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Recently, polyether ether ketone (PEEK) and its particle-reinforced composites have found a special place in various industries due to their high strength-to-weight ratio, anti-allergic properties, high resistance to buckling, and other superior properties. These materials have widely been used in the aerospace and medical industries and are commonly finished in the final step through the grinding process. In this work, the single grain scratch test was performed to fundamentally study the grinding process and material removal mechanism of PEEK and its particle-reinforced composites. In this method, the material removal is realized by a single grit penetrating the workpiece. It was found that the amount of flowed or piled-up (side flow) materials around the scratch in the pure polymer is higher than the other two composites. Pure polymer with 2.5 J/mm3 and glass fiber-reinforced composite with 1.1 J/mm3 resulted in the highest and lowest specific energies, respectively. The specific energy of all three materials is reduced significantly by increasing the grit penetration depth, showing the significant role of the size effect in grinding these materials. The main reasons for the different results are the high heat transfer coefficient and higher strength of CFRP composite compared to PEEK and PEEK GF 30. [ABSTRACT FROM AUTHOR]

Torrefaction treatment improves biomass grindability by transforming the fibrous herbaceous to a more brittle and lighter coal-like material. Microwave-assisted torrefaction is a promising technology for biomass conversion into energy, fuels, and chemicals. The study applied microwave absorbers in the torrefaction process to improve the thermochemical characteristics and grindability of switchgrass. Switchgrass in two particle sizes was torrefied in a microwave reactor with biochar added as a microwave absorber under inert conditions. After torrefaction, the geometric mean particle and size distribution and selected physical characteristics were evaluated, and the grindability of the torrefied ground and chopped with and without biochar were compared with those of untreated switchgrass. The geometric diameter results decreased, and the specific energy required for grinding torrefied switchgrass with biochar was significantly reduced with extended residence times and at a torrefaction temperature of 300 °C. After grinding, the lowest grinding energy of 32.82 kJ at 300 °C/20 min was recorded with torrefied ground switchgrass/biochar. The 10% biochar added/250 °C resulted in deep cell wall disarrangement, whereas at a torrefaction temperature of 300 °C, large surface deformation and carbonized weight fractions were observed.

Abstract Improved energy utilisation, precision, and quality are critical in the current trend of low-carbon green manufacturing. In this study, three abrasive belts were prepared at various wear stages and characterised quantitatively. The effects of abrasive belt wear on the specific grinding energy partition were investigated by evaluating robotic belt grinding of titanium plates. A specific grinding energy model based on subdivided tangential forces of cutting and sliding was developed for investigating specific energy and energy utilisation coefficient E UC. The surface morphology and Abbott–Firestone curves of the belts were introduced to analyse the experimental findings from the perspective of the micro cutting behaviour. The specific grinding energy increased with abrasive belt wear, especially when the belt was near the end of its life. Moreover, the belt wear could lead to a predominance change of sliding and chip formation energy. The highest E UC was observed in the middle of the belt life because of its retained sharp cutting edge and uniform distribution of the grit protrusion height. This study provides guidance for balancing the energy consumption and energy utilization efficiency of belt grinding.

Improved energy utilisation, precision, and quality are critical in the current trend of low-carbon green manufacturing. In this study, three abrasive belts were prepared at various wear stages and characterised quantitatively. The effects of abrasive belt wear on the specific grinding energy partition were investigated by evaluating robotic belt grinding of titanium plates. A specific grinding energy model based on subdivided tangential forces of cutting and sliding was developed for investigating specific energy and energy utilisation coefficient EUC. The surface morphology and Abbott–Firestone curves of the belts were introduced to analyse the experimental findings from the perspective of the micro cutting behaviour. The specific grinding energy increased with abrasive belt wear, especially when the belt was near the end of its life. Moreover, the belt wear could lead to a predominance change of sliding and chip formation energy. The highest EUC was observed in the middle of the belt life because of its retained sharp cutting edge and uniform distribution of the grit protrusion height. This study provides guidance for balancing the energy consumption and energy utilization efficiency of belt grinding. [ABSTRACT FROM AUTHOR]

The present research work focuses on developing a mechanistic model for the specific grinding energy in UAG process. Based on the developed model, the effect of cutting parameters has been studied. The cutting force plays a significant role in appraising the performance of machining process. The effect of various forces such as tangential, normal, and vibrational forces has been considered during UAG machining process, and a model has been proposed based on these forces. In the UAG process, the grinding wheel is rotated, and the workpiece is simultaneously vibrated with small amplitude and high frequency. The experimental studies revealed that ultrasonic vibration in grinding operations enhanced the overall performance by reducing cutting forces and improving surface integrity, resulting in less energy consumption. The developed model included various parameter effects such as frequency, amplitude, speed of the wheel, table speed, depth of cut, and width of cut. This mathematical model showed favorable outcomes validated with the data obtained from an experimental setup. This model can be utilized for future research in the direction of effective force and specific grinding energy and can contribute towards realizing sustainable grinding studies. [ABSTRACT FROM AUTHOR]

