Residual Stress Prediction In Letterbox-Type Repair Welds

The influence of various modelling aspects on the prediction of residual stresses in a 3-bead letterbox-type repair weld is investigated in the present work. The repair is performed on a 2¼CrMo low alloy ferritic steel plate, containing a machined central groove of 9

mm

depth, 200

mm

length and 14

mm

width. Three weld beads are deposited in the groove using AL CROMO S 225 2¼ CrMo electrodes. The repaired region is considerably long and narrow to enable a 2D plane strain analysis. Using the commercial finite element code ANSYS and the very well known “birth and death” technique, the effect of material hardening rule, different heat input models such as prescribed temperature and heat generation rate approach, radiation boundary conditions and coefficient of convective cooling on the evaluation of residual stress field is examined in a sensitivity analysis frame work. Finite element 2D mesh and time step size are optimised affording useful information for a future 3D analysis. Metallurgical phase transformation effects are not included in the model, although it is general knowledge that its role in the formation of a residual stress field might be quite significant for ferritic steels. Recorded data for temperature and thermal strain histories are used to validate predictions obtained by finite element computer simulation. Comparisons reveal a good agreement between predicted and recorded temperature and thermal strain histories. Material hardening rule affects remarkably the results whereas the implication of radiation boundary conditions has a small contribution on the predicted results.