Fatigue life prediction for toe ground joints

TWI Industrial Member Report Summary 910/2008

By Y H Zhang

Background

Weld toe grinding is a well established technique for improving the fatigue performance of welded components. Design codes, such as BS 7608, allow an increase in the fatigue endurance (fatigue life) of 2.2 times after proper weld toe grinding. It is expected that crack initiation would become a more significant component in the total endurance for toe ground joints than for as-welded joints. Although many attempts have been made to predict the fatigue endurance of welded joints by considering crack initiation and propagation, work on ground joints is limited. Furthermore, there is little convincing data in the literature to verify any model predicting the life to crack initiation.

Objectives

• Develop a method to reliably detect crack initiation and accurately determine crack size in toe ground welded joints.
• Predict the fatigue lives of toe ground joints using a local stress approach.