Research On Mechanism And Structure Of Ultrasonic Torsional Vibration Conversion Of Circumferential Radial Chute

The importability of high-frequency ultrasonic vibration assistance in machining has the advantages of reducing cutting force,improving the precision of formed surface and prolonging tool life.Therefore,it is widely used in machining such as grinding,drilling and turning.The limitation of the special conditions results in slow development of ultrasonic vibration assistance in the field of milling.Ultrasonic vibration work platform,one-dimensional longitudinal vibration of tool head using consolidated abrasive particles,and longitudinal torsional composite resonance are the main processing methods in ultrasonic milling at present.The above can not apply parallel ultrasonic vibration in the cutting direction of the tool,and are prone to problems such as material delamination and residual height distribution after machining,which seriously limits the advantages of ultrasonic vibration assisted machining in the milling field.Therefore,it is of great significance to research the torsional ultrasonic transducer whose cutting direction is parallel to the vibration direction.Based on the reflection principle of stress wave from the radial chute,the mechanical model of the radial wave entering the chute disc and synthesizing the circumferential wave is established,and the stress state of the stress wave after the radial wave acts on the chute is deduced.On this basis,the influence of the chute angle on the circumferential wave is obtained.Theoretical analysis shows that there is an optimal chute angle for the synthesis of the circumferential wave.Then,the transducer and the optimal inclined chute disc are chosen for modal analysis.In the simulation,the radial waves generated by the excitation is evenly distributed at the disc and effectively converted into circumferential waves;The converted circumferential wave is transmitted to the output end through the horn of pure torsional mode,and the transducer realizes pure torsional output in the plane.The main contents of the thesis are as follows:(1)The mechanism of realizing torsional vibration is studied.Firstly,it is proposed to evenly arrange shear pieces on the circumference and realize torsional vibration through shear strain.Then,it is proposed that the radial chute is uniformly distributed on the circumference,and the torsional vibration is realized by synthesizing the circumferential wave through the propagation of the stress wave.Compared with its sound transmission mechanism and realization mode,the radial chute is selected as the research object of this thesis.(2)Based on the reflection principle of the stress wave in the radial chute,the dynamic model of the stress wave transformation is established,and the stress state of the radial wave after the action of the chute is deduced.The theoretical derivation shows that the stress wave generated by radial excitation will synthesize the main stress wave along the circumferential direction at the chute position,and there is a chute angle to synthesize the best circumferential wave.The vector output of the circumferential wave can be adjusted by the geometric parameters and characteristic parameters of the chute.(3)Combined with theoretical calculation and finite element simulation,a 20000 Hz radialtorsional vibration conversion ultrasonic transducer is designed.In the modal analysis,the radial wave generated by the magnetostrictive material is converted into the circumferential wave through the chute,and the circumferential wave of the circular surface in the disc is transferred to the output rod step by step through the horn in the pure torsional mode.The resonant frequency of the simulated radial and torsional vibration conversion ultrasonic transducer is 20795 Hz,and the amplitude of the radial wave generated by the excitation is about 10.33 times larger than that of the circumferential wave transmitted to the output rod.(4)The performance test verifies the correctness of the theory and simulation.The resonant frequency of the radial chute disk is 19660 Hz,and the radial and circumferential amplitudes at low driving power are 900 nm and 825 nm respectively,and the amplitude ratio is 1.09,which is consistent with the simulation results.At this time,the torsional amplitude at the output end can reach 4.7 μm.It can be used in general torsion machining.Through the above research,the design of the specific ultrasonic transducer has been completed.The theoretical derivation and finite element simulation have been verified through experimental tests.It has been proved that the circumferential vibration at the disc can be effectively transmitted to the output rod,laying the foundation for the subsequent torsional vibration processing experiments and the mechanism analysis of cutting parameters.