Ultrasonic vibration-assisted dry grinding is a sustainable hybrid manufacturing technology that decreases the negative environmental impact of coolant, reduces manufacturing costs, and improves surface integrity. The present investigation analyses the mechanisms associated with ultrasonic vibration-assisted dry grinding of AISI D2 tool steel with an alumina grinding wheel. It also compares the influence of traditional dry grinding and traditional wet grinding modes with the ultrasonic vibration-assisted dry grinding mode at different ultrasonic vibration amplitudes. Ultrasonic vibration was applied to the sample in the longitudinal feed direction. Further, kinematics of the abrasive grit path during the traditional grinding and ultrasonic vibration-assisted dry grinding is presented schematically. In this research, the impacts of ultrasonic vibration amplitude as well as the depth of cut on the process yields such as ground surface topography, grinding force, specific grinding energy, force ratio, surface finish, microstructure, and hardness were investigated experimentally. Experimental results revealed that the highest decline in tangential and normal grinding forces in ultrasonic vibration-assisted dry grinding at ultrasonic vibration amplitude 10 µm and the reduction in surface roughness parameter (Ra, Rq, and Rz) in ultrasonic vibration-assisted dry grinding was 43.23%, 42.59%, and 33.69%, respectively, in comparison to those in traditional dry grinding and 26.35%, 26.94%, and 27.48%, respectively, in comparison to those in traditional wet grinding. It was observed that ultrasonic vibration-assisted dry grinding is beneficial as the profile produced by ultrasonic vibration-assisted dry grinding has a comparatively flat tip, and profile points are shifted to the bottom of the mean line. This study is expected to assist ultrasonic vibration-assisted dry grinding of hard materials. [ABSTRACT FROM AUTHOR]

Polyether ether ketone (PEEK) and its composites are widely used in the biomedical industry due to their superior properties. The presence of glass and carbon reinforcing particles will improve the strength of the polymers while affecting their machinability. The cutting speed, dressing speed ratio, and different reinforcing fibers were defined as input parameters. Grinding forces, specific grinding energy, surface roughness, the surface topography of the workpiece, and wheel loading ratio were selected as output parameters of this research. Surface roughness is strongly affected by heat generation in the grinding zone. The experiments showed that pure polymer, GFRP (glass fiber–reinforced plastic), and CFRP (carbon fiber–reinforced plastic) induce maximum wheel loading ratio, respectively. The maximum wheel loading was calculated as 31% for pure polymer, and the main mechanism is melting. The highest cutting forces were measured when grinding pure polymer, followed by carbon, and glass fiber composites. The grinding forces were also affected by wheel loading ratio. Normal and tangential grinding forces increased up to 67% and 57%, respectively, by severe cutting conditions. The minimum specific grinding energy of PEEK and its composites was around 2.5 J/mm3. Additionally, increasing the cutting speed to vc = 15 m/s (despite lower inducing cutting forces) and decreasing the dressing speed ratio to qd = −0.3 surprisingly caused a rise in the roughness of the ground surfaces (for all three materials) due to a higher heat generation in the contact zone. [ABSTRACT FROM AUTHOR]

In the cylindrical grinding process, the residual grinding allowance is left owing to the rubbing of the abrasive grains and the elastic deformation of the grinding system caused by the large normal grinding force. Therefore, a sizing gauge is generally used to monitor the workpiece diameter during the process. However, the sizing gauge disturbs the grinding operations, such as loading and unloading the workpiece. In this study, a new method for estimating the grinding stock of a ground workpiece is proposed. In the proposed method, the grinding stock can be estimated without a sizing gauge. The removed volume of the workpiece can be calculated from the power consumption of the wheel motor, which is easily measured. Before the grinding experiments, the specific grinding energy is determined from several grinding results. During the grinding process, the grinding stock of the ground workpiece was estimated using the determined specific grinding energy. It was confirmed that the grinding stock could be accurately estimated under several grinding conditions. • Estimation method for grinding stock in cylindrical plunge grinding was proposed. • Grinding stock can be estimated with high accuracy from power consumption of wheel. • Change in grinding ability of the grinding wheel can be considered in proposed method. [ABSTRACT FROM AUTHOR]

Difficult-to-cut material, i.e., AISI D2 tool steel, has been widely adopted in metalworking industries to manufacture dies for piercing, blanking, drawing and thread rolling due to its excellent wear resistance and non-deforming properties. This article attempts an experimental study to determine the effect of cryogenic coolant (liquid nitrogen) on the grindability of AISI D2 tool steel as work material and its results are compared with the conventional dry and wet grinding methods. The effects of the cryogenic coolant on force components (i.e., tangential force, Ft and normal force, Fn), specific grinding energy (u), force ratio, surface roughness parameters (Ra and Rz) and microstructure were observed. The comparison results indicate a significant reduction in grindability indices such as 64% and 44% in Ft, 54% and 34% in Fn, 46% and 30% in Ra and 40% and 34% in Rz, respectively under cryogenic grinding at higher downfeed as followed to dry and wet grinding. The grinding performance in Ft, Fn, u and Ra was also improved with an increased delivery pressure of the liquid nitrogen (LN2). From the results, it is concluded that cryogenic coolant offers an influential method to improve grinding performance and surface integrity of AISI D2 tool steel. [ABSTRACT FROM AUTHOR]

