Multi-Scale Modeling and Simulation of Directed Energy Deposition Processes

The Directed Energy Deposition Process presented here is a metal additive manufacturing process in which focused thermal energy is used to fuse materials by melting as they are being deposited.  It includes deposition of wire and powder materials, and could include lasers and electron beams as the energy source.  It is an ideal process especially for feature addition and repair of metal parts.  A predicted model will be useful in design practices for additive manufacturing processes.  This presentation will discuss various modeling and simulation efforts to model Directed Energy Deposition Processes.  A residual model can impact the fatigue life, corrosion resistance, distortion, dimensional stability, brittle fracture, warping and buckling of the deposited parts.  Finite element analysis was carried out to divide the material addition onto the substrate into small time steps, and apply variable flux and boundary conditions in each time step. A melt pool model can help online monitoring deposition, monitoring melt pool size and geometry, controlling temperature and the uniformity of deposits and material properties.  Transient temperature distribution, fluid velocity, and pressure in the melt pool, as well as free surface were simulated without assuming melt pool shape as a priority. Microstructure model can predict how the process parameter can impact the resulting microstructure of the deposited parts.  For example, one could use certain process parameters to result in deposited parts with columnar or equiaxed grains.  The columnar-to-equiaxed transition being modeled is a function of temperature gradients, solidification speed, nucleation under-cooling, and number density of equiaxed grains. The experimental validation of these models will also be discussed.