A Research On Three-Dimensional Simulation Of Temperature Fields Of Laser Rapid Prototyping And Calculation Of Its Strain Fields

A computer simulation of the laser rapid prototyping process is developed by using the ANSYS parametric design language while considering the non-linear relationship between the heat flux loaded and the properties of material in the condition of high temperature in the fabrication process. The components of rapid prototype were fabricated with the laser generated by CO2 laser equipment. A two-dimensional mathematic model for laser heating was established for theoretical analysis and an analytical solution was evaluated for comparison with the results of simulation. A physical model for simulation was also created as well as an element model. A study was accomplished between the results of simulation and the ones of experiment, which showed that they agreed with each other, proved that the numerical modeling was feasible and further more evidence was given for the selection of processing parameters. By comparison between simulation and the two-dimensional analytical solution, it may be inferred that the heat transfer for single bead wall prototype is three-dimensional at the several preliminary layers and it becomes two-dimensional later. A key processing technology of laser rapid prototyping and the possibility of accuracy control of prototype were concluded-The control of heat flux of laser power is the key for laser rapid prototyping. Higher heat flux is needed at the beginning of fabrication and relatively lower heat flux is required when the part is a little higher. However, the heat flux of laser power has to be reduced at the position of velocity direction change of laser beam.Another key is the control of the width of prototype because, for single bead wall prototype, the width is determined by the size of molten pool.Obviously, the size of fusion zone is closely related to the heat flux of laser power, which is also needed to control in order to control the size of molten pool. Therefore, the size of molten pool can be controlled according to the control of heat flux. Under this situation, the width of rapid prototype can be controlled as well as the heat flux.With the addition of layers, the strains in the direction of height also increase. However, the largest deform is several micro-strains only, which can't impact on the accuracy of prototype at all. It can be seen that the accuracy of prototype mainly relies on the shaping process.