Research On Assisted Abrasive Water Jet Machining Based On Flow Focusing Principle

With the rapid development of advanced ceramic materials,composite materials and other high-performance materials technology,traditional processing methods have been difficult to efficiently process these materials.Special processing technology is widely used in the production of high-performance materials,abrasive water jet machining is a kind of special processing technology,its process will not generate heat in the processing area,there is no thermal deformation,is only a kind of cold working technology,the ability to processing and metal,nonmetal,almost all materials such as composite materials,ceramics,rubber,high material removal rate,as well as good surface integrity after processing,caused the wide attention of scholars both at home and abroad.But abrasive water jet machining technology also has some shortcomings,such as nozzle wear fast,jet easy to disperse,high requirements for sealing,lack of special software and so on.In this paper,an abrasive water jet machining method based on flow focusing principle is proposed.This machining method adopts the flow focusing principle to assist the abrasive water jet machining technology.On the basis of the advantages of no heat generation and no tool contact with the workpiece,it can also reduce the diameter of the jet and inhibit the divergence of the jet.In this paper,the theoretical research,simulation analysis and experimental verification of the machining method are carried out,and the research results are summarized,and the prospect of the machining method is given.In terms of theory,this paper analyzes the jet focusing principle according to the structure of the jet,discusses the change of the velocity pattern of the internal unit of the jet due to the deformation when the flow focusing,discusses the processing parameters that affect the jet velocity and the processing effect according to the relevant knowledge of fluid mechanics,and establishes the velocity pattern when the jet focusing.Draw a jet machining effect mainly by the jet liquid pressure,focus on the gas pressure and the nozzle exit diameter and the distance between the nozzle exit and focused holes affect the four processing parameters,force of workpiece,abrasive particles are studied according to the results to choose the suitable abrasive particles,jet processing material removal function is established,the target distance is determined according to the jet velocity pattern.In terms of simulation,this paper solved the jet cloud and flow charts under different gas-liquid ratios based on the Fluent software.According to the experimental results of each group,the focusing effect was the best when the gas-liquid pressure ratio was between 0.5-0.8,and the gas-liquid pressure ratio was determined for the experimental part of the next chapter.And set up under different processing parameters of single factor experiment,the focus on theoretical research of the liquid pressure,the gas pressure and the nozzle exit diameter and the nozzle exit and focus on hole spacing between the four processing parameters on the simulation analyses the influence of the jet velocity,analysis of experimental results,it is concluded that the processing parameters on the focus after the influence of the jet velocity is as follows: With the increase of liquid pressure,gas pressure,the distance between the nozzle outlet and the focusing hole,the jet velocity gradually increases after focusing,and with the increase of the diameter of the nozzle outlet,the jet velocity gradually decreases after focusing.In the experimental aspect,in order to research on theory and simulation results verify that this article according to hydraulic principle,design and build the flow is focused on the auxiliary abrasive water jet machining equipment,design and production of the circuit system control equipment,and use the theory of processing equipment for the target from the experimental verification,and the residence time of processing was determined by the experiment.Through single factor experiment and orthogonal experiment,the influences of liquid pressure,the distance between nozzle outlet and focusing hole,gas pressure and the diameter of nozzle outlet on the diameter and machining capacity of the jet after focusing were studied,and the experimental results were analyzed.According to the experimental results and the combination of theoretical research and simulation analysis,it can be known that the influence intensity of each processing parameter on the jet diameter after focusing is as follows: the diameter at the nozzle exit,the gas pressure,the space between the nozzle exit and the focusing hole,and the liquid pressure.The increase of liquid pressure will weaken the jet diameter after focusing,but can greatly improve the jet machining ability.The increase of gas pressure can reduce the jet diameter,but too large pressure will crush part of the jet area,resulting in a decline in processing capacity;the increase of the diameter of the nozzle outlet will lead to the sharp increase of the diameter of the abrasive water jet after focusing,and will also reduce the machining ability of the abrasive water jet after focusing.If the spacing between the nozzle outlet and the focusing orifice is increased,the jet diameter will increase after the jet focusing,and the machining ability of the jet will decrease,but the influence is relatively slow.When auxiliary abrasive water jet machining based on flow focusing principle,the optimal parameters should be: target distance 8mm,residence time 140 s,liquid pressure 0.3Mpa,focusing gas pressure 0.2Mpa,nozzle outlet diameter should be 0.6mm,the distance between nozzle outlet and focusing hole should be 2.7mm.During processing,the appropriate liquid pressure and gas pressure can be selected according to the actual situation,and the ratio of liquid pressure and gas pressure value should be kept at about 0.67.