Pull-out tests on tube to sheet joints fabricated by endforming

In the present work, a detailed analysis of pull-out tests of Mild Steel tube-Stainless sheet joint fabricated by tube endforming has been done. The same has been compared with a welded joint. Pull-out tests are conducted at three different die angles. Both experimental and finite element simulations of the pull-out tests of joints are attempted. The load evolution and energy absorbed during pull-out tests are monitored. It is observed that the endformed joint fails by joint unlocking, while it is physical failure in case of welded structure. The flat die takes lesser displacement at failure, but larger maximum load for joint unlocking as compared to angular dies, except in one case. In the case of angular dies, due to slipping at the tube-sheet interface, lesser load is required for complete unlocking. The welded structure fails at lesser load when flat dies are used, while it takes larger load at failure in angular dies. So the performance of endformed joint is better than the welded joint only when flat dies are used. Same is the case with energy absorbed during tests. A significant difference is seen between finite element simulation and experimental results of pull-out tests. This could be attributed due to the difficulties in mechanical clamping in experiments and other approximations in modeling friction, strain-hardening etc. So pull-out tests simulations should be used with caution for joint performance evaluation before its accuracy is fully improved.