Papers by Author: Yung Cheng Wang

Abstract: Mechanical properties of materials, such as Young's modulus, shear modulus andlinear viscoelastic damping, are experimentally measured with a thin- lm cantilever shaker. Theexperimental apparatus consists of a bimorph piezoelectric transducer acting as an actuator togenerate base excitation to the cantilever, which is analogous to earthquake causing buildingvibration. The motion of the cantilever is monitored by a pair of ber optics to measure thedisplacements of the xed end and the sample. Linear viscoelastic properties of the materialare measured from the resonant frequencies of the vibrating cantilever. Young's modulus andshear modulus are measured from bending and torsion resonant peaks, respectively. For highloss materials, loss tangent of the materials is obtained from the Lorenzian curve t around theresonant peak. Material properties at various frequencies are measured by changing the lengthof the specimens. Furthermore, by introducing crack-like defects, the measured resonances,which may be viewed as a measure of e ective moduli, are able to be adopted to locate thecrack via the method of system identi cation.

Abstract: The grinding precision of end-mill is dependent on the surface roughness of the corresponding rake face and relief face. This precision will be influential in the surface roughness of workpiece and tool life of end-mill in high-speed milling. Firstly, the experiment of high-speed milling for SKD61 tool steel has been performed in the different cutting condition, and the end-mills have the different surface roughness. From the experimental results, it has shown that small relief surface roughness will decrease tool flank wear (increase tool life). The surface integrity of end-mill is very important for high-speed milling, so the different grinding parameters of end-mill have been utilized in the grinding experiment. Finally the surface roughness analysis model of the end-mill relief could be established by a polynomial network. The predictive model of surface roughness can be used to analyze the grinding precision of end-mill.

Abstract: Interferometric signals of a homodyne Michelson interferometer appear in sinusoidal forms. In this investigation, new concepts for signal processing of Michelson interferometer are demonstrated. With the utilization of detection of position sensitive detector (PSD) and by the procedure of differential signals and the characteristic of symmetric waveform, a compact signal processing for homodyne Michelson interferometer has been developed. Its advantages include simplified procedure, fast processing and few electronic hardware. For experiment tests of the signal processing, a conventional homodyne Michelson interferometer has been constructed. Major components of the interferometer consist of laser light source, beam splitter, mirrors, PSD and piezo transducer for driving measurement mirror. To verify the performance of the signal processing, a commercial nanopositioning stage as reference standard has been utilized for comparison measurements. Through theoretical analysis and experiment tests, it can be proved that by the developed signal processing an interferometer possesses the optical resolution of 79 nm. With support of the developed signal processing, interferometers will possess the benefits of simply structure, few components and lower cost.

Abstract: The construction of Fabry-Perot interferometer is very simple and it has been already utilized in different measurement systems. The result of displacement measurement is obviously influenced by the tilt angles of measurement mirror, if a Fabry-Perot interferometer is utilized for displacement measurement. Hence, the measuring range of current systems is rather small (less than 1 mm). The goal of this investigation is to develop a Fabry-Perot interferometer for large travelling range (till 60 mm) by aid of compensation of tilt angles with an angular sensor, piezo translators, control mechanism and self-designed software. To verify the measuring characteristic of the self-developed Fabry-Perot interferometer, some comparison measurements have been performed. A commercial laser interferometer serves as reference standard and the differences between Fabry-Perot interferometer and the commercial Laser interferometer are measured. Through experimental tests, the differences are less than 0.3 m in the full measurement range. The results show that the Fabry-Perot interferometer can meet the measuring requirement with high accuracy of sub-micrometer order and large measurement range.

Abstract: In order to increase the efficiency of machine tools, the development of machine tools is toward higher speed and accuracy. The higher speed of spindle causes more thermal deformation, which reduces the accuracy of machine tools. In this study, finite element method is used to simulate the thermal deformation of spindle caused by the friction loads between spindle and bearings. The bearing load is estimated by the basic load rating from the bearing vendor and the required life of bearing. The simulated results are compared with experimental measurements to verify the analysis model. The result shows that the stabilized temperature of spindle increases as the speed increaser, while the stabilized displacement of spindle slightly increases as the speed increases.

Abstract: Due to the rapid development in recent cutting technology, demands for different types of precise cutting tools become increasingly complicated. Since the design and grinding of end-mills are the last and the most important processing for cutting tools. The geometrical accuracy and the cutting performance of an end-mill depend essentially on the grinding. However, the complicated geometry of an end-mill will be ground by the specific software of CAD/CAM on the 5-axis CNC tool grinding machine. The precision of end-mill grinder will be determined by the performance of 5-axis CNC tool grinder and setting of grinding parameters. Three regulation factors for grinding are grit size of the diamond grinding wheel, grinding speed and the feeding speed. The variable ranges of each parameter can be divided in large, medium and small interval. In this study for an end-mill with fixed geometrical profile, a series of different grinding parameters have been utilized by the 33 factorial experiment planning. And tool grinding experiments for the rod material specification of tungsten carbide have been performed by 5-axis CNC tool grinder. After grinding, surface roughness of tools will be measured. The reliability and precision of the end-mill grinding can be enhanced by the prediction model of polynomial network for surface roughness of end-mills. Besides, the database system for cutting tool has benn established. Totally 4802 data were constructed in the relational database according to the characteristics of tools.

Abstract: Precision positioning is an essential basis for precision mechanical engineering, such as positioning for precision manufacture, or positioning control of robot arms. Due to the increasing demand for precision in the submicrometer range, precision positioning plays an important role for precision manufacture. In this investigation a nano-positioning stage is developed. With the positioning system, high precision positioning and large displacement range can be achieved simultaneously. Advantages of this developed system are positioning driver with single actuator, uncomplicated mechanical structure, low cost and lower hardware requirement. A laser interferometer is used for displacement measurements of the translation stage, and a mini-autocollimator serves as angle sensor for tilt angle measurements. The tilt angle can be minimized with piezo translators and control operations. By the displacement measurements of laser interferometer, the feedback control is performed for positioning in large travel range. High precision positioning in nanometer-order can be achieved with the positioning system. With this development, individual sensor modules are self-accomplished and dominating technologies for the complete nano-positioning system are established.

Abstract: This study presents an analysis of surfactant added by CuO and Al2O3 nano-sized particles of different percentages. After adding suspending nanocrystalline particles into lubricant of machines, the nano-sized particles will augment the heat transfer characteristics of fluids. Some former studies showed that such liquids pose a great potential for heat transfer enhancement. By applying nanofluids to heat transfer of machine lubricant, this paper attempts to explore dominating factors of heat transfer performance from various weight concentrations of nano-sized particles, the correlation among wall temperature, heat flux, rotational Reynolds number, Nusselt number, Grashof number and rotational Grashof number of four different concentrations. The results show that nano-sized particle lubricant offer a better heat transfer performance than typical lubricants. Since random movement and diffusing effect of nano-sized particles are one crucial factor for an increased heat transfer coefficient, adding 3.5% weight concentration nano-sized particle lubricant will produce an optimum heat transfer performance among Case I~IV.