Papers by Author: Yang Wang

Abstract: To study the relationship among the height amplitude of surface roughness , assessed area and assessed direction, the height amplitudes SRa, SRq, SRsk and SRku based on area-direction character are defined in the paper. And on the foundation of these parameters, relative assessed area indexes, assessed direction indexes and assessed total indexes are established. SRa, SRq, SRsk and SRku are the natural extension of 2D height amplitudes Ra, Rq, Rsk and Rku. They are different from 3D height amplitudes Sa, Sq, Ssk and Sku. They provide an evidence to study the quantitative relationship among surface roughness, assessed area and assessed direction. Relative assessed area indexes, assessed direction indexes and assessed total indexes can be used to assess the distribution situation of height amplitudes of surface roughness related to area, direction and entireness.

Abstract: A vibration simulation model of a dust-cast device for imitating the different environments has been established, and ADAMS has been used for analyzing the performance parameters. Through the analysis of the simulation results, the device has been designed, and the position of loading was optimized.

Abstract: Laser assisted milling (LAML) is a potential method for machining difficult-to-machine materials such as superalloys and ceramics, which uses a high power laser to focally heat a workpiece prior to material removal with a traditional cutting tool. A laser assisted milling experimental system was set up to investigate the cutting process of LAML of sintered silicon nitride. Effects of operating parameters on cutting forces, chip morphology, surface roughness and subsurface damage were investigated. The results showed the feasibility and advantages of LAML of ceramics including good surface, decreasing cutting force and tool wear, and no micro-crack zones.

Abstract: An experimental device capable of producing uniform metal droplet stream and electric charging and deflecting has been developed. Uniform spherical powder of 180μm in diameter was obtained after cooling and solidification. Numerical models of heat transfer and solidification of droplets were established. The thermal history including solid fraction of droplets in uniform droplet spray process were calculated. Under the common processing conditions, the cooling rate of a droplet of 180μm diameter is of the order of 103−104°C/s. To obtain homogeneous and dense preforms, the substrate should be positioned at a distance of 1.1-1.3m from the nozzle.

Abstract: Sapphire is an important wide bandgap semiconductor material for developing UV/blue optoelectronic devices, however because of its high hardness and chemical stability; it is mechanically and chemically difficult machine. In this paper, the scribing of sapphire by UV laser pulses is investigated under various conditions of pulse energies, scanning speed and repetition rate. The quality and morphology of the laser ablation of sapphire surface are evaluated by scanning electron microscopy. The mechanism of UV laser ablation of sapphire is discussed. The formation of grooves with high aspect ratio and good surface quality is achieved by selecting appropriate laser parameters. Scribing by pulsed UV laser therefore provide a new approach in the development of sapphire-based devices.

Abstract: In this study an experimental device capable of producing uniform metal droplet stream with image gathering was set up. A periodic vibration was applied to a compound liquid jet for an experimental study on its breakup. The breakup processes of the compound jet were discussed from the image taken from the experiment. The aim is to study the relationship of the factors which determine the jet breakup into a series of uniform droplets.

Abstract: New forms of trapping force are proposed for the design of near-field optical tweezers. Without the limitation of dipole approximation, the trapping force acting on a nano-particle located in near-field region can be solved by direct calculation of Maxwell stress tensor using 3D FDTD method. The new forms are used to design near-field optical trapping with a metal-coated fiber probe. Calculations show that the fiber probe can trap a nano-particle with tens of nanometres diameter to different positions with different distance from the probe tip. In order to achieve higher trapping capability, the feasibility of near-field trapping near the optical fiber probe after adding the AFM metallic probe is shown by analyzing trapping forces along three axis directions. The correctness of new forms is demonstrated by numerical results.

Abstract: The generation of uniform droplets in the size of hundred microns was described in this paper. An experimental device capable of producing uniform droplet has been developed. For the purpose of adjusting the signal generator for both continuous droplets spray and drop-on-demand, the piezoelectric driving signal was set up with a PC and software of Labview. With the signal generation system, Flexible signal adjustment appears to be more suitable than simple signal generator to generate uniform droplets.

Abstract: The Processing advantages of UV laser were discussed in this paper. A series of experiments were carried out, some good results was achieved, which proved UV laser is fit for sapphire wafer processing. Then how processing parameters affects machining quality was discussed, which provides guidance to machining practice. The formation of grooves with good surface quality can be achieved by selecting appropriate laser parameters.

Abstract: This paper describes a set of theoretical and experimental results based on thermoelastic effect measurement from Glass-Fiber-Reinforced-Polymer (GFRP) composite structure for full-filed stress analysis. The sum of the principle stress (The first stress invariant) can be measured by means of thermoelastic stress analysis (TSA), and this method is used to determine the stress concentration of the composite structure. A finite element analysis is proposed to predict the stress distribution for GFRP gluing structure. The lock-in thermography has been applied to measure the structure stress distribution by its high thermal resolution. The experiment was carried out with different GFRP composite structures by lock in thermography. The experimental results show the stress distribution can be measured and evaluated with good accuracies by using of lock-in thermography