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In grinding operation, cutting fluid is utilized for lubrication, cooling, chip removal from contact zone and also cleaning of grinding wheel. Despite these advantages, grinding fluids make many economic and environmental issues. On the other hand, dry grinding generally leading to thermal damages and reduction of surface quality level. Minimum Quantity Lubrication (MQL) technique is a new approach to elimination or reduction of cutting fluids that improves grinding performance by efficient penetration to the cutting zone. In this paper, in order to investigate the effect of MQL on grinding of steels, raw and hardened High Speed Steel have been selected. Grinding performance such as tangential grinding force, friction coefficient, roughness and morphology of the ground surface and chip form in three states of dry, conventional fluid and MQL have been studied and compared. The results show that MQL technique in comparison with the others lead to improvement of surface quality and also reduction of tangential grinding force and friction coefficient in hardened steel, but in the case of raw steel despite of reduction of tangential grinding force and friction coefficient, the surface quality is worst.

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Ultrasonic technology has been applied in many industrial processes such as ultrasonic machining, welding, cutting, sewing, homogenizing, etc. In an ultrasonic system, acoustic horn transmits the vibration energy of ultrasonic transducer to the application area and amplifies the oscillation amplitude. Depending on the application and industrial operating conditions, different horns with different geometries and magnifications are required to be designed. In the present study exponential horns with rectangular cross-section for application in ultrasonic assisted grinding process are designed and analyzed. An analytical approach is applied to model this type of horns. For evaluating the analytical model, some acoustic horns are designed using analytical method and then analyzed by the finite-element method (FEM) in ANSYS. Then, their design parameters such as resonance frequency and amplification factor are compared and verified. A very good agreement is obtained between the results of analytical modeling and those of FEM simulation. Furthermore, geometrical modification was introduced as a solution to coincide the vibration related parameters of the horn to the desired design values. Moreover, a horn-workpiece assembly for applying in ultrasonic assisted grinding was simulated.

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The creating scratch by an abrasive grit is mostly investigated to enhance the finishing processes. In grinding many distributed abrasive grits on grinding wheel surface engaged with workpiece to remove material. To investigate the material removal mechanism in grinding process a scratch and removed material by an abrasive grit is assumed and simulated. The results are developed for all engaged abrasive grits on grinding wheel surface. This leads to improve the machining process and taking a deep sight in to the grinding mechanism. By analyzing a creating scratch by a single abrasive grit, the material removal mechanism is scrutinized in a different view. The effect of grinding wheel surface topography and input parameters on material removal mechanism is investigated. Results show that increasing cutting speed leads to changing material removal mechanism from ploughing to cutting. The shape of abrasive grits has more effect on material removal mechanism. In worn grits increasing the cutting depth cause the ploughing to be dominant mechanism in machining. This leads to less cutting efficiency. But in abrasive grits with sharp single cutting edge the converse results is achieved. When grit breaks down and self dressing occurs during machining, the multiple edges are formed on grit and the grit acts like a dull abrasive.

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Milling is one of the most important operational stages in processing the minerals. Lifters are usually used with mill liners to extend their life and to enhance the grinding and crushing efficiency. Lifters worn and consequently their dimensions change during the course of operation. These changes in dimensions have a significant influence on the overall economic performance of the mills. Therefore, it is useful to know the relationship between the mill operation and the lifter profile, and the influence of lifter wear on the change in lifter profile. The wear is influenced by a range of parameters such as: media charge level, slurry filling, slurry concentration, and mill speed. In this work, the influences of these operating parameters were investigated using a pilot mill (1000 * 500 mm). To this end, a Copper ore was used to prepare slurry at 40%, 50%, 60%, 70%, and 100% solids concentration by mass. The tests covered a range of slurry filling (U) from 0.5 to 3 with solid charge between 15% and 35% of mill volume and 3 different speeds 65%, 75% and 85% of critical speed. It is found that the mill charge and the mill speed significantly affect the wear rate. For wet condition, increase in the slurry concentration and slurry filling leads to a remarkable decrease in the amount of the wear. By increase in the feed filling (in dry condition) the wear increases too. Wear rate in wet conditions is 2-4 times of dry condition.

