Specific Grinding Energy Research Articles

Experimental research on the energy ratio coefficient and specific grinding energy in nanoparticle jet MQL grinding

Nanoparticles are solid nanoscale particles with features such as antiwear, antifriction, and high load-carrying capacity. This research applied nanoparticles in the cooling lubrication of grinding and theoretically analyzed the impact of cooling lubrication on the grinding surface through the energy ratio coefficient and specific grinding energy. First, the workpiece surface temperature was measured using a thermal infrared imager. A three-dimensional dynamometer was used to identify the tangential grinding force during grinding. Results showed that, with different cooling lubrication approaches, the grinding surface was distributed to workpiece, grinding wheel, grinding fluid, and abrasive debris according to different energy ratio coefficients. The calculation demonstrated that the energy ratio coefficient of dry grinding reached 64.3 %. However, the energy ratio coefficient of flood lubrication, minimal quantities of lubricant (MQL), and nanoparticle jet MQL was 36.8, 52.1, and 41.4 %, respectively. These findings indicated that nanoparticle jet MQL realized a cooling effect close to that of flood lubrication. The specific grinding energy of nanoparticle jet MQL was 35 J/mm3, which was close to that of flood lubrication at 29.8 J/mm3. This finding indicated that the lubrication effects of nanoparticle jet MQL were also similar to those of flood lubrication. Moreover, molybdenum disulfide, carbon nanotube (CNT), and zirconium oxide nanoparticles were added in the grinding fluid to conduct the grinding experiment with nanoparticle jet MQL. The comparison of energy ratio coefficients showed that the cooling performance of CNT nanoparticles was satisfactory. CNT nanoparticles were subsequently added into the grinding fluid at the volume concentrations of 1, 2, and 3 % for the grinding experiment. The results showed that the best cooling effects occurred under the 2 % volume concentration of CNT nanoparticles. Through rounds of selections and optimizations, our research acquired the nanoparticle types and volume concentration that had satisfactory cooling effects and should therefore be added in the grinding fluid.

Experimental and Analytical Investigation of Workpiece Thermal Load During External Cylindrical Grinding

This paper focuses on the correlation between process quantities of an external cylindrical grinding process (heat partition factor ɛ, specific grinding energy partition uw transported to the workpiece, specific grinding power Pc″) and resulting surface and subsurface properties of the ground workpiece. In order to identify this correlation, experimental investigations were carried out and the maximum contact zone temperature Tmax was measured by using a grinding wheel-integrated temperature measurement system. The resulting surface layer properties are linked with the process quantities by means of the regression analysis combined with analytical considerations using the moving heat source theory. The results may contribute to predict resulting surface and subsurface properties of ground workpieces without detailed prior knowledge about thermal and mechanical loads caused by the grinding process.

高速精密磨削9CrWMn冷作模具钢的磨削力和比磨削能

高速精密磨削9CrWMn冷作模具钢的磨削力和比磨削能

Vertical Agitated Media Mill scale-up and simulation

Vertical Agitated Media Mill modeling has become subject of a research project due to its potential application as a secondary grinding mill as well as regrind and pellet feed preparation projects. A test campaign with a pilot scale vertical mill was carried out with five different ore samples to elaborate a simple and robust methodology to scale-up vertical mills and perform simulations. The methodology proposed considers breakage parameters determined from tests in a conventional batch ball mill and population balance model for simulations. The tests can be performed very quickly in any process laboratory with a small quantity of sample. Two different models can be used for scale-up purposes: the first is based on the specific grinding energy and the corresponding tests were carried out on samples with natural size distribution. The second is based on particle residence time distribution and the tests carried out with narrow sized particles. Breakage and selection function parameters were estimated from each test procedure. The results indicate that it is possible to perform vertical mill scale-up and simulations with acceptable accuracy using the results from laboratory ball mill tests. The data analysis showed that the ratio of grinding net powers between ball and vertical mills is approximately 1.35 for all samples tested.