Owing to intense heat generation in the continuous generating grinding, a large amount of grinding fluid is supplied during the process. Recently, however, reduction in grinding fluid supply has been attempted. In this study, the specific grinding energy and heat partition ratio of continuous generating grinding was analysed under dry conditions. The results revealed that the specific energy reduced to 53.8% with the grinding wheel of nine starts compared to that of three starts. The heat partition ratio remained almost unchanged with varying number of starts. The results revealed that a wheel with higher number of starts is thermally beneficial. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Torrefaction treatment improves biomass grindability by transforming the fibrous herbaceous to a more brittle and lighter coal-like material. Microwave-assisted torrefaction is a promising technology for biomass conversion into energy, fuels, and chemicals. The study applied microwave absorbers in the torrefaction process to improve the thermochemical characteristics and grindability of switchgrass. Switchgrass in two particle sizes was torrefied in a microwave reactor with biochar added as a microwave absorber under inert conditions. After torrefaction, the geometric mean particle and size distribution and selected physical characteristics were evaluated, and the grindability of the torrefied ground and chopped with and without biochar were compared with those of untreated switchgrass. The geometric diameter results decreased, and the specific energy required for grinding torrefied switchgrass with biochar was significantly reduced with extended residence times and at a torrefaction temperature of 300 °C. After grinding, the lowest grinding energy of 32.82 kJ at 300 °C/20 min was recorded with torrefied ground switchgrass/biochar. The 10% biochar added/250 °C resulted in deep cell wall disarrangement, whereas at a torrefaction temperature of 300 °C, large surface deformation and carbonized weight fractions were observed., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper:The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Lope G. Tabil reports financial support was provided by Biofuelnet Canada. Lope G. Tabil reports financial support was provided by 10.13039/501100000038Natural Sciences and Engineering Research Council of Canada. If there are other authors, they declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Crown Copyright © 2024 Published by Elsevier Ltd.)

This paper is concerned with understanding the role of specific energy in micro-grinding of conventional and additively manufactured Ti6Al4V. The effects of grinding and dressing parameters, cooling-lubrication conditions, and the directions of material build-up are studied. It is demonstrated that the minimum specific energy in single grain tests is independent of the material-fabrication method. The lowest measured specific energy obtained is 11.5 J/mm3 for both workpiece materials. The direction of material build-up influenced the process only when grinding with low aggressiveness, where 20% higher specific energy was observed. Similar specific energies were obtained for oil-lubricated and dry conditions, indicating that lubrication had minimal effect. The effects of the diamond concentration in the wheel and the dressing parameters were also investigated. Comparable specific energies were observed for wheels with C150 and C200 concentrations. The specific energy was found being predominantly influenced by dressing. Coarse dressing conditions produced 18% lower specific energy and, therefore, a more efficient micro-grinding process. • Specific grinding energy is used as a fundamental process parameter to investigate the grindability of titanium alloys. • The same minimum specific energy is obtained for both conventional and AM-produced titanium alloys in single-grain scratching. • The AM build-up direction significantly affects the micro-grinding efficiency, especially at lower aggressiveness. • Micro-grinding with a sharply dressed tool results in lower specific grinding energy compared to a finely dressed tool. [ABSTRACT FROM AUTHOR]

Ultrasonic assisted grinding (UAG) is one of the most suitable methods for the processing of hard and brittle materials such as silicon carbide (SiC). During UAG of SiC, the machining quality is directly determined by the material removal mechanism. However, the research on the material removal mechanism for UAG of SiC is still not sufficiently developed. To achieve better comprehension of the material removal mechanism in UAG of SiC, this study conducted both UAG and conventional grinding (CG) tests with a brazed grinding wheel with defined grain distribution. The material removal mechanism in UAG of SiC was studied by comparing the ground surface/subsurface micro-morphology, surface roughness, grinding force, and specific grinding energy between both processes. The results showed that the material removal mechanism experienced a transition from ductile removal to brittle fracture with increasing undeformed chip thickness in both UAG and CG. In addition, the ground surface roughness, grinding force, and subsurface breakage size increased with increasing undeformed chip thickness, while the specific grinding energy first decreased rapidly and then stabilised. Compared with conventional grinding, UAG always resulted in lower surface/subsurface breakage, surface roughness grinding force, and specific grinding energy under identical operating conditions. [ABSTRACT FROM AUTHOR]

Thermal Barrier Coatings (TBC) are commonly used on exhaust muffle of engines and gas turbine blades to protect the component from generated heat and increase the operational temperature. Machining of ceramic coatings is comparatively more challenging than sintered ceramics. In this study, a commonly used TBC coating, namely yttria stabilised zirconia coating was subjected to surface grinding using a mono layer nickel bonded diamond wheel. The grinding forces and specific grinding energy were studied experimentally. The normal force obtained experimentally was compared with a force model and the correlation was studied. The forces obtained were significantly low as compared to sintered YSZ and a close relationship was observed with the existing model. In addition, the specific grinding energy was also found to be minimum. This indicates that most of the energy is expended in ploughing, micro-brittle fracture and rubbing. This was ascertained through scanning electron images of the ground surface and the fragmented chips. X-Ray diffraction images of the ground sample and as-sprayed sample showed an insignificant change in material structure owing to the material removal mechanism. The surface roughness of the ground specimen was reduced significantly. The fracture toughness obtained using the Evans and Charles method was used to calculate the critical load for crack initiation and a significantly low value was observed for ductile to brittle transition. SEM images of ground chips of YSZ sample showed fragmented and broken chips indicating that the primary mode of material removal is owing to micro-brittle fracture. [ABSTRACT FROM AUTHOR]

Grinding has lower green degree than other cutting methods, for which higher specific grinding energy is one of the important reasons. For reducing specific grinding energy to obtain a green process in grinding, a bionic structured surface inspired by phyllotaxis theory was developed in this paper. To verify its performance, some contrast experiments to measure specific grinding energy were conducted. The experiments of grinding surface roughness were also conducted to avoid pursuing lower specific grinding energy alone. The results showed that the bionic surface structured grinding wheel had smaller specific grinding energy with better grinding surface roughness due to the bionic pattern of grains. This research will provide a new mean for the development and application of green manufacturing technology. [ABSTRACT FROM AUTHOR]

