Abrasive Grains Research Articles

Study on the grinding force of single grain in rail grinding based on open-type belt grinding

In the realm of machining, there exists a heightened demand for improved surface integrity of workpieces. Abrasive belt grinding presents several advantages, including a high grinding ratio, superior surface finish quality, and lower grinding temperature. Additionally, the precision placement of abrasive grains in the form of triangular pyramids further enhances the efficacy of this method. It has played an important role in the field of precision machining. Accurately predicting its grinding force is vital for improving its processing quality. In this study, an open-type belt grinding method was developed, the grinding force of triangular pyramid-shaped abrasive grains in rail grinding was analyzed and calculated using oblique cutting theory, the accuracy of the proposed model was verified experimentally, and the effects of abrasive rotation angle, wear height, cutting depth, grinding speed, and rake angle on the grinding force were analyzed, and the relevant laws were obtained. According to the findings, the grinding force displays an initial rise followed by a decline as the triangular pyramid abrasive particles' rotational angle increases. The grinding force demonstrates a linear growth in tandem with an increase in grinding depth. Furthermore, the grinding force rises proportionally with an increase in abrasive wear height. The proposed model can be used for the prediction and calculation of grinding forces of other shape abrasive grains as well.

Theoretical and Experimental Analysis of Grinding Stability of Beam Workpiece

Grinding chatter is a kind of self-excited vibration in which the grinding system continuously absorbs energy from the grinding machine, increasing the mechanical energy of the system. Grinding chatter can damage the surface of the workpiece and accelerate the abrasion of the grinding wheel. The theoretical analysis of the grinding chatter for the beam surface was launched based on the behavior of a single abrasive grain, whose cutting thickness is a key factor affecting grinding stability. The dynamic grinding force model has been developed, which is the interaction interface between the grinding wheel and the workpiece. In this paper, rail beam grinding was taken as an example. The vibration performance of the rail beam was described with the Timoshenko beam. The characteristics of the frequency domain of the grinding wheel-workpiece system were observed, and the condition of the stability at any position in the longitudinal direction of the beam was gained, which could be quantitatively characterized with the stability limit curve. The grinding experiments of the rail beam surface demonstrated that as chatter developed, the chatter marks could be investigated on the surface of the rail, and the energy of the chatter signal was mainly concentrated around the chatter frequency, which was higher than the natural frequency of the grinding wheel.

Formation mechanism and controlling technique for fabrication of extremely sharp diamond micro mills

The extreme sharpness for superhard micro mills is urgently needed to improve the surface quality, restrain size effect and suppress burr formation for the widely used miniature components. Therefore, laser cutting and precision grinding are coupled to form a hybrid method for the fabrication of diamond micro mills with extremely sharp edge. Firstly, the laser cutting simulation of polycrystalline diamond (PCD) based on various laser energy density and laser scanning speed was conducted to provide temperature distribution. Then the laser cutting experiments were conducted, and the influence of laser cutting parameters applied on the machining consequences (kerf width, cutting cycles, affected layer thickness, and surface roughness of cutting section) were analysed according to the simulation model. On this basis, the laser energy density and scanning speed were optimized as 175 J/cm2 and 0.2 mm/s respectively to obtain the smooth and uniformly graphitized surface. Moreover, the grinding experiments were conducted on the cutting section obtained by the optimized laser parameters, the impact of the abrasive grain size, grinding depth per path and feeding speed on the grinding results were studied, these grinding parameters were optimized as 1 μm, 1 μm, and 2 mm/min to realise the micro abrasion during grinding process. In this way, PCD micro end mills (PCDMs) with surface roughness Sa of 57.3 nm, effective length of 600 μm, diameter of 400 μm, and radius of cutting edge of 0.19 μm were fabricated. Finally, the micro-milling experiments with PCDMs were performed on the Ti-6Al-4V material, the micro slots and thin-walled structure were processed with almost no burrs being observed and the obtained surface roughness Sa of 18.3 nm. With the obtained machining results, the remarkable cutting performance of PCDM was validated.

Analysis of nano grinding removal mechanism of 3C-SiC material under the coupling action of double abrasive grains

In order to study the influence mechanism of coupling effect on 3C-SiC material removal process under nanometer conditions, the repeated scratches of different abrasive grains, machined surface morphology, dislocation distribution, grinding force and abrasive wear were analyzed by molecular dynamics method, and the geometric characteristics and damage distribution of machined surface under the coupling effect of dual abrasive grains, as well as the influence rule of coupling effect on surface/subsurface characteristics were obtained. This study is of great significance to understand the mechanism of 3C-SiC removal in nano-scale grinding process, and is helpful to guide the preparation of fixed abrasive polishing discs.