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Consumption of cutting fluids imposes high costs on industry. These cutting fluids contaminate the environment and are harmful to human health. Minimum quantity lubrication technique (MQL) is a new approach to reduction of cutting fluids consumption, improving efficiency of cutting fluid at machining zone and using harmless fluids. However, this technique faces cooling limitation in grinding. The purpose of this study is an accurate study of heat transfer mechanism in minimum quantity lubrication technique by its temperature numerical simulation and improving the cooling ability of its air jet by using a simple and inexpensive vortex tube. For this purpose, a system was designed and manufactured to measure the convection heat transfer coefficient of different conditions of MQL environments. The result of convection heat transfer tests shows 95% share of compressed air in heat transfer and also air pressure is a more important factor than temperature in cooling process. The result of temperature numerical simulation shows that by increasing pressure, the increasing rate of convection heat transfer coefficient decreases; also, the cooling ability temperature of the vortex tube at low thermal power is tangible. In grinding of soft steel, the minimum quantity lubrication technique with cold air (CAMQL) in comparison with other methods lead to significant reduction of tangential grinding force and friction coefficient, but in general, except in the case of optimum condition which has the highest heat transfer coefficient, surface finish is worse which relate to low heat transfer coefficient of gases at low pressures.

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Today, in the most of mining projects, especially in high volume mining using SAG and AG due to the special features respect to the other conventional methods has been developed. Usually in comminution process a small percentage of energy consumed by grinding and crushing processes. Also, the comminution process depended on many parameters such as: ore hardness, charge volume, size and geometry of ore, charge and size of ball, percentage of critical velocity of mill and liner profile. Therefore, achieving to optimum mentioned factors and consumed energy is of particular importance. Since it is impossible to consider interaction of all effective parameters simultaneously by experimental methods and are expensive and time consuming, in this research the effect of liner profile on comminution process has been investigated by changing the height and angle of liners using numerical method. In recent work the results of scaled experimental mill has been used for validation of numerical method. The results show a liner with a height of 140 mm and an angle of 15 degrees has the maximum impact and comminution. The results from FEM model of the SAG mill at Sarcheshmeh Copper Complex, are in good agreement with the measured data from experimental SAG mill.

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Minimum quantity lubrication (=MQL) technique has many technological and economic advantages in grinding operation. It not only improves general grinding performance such as surface integrity, grinding forces and wheel wear but also, it is eco-friendly technique because of its small consumption of cutting fluid. Despite these advantages, MQL technique has a serious thermal problem in grinding operations due to small amount of cooling. To overcome this problem combination of hybrid nanofluid and ultrasonic vibration has been suggested. Nanofluid can increase heat transfer from workpiece/wheel interface due to its high thermal conductivity. Also ultrasonic machining can decrease heat generation due to its reciprocating mechanism and reduction of time and length of contact between grain and workpiece. In this research hybrid Multi Walled Carbon Nano Tubes (=MWCNT) (with high thermal conductivity) and Al2O3 (with good lubrication effect) nanofluid has been utilized. The results have been shown that combination of MQL and UAG leads to decreasing of maximum grinding temperature up to 60.2% in comparison to dry grinding (from 254ºC to 101ºC). Moreover, friction coefficient and tangential grinding force have been reduced up to 35.9 and 69.2 percent respectively. Furthermore, any burning has not been observed with combinations of these techniques while severe burning has been observed in dry grinding. Surface morphology analysis has been shown decrease of plastic deformation and side flow. And finally the generated chips have been shown similarity of cutting mechanism in in the utilized techniques and conventional cutting fluids.