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• Effects of undeformed chip thickness nonuniformity on grinding process are investigated. • Models of specific grinding forces and energy are developed. • Grinding force and energy increase with increased percentage of active grains. • Tool life and grinding efficiency are improved in grinding Inconel 718. The development of modeling and predicting grinding force and energy has great significance in improving tool life and grinding efficiency. As an important parameter to study the grinding mechanism, the undeformed chip thickness catches more and more attentions in modeling the grinding process, and the investigation on its nonuniformity still has much potential. In the current work, the surface topology measuring and modeling methodologies were described. Models of the specific grinding force and energy were developed. Grinding experiments were conducted to investigate the effects of undeformed chip thickness nonuniformity. It is found that the specific grinding forces increase with increased mean value, decreased standard deviation (or variable coefficient) and increased percentage of active grains. The specific grinding energy increases with decreased mean value, increased standard deviation (or variable coefficient) and increased percentage of active grains. The undeformed chip thickness nonuniformity has a certain effect on the specific grinding forces and energy but less significant than the percentage of active grains. Finally, the tool life and grinding efficiency are improved according to the developed models with acceptable errors. [ABSTRACT FROM AUTHOR]

Abstract Most of the reported studies on the optimization of grinding parameters do not consider the evolution of the surface topography of grinding wheels, and the established empirical models will no longer apply when the surface conditions of the grinding wheel changes. In this paper, an integrated model based on the surface topography of grinding wheel is established. The grinding process of cemented carbide is simulated using the established model, and the simulation results are analyzed to obtain the surface roughness model and the specific grinding energy model based on the undeformed chip thickness distribution. Subsequently, the grinding constraint models are defined according to the two grinding constraints—surface roughness and specific grinding energy. Through inversion analysis, the maximum material removal rate of the given grinding wheel surface conditions satisfying the defined grinding constraints are obtained, and the influence rules of the grinding wheel surface conditions on the maximum material removal rate are analyzed. Then the grinding wheel surface conditions are adjusted by changing the radial dressed height of the grinding wheel and the arrangement distance of the grains in wheel circumferential direction to improve the maximum material removal rate of the grinding wheel. Finally, the optimization results are verified through grinding tests of cemented carbide. Highlights • An integrated model based on the surface topography of grinding wheel is established. • The influence of the surface topography evolution of grinding wheel on the optimal material removal rate is revealed. • The optimal material removal rate can be improved by adjusting the surface conditions of grinding wheel. [ABSTRACT FROM AUTHOR]

A back-propagation neural network BP model and a genetic algorithm optimizing back-propagation neural network (GABP) model are proposed to predict the grinding forces produced during the creep-feed deep grinding of titanium matrix composites. These models consider quantitative and non-quantitative grinding parameters (e.g. up-grinding mode and down-grinding mode) as inputs. Comparative results show that the GA-BP model has better prediction accuracy (e.g. up to 95%) than the conventional regression model and the BP model. Specific grinding energy was calculated against the grinding parameters and grinding modes based on the grinding forces predicted by the GA-BP model. [ABSTRACT FROM AUTHOR]

The present work is an attempt to model the components of specific grinding energy in a pragmatic manner. This work explores the contribution of specific energy constituents such as shearing, primary rubbing, secondary rubbing, and ploughing energy while grinding Inconel 718 (IN-718) superalloy. Specific shearing energy has been calculated using the dynamic yield strength of IN-718 as obtained by adopting the Johnson–Cook material model. Specific rubbing energy has been estimated using real contact length measured experimentally. Rubbing grit density has been estimated by considering grinding infeed, grit size, wheel structure, and work material hardness unlike the previous models, where it was mostly taken as a constant value. Single grit grinding experiments have been performed with 36 and 20 mesh size single alumina grits to obtain the insight of ductile flow in IN-718 grinding. These experiments have been conducted at grinding speeds of 5, 10, and 15 m/s using vacuum brazed single alumina grit shank fitted into aluminium make dummy grinding wheel. Specific ploughing energy has been estimated after suitably apportioning the tangential forces as obtained from single grit grinding. Two-dimensional study of the scratch profiles has been performed using a compound microscope to investigate plausible ploughing mechanisms of IN-718. The present studies indicate that at lower infeeds, micro-fracturing of alumina grits is more recurrent, whereas wear flattening is more common at higher infeed. The higher pile-up ratio at lower infeed signifies more ploughing resulting into inefficient cutting causing more energy consumption. The micro-fracturing of single alumina grit while scratching has also been observed. The present model for specific grinding energy is an improved version of earlier energy models as it incorporates variables which are much closer to the actual grinding conditions. [ABSTRACT FROM AUTHOR]

