FATIGUE CRACK GROWTH STUDIES IN THE BUTT WELDED JOINT

Abstract

Welded structures are found to contain micropores, slag inclusions, cracks or _crack-like flaws etc. In most of welded joints fatigue failure occurs due to propagation of a crack arising from any welding defects. In most of butt welded joints failure occurs by the propagation of a semi- elliptical surface crack which initiates at the weld toe . In order to analyse the progress of these cracks using fracture mechanics techniques , the solutions for the stress intensity factor; K, is required.Stu4y of fatigue crack growth in transverse butt welded joints includes the study of surface crack pr agtion penetrating through thickness of the plate . This semi- elliptical surface cracks adapt front shapes giving low a/2c values approximately 0.3 . Solutions in the literature are more applicable to a/2c values close to 0.5. Therefore the results in the literature were used to estimate the stress intensity factor with low a/2c value. In the present work crack propagation data for surfce cracks of different a/2c values were obtained by testing transverse butt welded specimens encorporating different correction factors such as plate thickness correction factor,back surface correction factor,stress intensity magnification factor etc. The solution for obtaining fatigue crack propagation data takes account of crack geometry i.e.the different crack front shapes. The results obtained found to have no remarkable effect of stress concentration caused by weld bead though the stress concentration factor was