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Ceramic matrix composites (CMCs) are a new class of high technology materials which can be utilized as a replacement for metallic super-alloys. CMCs have a vast array of applications in modern industries due to their upstanding properties, including low density, relatively high hardness and fracture toughness, and high corrosion and wear resistance. Extremely high hardness and inhomogeneous structure of CMCs cause unstable process and high grinding forces and temperature. This research was conducted in order to overcome the grinding challenges of these composites by recognizing and analyzing the effects of main process parameters comprising cutting speed, feed speed, and depth of cut on the grinding forces, specific energy, and grinding force ratio in three different environments including dry, wet and MQL grinding. To evaluate the significance of input parameters and their influence on the responses and also to derive predicting equations, Analysis of Variance (ANOVA) was employed. It was concluded that MQL technique is the most efficient cooling-lubrication method where implementation of this process reduces the tangential grinding force by 38.88% and normal grinding force by 31.16%, relative to dry grinding; however, the amount of force reduction in wet grinding is 34.22% for tangential grinding force and 24.81% for normal grinding force, relative to dry grinding. In addition, increase of cutting speed leads to reduced grinding forces and force ratio and higher amounts of specific energy, and also increase of feed speed and depth of cut cause higher grinding forces and force ratio and lower amounts of specific energy.

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Advanced ceramics are a group of materials that have been used in many industries due to their properties such as high temperature stability, high strength, high abrasion resistance and high corrosion resistance. Grinding process is one of the most important and most commonly used techniques for machining and polishing of ceramics. However, poor grindability, high surface defects in the workpiece due to the brittleness of ceramics and the high grinding forces, high wear rate of diamond wheel (tool), high costs due to the use of cutting fluid, low cutting productivity (low production rate), are of the problems of ceramics grinding. The minimum quantity lubrication (MQL) new technique is one of the methods recently introduced in machining processes aimed at improving lubrication performance of cutting fluids, reducing fluid consumption and promoting the use of low-hazard and environmentally friendly fluids. In this study, the minimum quantity lubrication technique was used in the grinding process of zirconia ceramic in order to investigate its effects on the grindability of ceramics. Also, since the type of lubricant and grinding wheel can affect the performance of minimum quantity lubrication in this process, the type of lubricant and diamond wheel were used as variables in the experiments. The grinding forces, surface roughness and surface texture of the grinded samples have been evaluated. The results show that under the minimum quantity lubrication conditions, applying the appropriate type of lubricant and grinding wheel can significantly affect the grindability of zirconia ceramic.

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Titanium is currently widely used as dental implant, but it may cause allergic problems. For this reason, the use of partially stabilized zirconia (PSZ) in dental applications has increased in recent years. Because of extreme hardness and brittleness of ceramic (PSZ) and in order to achieve dimensional and geometrical accuracy, grinding is necessary. In this research, a comprehensive study was carried out to investigate the effect of the grinding parameters of PSZ on surface roughness, grinding cost and PSZ phase transformation. It was observed that, increasing both depth of cut and feed rate results in an increase on tetragonal to monoclinic phase transformation. It was also observed that using a metal bond grinding wheel with higher concentration and larger abrasive size results in lower grinding cost. It was observed that using resin bond grinding wheels instead of metal bond grinding wheels, results in average 8% lower surface roughness. However, an increase in grinding wheel concentration results in a decrease in the surface roughness. Response surface method (RSM) was used to find an optimum condition and create a mathematical model between inputs and outputs and it was shown that the average R-square of the model was more than 0.90. PSZ microstructure and surface roughness could be controlled by controlling the grinding parameters. Using a metal bond grinding wheel with higher concentration and larger abrasive size results in lower grinding cost.

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Recently, increasing attention has been directed to the isolation of natural active components from various medicinal plants. In the present research, the extraction of essential oil from horehound (M. vulgare L.) is presented. Effects of mass ratio and particle size on the process performance were studied and kinetics were determined. The chemical composition of the volatiles present in M. vulgare L. was evaluated for the sample extracted in the optimum conditions (mass ratio, 3 kg/m3 and particle size,0.1

