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以作者建立的焊趾半椭圆表面裂纹应力强度因子数据库以及复杂应力场中焊趾半椭圆表面裂纹前缘应力强度因子分布计算的基本模式法为基础，给出了复杂应力场中焊趾表面裂纹在疲劳扩展过程中形态变化规律及寿命的工程分析方法；并用这个方法计算了一些典型焊接接头在一些典型的外加应力场和残余应力场中的裂纹形态发展曲线。实例计算表明，只有按裂纹扩展的自然途径，即沿着裂纹形态发展曲线来估算疲劳寿命，才能得出正确的结论。对表面裂纹的扩展规律作人为假定来进行疲劳分析，（比如，用线弹簧模型法来分析时，常对裂纹形态比ａ／ｃ的变化规律作人为假定），很可能得出极错误的疲劳寿命预测。残余应力及角接接头中支板的存在对裂纹形态发展曲线和疲劳寿命有明显的影响
Based on the database of the stress intensity factor of weld toe semi-elliptical surface crack and the basic mode method of calculating the stress intensity factor distribution of the weld toe semi-elliptical surface crack in complicated stress field, the weld toe surface crack In the process of fatigue expansion, the morphological change rule and engineering analysis method of life are calculated. And the crack shape development curves of some typical welded joints in some typical applied stress field and residual stress field are calculated by this method. The case study shows that the correct conclusion can only be drawn if the fatigue life is estimated according to the natural way of crack growth, that is, along the crack growth curve. Fatigue analysis is made on the assumption that surface cracks propagate (for example, it is often assumed that the crack morphology ratio a / c changes when analyzed by the wire spring model method), and it is likely to result in extremely erroneous fatigue Life expectancy. Residual stresses and the presence of braces in the corner joint have a significant effect on the crack growth curve and fatigue life