Papers by Author: Jia Jin Zheng

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Authors: Jia Jin Zheng, Shi Lang Xu, Xin Zhu Zhou
Abstract: A three-phase composite circle model is presented in this paper to assess the effect of interfacial transition zone (ITZ) on the chloride diffusion coefficient of concrete. Firstly, the distribution of circular aggregate particles was simulated in a square concrete element. Based on the simulated concrete mesostructure, the Monte Carlo algorithm was adopted to numerically evaluate the ITZ area fraction for different concrete mixes. A parametric study was then conducted to quantify the effects of the largest aggregate diameter, ITZ thickness and aggregate gradation on the ITZ area fraction. Secondly, the ITZ was modeled as a thin-wall annular plate located between a circular aggregate particle and a thick-wall cement paste annular plate. With the three-phase composite circle model, an analytical solution was derived for the chloride diffusion coefficient of concrete. Finally, the derived solution was verified by experimental results obtained from the research literature and a quantitative relationship between the thickness and chloride diffusion coefficient of ITZ was established.
Authors: Ju Long Yuan, Bin Lin, Z.W. Shen, Jia Jin Zheng, Jian Ruan, L.B. Zhang
Authors: Yong Dai, Ju Long Yuan, Zhao Zhong Zhou, Jia Jin Zheng, Ping Zhao
Abstract: It is of high importance to avoid scratches in lapping process. A Grain Size Sensitivity (GSS) model is put forward in this paper. The GSS is a relative parameter which defines the relative change of the depth of cutting, influenced by the change of the size of grain powders, by which it is possible to evaluate quantificationally the capability of lapping machines in avoiding scratches. It is useful for designing and using lapping machines. The simulating of lapping processes based on GSS model is carried out. The transferring of error is also discussed and a new structure of lapping plate with spring cells developed by the authors is introduced.
Authors: Ju Long Yuan, Bin Lin, Z.W. Shen, Jia Jin Zheng, Jian Ruan, L.B. Zhang
Authors: Jia Jin Zheng, Xin Zhu Zhou, Shi Lang Xu
Abstract: Crack width is a significant parameter for assessing service life of reinforced concrete structures in chloride-laden environments. Corrosion-induced concrete cracking is a predominant causal factor influencing premature degradation of reinforced concrete structures, incurring considerable costs for repairs and inconvenience to the public due to interruptions. This gives rise to the need for accurate prediction of crack width in order to achieve cost-effectiveness in maintaining serviceability of concrete structures. It is in this regard that the present paper attempts to develop a quasi-brittle mechanical model to predict crack width of chloride contaminated concrete structures. Assuming that cracks be smeared uniformly in all directions and concrete be a quasi-brittle material, the displacement and stress in a concrete cover, before and after surface cracking, were derived respectively in an analytical manner. Crack width, as a function of the cover depth, steel bar diameter, corrosion rate and time, was then determined. Finally, the analysis results were verified by comparing the solution with the experimental results. The effects of the cover depth, steel bar diameter and corrosion rate on the service life were discussed in detail.
Authors: Z.W. Shen, Ju Long Yuan, Bin Lin, Jia Jin Zheng, Jian Ruan, L.B. Zhang
Authors: Ju Long Yuan, Z.W. Wang, Bing Hai Lv, Yong Dai, Jia Jin Zheng, Ping Zhao, Fei Yan Lou, B.C. Tao
Abstract: A novel lapping mode is developed on the base of present eccentric v-grooves lapping mode for precise balls. The kinematics analysis shows that the ball spin axis can wiggle up to 180° under the developed mode, so the lapping trace will be dispersed onto the whole surface of the ball. The effect of offsetting and groove radius on the lapping uniformity in the developed eccentric v-grooves, the present eccentric v-grooves and the traditional v-grooves lapping mode are compared, and the advantage of the developed mode is that the impact offsetting is less while the groove radius has no impact.
Authors: X. Pei, Jia Jin Zheng, Jian Ruan, Ju Long Yuan, L.B. Zhang
Authors: Zhao Zhong Zhou, Ju Long Yuan, Bing Hai Lv, Jia Jin Zheng
Abstract: Polishing pad plays a key role in determining polish rate and planarity of a chemical mechanical planarization (CMP). The properties of the pad would deteriorate during polishing because of pad surface grazing, which results in reduced removal rates and poorer planarity of wafer surface. Pad conditioning and its influence on pad surface structure and CMP process is introduced and discussed in this paper. The study shows that the surface structure can be regenerated by breaking up the glazed areas with conditioner, MRR(Material Removal Rate) can be maintained at high level with proper pad conditioning, and UN(Non-uniformity)can also improved. Orthogonal experiments design is employed in this study to determine the best conditioning parameters.
Authors: Zhao Zhong Zhou, Ju Long Yuan, Bing Hai Lv, Jia Jin Zheng
Abstract: The correction process of balls roundness error during lapping is discussed qualitatively. Dynamic analysis for rotated dual-plates lapping mode of ceramic balls is performed, under the assumption of a fluid loading system. The effect of the damping of the loading system on the correction of balls roundness error is discussed. And the result shows large damp causes an increase of magnification of load, and improves the correction of roundness error of balls.
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