Papers by Author: Cheng Hui Gao

Abstract: A method is presented to accurate face-mating point cloud registration after dealing with noise point. Point cloud registration is divided into two parts,firstly,coarse registration is applied for visual point cloud,then three local sufaces of overlap cloud region are selected to be mating calculated after denosing base on least squares fitting , at last accurate splicing parameters of translation and rotation are acquired by nonlinear least square .This algorithm is easy to deal with the denosing, has faster convergence speed and higher registration accuracy.Its feasibility is proved by samples.

Abstract: Image stereo correspondence is the core technology of stereo vision. It has been widely studied and applied in the fields such as 3D reconstruction, vision measurement and target recognition. According to characteristics and application of stereo matching technology, the image stereo correspondence methods can be classified into three categories: local stereo correspondence, global stereo correspondence and semi-global stereo correspondence. Some image stereo correspondence solutions and problems are emphatically analyzed. Finally some future research issues on image stereo correspondence are highlighted.

Abstract: This paper proposes the third generation wavelet--double tree complex wavelet (DT-CWT) transformation used in nanometer roughness rating, based on the explanation of the shortcomings of the current nanometer roughness rating reference and conventional three dimensional datum evaluations due to the insufficient study. The experiment got porous anodic alumina film as the object of surface roughness of nanotechnology study. Through the comparisons of the three generations of the wavelet reconstruction after the maximum reconstruction error, a conclusion can be made that the superiority of DT-CWT in application is very obvious, a result meeting the16% principle of the surface roughness rating on the bases of DT - CWT extracted datum to compute income parameters, which indicates the feasibility of this application to the extraction of the nano3-D roughness evaluation. Keywords: nanometer roughness;dual-tree complex wavelet;three dimensional datum

Abstract: Since the tribology properties of rough surfaces are closely related to its topography, one of the most important ingredients in tribology research is to find an appropriate tool to analyze and characterize rough surfaces. The elementary theory of contourlet which is a good method for multi-scale and multi-direction signal analysis was introduced and an application of contourlet in rough surface analysis was demonstrated. It was found that contourlet is more sensitive to curved features than general two dimensional wavelets; it is possible to become a new powerful tool for rough surface analysis and characterization.

Abstract: A three-dimensional contact model was established between two isotropic rough surfaces exhibiting fractal behavior,and the equivalent plastic strain was discussed using the finite element analysis. The maximum equivalent plastic strain and its depth are presented with the different paths of rough solid when loading. The result showed that the equivalent plastic strain versus different depth which at different locations showed different laws, in the top area of the asperities versus different depth, the maximum equivalent plastic strain occurs in the subsurface which range about 5 um from the surface. In addition, with different deformation characteristics, the degree of the equivalent plastic strain was different. The contact model between two rough solids will lay a foundation to further research on the substance of the process of friction and wear.

Abstract: A FEA model of two-dimensional (2D) sliding between two interfering fractal rough solids was build, and the results was presented. The trends in shear stress between the rough solids were provided by the FEA. Combined with the delaminating theory of wear, the Maximum shear stresses and its distance are presented when loading and sliding. The result showed that the Maximum shear stresses was located in the subsurface which range about 2 to 8 um from the surface. In addition, with different plastic characteristics, the location of Maximum shear stresses were different. With modeling the contact and sliding between rough surfaces, the friction, sub-surface crack initiation and propagation and wear mechanisms can be understood deeply.

Abstract: In order to import a synthesized fractal profile into finite element software, the profile synthesized by discrete Fourier transform was studied. The synthesized profile was filtered in frequency domain in order to filter its high frequency components and to make it smooth, and then the chord deviation algorithm was used to reduce its redundant data in space domain. It was found that: after filtering, the profile is smooth but with lots of redundant data; the chord deviation algorithm can simplify the profile which is redundant in space domain; the time needed in the process of importing a profile into finite element software can be reduced greatly after profile simplification.

Abstract: Ni-Mo alloys have been studied as a prospected cathode for its higher hydrogen evolution reaction properties than other binary compounds. The eletrodeposition parameters and its effects have been investigated in forming Ni-Mo alloys in the present study by measuring the structure and properties of deposits. The forming mechanism of Ni-Mo amorphous deposit is discussed from point of the elements component of view. The X-ray diffraction (XRD) analysis and scanning electron microscopy (SEM) microstructures show that the molybdenum content in the deposit is increased with the molybdate concentration increase, and the deposit structure can be parted several stages- nanocrystal, nanocrystal/amorphous, amorphous, crystalline, or the mixed configuration due to the variation of Mo atom content. The forming mechanism of the deposit of Ni-Mo alloys is attributable to the repulsive aggradations as of the molybdenum chemical properties and electronic shell structure. When the atom rate of Ni/Mo is higher than 0.35, the deposit is the face center cubic (fcc) configuration, while lower than 0.35, the deposit is the monoclinic hexagon crystalloid configuration or body center cubic (bcc) dimensional structure.

Abstract: In this paper, a novel no-asbestos brake composite reinforced by natural bamboo fibers is studied. The bamboo fibers are modified by heat treatment, alkali treatment and coupling treatment respectively. Tribological performance of different fibers reinforced composites are developed by means of friction test and microstructure observation. The results show that heat treatment of bamboo fibers at 140 for 4 hours makes the friction and wear characteristics of brake composites more stable than the untreated ones, but poor wear resistance at low temperature and heat fade still exist. There is no significant change on fiber surface. The alkali treatment of 17% NaOH solution for 12 hours contributes to desirable combination of higher friction coefficients and lower wear rates, and the surface morphology shows a number of deep grooves that avail the interface bonding. The effect of coupling treatment with KH550 on tribological performance of composites have the similar rule to that of the alkali treated ones except of heat fade, and the fiber surface is evenly coated with the coupling agent, which enhances the bonding of fibers and resin but fails at elevated temperature.

Abstract: The tribological properties of PEEK composites filled with CaCO3 whisker in various content of 0-30%(weight percent) were investigated.The composite specimens were prepared by compression molding. Tribological testing of composites in water lubrication against carbon steel ring was carried out on a MM200 block-on-ring apparatus.Data on neat PEEK were also included for comparison. The morphologies of wear traces were observed by SEM.It was observed that inclusion of CaCO3 whisker significantly improved the wear resistance and reduced the friction coefficient of PEEK composites under water lubricated condition. With an increase in CaCO3 whisker contents, the specific wear rate of composites decreased and showed minima for 20% CaCO3 content as 5.2% of that for PEEK. In terms of friction applications under water lubrication, the optimal content of CaCO3 whisker in PEEK composites should be recommended as 15% to 20%.The SEM observation of the wear traces indicated that the transfer film is not the main reason for the enhancement of wear resistance of the composites in water lubrication.CaCO3 whisker contributed to increase the load-carrying capacity and abate the scuffing and adhesion of PEEK composites, finally led to a significant improvement of the wear resistance.