Determination of Specific Energy Consumption and Grain Size for Corn Grinding Using the Hammer Mill MB7,5

Changing the degree to which animals feed is grinded can be done for hammer mills in several ways, namely: the use of sieves with different diameters, different hammers, different engine speeds.Grain milling energy consumption is influenced by the type of material used, its moisture content, size and type of hammers, sieves holes etc.In the present study we determined the influence of moisture and sieve mesh size on milling maize grain moisture of 11.1% and 17.6% using conventional hammer mill. Using three kinds of sieve apertures with a diameter of 4, 6 and 8 mm was determined from the specific grinding energy.

Experimental verification of nanoparticle jet minimum quantity lubrication effectiveness in grinding

In our experiment, K-P36 precision numerical control surface grinder was used for dry grinding, minimum quantity lubrication (MQL) grinding, nanoparticle jet MQL grinding, and traditional flood grinding of hardened 45 steel. A three-dimensional dynamometer was used to measure grinding force in the experiment. In this research, experiments were conducted to measure and calculate specific tangential grinding force, frictional coefficient, and specific grinding energy, thus verifying the lubrication performance of nanoparticles in surface grinding. Findings present that compared with dry grinding, the specific tangential grinding force of MQL grinding, nanoparticle jet MQL grinding, and flood grinding decreased by 45.88, 62.34, and 69.33 %, respectively. Their frictional coefficient was reduced by 11.22, 29.21, and 32.18 %, and the specific grinding energy declined by 45.89, 62.34, and 69.45 %, respectively. Nanoparticle jet MQL presented ideal lubrication effectiveness, which was attributed to the friction oil film with strong antifriction and anti-wear features formed by nanoparticles on the grinding wheel/workpiece interface. Moreover, lubricating properties of nanoparticles of the same size (50 nm) but different types were verified through experimentation. In our experiment, ZrO2 nanoparticles, polycrystal diamond (PCD) nanoparticles, and MoS2 nanoparticles were used in the comparison of nanoparticle jet MQL grinding. The experimental results manifest that MoS2 nanoparticles exhibited the optimal lubricating effectiveness, followed by PCD nanoparticles. Our research also integrated the properties of different nanoparticles to analyze the lubrication mechanisms of different nanoparticles. The experiment further verified the impact of nanoparticle concentration on the effectiveness of nanoparticle jet MQL in grinding. The experimental results demonstrate that when the nanoparticle mass fraction was 6 %, the minimum specific tangential grinding force, frictional coefficient, and specific grinding energy were 1.285 N/mm, 0.382, and 57.825 J/mm3, respectively. When nanoparticle mass fraction was smaller than 6 %, lubrication effects of nanoparticle jet MQL increased with the rising nanoparticle mass fraction. When nanoparticle mass fraction was larger than 6 %, lubrication effects of nanoparticle jet MQL decreased with the rising nanoparticle mass fraction.

Comparative study on cutting behavior of vitrified cubic boron nitride wheel and electroplated cubic boron nitride wheel in high-speed grinding of (TiCp + TiBw)/Ti-6Al-4V composites

High-speed grinding experiments of particle reinforcing titanium matrix composites ((TiCp + TiBw)/Ti-6Al-4V) were carried out with vitrified cubic boron nitride wheel and electroplated cubic boron nitride wheel, at the wheel speed ranged from 80 to 140 m/s. The cutting behavior, that is, grinding force, grinding temperature, specific grinding energy, and ground surface morphology, and grinding chips are analyzed. The results indicate that compared to the workpiece speed and the depth of cut, the wheel speed has a more significant influence on the grinding forces. The grinding temperature and specific grinding energy obtained with the vitrified cubic boron nitride wheel are always larger than those with the electroplated cubic boron nitride wheel. Based on the comprehensive consideration in terms of grinding force, grinding temperature, and specific grinding energy, the electroplated cubic boron nitride wheel is more suitable than vitrified cubic boron nitride wheel for high-speed grinding particle reinforcing titanium matrix composites. The removal of the reinforcements of particle reinforcing titanium matrix composites is mainly by means of pullout, fracture or crushing, micro-cracks, voids, and smearing. The segment chips containing the reinforcements are formed during high-speed grinding of particle reinforcing titanium matrix composites.

