Modelling of directed energy deposition processes

The laser additive manufacturing technique of laser deposition allows quick fabrication of fully-dense metallic components directly from Computer Aided Design (CAD) solid models. The applications of laser deposition include rapid prototyping, rapid tooling and part refurbishment. The development of an accurate predictive model for laser deposition is extremely complicated due to the multitude of process parameters and materials properties involved. In this work, a heat transfer and fluid flow model is developed. In the heat transfer and fluid flow model, the governing equations for solid, liquid and gas phases in the calculation domain have been formulated using the continuum model. The free surface in the melt pool has been tracked by the Volume of Fluid (VOF) method. Surface tension was modeled by taking the Continuum Surface Force (CSF) model combined with a force-balance flow algorithm. Laser-powder interaction was modeled to account for the effects of laser power attenuation and powder temperature rise during the laser metal deposition process. Temperature-dependent thermal-physical material properties were considered in the numerical implementation. The calculation domain is logically partitioned into smaller cells in 3D space. This makes the numerical implementation consume large amounts of computational resources as each cell is considered at each step of the implementation. This challenge has been addressed through the use of parallel computing by way of message passing interface. Simulations were performed and a comparison between the sequential and parallel implementations was also made --Abstract, page iv