NUMERICAL-SIMULATION OF STRESS INTENSITY FACTORS VIA THE THERMOELASTIC TECHNIQUE

The purpose of this study is to investigate the accuracy of the least squares method for finding the in-plane stress intensity factors K-I a nd K-II using thermoelastic data from isotropic materials. To fully un derstand the idealized condition of K-I and K-II calculated from therm oelastic experiments, the total stress field calculated from finite el ement analysis is used to take the place of data obtained from real th ermoelastic experiments. In the finite element analysis, the J-integra l is also calculated to compare with (K-I(2) + K-II(2))/E evaluated by the least squares method. The stress fields near the crack tip are do minated by the two stress intensity factors; however, the edge effect will cause inaccuracy of the thermoelastic data near the crack tip. Fu rthermore, the scan area of thermoelastic experiments cannot be too sm all. Therefore, we suggest that three or four terms of stress function be included in the least squares method for evaluating stress intensi ty factors via the thermoelastic technique. In the idealized condition , the error can be smaller than 3 percent from our numerical simulatio ns. If only the r(-1/2) term (K-I and K-II) is included in the least s quares method, even in the idealized case the error can be up to 20 pe rcent.