Stress intensity factor solution for root defects in fillet and partial penetration welds

• Main Author: Kang, Cheng Xi.
• Other Authors: Lie Seng Tjhen
• Format: Final Year Project
• Language: English
• Published: 2009
• Subjects: DRNTU::Engineering::Civil engineering::Structures and design
• Online Access: http://hdl.handle.net/10356/16070
• Institution: Nanyang Technological University

This study investigates the stress intensity factors for surface cracks contained in a T-butt joint. This study comprises of three main phases. Phase 1 of the study involves the boundary element modeling of a the 3-D model using AutoCAD. Models with differing geometric parameters were created so as to conduct a parametric study conducted to study the effects of selected parameters on the stress intensity factor. In this case, we varies the attachment thickness t and the weld leg length w. Phase 2 of the study involves the analysis of the various T-butt models created in phase 1, using the BEM_J.exe, as the numerical solver to calculate the stress intensity factors values. Phase 3 involved the analyzing and understanding of the results generated. At phase 3, the relationship of attachment thickness t with stress intensity factor is established. The stress intensity factor will increase at an increasing rate as the attachment thickness increases. The effects of the weld leg length with stress intensity factor is also studied. The stress intensity factor increases at a decreasing rate as w increases. After the study of this 2 variables, the behavior of stress intensity factor along the crack line is studied. The studies will show the higher and lower stress intensity point which is a inverted W shape which will explain that occurring of semi-elliptical cracks. The objective of 2D approximation compared to 3D modeling solutions is compared after all models is completed and the buffer and differences between the 2 is established. It is understood that stress intensity factor increase with the increase in attachment footprint L/T. Further studies includes a new sets of 3D models with the crack line further deepens to (a = 0.7T) and the effect of the increase in crack depth is analyzed and found out that a little increase in crack depth will have a dramatic increase in stress intensity factor.