Research On Numerical Simulation Of Impact And Solidification For Droplet Deposition On Substrate

As a new developed rapid manufacturing technology, droplet deposition increasing material manufacturing technique is based on a layered manufacturing paradigm: the fused drops are deposited exactly onto a movable substrate through alternative charging and deflecting to fabricate complex shape prototyping. Compared with conventional rapid prototyping technology, this kind of technology can form higher melting point material with good performance. Moreover, the technique has the advantages over low cost and non-aftertreatment, therefore it has a bright foreground. The key and difficulty of the technique is to control the fused drop's deformation accurately, because it influenced the part forming and precision directly. However, there are a lot of factors that have influences on the fused drops, so only when all parameters selected properly, can we get deforming fused drops satisfactorily.At first, this paper analyzes the progress of deformation, and then establishes the theoretical mode of the Droplet deposition according fluid mechanical governing equation. VOF method was used to track and adjust the free surface of fused drop, enthalpy-porosity technique was used to track the growth of solidifying layer. Combined finite volume method with theoretical mode of the Droplet deposition, the colliding process has been simulated successfully via computational fluid dynamics software FLUENT.According to the visual results of simulation, the effects on droplet deposition with different temperature, velocity and thermal resistances are investigated in this paper. Flow field and temperature field affects each other, which together determine the shape of spreading and frozen layer growing. The concept of semi-solidification was put forward, analyze defects that may be occurred from different aspects such as collapsed, cold lap, gap and so on. The time, the radius and thickness of frozen layer can be obtained for semi-solidification drop, which was used to guide the choice of technological parameters, for example, the distance between adjacent drops, the moving of substrate and so on. The simulation results agree well with experimental results, it means the model is reasonable.This thesis applies numerical simulation method to discuss the impact and solidification of droplet deposition, through studying the rules of spreading and solidification, which lay a good foundation for droplets deposition, and can provide the theory basis and parameters for droplet deposition increasing material manufacturing.