Guoqin Huang

An experimental study of machining characteristics and tool wear in the diamond wire sawing of granite

A diamond wire sawing process was developed for slicing granite in order to complement the disk sawing. Machining characteristics and tool wear during wire sawing of a granite material that consists of three major minerals, that is, quartz, feldspar and mica, were systematically investigated. The material removal mechanism involved in the sawing was explored. The scanning electron microscope examination of the sawn surfaces of the granite and the analysis of the force and temperature involved in the sawing process indicated that the material removal of the granite was dominated by brittle fracture. The typical cleaving and slipping behaviors of feldspar and mica associated with sawing resulted in unique morphologies on the sawn granite surfaces. The tool wear of the process was characterized by the nonuniform wear of diamond beads impregnated on the wire, with the fore end of the diamond beads experiencing greater wear than the rear part.

Wear of a brazed diamond grinding wheel with diamonds precovered by brazing alloy

The wear of a brazed diamond wheel with diamond grits precovered by brazing alloy was investigated in comparison with a traditional brazed wheel whose grits were without coverings. The two wheels were brazed in vacuum. The wear of the two wheels was tested through grinding of granite, during which grinding forces were measured and the wear states of diamond grits were observed. It is shown that the brazed diamonds precovered with brazing alloy exhibited stronger self-sharpening ability and rupture resistance. Subsequently, the wheel with precovered diamonds performed lower grinding force and better wear performance.

Estimation of Power Consumption in the Circular Sawing of Stone Based on Tangential Force Distribution

Circular sawing is an important method for the processing of natural stone. The ability to predict sawing power is important in the optimisation, monitoring and control of the sawing process. In this paper, a predictive model (PFD) of sawing power, which is based on the tangential force distribution at the sawing contact zone, was proposed, experimentally validated and modified. With regard to the influence of sawing speed on tangential force distribution, the modified PFD (MPFD) performed with high predictive accuracy across a wide range of sawing parameters, including sawing speed. The mean maximum absolute error rate was within 6.78%, and the maximum absolute error rate was within 11.7%. The practicability of predicting sawing power by the MPFD with few initial experimental samples was proved in case studies. On the premise of high sample measurement accuracy, only two samples are required for a fixed sawing speed. The feasibility of applying the MPFD to optimise sawing parameters while lowering the energy consumption of the sawing system was validated. The case study shows that energy use was reduced 28% by optimising the sawing parameters. The MPFD model can be used to predict sawing power, optimise sawing parameters and control energy.

Percent Reduction in Transverse Rupture Strength of Metal Matrix Diamond Segments Analysed via Discrete-Element Simulations

The percent TRS reduction, DTRS, which is the percent reduction of the transverse rupture strength of metal matrix diamond segments with or without diamonds, is a key metric for evaluating the bonding condition of diamonds in a matrix. In this work, we build, calibrate, and verify a discrete-element simulation of a metal matrix diamond segment to obtain DTRS for diamond segments with various diamond-grain sizes, concentrations, and distributions. The results indicate that DTRS increases with increasing diamond-grain concentration and decreases with increasing diamond-grain size. Both factors can be explained by the total diamond contact length, the increase of which causes the increase in DTRS. The distribution of diamond grains in segments also strongly influences the increase of DTRS. The use of DTRS as a metric to assess the bonding condition of diamonds in matrixes is not valid unless the diamond-grain size, concentration, and distribution and total diamond contact length are the same for all diamond segments under consideration.

The effects of temperature curves on the diamond/Ni-Cr interfacial properties in high-frequency induction brazing

The present study alters the temperature characteristics during high-frequency induction brazing of diamond grits and investigates their effects on the properties of the diamond/brazing alloy interface. The high-frequency induction brazing was conducted in a vacuum using Ni-Cr as active filler alloy. An active temperature range was identified for the brazing of high-quality diamond tools. This temperature range, coupled with long heating time, favours the wetting of filler alloy to diamonds, and the chemical reactions and element diffusion at the diamond/alloy interface, but reduces the static compressive strength of the diamonds. If the temperature is slowly raised, the protrusion height and location of brazed diamonds can be more precisely controlled. Brazed diamonds with 30%-50% protrusion are optimal for cutting.