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"Grinding"
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Comparative investigation on creep feed grinding of particle-reinforced titanium matrix composites under different grinding modes
Despite the broad employment of particle-reinforced titanium matrix composites (PTMCs) in the aerospace and automotive industries, the process of grinding PTMCs is not highly effective. To grasp a deeper understanding of the effect of grinding modes on grinding performance, the grinding tests of PTMCs were carried out with two independent grinding modes (i.e., down- and up-grinding) using a microcrystalline corundum wheel on a creep feed surface grinding machine. The findings indicate that the grinding forces of down-grinding are 6–22% larger than that of up-grinding. This impunity is given credit for the different conditions of undeformed chip thickness for an individual abrasive grain. The shape of the grinding temperature signal curve is similar to a right triangle under the up-grinding, and the shape is similar to the scalene triangle under down-grinding. The heat distribution ratio to workpiece during the film boiling stage is determined to be 73% through simulation with finite element analysis. Down-grinding adds further opportunities for grinding burn when compared with up-grinding. The material removal rate of up-grinding process is 2.6 times more than that of down-grinding without grinding burn. The surface roughness value in down-grinding is always larger than that in up-grinding. Cracks and adherence are produced in down-grinding except for scratches and plastic flow. The white layer is up to 50 µm thick in down-grinding. A better surface quality is obtained in up-grinding compared with down-grinding. Up-grinding of PTMCs can be considered as a high-efficiency creep feed grinding machining technology. This study provides data and practical guidance for achieving efficient and high-quality grinding of PTMCs.
Journal Article
The continuous generating grinding method for face gears based on general cylindrical gear grinding machine
This study achieves precision grinding of face gears in the general cylindrical gear grinding machine, meeting the increasing demand for efficiency and accuracy in face gear manufacturing. The machining motion of face gears is more complex than that of cylindrical gears, and the general gear grinding machine cannot meet the motion of continuous generating grinding of face gears. The worm forming dressing method based on virtual center distance is proposed to replace diamond wheel deflection with worm deflection, to solve that the diamond wheel cannot be deflected when dressing the crown worm wheel. The radial feed trajectory for grinding face gears is replanned to replace the linear feed with diagonal feed, to solve that the crown worm wheel cannot deflection horizontal during face gear grinding. Finally, the tooth surface errors caused by the misalignment of the crown worm wheel during grinding are analyzed, and the numerical simulation and machining experiments are conducted for worm dressing and face gear grinding. The results show that the shape of the dressed worm is consistent with the simulation results, and the deviation of the machined face gear is within the error range of grade 5 accuracy.
Journal Article
The spiralizer! cookbook : the new way to low-calorie and low-carb eating : how-to techniques and 80 deliciously healthy recipes : the ultimate guide to the newest kitchen appliance for preparing vegetables and fruits, with over 450 step-by-step photographs
The spiralizer is the newest tool in healthy eating -- creating tasty low-carb, low-calorie noodles, ribbons and 'rice' from everyday fruits and vegetables, all with the feel-full factor of real pasta. This book features 80 recipes which show you how to get the most out of your spiralized dishes.
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Residual stress of grinding cemented carbide using MoS2 nano-lubricant
The special mechanical properties of cemented carbide with high strength and hardness will cause complex stress due to excessive force and heat in the process of precision manufacturing, which will affect precision retention and endurance limit. Given the health and environmental threat of conventional flood cooling and the harsh processing environment of dry grinding, minimum quantity lubrication (MQL) has become an irreplaceable method to machining cemented carbide. However, the addition of nanoparticles changes the force and heat during grinding, which makes the influence on the residual stress of cemented carbide complicated. Therefore, based on the single abrasive grinding force model, the effective abrasive particle number was obtained by simulating the distribution of abrasive particles on the grinding wheel surface, and the mechanical stress model was established, which was loaded onto the workpiece in iterative attenuation mode. The thermal stress model was established based on the temperature field model. The final residual stress prediction model was obtained by determining whether the grinding process yields results and carrying out stress loading and stress relaxation. Experimental verification of the model was carried out under four different grinding conditions of YG8. The minimum friction coefficient of 0.385 was obtained under nanofluid minimum quantity lubrication (NMQL). In the precision analysis of the model, the minimum error value was 5.9% in the direction perpendicular to the feed direction of the workpiece in the dry grinding condition, which proved that the residual stress model had certain reliability.