Sustainable development and green manufacturing are becoming an international consensus in the face of the threat of severe environmental pollution and waste of resources. Cryogenic air (CA) and nanofluid minimum quantity lubrication (NMQL) are state-of-the-art green manufacturing technologies. However, the lubricating performance of cryogenic air is ineffective, and the cooling ability of nanofluids minimum quantity lubrication is unsatisfactory. To specifically address the bottlenecks in these manufacturing methods, a new green processing technology combining their advantages was proposed, namely, cryogenic air nanofluid minimum quantity lubrication (CNMQL). Compared to traditional processing modes and other green technologies, cryogenic air nanofluid minimum quantity lubrication is superior for its economic efficiency, low carbon use, high utilization efficiency, energy saving as well as excellent cooling and lubricating performances. A surface grinding experiment was conducted under three lubricating conditions (cryogenic air, minimum quantity lubrication, and cryogenic air nanofluids minimum quantity lubrication) with Ti 6Al 4V as the workpiece material. Experimental results showed that: cryogenic air nanofluids minimum quantity lubrication achieved the best lubricating effect and obtained minimum specific grinding energy (51.96 J/mm 3 ) and friction coefficient (0.60), followed by nanofluids minimum quantity lubrication and cryogenic air. The lubricating mechanisms under cryogenic air nanofluids minimum quantity lubrication and nanofluids minimum quantity lubrication conditions were also analyzed according to the viscosity of nanofluid lubricants in grinding zone, contact angle, stability of lubricating oil film, atomization effect of droplets, and microtopography of workpiece surface. Relative to other conditions, the higher viscosity and larger contact angle of nanofluid lubricants under cryogenic air nanofluids minimum quantity lubrication condition led to higher stability and better lubricating effect of the lubricating oil film in the grinding zone. Droplets sprayed onto the grinding zone had a larger atomization angle, and the distribution density of droplets in the entire atomization spraying zone was relatively uniform. The droplets were uniformly distributed and had a larger spreading area, facilitating superior atomization effect in the grinding zone. On the other hand, workpiece surface had clear and smooth grinding pipelines, which presented minimal obstruction for the longitudinal flow and horizontal spreading effect of the micrometer pipelines, so the nanofluid lubricants achieved better spreading infiltration effect. Under the joint influence of the above factors, cryogenic air nanofluids minimum quantity lubrication achieved optimal lubricating effect, thus obtaining minimum specific grinding energy and friction coefficient. [ABSTRACT FROM AUTHOR]

Accurate simulation about the grinding temperature distribution helps to decrease the thermal damage and microcracks during the grinding process. In this article, the grinding heat transfer process of form grinding was analyzed and a temperature distribution model was derived in form grinding of 9Mn2V thread gauge. Considering the characteristics of form grinding, the temperature rise of the intersection region can be affected by two kinds of heat sources, and the impact between the two heat sources has been investigated. Also, the influence of the grinding depth on the temperature rise was analyzed. Depending on the analysis, an improved heat partition model has been derived, which is based on single-grain energy partition model. A series of experiments were carried out to investigate the grinding performance of 9Mn2V. The grinding force was obtained, the specific grinding energy was discussed, and the experimental temperature was measured by infrared imager. It is shown that the experiment results correspond well to the theoretical temperature calculated by the prediction model. This temperature model can be used to optimize the grinding conditions and the critical depth in form grinding of 9Mn2V thread gauge. [ABSTRACT FROM AUTHOR]

A single grain grinding experiment with fixed speed ratio v s / v w was designed to decouple the effect of grinding speed and undeformed chip thickness (UCT) on the SiC material removal mechanism during elevating the grinding wheel speed. Ground surface and subsurface topography, grinding forces, and specific energy were measured with grinding speed ranging from 20 to 160 m/s and maximum UCT a gmax from 0.02 to 3 μm. The results demonstrated the grinding force and specific grinding energy show an evident decreased tendency with the increasing of grinding speed, despite the a gmax value was kept at 0.03, 1 μm. However, at a gmax = 0.3 μm, the grinding force has a peak value with the increment of grinding wheel speed. The subsurface has the same trend. Based on the subsurface morphologies, grinding forces, grinding energy, the critical grinding wheel speeds v s = 100, 80, 80 m/s were determined at the a gmax = 0.03, 0.3, 1 μm, respectively. Besides, grinding forces show different growth rates with the gradually increasing a gmax at three stages under typical grinding speeds due to the transition of material removal mechanism. The critical a gmax values for ductile-brittle transition and beginning of brittle regime grinding are determined as 0.3 and 1 μm by surface and subsurface morphologies, grinding forces, grinding energy, respectively. [ABSTRACT FROM AUTHOR]

A novel laser assisted grinding process is developed to increase the material removal rates in grinding Si 3 N 4 . Micro structuring of the workpiece surface by nano- and pico-second laser radiations prior to the grinding led to a reduction of up to 55% in the specific grinding energy while simultaneously a slightly improved ground surface quality could be achieved. Ablation mechanism of nano- and pico-second lasers and surface integrity of the ground samples are studied. The results of single grain scratch tests suggest that the reduced specific grinding energy through laser structuring of workpiece is mainly due to the induced lateral cracks. [ABSTRACT FROM AUTHOR]

Cellulose nanofibrils (CNFs) are typically produced via wet milling pretreatment method to facilitate efficient disintegration of cellulose fibers by pre-fibrillation and fiber size reduction. However, the use of high energy and presence of water during wet milling methods leads to the increase in overall energy consumption during CNFs production and pose challenges during storage and handling. The objective of this study is to investigate the dry grinding of cellulose fluff pulp using the shear cutting method to determine the specific energy required to produce cellulose precursors and their characteristics for manufacturing CNFs. The specific energy required to grind cellulose fluff pulp with a screen size of 0.25 mm in three cycles was measured. The ground sample received after each cycle was sampled to characterize its properties and its potential to produce CNF hydrogels. As the number of grinding cycles increased, the specific energy required per cycle decreased with an overall net energy consumption of 894 kWh/Mg for three grinding cycles. The cellulose powder from the third grinding cycle was successfully disintegrated into cellulose nanofibrils with an average diameter of 119 nm without any fiber clogging. In conclusion, the three-cycle shear cutting process was sufficient to produce dry cellulose precursors for CNFs production, while reducing the overall energy consumption and handling and storage problems. [ABSTRACT FROM AUTHOR]