Grinding temperature during high-efficiency grinding Inconel 718 using porous CBN wheel with multilayer defined grain distribution

Porous cubic boron nitride (CBN) wheel with multilayer defined grain distribution was developed based on pore-forming effect of alumina bubbles and sintering technology. High-efficiency grinding experiments were carried out on a typical nickel-based superalloy Inconel 718, and grinding temperatures within the contact arc were measured. A strategy to control the grinding burn by clapping flake graphite around the workpiece was proposed, which was verified could improve the cooling effect in contact zone and increase the specific material removal at least three times higher in deep grinding. Being an attribute to the faster heat moving speed and good thermal conductivity of metal bond and CBN grains, grinding temperature reached 790 °C in the contact arc but nonvisible burnout marks were found on ground surface at Q′w = 25 mm3/(mm·s). At a wheel speed of 80 m/s, force ratio remains around 6 and specific grinding energy decreased from 187 to 67 J/mm3 at elevated specific material removal from 3 to 25 mm3/(mm·s). Results show that the developed porous CBN wheels have a promising application in high-efficiency deep grinding nickel-based alloy.

Effect of parameters on grinding forces and energy while grinding Al (A356)/SiC composites

Grinding processes require a high energy input per unit volume of material removed, which is converted to heat at the grinding zone, resulting in increased force and wear. In the present study, the influence of grinding parameters like work speed and depth of cut on grinding forces and energy was studied. An attempt has been made to study the forces and energy involved while grinding aluminium alloy (A356)/silicon carbide (SiC) composite material with different grinding wheels. Experiments were carried out on a surface grinding machine. Three different types of wheels like SiC, cubic boron nitride (CBN) and diamond wheels were used. The grinding forces increased with increase in depth of cut and work speed. SiC exhibited high grinding force compared to the CBN wheel. In the case of the diamond wheel, it was even less. The specific grinding energy was highest for the diamond wheel followed by CBN and SiC wheels. The specific grinding energy decreased with increase in depth of cut and work speed.

Grinding behavior and surface appearance of (TiCp + TiBw)/Ti-6Al-4V titanium matrix composites

(TiCp+TiBw)/Ti-6Al-4V titanium matrix composites (PTMCs) have broad application prospects in the aviation and nuclear field. However, it is a typical difficult-to-cut material due to high hardness of the reinforcements, high strength and low thermal conductivity of Ti-6Al-4V alloy matrix. Grinding experiments with vitrified CBN wheels were conducted to analyze comparatively the grinding performance of PTMCs and Ti-6Al-4V alloy. Grinding force and force ratios, specific grinding energy, grinding temperature, surface roughness, ground surface appearance were discussed. The results show that the normal grinding force and the force ratios of PTMCs are much larger than that of Ti-6Al-4V alloy. Low depth of cut and high workpiece speed are generally beneficial to achieve the precision ground surface for PTMCs. The hard reinforcements of PTMCs are mainly removed in the ductile mode during grinding. However, the removal phenomenon of the reinforcements due to brittle fracture still exists, which contributes to the lower specific grinding energy and grinding temperature of PTMCs than Ti-6Al-4V alloy.

Experimental Study on Ultrasonic Assisted Grinding of C/SiC Composites

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.

Rail grinding for the 21st century – taking a lead from the aerospace industry

Rail grinding is a key maintenance activity for Network Rail. It is performed at night through possession of the track, so process speed is critical. Increasing the metal removal rate (MRR) of the rail grinding operations would be a way to improve the time taken for this operation. The aerospace industry has recently seen advances in grinding technologies that have increased MRR. This work was aimed at assessing their best practice and its application to rail grinding operations. Current Network Rail grinding operations include preventative and corrective re-profiling of the rail head. The majority of work performed in the UK is preventative re-profiling with current train speeds ranging from 1 to 10 mile/h. Opportunities exist to increase train speed and improve the productivity of this operation through the use of more advanced grinding technologies. The most relevant aerospace technology is high efficiency deep grinding (HEDG). This approach uses: a high surface speed of the grinding wheel, superabrasive tooling, and high workpiece feed rates to remove material quickly from the cut-zone. Productivity improvements were identified by applying theory on power requirements (by assessing the specific grinding energy) and chip thickness of the grinding process. Computer CAD/CAM modelling was also performed to assess the effect of changing grinding techniques on potential gouging of the track infrastructure and/or interference with example trackside obstructions. The work concluded that opportunities do exist to improve the current productivity of grinding operations. Utilizing HEDG technology theoretically provides a 100% train speed increase (utilizing the same power available with the current setup) for preventative re-profiling. This requires the application of high surface speeds of the grinding wheel and superabrasive technology. Further increases in train speed require increased spindle power. The chip thickness experienced by grinding grains is reduced for a peripheral grinding setup and high wheel surface speeds that is beneficial for wheel wear. The application of HEDG technology cutting on the periphery of the wheel provided optimum conditions during CAD/CAM simulation to avoid rail gouging, and any potential collision of the grinding stone with modelled trackside obstructions.

