Thermal Stress Cleaving near a Free Edge Using a Moving Heat Source

In order to understand warping of crack extension in a thermal stress cleaving near a free edge of a rectangular plate, unsteady thermal stress field was analyzed on a rectangular region with an extending edge crack and a moving heat. The thermal stress field in an infinite region corresponding to the temperature is similar to the one due to a line heat. Hence the thermal stress intensity factor of an edge crack whose tip locates in a middle region is expected not to depend strongly on the crack length. Using stress intensity factors, KI and KII estimated by FEM, their distribution maps against the heating position have been constructed. The crack warping toward the free edge is explained from the sign of KII in the case of heating on a crack extending line. Null KII is achieved by heating a little above the crack extending line and straight crack extension may occur by heating there. The region giving negative KI and positive KII by heating is effectively utilized to give positive KI and negative KII, by cooling and hence cooling reduces the warping tendency. It was concluded that for the thermal stress cleaving, the effective region to be heated or to be cooled exists around the crack tip.