| Ultrasonic elliptical vibration cutting (EVC) had an unparalleled advantage interms of improving the machinability of ferrous metals and hard brittle materials,such as dramatically lengthened the diamond tool’s life, reduced the cutting forceeffectively, suppress the wear of cutting tool and improve processing efficiency aswell as the surface quality. Thus, it was considered as the most promisingultra-precision machining method. However, the core of EVC technology was thecutting device. It was of great significance to develop a resonant high-frequency EVCdevice whose vibration parameters and trajectory could be flexible adjusted to adaptto different machined surfaces, different workpiece materials and different cuttingparameters, by which the processing range of EVC was broaden and the practicalapplication of this technology could be realized.This dissertation was committed to the development of an adjustable resonanthigh-frequency EVC device, the performance of the apparatus was verified bytheoretical analysis, FEA and experiments. The main contributions of this thesiscould be summarized as follows:1) The methods of the adjustment of the cutting tool’s three main additionalelliptical motion parameters: frequency, amplitude and oval posture were proposed.And the way to verify the frequencies of elliptical vibration was discussed in detail.The longitudinal vibration along the thickness direction of piezoelectric ceramic ringwhose electric terminals were loaded was derived; the resonance frequency equationand equivalent circuit of the piezoelectric ceramic ring were obtained. The effect ofelectrical load on the piezoelectric ring chip’s resonance frequency was simulated byMATLAB, which further clarified the physical mechanism of electrical load’sinfluence on frequency and verified the feasibility of this method.2) A novel EVC system which was composed by a compound multi-frequencypiezoelectric transducer (MFPT) was developed; two sandwich piezoelectrictransducers were orthogonally placed in the EVC device. Considering the symmetrical structure of the MFPT, only a single transducer’s frequency equationwas established by the use of equivalent circuit method. At the same time, thematerials, shapes and sizes of the transducer were determined. The vibrationfrequencies and the oval shapes of the cutting tool were adjusted by varying theelectrical loads and the phase differences of the input voltage signal respectively. TheEVC device’s dynamic characteristics such as modal, harmonic response, transientbehavior were analyzed by ANSYS. The FEA results were in good agreement withthe design calculations, which verified the correctness of the design. Finally, thedynamic match circuit was put forward to ensure the piezoelectric transducer and thesignal generator could work well on each working frequency.3) In order to obtain the performance parameters of EVC device, thetransmission circuit method was taken to measure the resonance frequencies of theapparatus. The results of the experiments and theoretical calculation coincide to eachother well. The change of electric load L would affect the transducer’s harmonicfrequency which got smaller with the increase of L; An open loop testing system,composed by signal generator, power amplifier, MicroSense’s capacitivedisplacement transducer, Power PMAC, Siemens IPC and air bearing vibrationisolation platform (Newport RS4000), was set up to test the EVC device. Themovement crosstalk in both directions and the displacement responses at eachresonant frequency were measured, and the corresponding elliptical trajectories werefitted. Compared with other frequencies, the oval tracks were more regular at29.41KHz,25.00KHz and40.98KHz. When the operating frequency was25.00KHz, theelliptical locus varied significantly with the phase differences of the input voltages,which had a good agreement with the theoretical analysis. |
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