Study Of Jet Stability In Micro-injection Flow-guided Laser Processing

Micro-jet water-guided laser processing technology,referred to as water-guided laser,is a precision processing technology that uses micro-jet water to guide the laser to the surface of the substrate,this laser and jet "coaxial" processing method,not only inherits the advantages of conventional laser processing high speed,high precision,processing parts without wear,but also makes up for the shortcomings of conventional laser processing,such as great heat affected zone,taper and burr on the machined surface,and effectively improves the surface quality of the processed parts and provides an effective solution for precision manufacturing of difficult-to-machine materials.Generating a stable water jet with sufficient distance is a prerequisite for water-guided laser processing.Based on the current domestic and foreign research,this thesis studies the key technologies of water guided laser stable generation of water jet theoretically and numerically,and uses the numerical simulation analysis of water-guided laser coupling device jet stability as a guide to develop a design scheme that can meet the requirements of water-guided laser high-speed stable water jet,and conducts preliminary experimental analysis.The main research contents of the thesis is as follows:(1)In order to form a shrinking water jet that meets the requirements of water-guided laser processing,the generation and fracturing mechanism of micro-water jet and the characteristics of jet generation under different orifice structures were analyzed,and the influencing factors of water jet stability were explored to provide a theoretical basis for the study of water guided laser jet stability.(2)The water-guided laser coupling device is a direct generation device of stable water jet.The rationality of the internal structure of the water cavity and the stability of the internal flow field are important factors affecting the generation of stable jet.In order to solve the problems of unstable internal flow field of the coupled water cavity and maintenance difficulties of the coupling device,the structure of the water-guided laser coupled water cavity is optimized,and the stability of the internal flow field of the water cavity is verified by CFD simulation.In addition,by analyzing the internal flow field of the water cavity and the velocity field at the outlet of the water cavity,the internal structural parameters of the coupled water cavity(thin water layer thickness,water cavity diameter,overflow gap width)are analyzed by numerical simulations to determine the final structural parameters.(3)The cross-sectional shape and surface morphology of the high-speed water jet formed by the coupling device are analyzed by the fluid dynamics simulation software,and the influence of different water cavity inlet pressure,nozzle diameter and nozzle edge chamfer angle on the stable length and diameter of the jet is explored.It provides a certain guiding role for the water-guided laser processing distance and processing range under different inlet pressure and nozzle structure.(4)The jet stability test platform of water guide laser coupling device was built.The reliability of the coupling device is verified by analyzing the state of the water jet actually generated by the coupling device,and the stable distance of the generated jet is measured by the optical waveguide tracing method,and the numerical simulation results are preliminarily verified.