Papers by Author: Li Ding Wang

Abstract: The ultra-precision master gears have important application in calibrating high precision gear measuring instruments or coordinate measuring machines and in military industry. Firstly based error interference of the angle-transferring curve, the periodical translocation technique (PTT) of gear-grinding to improve the indexing accuracy of ultra-precision gears is proposed. The conclusions are drawn by precision experiment: (1) controlling 2/3~3/4 of total teeth participating in regrinding process can obtain the smaller total cumulative pitch deviation; (2) with increasing of the number of teeth participating in regrinding processes, the effects on single pitch deviation is more obvious. Finally, the total pitch deviation F_p of the specimen reaches to 0.79 μm (2.7′′), and the single pitch deviation f_p reaches to 0.30 μm (1.0′′) by adopting PTT technique and both of them reaches to submicron level.The precision gear-grinding experiments show the efficiency and practicability of the PTT technique.

Abstract: Micro-channels were the main microstructures in most micro-fluidic devices. In this paper, the effects of injection molding process parameters on the replicability of micro-channels profile are studied. Orthogonal experiments (Taguchi method) are carried out to establish the relationship between injection process parameters and replication accuracy for various micro-channels. Experimental results show that mold temperature and packing pressure are the principal factors in molding process. The replication accuracy depends strongly on the processing conditions. The replication accuracy reached about 99.84% using the optimum parameters.

Abstract: This paper chose multi-index to provide a comprehensive evaluation model to evaluate the use reliability of CNC machine tools as a single assessment indicator is biased. As the number of evaluation factors is huge and it is difficult to get the exact values, a fuzzy theory is applied. Reliability mathematical model and maintainability mathematical model were established based on failure data selected from filed test and calculated the estimation values of reliability indexes. Subsequently, a fuzzy comprehensive evaluation mathematical model of CNC machine tools was constructed which combined fuzzy with comprehensive evaluation theory. Using this model could evaluate reliability level of CNC machine tools accurately and integrative.

Abstract: The involute cam is used for generating tooth form of an involute gear in gear grinder with involute cam-link stopper, and its profile error is one of the factors which decide the tooth form precision of gear. The conventional processing means of involute cams can't achieve a sufficient accuracy. In this paper, a double-disc mode grinding device is introduced. Based on analysis of grinding principle, the device's structure and working process are described, and the main sources of grinding profile errors are analyzed. It is confirmed that the introduced device has the ability of accomplishing a highly precise grinding of involute cams.

Abstract: As one part of the efforts to break the bottleneck of power sources in development of integrated micro systems, a silicon based air-breathing micro direct methanol fuel cell (μDMFC) was developed in this work. By using micro-machining technologies compatible with that in processing of the other MEMS devices, the anode and cathode micro flow-field plates had been successfully fabricated on a pair of 2-inch silicon wafers. The silicon μDMFC was evaluated under ambient conditions using aqueous methanol solution with different concentrations. Results show that open circuit potential (OCP) of the μDMFC was above to 0.6 V, and by using 3mol/L methanol, the peak current density and power density of the silicon μDMFC could reach 28mA/cm2 and 8mW/cm2, respectively.

Abstract: The fracture behavior of brittle materials under biaxial plane stress has been investigated by means of numerical simulation method with software MFPA2D (Material Failure Process Analysis). The aims of this study are to clarify the fracture dependence of brittle material on biaxial plane stress state. The observation of crack initiation and fracture behavior reveals that the biaxial stresses have strong influence on the fracture properties of glass. Thus, the fracture criterion by the stress intensity factor was questioned for the biaxial plane stress issues. It is confirmed that the tensile stress parallel to the crack plane is an important factor affecting crack arrest, while the compressive stress parallel to the crack plane contributes to crack opening.

Abstract: In micro stereovision system, false matching due to the randomicity of image signal makes 3D reconstruction data contain a large amount of abnormal data in the form of noise (pulse noise, Gauss noise). In order to obtain a more accurate 3D reconstruction shape, a novel method of 3D scattered data processing, which is a combination of wavelet transform and extended Vector Median Filters, is proposed to use wavelet transform to realize primary denosing, and use extended Vector Median Filters to further denoise thereby achieving higher precision 3D measurement. In wavelet based denosing, wavelet based edge detector in vector space removes edge abnormal points effectively, moreover, boundary tracking is used to prune out the image background from the matching area to remove exterior abnormal points. Then the local areas determined by edges are filtered by extended vector median filter. Experimental results indicate that the method proposed is effective to removing abnormal data from the 3D reconstructed data and enables 3D measurement position accuracy to reach 3 m µ .