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The grinding process is one of the most important and widely used machining processes to achieve the desired surface quality and dimensional accuracy. Since the undeformed chip thickness is not a constant value in the grinding process and is changing independently and momentarily for each abrasive, the determination of the undeformed chip thickness accurately is essential to determine the grinding forces and surface topography of the grinding wheel. Previous studies on grinding forces were mainly regardless of the micro-mechanisms between the abrasive and the workpiece. On the other hand, only the average values ​​of forces could be calculated by determining the average value for undeformed chip thickness. In this study, a new analytical model with the approach of kinematic-geometric analysis of abrasive grain trajectory is presented to determine the undeformed chip thickness and subsequent grinding forces. This model predicts the components of normal and tangential grinding forces (including sliding, plowing, and cutting forces) accurately and in detail based on the instantaneous undeformed chip thickness obtained from the kinematic analysis of abrasive movement and micro-mechanisms between abrasive and the workpiece. In the end, experimental tests were performed to validate the theoretical model.

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Today, polyether ether ketone composites are widely used in the medical and aerospace industries due to their high strength-to-weight ratio, anti-allergic properties, high buckling resistance and fatigue. Grinding has a high specific energy among traditional cutting processes. Usually a high portion of energy will converts to heat. Because heat has an important role in polymer grinding, the heat modeling of it is necessary. In addition to the energy of chip formation during material removal, there are other energies such as plowing and friction energy. The contribution of each of these energies affects the efficiency of the process. By theoretical calculating of the cutting energy and comparing it with the experimental specific grinding energy, the portion of chip formation energy versus friction and plowing energy can be calculated. By performing differential scanning calorimetry test and theoretical calculations, the amount of chip formation energy was 0.089 and 0.119 J/mm^3 for GFRP and CFRP, respectively. While the experimental results of grinding showed a minimum specific energy of 2.2 J/mm^3 and 2.4 J/mm^3 for GFRP and CFRP, respectively. This difference indicates the very high portion of plowing energy in the grinding of this material and especially polymeric materials. The percentage of the chip-forming energy that enters the workpiece as heat was calculated to be 27%. Therefore, it can be stated that all energy except 73% of the chip formation energy enters the workpiece.

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Given the current demand for surfaces with non-polished morphology like structured surface that enhance its tribological properties, providing a method with minimal production cost and high performance has attracted attention. The present study focuses on presenting a new method for producing structured surfaces with hydrophobic performance. In this method, using the grinding process with a special grinding wheel, an attempt has been made to produce these widely used surfaces. By modifying the topography of the wheel surface and changing the arrangement of abrasive particles from random to arranged distribution with the diamond particles in predefined locations, an attempt was made to design and manufacture a special grinding wheel for the production of structured surfaces. A segment with 1*1 cm2 including diamond particles with mesh size of 40/50 were manufactured during the electroplating process in a nickel bath medium and by installing the segment on the wheel hub and performing the grinding process with this developed wheel, surfaces containing continuous and discontinuous scratches with the same geometry were produced. Static contact angle test for the unstructured surface was about 37 degrees that improved to 141 degrees with the structured surface, which is an impressive improvement.

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Mounted point grinding is a machining method to reduce surface roughness and improve surface finishing on workpiece walls and hard-to-reach areas. This process is usually used without preparing the grinding wheel before and during the grinding operation, which reduces the proper performance of the process. Environmental contamination, surface integrity, coolant-lubricant-related diseases that affect workers' health, and machining costs heavily depend on the appropriate dressing and proper coolant-lubricant usage. In this study, as a novel approach, the effects of dressing conditions (depth of dressing and dressing feed rate) and the feed rate of the workpiece during the grinding of a hardened Mo40 steel workpiece in two traditional cooling-lubricant minimum lubrication environments have been investigated. Surface roughness and wheel loading are two significant outputs in every grinding operation. The experimental result of this study reveals an improvement in enhancing the surface roughness in a soft dressing. Moreover, another aim of this study was to achieve proper surface roughness by implementing minimum quantity lubrication to significantly reduce total cutting fluid usage compared to traditional continuous coolant-lubricant. In this study, higher wheel loading in the Minimum Quantity Lubrication (M.Q.L.) technique was observed compared to the traditional continuous coolant-lubricant technique.