By changing the geometric parameters such as the size

shape ratio and depth of semi-elliptical surface cracks and elliptical buried cracks in cross-welded joints and oblique welded joints commonly used in high-speed rail bogies

the influence of the geometric parameters on the type I stress intensity factor KI at the crack front was analyzed by a contour integral method.A mathematical expression for solving KI was fitted by a multivariate nonlinear regression method

and the sensitivity of KI to the change of crack size and shape ratio was analyzed by a countour integral method.The results show that KI increases with the increase of crack and gradually diverges or converges according to the difference of joint and crack form.KI decreases and converges gradually with the increase of the crack shape ratio.The location of the maximum point of KI was determined by crack size

crack shape ratio and crack location.The error of the fitted mathematical expression for solving KI was within 5%

and the accuracy is high.Among the four crack forms

the sensitivity of the surface crack KI of the cross joint to the crack shape ratio is obviously lower than that of the other three crack forms

and the sensitivity of the buried crack of the oblique joint to the crack size is obviously higher than that of the other three crack forms.