Theoretical And Experimental Study On The Interaction Of Laser And Metal Powder Flow In The Laser Remanufacturing

The laser cladding process has been investigated over the past decades. It is one of the advanced high energy beam techniques for repair metallic machine parts locally. But it has not been widely in a development stage and reached the desired result, developing high flexibility remanufacture technique has become the urgent need of the repairing industry. At present, study of the laser remanufacturing is concentrate on technics investigate and relevant development of equipments in the world. The theoretical to restrain technological development and influence the technology unique potentiality is scarce, especially as a requirement for an academic degree to further investigate that advantage give full play. The thesis primarily studies the basic theory of the laser interaction with metal powder particles cloud in the course of the laser remanufacturing, offers guidance for its application in industry.In this dissertation the development of laser manufacturing technology was overviewed. The relevant technical development of laser diffusion and gas-particle two-phase flow was expounded. The physics law of research object transport was theoretically and experimentally studied. The researches mainly include such as:In chapter three, the diffusion optical characteristics of the laser radiation particles flow was theoretically studied. The physics simple model with powder coaxial feeder into laser beam was first given. In order to give the light diffusion characteristics, the exact equations for the scattering of an electromagnetic wave from a single sphere was described by Mie theory and the addition theorem of Spherical Harmonics Method. The influence of particle size, particle flow density and properties of light on transport was analyzed and discussed by lots of numerical simulation.In chapter four, the physical model of laser transmit heat energy in powder flow was set up. A numerical method was presented for analyzing 2-dimensional quasi-steady heat transfer. Using the finite volume numerical technique, the temperature of space distribute was described by the ANSYS software. This method can express actual state of heat transfer and heat radiation in laser diffusion.In chapter five, on the basis of analyzing the two-phase flow, the physics and mathematics models were set up. This approach treats each phase separately, and the link between the gas and particle phase is through drag. The flow was simulated.The relation of parameters of gas flows and powder mass flow rates to velocity and the concentration of the powder stream was derived.In chapter six to eight, a new digital particle image velocimetry (DPIV) technology was applied to study the gas- particle motion. The DPFV proceeding software was developed. The results indicate that the newly developed algorithm describes the real flow field more accurately than the conventional cross-correlation method.In chapter nine, an experimental was performed to. identify the laser remanufacturing quality. The laser cladding has relations with particle size, particle flow density, laser power, light beam size.