Grinding is a precision machining process widely used for close tolerance and good surface finish. Due to aggregate of geometrically undefined cutting edges and material removal in the form of microchips, grinding requires more specific energy as friction is greater in the grinding interface. The optimum use and proper penetration of coolant is the prime requirement which is achieved by effective cooling and lubrication. In this research, a greater focus is on MQL technique, which is economical and eco-friendly. The paper presents important aspects of the grinding process considering the surface roughness and cutting force. The experiments were carried out on horizontal surface grinding machine using Response surface methodology (RSM). In addition, evaluation of grinding performance parameters like coefficient of friction, cutting forces, temperature and specific grinding energy for different machining environments has been discussed. The lowest surface roughness and coefficient of friction observed was 0.1236 μm and 0.3906, respectively for MQL grinding, whereas lowest specific grinding energy was found as 18.95 N/mm in wet grinding. The temperature recorded in MQL grinding was 29.07 °C, which is marginally higher than wet condition. The response obtained as cutting forces, temperature and surface roughness under MQL mode encourages its use for machining AISI D3 type material compared to other grinding environments. Mathematical modeling showing the relation between the factors and response variables was established using Response surface methodology. Regression analysis was performed to determine the accuracy of mathematical model, significant factors and interaction effects of parameters on responses. [ABSTRACT FROM AUTHOR]

The development of advanced ceramics such as zirconia has gained importance because of their desirable properties. However, the engineering applications of ceramics are still limited by the ability to develop cost-efficient machining techniques. To achieve the cost-efficient production of zirconia parts, laser irradiation was introduced as a step before grinding. In this study, this hybrid process was investigated by measuring the grinding force and the specific grinding energy in grinding tests. The results confirmed significant decreases in the grinding force and specific grinding energy. The decreases suggest that the hybrid process can be an economical and efficient way to overcome the limitation of the high specific energy required for grinding advanced ceramics. Scratch tests were performed to obtain a fundamental understanding of the decreases in the grinding force and energy, and the scratch morphology and crack types beneath the scratch tracks were observed. The transition of crack types and the chip-forming mechanism was confirmed. It was noted that the scratch hardness of ceramics reduced after laser irradiation, which explains the reduction in the grinding force. In addition, micro-debris and lateral cracks were induced by scratching on the surface with laser irradiation, which contributed to the decrease in the specific grinding energy. [ABSTRACT FROM AUTHOR]

The elliptical ultrasonic assisted vibration can lead to a higher comprehensive performance with better machined quality and lower grinding force during brittle materials machining. The undeformed chip thickness in grinding can be defined as the distance between two consecutive grinding surfaces formed by the adjacent abrasive grain trajectories. The ductile–brittle transition point of chip formation in brittle materials machining is believed to be represented by the threshold value of undeformed chip thickness (critical undeformed chip thickness). In this paper, an energy based method is proposed to predict the critical undeformed chip thickness in elliptical ultrasonic assisted grinding (EUAG). The effects of vibration parameters on grinding force and specific grinding energy are analyzed in detail. Results show that the axial vibration amplitude leads to a slight reduction in grinding force, whereas the vertical vibration amplitude results in a significant reduction of grinding force. The increase of wheel speed and ultrasonic vibration frequency can reduce the grinding force as well. Nevertheless, the grinding force ratio remains relatively steady fluctuating from 1.37 to 1.56. Additionally, the critical undeformed chip thickness increases with the increasing grinding speed, axial vibration amplitude and ultrasonic vibration frequency, while firstly increases and then decreases with the increasing vertical vibration amplitude. Especially, a ductile-mode grinding in micron-level can be achieved when the axial vibration amplitude is above 3 μm and a totally brittle fracture occurs when the axial vibration does not exist. Thus, a reasonable selection of vibration parameters in EUAG process is required. The above theoretical evaluations coincide well with the variable experimental results. [ABSTRACT FROM AUTHOR]

The present research investigated the lubrication performances of AlO/SiC nanofluid minimum-quantity lubrication (MQL) grinding in accordance with recent technologies used in conducting minimum-quantity lubrication grinding with nanofluids. The mean grain size of the AlO and SiC nanoparticles (NPs) was set to 50 nm, and the difficult grinding Ni-based alloy was used as the workpiece material in the experiment. Grinding force was measure by using a three-component dynamometer and then used to calculate grinding force ratio ( R). Workpiece surface roughness was measured by a roughness tester. Five groups of NPs were mixed with synthetic lipids at a mass fraction of 6 %. The lipids were then used as the grinding fluid for the nanofluid MQL grinding. Results showed that, compared with pure SiC NPs, pure AlO NPs obtained lower R = 0.3, lower specific grinding energy ( U = 75.93 J/mm), and lower surface roughness ( Ra = 0.386 μm), indicating better lubrication performance. The mixed NP consisting of AlO and SiC NPs achieved even lower R and surface roughness than pure NPs because of the 'physical synergistic effect.' The optimal ratio of the effect of mixed NPs was explored based on this finding. The AlO/SiC (2:1) mixed NPs obtained the smallest R = 0.28 and specific grinding energy ( U = 60.68 J/mm), thus indicating the best lubrication performance. Therefore, 2:1 is the optimal ratio for mixed NPs. [ABSTRACT FROM AUTHOR]

