Study on the Method of Bend Test for Butt Welded Joint

Abstract

Concerning the method of bend test for butt welded joint, the significance of the method of test and the influence of bend conditions on the test results were investigated.
The necessary conditions of the method of bend test for butt welded joint are thought to be the following four : (1) frirness : to be able to judge test results with fairness, (2) reasonableness : to be able to give bend elongations as uniformly as possible to both weld metal and base metal, in the test of joint, (3) severity : to be able to give a considerable magnitude of maximum local bend elongation, and (4) simplicity : to be able to perform a test simply and easily.
Conditions (1), (2) and (3) tend to conflict with one another. By synthetic estimation, a guided bend test and a roller bend test with a large radius loading-pin are tolerable, and a free bend test and a roller bend test with a small radius loading-pin are thought to be somewhat inadequate as bend test. But if selectively applied according to the characteristics and object of test, each of these bend tests will have its own significance.
With an increasing strength of base metal (when the strength of weld metal nearly equals to the one of base metal), the severity tends to rapidly increase, therefore in order to keep the severity constant in the case of a roller bend test, the loading-pin radius must be increased. Similarly, in the case of a guided bend test, it seems to be necessary to change the size of the guided bend test jig.
After all, the significance of the method of bend test for butt welded joint is thought to be confined to the under-cut (simple) test. As the above-mentioned characteristics fluctuate on account of the variation of shape and size of test specimen (plate thickness, width and shape and size of weld metal etc.) etc., it is considered important to inspect the characteristics of bend test method before a special bend test is performed.