Research On The Erosion Mechanism And Processing Craft On Curved Surface By Abrasive Water Jet Polishing

The machining process of the hard to machine materials,such as titanium alloy and alumina,is usually very poor,which can easily cause micro cracks and stress concentration by traditional polishing methods,further affecting the comprehensive performance of the parts.Abrasive water jet machining has the characteristics,like high processing flexibility and no heat deformation zone,resulting in precise polishing of above materials.In this paper,the influence of processing parameters on jet energy is analyzed.Then,the influence of abrasive parameters on material removal is further studied.Based on above research,the polishing mechanism of abrasive particles on materials is detailedly analyzed.By combining experiments with simulations,the regression model of abrasive water jet polishing is constructed,offering a new optimization strategy for process parameters.To achieve this goal,the specific research content and conclusions are as follows:(1)Basic theoretical research on abrasive water jet polishing.Based on the characteristics of jet flow structure under thin-wall/thick-wall outflow conditions,the energy distribution of the initial,core and dissipative segments of the jet is described.Through studying the formation process of the waterjet,the three-phase mixing mechanism of solid,liquid and gas in the abrasive jet system are analyzed.;Accoding to the theory of elastoplastic mechanics,the material damage removal mechanism under the action of single abrasive is expounded,further analyzing the relationship between compressive stress and shear stress of jet on the wall of material.(2)Jet energy control and nozzle structure optimization research.Based on the Euler-Lagrangian principle,a rapid design of the nozzle structure,accurate tracking of solid,liquid and gas three-phase acceleration and distribution,and wall-to-abrasive collision analysis were constructed by CFD technology in K-e abrasive water jet model.The internal flow field calculation model is used to analyze the influence of process parameters on jet energy and internal wear of the nozzle.On this basis,an improved nozzle structure is proposed.The optimized nozzle increases the abrasive exit velocity by 7.1%,which also decreases 11.8% wear rates.(3)Study on the mechanism of microscopic erosion removal of abrasive particles.Based on the explicit dynamics and smooth particle technology,the microscopic damage simulation model of abrasive particle erosion material was constructed.The damage evolution process of the burr under the action of abrasive particles was analyzed based on the model,and the abrasive grain size,abrasive grain shape and impact were analyzed.The influence of parameters such as angle and surface profile on the erosion quality shows that the closer the size of the abrasive grain is to the surface peak size,the less the residual surface of the peak;the more similar the shape of the contact surface between the abrasive grain and the peak,the more obvious the peak damage removal;when the angle is tangent to the surface of the workpiece,the surface peak can be effectively removed and the damage of the surface of the workpiece can be effectively reduced;the tapered peak can change the polishing trajectory of the abrasive grain to cause residual surface damage,and the spherical peak can easily causesurface cracks.The most important thing here is to reveal the plastic extrusion mechanism in jet polishing process.(4)Optimization of abrasive water jet surface polishing process parameters.Through single factor experiment,the influence of abrasive flow rate,jet pressure,transverse velocity and polishing angle on polishing quality were studied.Based on orthogonal experiment and range analysis,the optimal horizontal combination was obtained,and the reasonable parameter range of jet polishing was obtained.Based on the regression analysis of experimental data,a mathematical prediction model based on polishing quality was constructed.According to cuckoo algorithm and elite retention strategy,an improved cuckoo algorithm model for abrasive water jet polishing was constructed,and the corresponding algorithm flow chart was developed.By using Matlab to carry out the algorithm visualization operation of the mathematical model,the results showed that the optimized process parameter combination got from the algorithm decreased by 9.73% on average surface roughness,compared with the optimal level in the preliminary test.