Predicting weld solidification cracking using damage mechanics -- LDRD summary report

Abstract

This report summarizes the efforts to develop and validate a finite element based model to predict weld solidification cracking behavior. Such a model must capture the solidification behavior, the thermal behavior in the weld pool region, the material mechanical response, and some failure criteria to determine when solidification cracking will occur. For such a program to be successful, each aspect of the model had to be accurately modeled and verified since the output of one portion of the model served as the input to other portions of the model. A solidification model which includes dendrite tip and eutectic undercooling was developed and used in both the thermal and mechanical finite element analysis. High magnification video techniques were developed to measure strains for validation of the mechanical predictions using a strain rate and temperature dependent constitutive model. This model was coupled with a ductile void growth damage model and correlated with experimental observations to determine capabilities of predicting cracking response. A two phase (solid + liquid) material model was also developed that can be used to more accurately capture the mechanics of weld solidification cracking. In general, reasonable agreement was obtained between simulation and experiment for location of crack initiation and extent of cracking for 606 1 -T6 aluminum.This page intentionally left blank 4

Three-dimensional numerical simulation of weld solidification cracking

“…Some researchers have indicated that the latent heat of fusion highly influences the shape and size of the weld pool, as well as the temperature distributions in the vicinity of the weld pool. Dike et al [27] and Brooks and Dike [28] evaluated three different latent heat release models. They obtained quite a good agreement with measured strains and temperatures.…”