Research On Acoustic System Of Ultrasonic Deep Rolling With Longitudinal-torsional Vibration

The mechanical structure and components are widely used in the field of oceanengineering, aerospace, power and metallurgical industry, which need smaller surfaceroughness, higher surface hardness in order to improve the mechanical propertiesincluding matching precision, surface wear resistance and corrosion resistance, and soon. The technology of longitudinal-torsional vibration of ultrasonic deep rolling takesthe advantages of ultrasonic deep rolling and the ultrasonic machining withlongitudinal-torsional vibration. This technology not only ensures high depth valueresidual compressive stress, a moderate amount of processing hardening and the surfaceof the metal nanotechnology, but further improves the processing precision of parts byusing the characteristics of longitudinal-torsional vibration. The design of ultrasonicacoustic system is one of the key technologies in the longitudinal-torsional vibration ofultrasonic deep rolling.This thesis dissolves the design problem of the ultrasonic acoustic system of thelongitudinal-torsional vibration of ultrasonic deep rolling. And two different methodsare proposed to design the acoustic system so as to make the acoustic system realizelongitudinal-torsional vibration under single excitation along longitudinal direction.Firstly, the resonance conditions of longitudinal and torsional vibration in conicalcompound ultrasonic horn are studied combined with the longitudinal vibration andtorsional vibration wave equation based on one-dimensional wave theory. Thenumerical results show that longitudinal-torsional vibration may be realized by theconical compound ultrasonic horn under single excitation along longitudinal directionwhen appropriate geometric structure parameters are chosen. While it is difficult to fixthe ultrasonic horn or acoustic system as the displacement nodes of longitudinalvibration and torsional vibration are not the same.Secondly, the converter with multiple diagonal slits is studied so as to inducelongitudinal-torsional compound vibration modal by single longitudinal vibration modal,and the longitudinal-torsional vibration frequency are studied through analyzing thevibration characteristic of the converter with multiple diagonal slits. The numericalresults show that the longitudinal-torsional vibration may be realized by the acoustic system made of stepped compound horn and converter with multiple diagonal slits, andthe acoustic vibration system may be fixed on the displacement node of stepped horn.The output trajectory of acoustic vibration system is two-dimension spiral curve, whilethe amplitude is periodical. Impedance characteristics test of acoustic system are carriedout, and the experiment results show that acoustic vibration property is favorable andmeets well with the results of finite element analysis.This study can provide a new method for the design of the ultrasonic acousticsystem with longitudinal-torsional vibration.