Computational mechanics of crack growth in selective laser sintering by means of eXtend finite element method (XFEM)

Additive Manufacturing (AM) as a material additive manufacturing process represents a significant breakthrough in manufacturing philosophy; this differs significantly from traditional material removal manufacturing processes e.g. metal cutting. Selective laser sintering (SLS), which comprises many elements such as mechanical processes, material, powders sintering, laser processing, and heat transfer, is an important branch of AM. Several fundamental problems including the interaction between the degree of particle melt (DPM) and crack behaviour of SLS printed part, eXtend finite element method (XFEM) based on material thermoelastic fracture performance are investigated in depth in this dissertation.
The DPM is defined by the proportions of the existence of both melted and crystallised parts, and un-melted particles within the SLS printed component. As un-melted particles come close to the initial crack, the crack attempts to evade these un-melted particles; as the hole is close to the initial crack, and the crack attempts to stay close to the hole.
There are two approaches, the virtual crack closure technique (VCCT) and the cohesive segment approach, used in each simulation. In some cases, VCCT results are similar to the results of the cohesive segment approach, however, the crack path of VCCT results is usually generated more smoothly than the results of the cohesive segment approach; this phenomenon is attributed to the fact that the method of VCCT for opening the crack is based on a combination of the critical energy release rates of normal and shear separation.
Further, the XFEM can be used to analyse the thermoelastic fracture problem. The displacement field of XFEM discretisation is similar to the temperature field discretisation. The test indicates that XFEM allows steady-state 2D thermoelastic problems to be dealt with precisely on a mesh independent of the location and length of the crack.