Grinding is a critical machining process because it produces parts of high precision and high surface quality. Due to the semi-artisan production of the wheel, it is not possible to know in advance the performance of the wheel. One of the most useful parameters to characterize the grinding process is the specific grinding energy, which varies with the wear of the grinding wheel during its lifecycle. Thus, it would be useful to model the specific grinding energy in order to get information about the performance of the wheel before buying it. Unlike the typical applications of time series forecasting, in this work, a totally different issue is presented: the prediction of new and complete time series bounded in time without initial or historic values. In this context, an analysis of the effect of the time characteristics and the number of points of the time series on the prediction capabilities of the ANN is presented. The results of the analysis show that 200 points are enough to predict a complete time series up to 2000 mm/mm of specific volume of material removed. Actually, it is shown that modelling the evolution of the grinding specific energy up to 2000 mm/mm is possible. The net shows good capability to generalize to new grinding conditions, with errors below 23.65 %, and to new wheel characteristics, with errors below 20.01 %, which are satisfactory from the grinding process perspective. [ABSTRACT FROM AUTHOR]

Given the increasing attention to environmental and health problems caused by machining, the development of an environment-friendly grinding fluid has become an urgent task. As an environment-friendly grinding fluid, vegetable oil has gained considerable attention. In this study, seven typical vegetable oils (i.e., soybean, peanut, maize, rapeseed, palm, castor, and sunflower oil) were used as the minimum quantity lubrication (MQL) base oil to conduct an experimental evaluation of the friction properties of the grinding wheel/workpiece interface. With nickel-based alloy GH4169 as workpiece material, the flood grinding working condition and MQL grinding working condition (i.e., using the seven vegetable oils and paraffin oil) were selected. The evaluation of the lubrication property mainly referred to grinding force, friction coefficient, specific grinding energy, and grinding ratio (G-ratio), as well as surface morphology and surface roughness. Experimental results indicated that MQL grinding using vegetable oil achieved a lower friction coefficient, specific grinding energy, and grinding wheel wear than flood grinding. Among the grinding fluids, castor oil achieved the best lubrication property and the best surface quality of workpiece. Castor oil had a friction coefficient and specific grinding energy of 0.30 and 73.47 J/mm 3 , which decreased by 50.1% and 49.4%, respectively, compared with flood grinding. Moreover, various grinding fluids changed cutting forces through changes in their lubrication property and further changed G-ratio. However, lubrication property was one of factors that influenced the G-ratio. Maize oil had the highest G-ratio of 29.15. Peanut, sunflower, and soybean oil with more saturated fatty acids, castor oil with more castor acids, and palm oil with numerous palmitic acids were suitable as lubricating fluids. [ABSTRACT FROM AUTHOR]

In path-controlled grinding, unlike the cylindrical plunge grinding, the contour of the pin journal is achieved with the coupling actions both of the eccentric rotation of the pin and the grinding wheel linear movement. Since the circumferential feed rate varies periodically in path controlled grinding of crankshaft pin, the tangential and normal grinding force keep unsteady during the whole process. Therefore, it is necessary to acquire thorough understanding on the grinding characteristic in terms of grinding force, grinding force ratio, and specific grinding energy during path-controlled grinding. The rotational measurement method was used for achieving the grinding force information during grinding. A series of experiments were performed to investigate the machinability in crankshaft pin journal path-controlled grinding of 40Cr using vitrified bonded cubic boron nitride (CBN) abrasive. The effects of grinding parameters on grinding force are illustrated. Experimental results show that the grinding force ratio rises with increasing workpiece peripheral speed. The specific grinding energy is found to decline with increasing material removal rate. It is beneficial that the undeformed chip thickness should be designed largely for reducing the energy consumption. [ABSTRACT FROM AUTHOR]

Based on research on nanofluid minimum quantity lubrication (MQL) in grinding, a plane grinding experiment was performed on Ni-based alloy using a K-P36 precision numerical control surface grinder. Uniform grinding parameters were used in the experiment, but three groups of MQL jet parameters were changed. The grinding force was measured using a YDM-III99 three-dimensional dynamometer to calculate the specific grinding energy and coefficient of friction. The surface roughness of the workpiece was measured using a TIME3220 roughness tester. An experimental research was also conducted on the droplet size and velocity of the jet using a high-speed camera system. Results showed that the most ideal lubricating effect was achieved under 0.5 MPa compressed gas, 0.4 gas-liquid ratio, and 0.005 kg/s liquid flow rate. Under the best jet flow condition, the specific tangential grinding force, specific grinding energy, and coefficient of friction were 1.45 N/mm, 74.57 J/mm, and 0.414, respectively. The surface roughness of the workpiece was at its most ideal at this point, where Ra, Rz, and RSm were 0.249 μm, 1.972 μm, and 0.028 mm, respectively. Based on high-speed continuous shooting at the jet, the mean droplet size was about 171.82 μm under the optimum jet parameters, and the droplets exhibited variable accelerations at a high accelerated velocity (>500 m/s). [ABSTRACT FROM AUTHOR]

Surface grinding being the final finishing process has to be performed and evaluated with care as the surface being machined could get damaged due to high temperatures being generated. This is evaluated with the help of mathematical modelling of the temperature generated is compared with experimental results obtained during surface grinding of the selected tool steel workpieces in both dry as well as wet environment and further compared with a simulation performed using ANSYS 14 software. The results are found to be correlating and satisfactory and are in tandem with the ones found from experimentation. The usage of production type grinding wheel reduces the temperature being generated during grinding. The dressing depth also plays an important role of reducing the temperatures during surface grinding. [ABSTRACT FROM AUTHOR]

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/mm, which was close to that of flood lubrication at 29.8 J/mm. 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. [ABSTRACT FROM AUTHOR]

