Key Engineering Materials Vol. 620

Abstract: In the present work, ultrasonic assisted grinding (UAG) and conventional grinding (CG, without ultrasonic) tests of Carbon fiber reinforced silicon carbide matrix (C/SiC) composites were conducted. In addition, analysis was done by comparing the machining quality, grinding force, and specific grinding energy between the two processes. The results showed that material removal mode of carbon fiber both in CG and UAG were brittle fracture, and fracture size had no obvious difference. Compared with CG, brittle fracture area of SiC increased during UAG. In comparison with CG, the normal grinding force and tangential grinding force for UAG were reduced maximally by 45%, 39% respectively of those for CG. Accordingly, specific grinding energy was also reduced by UAG. Therefore, UAG can improve the grinding performance of C/SiC composites significantly.

Abstract: This Paper has analyzed the relationship between the generation of multiple piezoelectric effects and boundary conditions of piezoelectrics and the experiments have studied tertiary piezoelectric effect of piezoelectric quartz which is applied extensively in engineering practice. We processed our experiment by piezoelectric quartz crystal unit made by two pieces of X-cut piezoelectric quartz, parallel connected it to a capacitor with the equivalent capacitance of about 1,000 times of that of piezoelectric quartz crystal unit and then got the result of pure primary piezoelectric effect excluding tertiary induced effect; then compared it with conventional primary piezoelectric effect and concluded that tertiary piezoelectric effect of piezoelectric quartz is about 1.7% of primary piezoelectric effect; thus quantified longitudinally tertiary piezoelectric effect of piezoelectric quartz crystal, concluded that piezoelectric coefficient of tertiary effect of X-cut piezoelectric quartz is about 0.04 pC/N by experiment and got relative uncertainty and standard uncertainty of the results by such experiment methods respectively as 9.49×10^-3 and 1.37×10^-2. This study on tertiary piezoelectric effect has provided a new approach for improving precision and sensitivity of piezoelectric sensors.

Abstract: The porous ceramic holds good potential as acoustic resistance and vibration reduction material during ultra-precision machining. Porous materials absorb acoustic energy by friction with the air that moves inside the pores, and in this paper, the motion is simplified as the incompressible fluid in a single cylindrical pore. The analysis and calculation results show that the acoustic coefficient of porous ceramic is a complicated wave function and the acoustic absorption coefficient calculation model is feasible based on fluid thermal viscous theory. The acoustic absorption coefficient of porous ceramic increases with the increase of thickness, and its period and amplitude decreases with the increase of porosity of ceramic.

Abstract: This paper analyzes the factors, which causes the no-linear of the ultrasonic in the processing system, and the reasons of the ultrasonic reflection and transmission at the contact interface according to the wave theory. In this paper, the ultrasonic displacement coefficient, the pressure reflection coefficient, the displacement transmission coefficient and the pressure transmission coefficient are deduced. The relation among the x-axis and included angle, the incident wave, reflected transmitted waves. The relationship between the preload of the piezoelectric ceramics and the ultrasonic propagation is established, and the best of the bolt preload is investigated. The experiment is done to verify the relationship between the amplitude-frequency characteristics and the ultrasonic transducer at different preload, which provides a reliable basis for the ultrasonic system design, installation and maintenance.

Abstract: In this paper, a unique design of low temperature of BTA deep-hole machining system based on the green manufacturing was proposed,in which the low temperature air cutting technology was applied to the BTA deep hole processing. Consequently, the system have the characteristics of low temperature air cutting and deep hole processing. The system presented here uses the large flow of cold air (-30 °C ~-20 °C) and oil mixing atomization gas (MQL) for chip removal, cooling and lubricating the tool, thus the use of deep hole cutting oil was decreased, the cooling and lubricating effect of the tool was strengthened and the tool life was also strengthened. In this article, the ANSYS CFX was used for simulating the internal flow field of chip removal channel. By means of simulations, it is concluded that the pressure difference between the low temperature cold wind is significantly greater than the pressure difference between the liquid, and the gas flow rate is greater than the liquid flow rate. The comprehensive analysis indicate that low temperature air system are likely to bring about a better ability of chip removal, which provides theoretical basis for the low temperature air cutting technology was applied to deep-hole machining system.

