Papers by Author: Zhi Wei Wang

Abstract: Abrasive machining is an important process for the manufacturing of advanced ceramics. The demand for advanced ceramics with better quality and higher efficiency presents tremendous challenges for abrasive tools in the advanced ceramics industry. The concept of semi-fixed abrasive machining with a newly developed semi-fixed abrasive tool (SFAT) as machining tool is put forward. This paper presents an experimental investigation for SFAT wear into course of machining single crystal silicon with SFAT. Process parameters (water flow, load and velocity) influencing the SFAT wear are analyzed. Influencing factor of SFAT wear in processing course has been clearly demonstrated.

Abstract: Surface texture of tribological interfaces has the potential to improve friction and lubrication performance of various mechanical components. This review paper emphasizes on the current status of the research of surface texture, including the features, the effects on tribological performance, the forming techniques, and the modeling and simulation of surface texture. It is intended to help readers to gain a more comprehensive view on surface texture of tribological interfaces.

Abstract: In order to reduce or eliminate the surface defects caused by abrasive grains and improve the efficiency of ultra-precision processing, the technique of semi-fixed machining has been proposed for machining advanced ceramics. A semi-fixed abrasive tool (SFAT) has been manufactured; it has performances of semi-fixed machining technique. This document demonstrates wear characteristics of SFAT through experiments of machining silicon wafer. It showed that wet status or dry status of SFAT has greatly influenced wear characteristics of SFAT. Wear characteristic of SFAT presented mostly blockage and little grain-off occurred in dry status; mostly grain-off and little blockage presented in wet status.

Abstract: ‘Trap’ effect of the newly developed semi-fixed abrasive tool (SFAT) plays key role in decreasing the surface damages of advanced ceramics caused by the undesirable large particles emerging in machining area. Influences of characteristics of the large particle, such as size, shape and concentration, on the ‘trap’ effect of SFAT are studied with Particle Flow Code (PFC) simulation and lapping experiments. A normalized normal force is defined to evaluate the ‘trap’ effect in PFC simulation, and surface roughness is taken as an indicator in lapping experiments. The results show that the change of surface roughness is according to the one of normalized normal force. Bigger normalized normal force is better for ‘trap’ effect and surface roughness. ‘Trap’ effect works well when the large particle is in small size, sharp shape, and low concentration. In this study, the followed characteristics of the large particle are good for ‘trap’ effect of SFAT made of 1000# SiC abrasive: size <17µm, corner angle < 60°, and concentration <18 particles per mm2.

Abstract: The most typical example of hard and brittle material is advanced ceramics, for its ultra-precision machining difficulty and wide applications, now it becomes a focus of attention. Semi-fixed abrasive plate (SFAP) is newly developed for preventing larger particles from doing workpiece surface damage in machining advanced ceramics, for larger particles from grain size dispersion or from outside of processing area could bring uneven load distribution on processing region of advanced ceramics. In this paper, Shearing strength, surface hardness and Young’s modulus as characteristics of SFAP are investigated. They were influenced by Grain size and abrasive weight ratio are analyzed and discussed, as well as the qualitative estimation of these influences on the characteristics of SFAP are deduced.

Abstract: The precision and efficiency of lapping for balls are determined by the lapping uniformity. One method of evaluating the ball lapping uniformity for different lapping mode is proposed, which is based on kinematics analysis under the assumption of pure rolling. Lapping experiments of V-groove lapping mode, dual rotating plates (DRP) lapping mode, and dual-rotating eccentric V-groove (DREVG) lapping mode are carried out on steel balls, and the lapping traces are observed. The prediction of the evaluating method is in accordance with the experimental results.

Abstract: This paper analyses the influence of indenter’s vertex angle on the ‘trap’ effect of the semi-fixed abrasive plate (SAP) with discrete element method. The indenters of different degree vertex angle are generated by discrete element method, then the indenter is applied processing velocity, which let the indenter press into the SAP, finally three curves of normal force and displacement are gained. From the curves, the normal force of the indenters doesn’t increase quickly and stay in stable in the beginning, because the SAP is full of pore, which let the indenter easily press into the SAP. Through the above indenter simulation, the relations between the lasting time of the ‘trap’ effect and the indenter’s vertex angle are in reverse proportion, if the indenter’s vertex angle is smaller, the lasting time of the ‘trap’ effect of SAP is longer, and the size of large grain is an influence factor in the ‘trap’ effect of SAP.

Abstract: Aluminum is a non-ferrous metal material which has excellent comprehensive performance. It has been widely used in many sectors. In this paper, plane abrasive machining is carried out for the aluminum. The quality of the Al specimen’s surface is compared after the semi-fixed and loose abrasive processing. The experiment proved that semi-fixed abrasive machining is better than loose abrasive in reducing surface roughness of Al-blocks. In the semi-fixed abrasive machining, the surface roughness of Al-block continued to drop and become stable after 40 minutes. It can prevent deep scratches on Al-blocks’ surface effectively and can get a mirror effect. The surface roughness can reach to Ra 22nm, Rmax 490nm, Rv 130nm. Its removal efficiency is also higher than loose abrasive machining. It is proved that semi-fixed abrasive machining can take the place of rough polishing processing.

Abstract: To reach high surface integrity and processing efficiency, the semi-fixed abrasive wheel (SFAW) is developed. Compacting process plays key role in adjusting the structure and machining ability of SFAW. In this paper, the manufacturing of SFAW is introduced, and the effect of compacting patterns and process parameters on the structure of SFAW is discussed with experimental results and a developed model based on particle flow method. It is found that the lower compacting velocity result into longer time to achieve a certain compacting force. It needs greater compacting force to achieve a certain compacting density with higher compacting force loading rate. The higher friction factor and contact module of grits result into greater compacting force to achieve a certain compacting density.

Abstract: In order to get high precision balls used in oil exactor, Eccentric dual-rotating (EDR) V-groove lapping mode and Rotated dual-plates (RDP) lapping mode are applied for the batch processing of WC-Co cemented carbide balls of Φ35mm. After comparing two innovated modes, firstly EDR V-groove lapping mode is used in rough lapping stage for high efficiency, and then semi-finishing lapping stage, finishing lapping stage and polishing stage are carried out by RDP lapping mode. Through changing the processing parameters legitimately, including abrasive grain, adjustable rotating velocity and load, the rational course and parameters are defined, and WC-Co cemented carbide balls of Φ35mm satisfy the end products’ demand which means the sphericity is less than 1μm and the roughness of surface (Ra) is better than 50nm, so these balls can be applied in one-way hydraulic value used in oil exactor.