Comparison of the fatigue performance of full-scale girth welded pipes and small scale strip and plate specimens

TWI Industrial Member Report Summary 986/2011

By Yan-Hui Zhang

Background

Fatigue design rules for girth welded pipes are mainly based on test results from either welded plate or strip specimens cut from girth-welded pipes. However, strictly speaking, a strip specimen does not represent all the features of a full-scale pipe specimen. A potential problem is that strip specimens can give optimistic fatigue lives, leading to unsafe life prediction, especially in the low stress (long life) regime.

Objectives

• Compare the fatigue performance of full-scale pipes with that of strip specimens cut from these pipes.
• Identify the main reasons for the difference in fatigue performance between the two types of specimen.
• Review available methods for correlating the two sets of data to provide design guidance.