Journal Article
Machinability of ultrasonic vibration-assisted micro-grinding in biological bone using nanolubricant
Bone grinding is an essential and vital procedure in most surgical operations. Currently, the insufficient cooling capacity of dry grinding, poor visibility of drip irrigation surgery area, and large grinding force leading to high grinding temperature are the technical bottlenecks of micro-grinding. A new micro-grinding process called ultrasonic vibration-assisted nanoparticle jet mist cooling (U-NJMC) is innovatively proposed to solve the technical problem. It combines the advantages of ultrasonic vibration (UV) and nanoparticle jet mist cooling (NJMC). Notwithstanding, the combined effect of multi parameter collaborative of U-NJMC on cooling has not been investigated. The grinding force, friction coefficient, specific grinding energy, and grinding temperature under dry, drip irrigation, UV, minimum quantity lubrication (MQL), NJMC, and U-NJMC micro-grinding were compared and analyzed. Results showed that the minimum normal grinding force and tangential grinding force of U-NJMC micro-grinding were 1.39 and 0.32 N, which were 75.1% and 82.9% less than those in dry grinding, respectively. The minimum friction coefficient and specific grinding energy were achieved using U-NJMC. Compared with dry, drip, UV, MQL, and NJMC grinding, the friction coefficient of U-NJMC was decreased by 31.3%, 17.0%, 19.0%, 9.8%, and 12.5%, respectively, and the specific grinding energy was decreased by 83.0%, 72.7%, 77.8%, 52.3%, and 64.7%, respectively. Compared with UV or NJMC alone, the grinding temperature of U-NJMC was decreased by 33.5% and 10.0%, respectively. These results showed that U-NJMC provides a novel approach for clinical surgical micro-grinding of biological bone.
Journal Article
Grinding efficiency and profile accuracy of diamond grinding wheels dressed with wire electrical discharge conditioning (WEDC)
Super abrasive diamond grinding wheels are the most promising tools for the precision machining of advanced ceramics and carbide materials. However, the efficiency of conventional conditioning of these tools is limited owing to high dressing tool wear, long process time, low form flexibility, and induced damage to the abrasive grains. Wire electrical discharge machining (WEDM) is an alternative method for conditioning of superabrasive grinding wheels with electrically conductive bonding materials. In this study, cylindrical plunge grinding of an alumina ceramic with a resin-bonded diamond grinding wheel is investigated. The assigned type of resin bond contains copper particles and is accordingly electrically conductive for wire electrical discharge conditioning (WEDC). Conventional (mechanical) and WEDC methods are used for generating the same profile on two similar diamond grinding wheels. As a result, the specific grinding energy was reduced up to 26% and 29% during rough and finish plunge grinding, respectively. Reduced specific grinding energy and forces, along with more effective grain protrusion and sharpness by using WEDC for profiling of grinding wheels, have contributed positively to the ground surface conditions despite the relatively rougher wheel surface topography in comparison to the conventional profiling. The more considerable reduction in the mean roughness depth (Rz) than in the arithmetical mean roughness value (Ra) (11% smaller Rz values in WEDC versus mechanical conditioning) verifies that the workpiece surface underwent less surface degradation in case of WEDC because of smaller grinding forces. Furthermore, the profile wear behavior of the workpiece ground with the WED conditioned grinding wheel was superior to the conventionally conditioned one.
Journal Article
Comprehensive analysis of the effects of different parameters on the grinding performance for surfaces
Compared with the parameters of surface grinding, those of the curved surface abrasive belt grinding are more diverse, and the material removal mechanism is more complicated. This makes the selection of the parameters of the curved surface grinding process extremely difficult. This study investigates the effects of different parameters on the grinding performance of convex surface workpieces. The material removal (material removal efficiency and microchips), grinding heat (overall grinding temperature and single abrasive grain temperature), and grinding surface quality (surface roughness and removal profile) were analyzed in detail at the macro- and microscales. The effects of the grinding parameters on the above three performance indices were analyzed and discussed. The results showed that an increase in the theoretical grinding depth results in a higher material removal efficiency and grinding temperature as well as a superior ground surface quality. The effects of belt speed on the material removal efficiency and grinding temperature are less significant than those of the theoretical grinding depth. Comprehensive consideration of three indicators of grinding performance, when the theoretical grinding depth is 0.16 mm and the belt speed is 26–28 m/s, the abrasive belt grinding performance is relatively superior. Therefore, by comprehensively analyzing the grinding performance, more suitable grinding parameters can be selected to improve the grinding quality of curved workpieces.
Journal Article
3D grinding mark simulation and its applications for silicon wafer grinding
A three-dimensional mathematical model based on homogenous coordinate transformation was developed and later experimentally validated to simulate the abrasive trajectories caused by the grit of grinding wheel onto the wafer. Those abrasive trajectories become the cross-hatch grinding marks on the ground wafer surface. The resulting convex or concave face profile of wafer after the grinding process as well as the abrasive trajectories which correlated to the wafer surface quality in terms of total thickness variation (TTV) can be predicted accurately. Simulations revealed that the relative orientation between the chuck table and the grinding wheel most affects TTV, followed by the offset distance if only the grinding geometry is considered. Moreover, the spindle speed should be coprime to chuck table in order to avoid overlapped trajectory, which may ensure a better grinding quality and grinding efficiency as well. Similarly, the spindle speeds for fine grinding should be coprime to rough grinding to effectively eliminate the grinding marks left by the rough grinding for better grinding quality. The model was implemented in software to generate grinding trajectories to predict wafer TTV given the process parameters such as rotational speeds and relative orientation between the grinding wheel and chuck table, which plays an essential tool for further process parameters optimization for wafer grinding.
Journal Article