焊接残余应力作为平均应力影响裂纹扩展. 将残余应力与外载平均应力分离，通过构建典型焊接残余应力场，借助扩展有限元计算焊接残余应力场的应力强度因子. 开展了紧凑拉伸（CT）试样的疲劳扩展试验，基于Walker公式将裂纹尖端平均应力强度因子Km（静态量）和应力强度因子幅值ΔK（动态量）分离，获得疲劳裂纹扩展速率da/dN与Km及ΔK的非线性关系. 结果表明，不同外载荷下，应力比与裂纹长度为非线性关系；残余应力对裂纹扩展存在尺度效应：CT试样裂纹长度小于2 mm时，残余应力场明显影响疲劳裂纹扩展速率；当裂纹长度大于2 mm，外载荷为主导因素.
Welding residual stress affects crack propagation as an average stress. Residual stress was separated from the average load stress. By constructing a typical welding residual stress field, the stress intensity factor of the welding residual stress field was calculated with the extended finite element method. The fatigue expansion test of the compact tensile (CT) specimen was carried out. Based on the Walker formula, the average stress intensity factor Km (static amount) at the crack tip and the magnitudeΔK (dynamic amount) of the stress intensity factor were separated to obtain the nonlinear relationship between da/dN versus Km andΔK. The results showed that the stress ratio was nonlinear with the crack length under different external loads and the residual stress had a scale effect on crack propagation. When the crack length of CT specimen was less than 2 mm, the residual stress field obviously affected the fatigue crack growth rate while the external load was the dominant factor, when the crack length of CT specimen was more than 2 mm.
[1] 王苹,刘永,常荷茜,等.焊接结构学中的热-力耦合问题简析[J].焊接学报, 2019, 40(7):6-11 Wang Ping, Liu Yong, Chang Heqian, et al. Brief analyses of thermo-mechanical coupling issue on welding residual stresses and distortions[J]. Transactions of the China Welding Institution, 2019, 40(7):6-11
[2] Dong P. Length scale of secondary stresses in fracture and fatigue[J]. International Journal of Pressure Vessels and Piping, 2008, 85:128-143.
[3] Božić Ž, Schmauder S, Wolf H. The effect of residual stresses on fatigue crack propagation in welded stiffened panels[J]. Engineering Failure Analysis, 2018, 84:346-357.
[4] Gadallah R, Osawa N, Tanaka S, et al. Critical investigation on the influence of welding heat input and welding residual stress on stress intensity factor and fatigue crack propagation[J]. Engineering Failure Analysis, 2018, 89:200-221.
[5] Hensel J, Nitschke-Pagel T, Tchoffo Ngoula D, et al. Welding residual stresses as needed for the prediction of fatigue crack propagation and fatigue strength[J]. Engineering Fracture Mechanics, 2018, 198:123-141.
[6] 薛彬,张天会,徐人平,等.残余压应力场对B780CF钢焊接接头疲劳裂纹扩展的影响[J].焊接学报, 2016, 37(6):103-108 Xue Bin, Zhang Tianhui, Xu Renping, et al. Effect of residual compressive stress field on fatigue crack growth of B780CF steel welded joints[J]. Transactions of the China Welding Institution, 2016, 37(6):103-108
[7] Seo S, Huang E W, Woo W, et al. Neutron diffraction residual stress analysis during fatigue crack growth retardation of stainless steel[J]. International journal of fatigue, 2017, 104:408-415.
[8] 祝金丹,张礼敬,巩建鸣.裂解炉管焊接残余应力场中裂纹扩展行为的数值分析[J].焊接学报, 2008, 29(5):101-104 Zhu Jindan, Zhang Lijing, Gong Jianming. Numerical simutation on cracking growth behavior under effect of residual stresses in welding of pyrolysis tube[J]. Transactions of the China Welding Institution, 2008, 29(5):101-104
[9] Xu Y, Bao R, Liu H, et al. A modified loading method for separating the effect of residual stress on fatigue crack growth rate of welded joints[J]. Fatigue&Fracture of Engineering Materials&Structures, 2017, 40(8):1227-1239.
[10] Ngoula D T, Beier H T, Vormwald M. Fatigue crack growth in cruciform welded joints:influence of residual stresses and of the weld toe geometry[J]. International Journal of Fatigue, 2017, 101:253-262.
[11] 张正伟,张昭,张洪武.焊接残余应力对2024铝合金薄板疲劳寿命的影响[J].焊接学报, 2014, 35(10):29-32 Zhang Zhengwei, Zhang Zhao, Zhang Hongwu. Influence of welding residual stresses on fatigue life of Al 2024 plate[J]. Transactions of the China Welding Institution, 2014, 35(10):29-32
