with the increase of the stress ratio, while in the zone L_2,the k_2 varies little with the stress ratio R.
引文
[1] 倪维源,杨尚磊,贾进,等.高速列车用高强A7N01铝合金焊接接头的疲劳性能[J].稀有金属材料与工程,2016(11):2774-2778.
[2] 代鹏.用塑性修正的应力强度因子幅描述疲劳裂纹扩展[D].上海:上海交通大学,2014.
[3] 周桂芬.铝合金MIG焊接工艺试验与分析[J].热加工工艺,2009,38(17):150-151.
[4] RANC N,PALIN-LUC T,PARIS P C,et al.About the effect of plastic dissipation in heat at the crack tip on the stress intensity factor under cyclic loading[J].International Journal of Fatigue,2014,58:56-65.
[5] 李敬勇,李标峰,冯刚宪.焊缝几何特征对5A30铝合金焊接接头疲劳性能的影响[J].中国有色金属学报,2004,14(11):1895-1900.
[6] YODER G,COOLEY T,CROOKER T.On microstructural control of near-threshold fatigue crack growth in 700-series aluminum alloys[J].Scripta Metallurgica,1982,16(9):1021-1025.
[7] 马英杰,刘建荣,雷家峰,等.钛合金疲劳裂纹扩展速率Paris区中的转折点[J].金属学报,2008,44(8):973-978.
[8] 曾春华.疲劳裂纹扩展门槛值的研究进展[J].力学进展,1986,16(2):123-134.
[9] 熊缨.基于新裂纹扩展驱动力参量的焊接接头疲劳裂纹扩展的研究[J].机械工程学报,2011,47(18):72-79.
[2] 代鹏.用塑性修正的应力强度因子幅描述疲劳裂纹扩展[D].上海:上海交通大学,2014.
[3] 周桂芬.铝合金MIG焊接工艺试验与分析[J].热加工工艺,2009,38(17):150-151.
[4] RANC N,PALIN-LUC T,PARIS P C,et al.About the effect of plastic dissipation in heat at the crack tip on the stress intensity factor under cyclic loading[J].International Journal of Fatigue,2014,58:56-65.
[5] 李敬勇,李标峰,冯刚宪.焊缝几何特征对5A30铝合金焊接接头疲劳性能的影响[J].中国有色金属学报,2004,14(11):1895-1900.
[6] YODER G,COOLEY T,CROOKER T.On microstructural control of near-threshold fatigue crack growth in 700-series aluminum alloys[J].Scripta Metallurgica,1982,16(9):1021-1025.
[7] 马英杰,刘建荣,雷家峰,等.钛合金疲劳裂纹扩展速率Paris区中的转折点[J].金属学报,2008,44(8):973-978.
[8] 曾春华.疲劳裂纹扩展门槛值的研究进展[J].力学进展,1986,16(2):123-134.
[9] 熊缨.基于新裂纹扩展驱动力参量的焊接接头疲劳裂纹扩展的研究[J].机械工程学报,2011,47(18):72-79.