Simulation Of Cavitation Effect And Ultrasonic Field During Ultrasonic Assisted Soldering

Ultrasonic-assisted brazing enables reliable joining of difficult-to-wet materials and complex components.At present,the ultrasonic assisted brazing process is quite mature,but the mechanism of action of ultrasonic in the welding process is still unclear.In this paper,the narrow gap lap ultrasonic assisted brazing is studied.The distribution of the vibration field in the base metal and the sound pressure distribution in the brazing material under ultrasonic action are studied.The relationship between the sound pressure value and the cavitation in the molten solder is established.And verify the results by calculation and experiment of cavitation effect.Based on COMSOL Multiphysics simulation software,a model of 1060Al narrow gap lap ultrasonic assisted brazing was established.It is found that under the ultrasonic displacement load of 20KHz and 3.5?m,the vibration field formed by the reaction of the base metal has regularity and periodicity.The base material changes direction once in one cycle,and the vibration direction of the base material is opposite to the input load direction.The maximum displacement occurs at a position 13 mm from the center of the action position of the ultrasonic horn,that is,the x coordinate is 67,where the maximum value of the positive displacement is 1.76?m,and the maximum value of the negative displacement is-2.54?m.The vibration field distribution of different base metals is different.The displacement value and distribution of the brazing material type and the thickness of the brazing material layer to the vibration field of the parent metal are smal,and there are only nanometer differences.When the amplitude of the ultrasonic wave changes,the vibration field distribution of the base metal does not change,but the vibration intensity is affected.The larger the ultrasonic amplitude,the larger the displacement of the base metal.The liquid solder field can be divided into three regions according to the sound pressure:a dumbbell-shaped region with a strong sound pressure,a triangular region with a weak sound pressure on both sides of the dumbbell shape,and a region with almost no sound pressure at the boundary of the solder region.The acoustic positive pressure extreme value of the dumbbell-shaped region in the brazing filer metal is 2.63 MPa,and the acoustic negative pressure extreme value is-2.42 MPa.The acoustic positive pressure extreme value of the triangular sound pressure zone is 0.51 MPa,and the acoustic negative pressure extreme value is-0.6 MPa.The dumbbell-shaped area is opposite to the sound pressure at the same time in the triangular region where the sound pressure is small on both sides.Different ultrasonic excitation amplitudes will not affect the change trend and distribution of sound pressure in the solder field,and will only change the magnitude of the sound pressure extreme value.The larger the ultrasonic excitation amplitude is,the larger the sound pressure is.The influence of different solders on the sound pressure is between 0.0038 and 0.14 MPa.Different lap lengths will change the sound pressure distribution in the solder field.After calculation by K-M equation,the cavitation threshold decreases with the increase of cavitation nucleus.When the cavitation nucleus radius is 5?m,the threshold of transient cavitation of pure Sn solution under ultrasonic action is 2.5×10~5Pa.The greater the amplitude of the ultrasonic wave,the greater the pressure of the pressure wave produced,and the greater the range of action of the generated pressure wave.The cavitation experiment shows that the density and radius of the cavitation pits in the dumbbell-shaped area are larger than those in the triangle with small sound pressure,and the cavitation area is in good agreement with the simulation results.