Advanced Materials Research Vols. 189-193

Abstract: In this investigation, we extend our previous works to improve piezoelectric properties of Pb(Zr,Ti)O₃ ceramics. Modified lead zirconate titanate (PZT) piezoceramics with a composition Zr/Ti=53/47 containing a trace of mixing dopants were prepared by conventional ceramic technology sintering powder compacts. Replacement of (Zr, Ti)⁺⁴ by Nb⁺⁵, Pb⁺² by Sb⁺³ and Mn⁺⁴ in PZT perovskite type solid solutions was accomplished by the creation of cation and anion vacancies. Modified ceramics were explored as a function of firing temperature to acquire exceedingly good piezoelectric characterizations. From the analysis results, calcined at 850°C for 2 h, and then sintered at 1280°C for 2 h, PZT piezoceramic showed the larger dielectric constant er 2013, mechanical quality factor Qm 120 and maximum electromechanical coupling factor kp 0.67. Besides, the bulk ceramic grains distribution were found to be uniform. Furthermore, the sample was found to possess piezoelectric properties, the resonance frequency being about 200 KHz suitable for acoustic sensor.

Abstract: The proof mass of micromechanical silicon oscillating accelerometer is small in size and light in weight, which badly restricts the improvement of accelerometer sensitivity. So a method of using micro leverage mechanisms to amplify the inertia force is widely accepted. There are restraints existing in the input and output beam end of the leverage mechanism, and the whole structure is flexible body. Therefore the Card Theorem is adopted to deduce the theoretical formula of the leverage amplification factor. The finite element analysis (FEA) is conducted to verify the theoretical formula. Then optimize the leverage mechanics with the complex optimal method to get the reasonable design parameters of the leverage mechanism. Finally, another simulation is conducted to test the optimized result.

Abstract: In order to solve the difficult problem of detection of pitch deviations of high-precision master gears, a new measuring instrument is developed. Detail description about measuring apparatus of pitch deviations developed for master gears was presented in the paper. Computer aided technology was used to deal with data collected by computer, and error analysis about the measuring apparatus was introduced, which affected measurement accuracy. The results confirm that the measuring apparatus is able to meet measurement requirement and improve efficiency through the measuring experiments on master gears of precision grade 2 and 1 with modulus 2 mm and 2.5 mm, respectively. And the uncertainties of single pitch deviation and total cumulative pitch deviation are 0.07and 0.26, respectively.

Abstract: Compared with the traditional chemical mechanical polishing (CMP) technique, the precision atomization ultra-polishing (PAUP) technology has the advantages of friendly environmental and damage-free. This paper established a novel PAUP tester based on the atmospheric pressure theory, and explored the possibility of PAUP technique. Furthermore, effects of operated parameters on the material removal rate and surface roughness were investigated in PAUP process. It was found that a material removal rate of 78.302 nm/min was obtained with a surface roughness of 0.015 µm at the optimal parameters. This study provides insight into the development of the novel ultra-polishing methods and its underlying theoretical foundation.

Abstract: Thermal errors are the major contributor to the dimensional errors of a workpiece in precision machining. Error compensation technique is a cost-effective way to reduce thermal errors. Accurate modeling of errors is a prerequisite of error compensation. In this paper, a thermal error model was proposed by using projection pursuit regression (PPR). The PPR method improves the prediction accuracy of thermal deformation in the CNC turning center.

Abstract: Ultrasonic cavitation is an extremely complex physical phenomenon. It displays a series of nonlinear dynamics as the bubbles oscillating, growth, shrinkage and even collapse. For ultrasonic honing, it causes the device to generate chatter and noise because of the cavitation effect, and even generates denudation on the workpiece surface. In this paper, it describes the cavitation mechanism in ultrasonic honing, and analysises the acoustic pressure of the formation of cavitation from the numerical, furthermore it experimentally demonstrated. It also analyzes the nonlinear oscillation of cavitation bubbles for the impact on the ultrasonic honing chatter. Through studying on ultrasonic cavitation mechanism of honing, it provided a theoretical basis to solution the problem of the ultrasonic honing chatter and improves the level of precision and ultra precision machining.

Abstract: In the chemical mechanical polishing process, the relationship of relative motion of polishing pad and polishing head plays very important role for CMP quality. This paper established the mathematical model in order to investigate the relative motion of polishing pad and polishing head. It was found that the speed ratio of polishing pad and polishing head shows great influence on the CMP uniformity. And when the value of speed ratio of relative rotation approaches 1.23, the distribution of abrasives’ trajectories is close and uniform. Theoretically, the surface quality of workpiece is better.

Abstract: In this paper, the adsorption characteristics of cationic polyelectrolyte PDADMAC on BGF particles and Zeta potential of BGF particles have been investigated. A new type of composite abrasive slurry was obtained with cationic polyelectrolyte modified BGF particles and its polishing performance was studied. Experimental results showed that the Zeta potential of the modified BGF particles was changed from negative to positive and the maximum value (+35mv) was obtained when the adsorption saturation was achieved, and the adsorption capacity of SiO₂ abrasives on BGF particles was improved significantly as well. The material removal rate was 469nm/min with the modified BGF/ SiO₂ composite abrasives slurry containing 5% SiO₂ and 3% modified BGF particles, increasing by 47% and 89% than those of the unmodified BGF/SiO2 composite abrasives slurry (319nm/min) and the single silica abrasives slurry (248nm/min), respectively.

Abstract: The longitudinal piezoelectric transducers compound and reasonable structure is derived and presented, in addition, the paper designed a experimental system that adapt to the longitudinal measurement of high-power transducer performance parameters; Measurement of performance parameters through experimental of the transducer by home-made, which including the phase and amplitude spectrum and impedance of the current and voltage, Ultimately the admittance circle can be gotten to improve the performance of the displacement amplitude, The paper provides a new way to analyze transducers.

Abstract: Billet is designed by utilizing the flow relief-hole principle to improve the dimensional accuracy during the precision cold forging of helical gear . An optimization method for the initial diameter of the relief-hole was proposed based on the finite element method(FEM) and response surface method (RSM). The degree of uniformity of effective strain in helical gear precision forging was considered as the optimal objective. The empirical equation built through Response Surface Method shows the relationship between the the initial diameter of the relief-hole and the degree of uniformity of effective strain. The optimal diameter is obtained through gold section method based on the empirical equation . The optimal result has been verified by using the commercial software DEFORM 3D.