Papers by Keyword: Grinding Force

Abstract: In this study, the grinding force variation mechanism in ultrasonic assisted grinding (UAG) of SiC ceramic is investigated by simulation method using a single diamond abrasive grain scratching. In simulation, the workpiece is modeled by smoothed particle hydrodynamic (SPH) method while the abrasive grain is modeled by finite element method (FEM). To reliably predict the grinding forces in UAG, an analytical model of average undeformed chip thickness h_a is established. Grinding forces under different grinding parameters, i.e., depth of cut, and different ultrasonic vibration amplitudes are calculated by setting average undeformed chip thickness h_a as scratching depth during SPH simulation process. The simulation results indicate that the normal force in UAG is reduced by about 20%, while the tangential force decreases up to 30% compared with those in conventional grinding (CG). The influences of grinding parameters and ultrasonic vibration on grinding forces will be investigated and the preliminary explanations will be presented.

Abstract: In the present work, ultrasonic assisted grinding (UAG) and conventional grinding (CG, without ultrasonic) tests of Carbon fiber reinforced silicon carbide matrix (C/SiC) composites were conducted. In addition, analysis was done by comparing the machining quality, grinding force, and specific grinding energy between the two processes. The results showed that material removal mode of carbon fiber both in CG and UAG were brittle fracture, and fracture size had no obvious difference. Compared with CG, brittle fracture area of SiC increased during UAG. In comparison with CG, the normal grinding force and tangential grinding force for UAG were reduced maximally by 45%, 39% respectively of those for CG. Accordingly, specific grinding energy was also reduced by UAG. Therefore, UAG can improve the grinding performance of C/SiC composites significantly.

Abstract: According to broken edges and cracks emerging in traditionally machining cemented carbides (CP1) materials, this paper carried out some experimental researches on high and ultra-high grinding process for these materials, and considered the effect of process parameters on grinding forces, surface roughness, surface quality; discusses the calculation of the single grinding average normals force and relationship with maximum undeformed chip thickness and theoretical critical normal loads; probes the removal mechanisms of cemented carbide in high/ultra-high grinding process.

Abstract: Due to the requirements of on-line detection of grinding force in the grinding process, this paper utilizes the structural characteristics of ultra-precision grinder with double-spindle and single-workstation, and then presents a grinding dynamometer based on piezoelectric effect of quartz crystals. Besides, the grinder dynamometer can measure grinding force in three directions, and the static properties of dynamometer are experimentally tested in a special experiment table. Moreover, the on-line static calibration and the actual grinding experiment of dynamometer installed in the silicon wafer grinder are performed. The results indicate that the grinding dynamometer has satisfactory static properties, that is, the linearity and repeatability are less than 1%, and the cross-talks are also less than 5%. As a result, each indicator has full reached the operating requirements in using of large diameter silicon wafer grinding force measuring.

Abstract: The adhesion property of oxide film has great effects on the grinding quality and efficiency of ELID grinding. In this paper, adhesion strength model of oxide film is established, ELID grinding is conducted to nanometric cemented carbide and ordinary cemented carbide, ELID grinding force is measured, adhesive stress is calculated and the correctness of adhesion model is verified. The results show that the adhesion strength of oxide film is relatively greater, the transition from γ-Fe₂O₃ to α-Fe₂O₃ in the oxide film is relatively fuller and the polishing performance is relatively better while the grinding depth is smaller; with the deepening of grinding, the adhesion strength of oxide film reduces, the composition of the oxide film that transforms into α-Fe₂O₃ is less and the polishing ability reduces. The adhesion model of oxide film well reflects the adhesion property of oxide film, and the application of this model can represent the distribution, shedding and updating of the oxide film on the surface of grinding wheel.

Abstract: Take M210 internal grinder as an example, design a sensors of measure internal grinding force that not affected by vertical feed, determining the basic dimensions of the elastic element, analyzes the elongation of elastic curve after two fixed beam bending, the force of the elastic member is analyzed. The relationship of grinding force and parameter is established, it can be the reference of relevant manufacturing technology.

Abstract: The mathematical models of the dynamic grinding force and the average grinding force were established by introducing the unit grinding force F_u. And the formula of the average grinding force in the grinding zone was derived. The experiments were conducted in the traditional grinding (TG) mode and tangential ultrasonic vibration grinding (TUAG) mode. The results show that the unit grinding force in TUAG is lower than that in TG in the same machining condition; the grinding force ratio is decreased due to the tangential ultrasonic vibration of the workpiece. It is helpful to improve the machinablity of the hard-brittle material.

Abstract: In this work, machining test was carried out in various machining conditions using ultrasonical vibration capable CNC machine. For work material, alumina ceramic (Al2O3) was used while for tool material diamond electroplated grinding wheel was used. To evaluate ultrasonical vibration effect, grinding test was performed with and without ultrasonic vibration in same machining condition. In ultrasonic mode, ultrasonic vibration of 20kHz was generated by HSK 63 ultrasonic actuator. On the other hand, grinding forces were measured by KISTLER dynamometer. And an optimal sampling rate for grinding force measurement was obtained by a signal processing and frequency analysis. The surface roughness of the ceramic was also measured using stylus type surface roughness instrument and atomic force microscope (AFM). Besides, the scanning electron microscope (SEM) was used for observation of surface integrarity.

Abstract: Single-grain grinding test plays an important part in studying the high speed grinding mechanism of materials. In this paper, a new experimental system for high speed grinding test with single diamond grain is presented. The differences of surface topography and chip morphology of Inconel 718 machined by single diamond grain and single CBN grain were evaluated. The grinding forces and corresponding maximum undeformed chip thickness were measured under different grinding speeds. The chips, characterized by crack and segment band feature like the cutting segmented chips, were collected to study the high speed grinding mechanism of nickel-based superalloy. The results show that the grinding speed has an important effect on the forces and chip formation, partly due to the temperature variation. As the speed increases, the groove surface becomes smoother.

Abstract: In order to calculate the grinding force of the basin-like grinding wheel in grinding outer race elliptical grooves, the thesis simplifies the grinding process as follow: the evenly distributed abrasive grains move around grinding wheel axis along an imaginary ellipse at high speed, while the imaginary ellipse moves along the trace deflected from the grinding wheel axis simultaneously. The analysis of grinding force in CVJ outer race elliptical groove grinding with basin-like grinding wheel reveals that, the grinding force will be decreased, if wheel velocity increased and feed velocity decreased. On the other hand, with the decrease of inter-grain spacing, the grinding force of basin-like grinding wheel will be increased, but the grinding force of abrasive grit will be decreased.