Papers by Keyword: Granite

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Authors: Shu You Zheng, Xi Peng Xu
Abstract: Ultrasonic machining has been proven to be a promising machining method on hard and brittle materials. However, due to the absence of high power ultrasonic machine tools, reported studies on ultrasonic machining were mainly concerned of relatively small hole drilling of the given materials. In the present work, with the development of the higher power Rotary Ultrasonic Machine Tool, two kinds of ultrasonic face machining with free abrasives, namely, Non-rotating Ultrasonic Machining with Free Abrasives (NRUSM) and Rotary Ultrasonic Machining with Free Abrasives (RUSM) are designed and comparatively conducted for the red granite, which is a typical hard-to-machine natural material. The effects of static force, spindle speed and amplitude of ultrasonic vibration on the performance of the machining are evaluated in terms of the material removal rate and surface quality. Experimental results indicate that ultrasonic machining is effective for face milling of the stone material with the designed machine tool. Furthermore, machining performances in RUSM are superior to those in NRUSM.
Authors: Zhong Zhou, Xiao Jun Wang
Abstract: A damage constitutive model of dry/water-saturated granite is proposed within the framework of continuum mechanics and mixture theory, and the model allows for the simulation of the effects of micro-cracks, micro-pores and saturated water. By implementing the model into wave propagation code, one dimensional stain waves in dry granite induced by a rectangular impulsive loading and spherical waves in water-saturated granite due to underground explosion are studied. The simulation results demonstrate the main features of the model, and it is shown that the theoretical model developed is valid for study on the characteristics of stress waves in rock medium.
Authors: Fang Yi You, Jian Yun Shen, Xi Peng Xu
Abstract: In the present study, grinding temperature was measured by using a foil thermocouple when granite was ground by SiC wheel. De-noised the temperature signals with soft threshold method base on wavelet transform was conducted to analyze the grinding process. Energy partition to workpiece was estimated to be about 10%~30% by matching the measured temperature to analytically value. The number of active grains was determined by counting the high frequency impulses in the measured temperature signals. The ratio of active grains to total grains was about 4.5%~6.1%. Based on the results, a formula was deduced for calculating the temperature of single grain in the grinding process.
Authors: Cheng Yong Wang, Zhe Qin, Xin Wei, Yun Xia Wu
Authors: Xiu Hong Hao, Yan Min Wang, Ai Qin Zhang
Abstract: Granite, due to the poor adhesiveness with asphalt, cannot be widely used as aggregate in asphalt pavement. In this study, nanoscaled calcium carbonate (CaCO3), was selected as modifier to modify asphalt. The adhesion of aggregate and asphalt was evaluated by Boiling test method and the Marshall Test and Immersion Marshall Test were conducted on asphalt concrete (AC-16) according to the Standard Test Methods of Bitumen and Bituminous Mixture for Highway Engineering (JTG E20-2011). The results showed that When the Doping content of CaCO3 (%) is 7%, the adhesion levels reached up to 5 grade and achieved the project requirements. The Immersion Marshall Stability (MS1) of AC-16 CaCO3 modified asphalt concrete can improve 27.6% than that the Matrix asphalt concrete.
Authors: Zeng Wen Liu, Chuan Zhen Huang
Abstract: It is desirable that the precision of the shape and the dimension of stone products in top grade decoration is getting higher. Grinding is one of the main technology in machining stone which ensures the precision of the shape and the dimension of stone products, and influences the machining efficiency. This investigation aims to experimentally find out the reasons causing grinding wheel wear and the factors influencing smoothness. It is found that the wear of grinding wheel is mainly caused by the hardness and removal quantity of stone. The harder the stone, the shorter the life of grinding wheel. The greater the removal quantity of stone, the bigger the wear of grinding wheel. The surface smoothness of stone is mainly related to the size of abrasives and the spindle speed. The smaller the abrasives and the higher the speed, the higher the smoothness.
Authors: Zai Qin Wang, Chong Xi Liu, Zi Yun Wen, Zhen Li, Liang Xiao
Abstract: On the basis of the existing standardized test methods of concrete aggregates alkali activity, the alkali activity of the granite aggregates is studied by extending the observation time. The results showed that the alkali reaction expansion ratio of the fresh granite broke through the 0.1% criterion limit after a decade of time. The reactant microstructure characteristic is similar to the structure of the alkali-silica reaction, the thickness of reaction layer is about 2~4 µm. Controlling the total alkali content of the dam concrete and replacing cement by mixing a certain proportion of fly ash can effectively prevent the occurrence of the AAR in the Three Gorges Project.
Authors: Yi Qing Yu, Yuan Li, Xi Peng Xu
Abstract: An investigation is reported of the characteristics of specific energy in grinding of granite using diamond abrasives. The effects of many parameters, such as the types of diamond tools, the types of abrasives, the properties of granite, the conditions of lubrication, and the working conditions of diamond tools, were studied. The power consumed in grinding was measured in order to obtain the specific energy, which is defined as the energy expended per unit volume of material removal. It is found that the specific energy for grinding of granite was closely related to the removal mechanisms of granite, the failure modes of diamonds and the interactions of the swarf with the applied fluid and bond matrix.
Authors: Xi Peng Xu, X.W. Zhu, Yuan Li
Abstract: An experimental study was undertaken to investigate the grinding of granite at different grinding speeds over a wide range of material removal rates. A metal-bonded diamond blade was used as the grinding wheel with natural gray granite as the workpiece material. The tangential and normal force components were obtained through measuring the horizontal and vertical force components as well as the consumed power. The experiments were conducted with a constant wheel surface state to study the influence of grinding speed under different material removal rates. An additional test was also carried out to examine the grinding process while the wheel surface state progressively changed, in which case both forces and the morphologies of diamond grains were monitored at regular intervals. At a fixed material removal rate, both the tangential and normal forces reduced slightly with the grinding speed. But the specific energy increased greatly at higher grinding speeds especially at a shallower maximum grain depth of cut.
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