Abstract: To meet the demand of rotating mechanism for self-powered monitoring system, piezoelectric energy generator (PEG) excited by the magnetic coupling force between rotating magnet fixed on a rotator and one magnet fixed on piezo-beam under different holding condition was presented. The influence of holding conditions (both sides holding, free holding, right side holding and left side holding) and rotating speed on energy generation of the PEG was investigated experimentally. The research results show that the holding condition exerts great influence on the peak voltage and the relative optimal rotating speeds at speed range of 0 to 1200 r/min under one magnet fixed on the end of the piezo-beam and one rotating magnet. Taking a example, when the configuration mode of rotating magnet and the fixed magnet is attract, under free holding the achieved peek voltages from the PEG are 23.6/49.6/69.2V at 300/336/456 r/min respectively. When rotating magnet and the fixed magnet attracting, under left side holding the achieved peek voltages from the PEG are 32.4/33.6/29.2V and under both sides holding the achieved peek voltages from the PEG are 16.4/16.4/16.8V at 300/336/456 r/min respectively.

Abstract: A new type of forging steel structure piston was introduced. Due to its features of structure and detection requirements, a detecting system used for the detection of its welding surface was designed, which is based on ultrasonic flaw detection technology. The probes posited under the end plane of the piston, facing accurately to the welding faces which contains of the inside ring and the outside ring. Using the longitudinal wave method after being water coupling, the detections can be detected. The detection theory, the hardware composition of the system, the software functions and the detection result were described in detail. The hardware structure of this system is simple and reliable; the software module is clear and stable and has very high flexibility, easy to modify and extend. The system has been applied to the actual production process, the performance has been verified. A nondestructive testing equipment of good performance for the forging steel structure piston’s quality control was provided.

Abstract: A high-efficient method is introduced, which is used for manufacturing long metal fiber. It is based on a special cutting tool, charactered by its multi-tooth shape edge, which can manufacture several metal fibers simultaneously, therefore improve the productivity and the quality of metal fiber greatly.

Abstract: Face 3D modeling is the difficulty problem in the field of computer graphics, computer vision and artificial intelligence. In recent years, it has become the most active research focus both at home and broad. 3D modeling of face is the key step to realize face recognition, and the technique of face 3D modeling has obtained extensive applications in many fields, such as film, animation, interactive games, video conference, human-computer interaction, reverse engineering, medical and public safety. In this paper, the technology of face 3D modeling based on projective rectification is presented and the reconstruction of face 3D digital model can be achieved by it. Firstly, BP neural network is used to simulate the mapping relationship between the 3D object and its images. Then, the rectification on the left and right images acquired by stereo vision system is implemented according to the principle of epipolar line constraint. On the left and right rectified image planes, the match researching of corresponding points are reduced from 2D plane to the horizontal lines, so the image matching and face 3D modeling can be implemented efficiently.

Abstract: Downhole motor is an instrument to drill oil wells, different from rotary drilling in working methods. While downhole motor works, the drilling stem of which remains still supplies power to bits directly so that a much higher transmission efficiency of power can be achieved. Downhole motor has been a key developing downhole tool recently. It is installed in a limited space with a certain diameter, asking for a higher power, so the design of which is rather difficult. This paper mainly studies the key components of downhole motor in structure design and its working characteristics. And parametric design employed in series design to shorten design cycle is presented in this paper. After taken Solidworks as a basic software platform and turbodrill turbine section with diameter of 245mm as an original model, parametric design of key components in downhole motor has been achieved by setting the parameters of key components, adding relations, editing program, creating a new part etc. Parametric design methods presented in this paper has already been applied in series design of downhole motor at Yangtze University.