Parametric equation of stress intensity factor for tubular K-joint under balanced axial loads

In this paper, an automatic mesh generation method, which is for a uni-planar tubular K-joint containing an arbitrary surface crack located along the chord weld toe, is developed for producing the complete finite element mesh model. Using the proposed model, the stress intensity factors along the crack front have been evaluated by an interaction J-integral method in this study. To evaluate the reliability and accuracy of the numerical stress intensity factor results, a full-scale K-joint specimen was tested to failure. Using alternating current potential drop (ACPD) technique, the crack growth rate is captured and the stress intensity factors of the specimen are obtained using Paris' equation. It has been found that numerical stress intensity factor results agree with experimental results quite well. Thereafter, altogether 5120 numerical models of tubular K-joints containing a surface crack at the crown subjected to balanced axial loads have been analyzed. A parametric stress intensity factor equation has then been proposed. The accuracy of the proposed stress intensity factor equation has been assessed by comparing the computing results from the equation with the numerical results. Error analysis has been conducted and it shows that the proposed equation can provide reliable and accurate estimation of stress intensity factor for cracked tubular K-joints under balanced axial loads.