A novel technique for determination of histories of SIF distributions along 3D crack fronts of a body subjected to thermal shock

The thermal weight function (TWF) is dependent only on the crack con guration and body geometry, and is independent of temperature elds. TWF is independent of time during thermal shock, so the whole variation of transient stress intensity factors (SIFs) can be directly calculated through integration of products of TWF and transient temperatures and temperature gradients. The basic equation for the 3D TWF method for Mode I is derived. Then a novel technique, referred to as the multiple virtual crack extension (MVCE) technique, is proposed to solve the basic equations in the 3D TWF method. The specially selected linearly independent VCE modes are directly used as shape functions for the interpolation of unknown SIFs. The coe cient matrix of the nal system of equations is a triplediagonal matrix and the values of the coe cients on the main diagonal are usually large. The system of equations has good numerical properties. The number of linearly independent VCE modes which can be introduced in a problem is unlimited. The complex situations that the SIFs vary dramatically along the crack fronts can be numerically well simulated by the MVCE technique. Examples show that the scheme is of very high e ciency and of good accuracy. The results show that the histories of SIF distributions along 3D crack fronts are very complex. In order to understand the behaviour of 3D cracks correctly it should be calculated in detail