FATIGUE STRENGTH OF TUBULAR JOINTS.

Abstract

Parametric equations developed earlier for stress concentration factors (SCF) and strain concentration factors (SNCF) for tubular joints are mainly dependent upon the increase in stress and strain due to geometric, notch and weld effects. Fatigue failure criteria were also formulated from the above. However, previous loading history to levels beyond working loads due to abnormal environmental forces will result in permanent stresses which will have a large bearing on the design of the structure both for static and fatigue loadings. The paper presents some relevant information from the authors' tests to bring out the importance of permanent stresses and their relation to the fatigue strength of tubular joints. The influence of a defect (preformed) on the performance of a tubular joint has also been discussed.