Mechanical/thermal stress intensification for mode I crack tip: Fracture initiation behavior of steel, aluminum and titanium alloys

Abstract

A line crack in an infinite plate is subjected to the combined mechanical and thermal loading. The problem is solved in the framework of thermoelastic theory by integrating with the complex function method. An analytical solution is obtained under the boundary condition that the constant temperature is retained on the crack surfaces while the remote uniform heat flow is applied. In this case, the mode II thermal stress intensity factor vanishes. Thermal loading only induces the mode I stress intensity factor. The heat flow along the vertical direction to the crack line has no influence on the thermal stress intensity factor. The problem is a typical mode I crack problem. Three materials, say 38Cr2Mo2VA steel, LY12 aluminum and TC6 titanium alloys, are studied. The applied failure stresses are calculated under the combination of mechanical and thermal loading by using the strain energy density factor theory. The fracture behaviors of three materials are compared. Their fracture resistance is quite different. It is found that the thermal loading would enhance the crack propagation. If the direction of heat flow is changed to an opposite direction, the thermal effect would impede the crack growth. That is the thermal effect has the positive or negative effect which depends on the direction of heat flow.