Stress intensity factor and fatigue analysis of cracked cruciform welded joints strengthened by CFRP sheets considering the welding residual stress: Fid-Bau Portal

Stress intensity factor and fatigue analysis of cracked cruciform welded joints strengthened by CFRP sheets considering the welding residual stress

Jie, Zhiyu / Wang, Wujun / Fang, Rufeng / Zhuge, Ping / Ding, Yong

Abstract

Abstract In order to investigate the strengthening effect of carbon fiber reinforced polymer (CFRP) on the fatigue performance of cracked cruciform welded joints, numerical analyses and fatigue tests were presented. Considering the effects of initial crack depth, CFRP modulus, and CFRP thickness, three different methods were employed to assess the SIF ranges of unrepaired and CFRP sheets repaired cruciform welded joints, and a new formula to calculate the SIF range was fitted via numerical results. Two different welding residual stresses obtained from literatures were taken into account to evaluate the effective SIF range. Fatigue life predicted results were determined via the modified Paris equation considering two different crack closure factors. The results demonstrate that the SED method can be successfully and conveniently used to estimate the SIF range, the accuracy of the new equation is verified. CFRP sheets can decrease the SIF range of the crack tip and extend the fatigue life, and the maximum increase in the fatigue life reaches 66%. The effect of different CFRP sheets is nearly the same owing to a small stiffness ratio. Fatigue strength of cracked cruciform welded joints strengthening with CFRP sheets at 2 million cycles increases by 26% compared to that of specimens without CFRP. Good agreement with experimental results indicates that the residual stress B and the Schijve model are recommended to predict the fatigue life of cruciform joints.

Highlights • A new equation is proposed to assess the SIF range of CFRP sheets repaired cruciform welded joints. • The residual SIF considering two different residual stress distributions is calculated by the weigh function method. • The effective stress ratio is used to consider the influences of the strengthening effect and the welding residual stress. • Two different closure factors are employed to assess the fatigue life.