Design And Optimization Of Horn For Medical Ultrasonic Lithotripsy System

For small trauma to the human body,wide range of application,rapid postoperative recovery,thorough stone removal and low postoperative recurrence rate,ultrasonic lithotripsy can be used widely.The horn of medical ultrasonic vibration system is the main component of ultrasonic lithotripsy equipment and the main component of ultrasonic lithotripsy system,and it is also the medium of energy transfer between ultrasonic lithotripsy equipment and lithiasis.In the ultrasonic macadam system,horn main plays the role of guiding vibration and amplifying amplitude,and its performance directly affects the effect ofmacadam.There are many factors affecting the ultrasonic horn,which mainly include horn material,horn type,input end and output ratio.In lithotripsy,the length and frequency of the ultrasonic hornhas certain requirements,to be more specific,the length is more than 300mm,and the frequency is50k Hz.A single horn can not meet the length requirements,so it needs to be connected with the vibration guide rod,the size of the vibration guide rod have a greate ffect on the overall vibration system,it should be joint together with horn,and the size of the vibration guide rod has a great influence on the overall vibration system.In order to meet the requirements of lithotripsy,the vibration guide rod was hollow,and the outer diameter should not be too large,so that the wall thickness of the vibration guide rod is thin and it is difficult to connect with the horn.The purpose of this paper is to explore the influence of the material and structure of the luffing rod on its vibration performance,study the influence of welding process on fatigue life,and provide experimental results and process reference for the design of the luffing rod and connection mode.In this paper,according to the material and structure of horn,titanium alloy,brass and stainless steel with better vibration effect were selected,and stepped horn and composite horn were selected for the structure type of horn.The horn with different materials and structures was designed by the analytical method,and the modal analysis and response analysis of the horn were carried out by the finite element method to explore the difference between the natural frequency and the design frequency of the horn with different materials,and the resonance state of different materials under natural frequency resonance was studied,including amplitude-frequency characteristic curve,amplitude magnification,equivalent stress and so on.By comparing the magnification and equivalent stress of the horn with different materialsand different structural types,the appropriate material and structure type of the horn were selected.At the same time,the influence of the size of the input and output on the resonant state of the horn was studied,and the appropriate size of the output was selected.With the help of the finite element analysis method,the length of the vibration guide rod is determined to meet the length requirements under the condition of right frequency.And the influence of the size of the vibration guide rod on the natural frequency and resonance state of the horn was studied,and the size of the vibration guide rod that meets the requirements of crushed stone was selected.In this paper,the connection mode of horn and vibration guide rod was studied,and it was found that TC4 titanium alloyshowed an excellent vibration characteristic.Due to the wall thickness of the vibrator,the screw connection cannot be achieved.the laser pulse welding method suitable for thin-walled metal connection was selected in this paper.By studying the weld morphology,microstructure and mechanical properties under different laser current,pulse width and defocus,the suitable welding process was found.It was found that the thin-walled TC4 titanium alloy with 0.3mm thickness has good weldabilityunder the condition of current 90A,laser pulse width 3.5ms,defocus amount+3mm,welding speed100mm/min and pulse frequency 15Hz.The software of fatigue analysis（ncode Design Life）was used to analysis the fatigue life of the harmonic response results of the ultrasonic horn,and the fatigue life of the weld joint of the ultrasonic horn was predicted.The results of simulation showed that the fatigue life of ultrasonic horn was more than 10¹⁰times,the arc transition of the ultrasonic horn was the weakest,the weld indecidedan excellent fatigue and had no effect on fatigue.To joints the horn and guide rod,welding is a better method.