Inverse Simulation Of Load Induced By Cavittation Microjet And Study Of The Distribution Law Of Cavitation Erosion On Anodized Aluminum

Ultrasonic-assisted brazing can be achieved in the atmosphere without flux.It has a wide application prospect in the field of low temperature brazing of aluminum alloy.However,at present,the mechanism of removing the oxide film on the surface of aluminum alloy in the process of ultrasonic-assisted brazing is not mature,and most of the studies were based on the experimental results,and the quantitative relationship between ultrasonic parameters and cavitation has not been realized.Tthis research is to figure out the mechanism in the process of oxides removal,replaced natural oxidation film with dense anodic oxidation film,obtained strain-rate power model by inverse analysis conbining simulation with experiment,simulated deformation of the anodic oxidation film/aluminium matrix composite structure under the effect of cavitation micro jet,established and the quantitative relationship between the cavitation erosion and the impact load,then the distribution of the impact load of the micro-jet could be deduced by using the statistical cavitation pits.Finally,the relationship between the sound pressure field distribution and the cavitation erosion distribution was analyzed.Since the mechanical parameters of anodizing film are mostly unknown,it is hard to simulate the wall deformation under the effect of single-bubble micro-jet impact.In this study,the material constitutive relationship under static load(initial yield stress is 2.5MPa,work hardening index is 0.22)was obtained through the inversion analysis of nanoindentation test and simulation.Then the effect of strain rate hardening was considered,then the material constitutive relationship under dynamic load(strain rate enhancement index was 0.20)was obtained through micro-jet impact simulation supplemented by cavitation erosion results.Gaussian distribution load was choosed as ultrasonic micro-jet load to simulate the the matrix composite structure deformation.The peak of micro jet impact load,characteristic diameter of function area and duration time were investigated about how they influenced the deformation,it was found that higher peak load,bigger function area,longer duration time caused deeper pit.A series of micro-jet impact load parameters were input into the simulation to get the pit depth,which was fitted in Matlab.It was found that the mathematical relationship between the micro-jet impact load parameters and the cavitation pit depth could be well described by using quartic polynomial.The statistic results of cavitation revealed that the density of cavitation pits increased with longer ultrasonic time and higher ultrasonic amplitude.Besides,the density of cavitation pits in the center area of the specimen was more serious than that in the surrounding area.The impact load distribution of microjet can be calculated by inputting the statistical size of cavitation pits into the ABAQUS model.And the caculation results showed higher impact load in the center of specimen.In addition,the distribution of sound pressure field inside the filler metal was simulated by COMSOL,and it was found that the largest acoustic negative pressure value occurred at the center point of the specimen.Combined with the distribution of micro-jet load and acoustic negative pressure,the cavitation erosion law is explained from the mechanical and acoustic perspectives.