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′ = 25 mm/(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/mm at elevated specific material removal from 3 to 25 mm/(mm·s). Results show that the developed porous CBN wheels have a promising application in high-efficiency deep grinding nickel-based alloy. [ABSTRACT FROM AUTHOR]

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, ZrO nanoparticles, polycrystal diamond (PCD) nanoparticles, and MoS nanoparticles were used in the comparison of nanoparticle jet MQL grinding. The experimental results manifest that MoS 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/mm, 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. [ABSTRACT FROM AUTHOR]

In view of the poor machinability of turbine blade root made of directional solidified nickel-based superalloy DZ125, high efficiency deep grinding(HEDG) process is conducted to analyze specific grinding energy and surface integrity with profiled electroplated CBN grinding wheel. The result shows that higher grinding speed vs can lower the specific grinding energy effectively when the speed ratio (vj vm) keeps constant. The specific grinding energy decreases with the increasing mean material removal rate and finally remains in range of 40-60 J/mm³. Under the same mean material removal rate, the specific grinding energy increases with the decreasing depth of cut. However, the difference of depth of cut has little effect on the specific grinding energy with the same undeformed chip thickness. The surface quality of the workpiece obtained under the highest mean material removal rate is analyzed. The surface texture is clear, and does not present wrinkles and ploughing marks. The phase transition and grain distortion are not observed from the metallographic microstructure. The degree of work hardening is in range of 7.7%-19%, and the hardening depth is about 40 µm. The result reveals the potential of HEDG in the high efficiency machining of turbine blade root DZ125, and provides reference for future application. [ABSTRACT FROM AUTHOR]

Abstract: Specific grinding energy is one of the most important performance parameter of the grinding process. Primary energy components of specific grinding energy are the major contributors to the total specific energy consumption in grinding. For high strength and hardness materials such as advanced ceramics, specific grinding energy requirement is extremely high which will eventually cause higher material removal cost of such materials. Detailed study of various components of specific grinding energy may help to reduce this energy consumption by appropriate choice of the grinding process parameters. This work studied in detail the four primary components of specific grinding energy namely chip formation energy, primary and second rubbing energy and the specific ploughing energy for two different engineering materials—a ductile mild steel and a hard conductive ceramic. Single grit experiments have been conducted in new and more realistic manner to replicate the actual grinding process and to develop the theoretical models of the specific energy components. Study of specific ploughing energy also helped to explain thoroughly the concept of size effect in grinding. [Copyright &y& Elsevier]

A monolayer diamond grinding wheel was fabricated by brazing in vacuum. The wheel was then used to grind alumina at three different grinding speeds. The horizontal and vertical grinding forces, and the grinding temperatures were measured during grinding. SEM observations were made for the ground workpiece surfaces. The influences of the peripheral wheel speed on the grinding forces, specific grinding energy and grinding temperatures were analyzed under different combinations of depth of cut and workpiece velocity. The dependence of the average grinding force per grain and specific grinding energy on the maximum undeformed chip thickness was discussed respectively. It was found that an increase in the peripheral wheel speed reduced grinding force, but increased force ratio, specific grinding energy, and grinding temperature. [ABSTRACT FROM AUTHOR]

In this study, effects of the maximum undeformed chip thickness on roughness of ground surface and specific grinding energy were investigated. The acoustic emission (AE) signals generated during grinding processes have been analyzed to find out the appropriate AE parameters for assessing the processes. SM45C steels were ground under conditions yielding volumetric removal rate per unit width of 100, 200, 300 and 400 mm3/min. From the experimental results, it is found that surface roughness (Ra) increases but grinding power (P), energy rate of AE signal (AErms2) and specific grinding energy(e) consumed decrease as the maximum undeformed chip thickness(g) increases. [ABSTRACT FROM AUTHOR]

• A wireless grinding force measurement module for wafer grinding machine is developed. • The variations of grinding force during the whole grinding process are revealed real-timely. • Effect of process parameter on grinding force, and parameter optimization are investigated. Grinding force is a crucial factor that affects the machining accuracy, wheel wear and the material removal efficiency for precision machining of semiconductor materials under nanometer accuracy. However, due to the complex rotational motion of both the grinding wheel and wafer workpiece, in situ measurement of the grinding force in wafer self-rotating grinding is still a big challenge. In this paper, a novel grinding force measurement method in silicon wafer grinding process is developed. The method is achieved by embedding four thin film force sensors into a self-designed force measurement device and real-time monitoring through wireless signal transmission. Based on this method, the grinding force under 5 groups of process parameters are measured. For the first time, the variations of grinding force during the whole grinding process are revealed real-timely. Effects of process parameters, i.e. spindle rotational speed and feed rate, on grinding force are investigated, and the parameters are also optimized based on the theory of specific grinding energy. The test results show that the force measurement method has the advantages of high precision, reliable and convenient implementation. [ABSTRACT FROM AUTHOR]

This paper deals with the effect of the CBN grit shape on the grindability of a low alloy chrome steel, 100Cr6. Firstly, a simple wheel-workpiece interaction model is introduced to investigate the grinding response. The formulation considers the global grinding forces, which embodies all the properties of the wheel acting at the interface. The use of this approach eliminates the need to consider the interaction of each individual grit with the workpiece during the grinding process. Next, a series of tailored grinding tests conducted with a creep-feed grinding machine are used to evaluate the grinding performance and the wheel wear. The results have shown that the specific grinding energy (u e) is affected by the CBN grit shape, and the wheel wear is proportional to the ratio of the CBN shape factor (Aspect Ratio) and the overall bearing surface of the wheel-workpiece contact area (a f). [ABSTRACT FROM AUTHOR]