Grinding performance evaluation of porous composite-bonded CBN wheels for Inconel 718

For high-efficiency grinding of difficult-to-cut materials such as titanium and nickel alloys, a high porosity is expected and also a sufficient mechanical strength to satisfy the function. However, the porosity increase is a disadvantage to the mechanical strength. As a promising pore forming agent, alumina bubbles are firstly induced into the abrasive layer to fabricate porous cubic boron nitride (CBN) wheels. When the wheel porosity reaches 45%, the bending strength is still high up to 50MPa with modified orderly pore distribution. A porous CBN wheel was fabricated with a total porosity around 30%. The grinding performance of the porous composite-bonded CBN wheel was evaluated in terms of specific force, specific grinding energy, and grinding temperature, which were better than those of the vitrified one under the same grinding conditions. Compared to the vitrified CBN wheel, clear straight cutting grooves and less chip adhesion are observed on the ground surface and there is also no extensive loading on the wheel surface after grinding.

Grinding Force, Specific Energy and Material Removal Mechanism in Grinding of HVOF-Sprayed WC–Co–Cr Coating

The present study applies the machining approach and other analysis techniques to investigate the material removal behavior during surface grinding of high-velocity oxy-fuel (HVOF) thermally sprayed WC–10Co–4Cr coating using a resin-bonded diamond wheel. The basic grinding factors such as force ratio, specific material removal rate, maximum undeformed chip thickness, and specific grinding energy have been investigated and discussed. The mathematical models containing linear terms and interactions of the first-order have been used to investigate the effect of the grinding parameters on the grinding force. The results have shown that both tangential and normal grinding forces depend not only on the depth of cut, feed rate, and cutting speed, but also on the depth of cut and feed rate interaction. Scanning electron microscopy (SEM) examination of the ground surface has revealed that the mechanism of material removal presents both brittle fracture and ductile flow modes. Considering the effect of the process parameters on the grinding mechanism, it has been inferred that the portion of the material removal mechanism associated with brittle fracture or ductile flow can be different according to the grinding parameters variations. Also, the SEM photographs have shown that large amounts of energy have been expended by plastic deformation due to plowing.

A comparison between conventional speed grinding and super-high speed grinding of (TiCp + TiBw) / Ti–6Al–4V composites using vitrified CBN wheel

Comparative grinding experiments of (TiCp + TiBw) / Ti–6Al–4V composites were conducted using vitrified CBN wheel at the conventional wheel speed of 20 m/s and the super-high wheel speed of 120 m/s, respectively. The grinding behavior, i.e., grinding force and force ratio, grinding temperature, specific grinding energy, and ground surface morphology were analyzed. The results obtained indicate that the normal and tangential grinding forces at the super-high wheel speed are smaller than that at the conventional wheel speed. However, the force ratio, the specific grinding energy, and the grinding temperature show a contradictory trend compared to the grinding force between the conventional speed grinding and the super-high speed grinding. The main defects of the ground surface of (TiCp + TiBw) / Ti–6Al–4V composites are voids, micro-cracks, fracture or crushed, pulled-out, and smearing.

Tribological characteristics in high-speed grinding of alumina with brazed diamond wheels

In this work, two brazed diamond wheels fabricated by brazing in vacuum were used to grind alumina at different grinding speeds. During the process, the horizontal and vertical grinding forces were measured by a force measurement device. The grinding forces, specific grinding energy, and friction in grinding of alumina at low and at high speeds were investigated. The results show that the friction coefficient decreases with the increase of the grinding speed and also relates to the grinding mode. A nearly proportional relationship between grinding power per unit width (Pm) and the rate of plowed surface area generated per unit time per unit width (Sw) reveals the effects of friction in grinding and most of the grinding energy is expended by friction. The surface energy per unit area generated by plowing friction (Js) for high-speed grinding is found to be lower than for low-speed grinding.

