Research On Cavitation Characteristics And Mechanism In Acoustic Spreading Liquid Thin Layers Of Solder

The application of ultrasonic brazing in industrial production is widespread recently,due to the effect of cavitation in the liquid phase,which can eliminate the oxide film on the surface of base metal.This issue mainly focuses on the acoustic cavitation in ultrasound-assisted brazing.For different base metal,a software named ANSYS is used in harmonic analysis firstly,and it is learned that the vibration distribution in axial direction in the solder tank like a kind of quadratic function.The vibration intensity in titanium alloy surface is greater than aluminum alloy.And then,high-speed photography system is used to record the acoustically spreading process with ultrasound.In different ultrasonic vibration conditions,the spreading behavior of liquid metal shows different characteristics,including the periodicity of spreading,surface spraying and ripples,and summarizes the process of liquid metal acoustic deposition.The surface dynamic characteristics,spreading rules and the different test conditions are summarized in spreading process.Then a CFD software Fluent is used to simulate the acoustic metal deposition process of liquid metal with a variety of detailed parameters.It is concluded that within a certain range,increasing the amplitude and frequency can increase the extent of spreading.By making the metal droplets acoustically spread on the surface of glass plate,a high-speed photography system was used to record the cavitation phenomenon on the entire spreading interface.With different experimental conditions,the cavitation effects also show differences in bubble density,bubble distribution,and cavitation rate.Then,after observing the effect of cavitation on the base metal,it is concluded that the increasing of ultrasonic amplitude can enhance the cavitation intensity,and then cavitation characteristics and effects are analyzed.The CFD software Fluent is used to simulate the cavitation effect of liquid metal.From the numerical point of view,the influence of the pressure change in fluid on the cavitation process,the distribution law of the velocity field and the cavitation rate in the fluid are summarized.The equations of fluid mechanics are used to derive the governing equations for the dynamic process of acoustic cavitation,and some approximations and simplifications of control equations are made for the physical characteristics of liquid metal.Then,kinetic equations of the movement of cavitation bubbles in liquid metal are deduced with three aspects: mass conservation conditions,momentum conservation conditions and boundary conditions.And then,a cavitation physics model is constructed with these equations which is applied to the process and effect of acoustic cavitation.An analysis is performed to clarify the relationship between the evaporation rate and condensation rate in the liquid metal.