Flexible forming of laminated-composite metal sheets (LCMS) using plasma arc is a latest technique, which produces LCMS components by thermal stress without mould and external force. Considering that the controllable temperature field is the key during the forming process, a three-layer FEM model, based on the characteristics along LCMS thickness direction, was developed to study the variation rules of temperature field, which was verified robustness by experimental validation. Besides, the influences of process parameters such as plasma arc power, scanning speed and plasma arc diameter on LCMS temperature field were performed. The comparisons of LCMS with single layer metal sheet (SLMS) show the temperature difference of LCMS along thickness direction is smaller than that of SLMS, but the heat-affected zone of LCMS along X axis is wider than that of SLMS under the same process parameters.
A two-dimensional axisymmetric model,with 8700 and 7500 quadrilateral elements for the fluid and substrate zone separately,was developed to simulate the impacting and flattening process. The volume of fluid technique was employed to track the interface between the air and droplet. The relationships between the droplet pre-impact parameters and the flattening time as well as the flattening ratio were investigated by altering one of the parameters while remaining the others unchanged. The results show that the droplet height reaches its minimum value at approximately half of the spreading time,which also indicates the finish of vertical fluid flow at that time. The flattening ratio increases with the increase of the three pre-impact parameters-droplet diameter,temperature and velocity,even though the flattening time decreases when the droplet velocity increase.
As the important evaluation parameters concerning the spray qualities, the porosity and surface roughness of the coatings obtained by thermal spray forming have great influence on their forming accuracy, mechanical properties and service lifetime. But it is difficult to predict or control the two parameters for such a highly nonlinear process. A two-dimensional simulation of coating porosity and surface roughness of nickel-aluminum alloy (Ni-5%Al) in plasma spray forming was presented, which was based on the multi-dimensional statistical behaviors of the droplets as well as the simplification and digitization of the typical splat cross sections. Further analysis involving the influence of the droplet diameters and the scanning velocities of the spray gun on the two parameters was conducted. The simulation and analysis results indicate that the porosity and surface roughness are more influenced by the droplet diameters, but less influenced by the spray gun velocities. The results will provide basis for the prediction or control of coating mechanical properties by depositing parameters.