Wet Torrefaction of Forest Residues

Wet torrefaction of forest residues, which is one of the cheap and most abundant biomass resources in Norway, was experimentally studied. Freshly cut branches of Norway birch and spruce were used as feedstock, without and with pre-drying to simulate the drying during fuel storage prior to torrefaction. The results show that both torrefaction temperature and holding time have significant effects on the solid yield and its fuel properties. Increases in heating value of up to 13.0-13.5% and reductions of specific grinding energy of 13.3-27.5 times could be achieved via wet torrefaction. Torrefied forest residues have lower ash contents compared with the raw materials. Pre-drying and especially the drying methods have significant effects on the solid yield.

Geometric, kinematical and thermal analyses of non-round cylindrical grinding

This paper is concerned with the analyses of grinding geometry and kinematics in the grinding zone and develops a thermal model, along with a chip-thickness-dependent value of specific grinding energy into the workpiece. The grinding geometry and kinematics are modeled for arbitrary non-round workpiece forms. Unlike other models, which are based on a fixed, constant geometry, the model presented here is based on first principles using a fundamental, transient, non-constant geometry and thus constitutes a much-needed advancement in grinding technology. A novel experimental approach is also taken, which uses the specific grinding energy into the workpiece, rather than the total specific grinding energy coupled with an estimate of the energy partition, an estimate which previously has proven difficult to achieve accurately. The model is verified with experimental work and predicted temperatures are in reasonable agreement with temperatures associated with the onset of thermal damage, determined via metallographic examination and Barkhausen noise. Finally, some of the challenges of using Barkhausen noise to evaluate thermal damage are investigated, namely the differing response characteristics of stressed and overtempered material vs. rehardened material, and how these can be overcome in practice.

Investigating the Minimum Quantity Lubrication in grinding of Al2O3 engineering ceramic

Minimum Quantity Lubrication (MQL) is an efficient and environmentally friendly method of applying cutting fluids in machining processes. The aim of MQL is to minimize the amount of cutting fluid and to simultaneously utilize ecologically friendly lubricants. Additionally, MQL has immense potentials to be successfully employed in various machining processes. In this study, the performance of four types of lubricants, namely mineral, hydrocracked, synthetic, and vegetable oils, are evaluated with regard to the reduction in cutting force, specific energy and surface roughness during near dry grinding (MQL grinding) of Al2O3 engineering ceramic. The Taguchi mixed level parameter design (L16) is used for experimental design and the signal-to-noise (S/N) ratio objective function is applied for optimizing the process. The optimal lubricant and grinding parameters including depth of cut, feed rate and abrasive grain size for minimal cutting force, specific energy and surface roughness are obtained and reported. Moreover, an analysis of variance (ANOVA) is carried out to identify the significant parameters influencing the grinding force, specific grinding energy and surface roughness.

Physicochemical and grinding characteristics of dragonhead seeds

Abstract The results of investigations on the physicochemical and grinding characteristics of Moldavian dragonhead seeds are presented. The data obtained showed that the physical properties (average size, sphericity, surface area, 1 000 seed mass, dynamic angle of repose, coefficient of static friction, and bulk and true densities) of the white and blue form of dragonhead seeds were not significantly different. Both forms of dragonhead showed similar levels of protein (average of 21%), whereas the blue form of dragonhead had a lower fat content (average of 23.1%) and higher mucilage content (13.35%) in comparison to the blue form of seed (24.6 and 9.95%, respectively). Antioxidant capacity of dragonhead seeds was comparable for both forms and averaged about 40%, which corresponded to EC50 values of 0.12 and 0.13 mgml-1 for the white and blue forms, respectively. The grinding material showed similar particle size distribution of ground material for both forms of dragonhead seeds. The lowest values of specific grinding energy were obtained for the white form of dragonhead seeds, those for the blue form were significantly higher. Grinding of dragonhead seeds using a screen 2.0 mm mesh size caused screen hole clogging. This problem did not occur when dragonhead seeds were mixed with wheat grain.