Study on Preparation and Processing Properties of Mechano-Chemical Micro-Grinding Tools

The application of hard and brittle materials such as single-crystal silicon in small parts has expanded sharply, and the requirements for their dimensional accuracy and processing surface quality have been continuously improved. This paper proposes using mechano-chemical micro-grinding tools to process single-crystal silicon, which can realize the high-quality and efficient processing of such tiny parts through mechano-chemical composite action. The microstructure composition of the mechano-chemical micro-grinding tools was designed, the theoretical analysis model of grinding force was established and verified by experiments, and the temperature field distribution during mechano-chemical micro-grinding of single-crystal silicon was simulated and studied, which provided a theoretical basis for mechano-chemical action. Special micro-grinding tools were developed, and mechano-chemical micro-grinding processing tests were carried out. The results show that the coupling synergy of grinding force and grinding temperature improves the chemical activity of the micro-grinding tools, thereby promoting the solid–solid phase chemical reaction of abrasives and additives at the sharp points of the surface of the micro-grinding tools. And when the content of cerium oxide abrasive is 25%, it is more conducive to the solid–solid phase chemical reaction, and calcium oxide can be used as an additive to promote the active agent of solid–solid phase chemical reaction, improve the degree of chemical reaction, and thus improve the removal rate of materials. Soft reactants that are easy to remove are generated on the surface of monocrystalline silicon and are removed by the mechanical friction between the abrasive grain and the surface of the silicon wafer, and finally achieve low-damage processing with a surface roughness of Ra1.332 nm, which is much better than the surface roughness of Ra96.363 nm after diamond abrasive processing.

Dynamic force modeling and mechanics analysis of precision grinding with microstructured wheels

The application of structured surfaces on advanced tools is an effective method for enhancing the machining performance. The modeling of dynamic grinding force is of great significance for improving tool surface structure design and improving grinding accuracy. In this paper, a novel dynamic force modeling and mechanics analysis of precision grinding with microstructured wheels was put forward. A grinding wheel topography model was established by considering the non-simplified position-posture-shape-size multiple random grains morphological characteristics. On this basis, the material removal pattern of the microstructured multiple random abrasive grains was identified based on grinding kinematics and undeformed chip thickness. The grain diameter, average bearing width, flat surface area, friction coefficient and total number of active abrasive grains in the grinding area were considered. Their effects on the amplitude and frequency of grinding force were discussed in detail, and the precision grinding experiment was carried out. The results show that the dynamic force model proposed could accurately evaluate the influence of microstructure tools on forces with an error rate of 6.7% or less. Compared with the original grinding wheel, the addition of microstructure reduces the grinding force by 49.6%− 94.3%. By controlling the force components, the force frequency is more concentrated, and the disorder of the grinding force signal is suppressed. Furthermore, the carbon emission model was calculated, and it can be seen that microstructured wheels can obviously reduce carbon emission, which is a novel processing technology to realize low-carbon manufacturing.

ON THE PRINCIPLES OF CONTROL OF THE PROCESS PART OF THE AIRBORNE CLASSIFIER DURING OPERATIONS OF SPECIAL-PURPOSE ABRASIVE MATERIALS

The article considers the methodical methods of practical use of a vibrodynamic classifier for sieving various abrasive materials, sets and solves the task of providing optimal tuning parameters of the electromechanical part of the vibration classifier to obtain the highest grade of abrasive grain with a high content of the main fraction and a given shape of abrasive particles. The distribution of particles of the material separated by size along the perimeter of the vibration rod was studied, depending on its parameters. It has been shown that the yield of products depends on the ratio of fractions in the starting material.

Model of Influence of the Machined Material Properties on Wear of the Polymeric-Abrasive Tool Filaments

Abstract For polymer-abrasive brush tools (PABT) working on CNC machines it is necessary to correct their wear constantly, since it is much higher compared to the wear of metal tools. Based on the dependence of tool wear on machining parameters for various materials, it is necessary to study the influence of the physical and mechanical properties of the material machined. The purpose of the paper is to study the process of finishing the surfaces of parts made of materials of different types with PABT. The analysis of dimensional wear of disc PABTs during the polishing various materials with certain physical and mechanical properties is provided in the article. The polishing was carried out in rational modes that ensure high quality and productivity of surface treatment. The similarity theory and dimensional analysis were used to assess the influence of the properties of the material machined on the intensity of PABT filament wear. To calculate it, dimensionless complexes were established, which take into account the physical and mechanical properties of the machined materials and evaluate their resistance to the penetration of abrasive grains, the ability of the material to absorb mechanical energy in the process of deformation and destruction under the impact of PABT filaments. The developed model was created for the first time. It made it possible to solve the problem of predicting the degree of dimensional wear of the disc PABT when polishing various materials, including difficult-to-machine ones. Prediction of the intensity of PABT filaments wear allows timely correction of the tool position during machining on CNC machines to ensure a constant pressing of the PABT to the surface being machined. The obtained Км material coefficient takes into account the influence of the physical and mechanical properties of the machined material and then estimates the intensity of PABT filaments wear. The KМ material coefficient can also be used to assess the PABT life and calculate the economic efficiency of the parts finishing treatment at the stage of technology development and the selection of polishing tools.

Investigation of the influence of cooling lubricants on workpiece topography

AbstractModel‐based prediction is becoming increasingly important to meet the ever‐increasing demands on manufacturing. In grinding, the prediction of the process forces and the generated surface by physical models are particularly important.Since cooling lubricants are almost always used on an industrial scale, the grinding model, developed at our institut, must be extended to include this component. Therefore, in order to implement cooling lubricants into the FEM‐based model, it is first necessary to investigate the behaviors and effects of cooling lubricants in real experiments. Various influencing factors such as the scratching speed of individual abrasive grains in interaction with cooling lubricants need to be investigated. However, the existing physical grinding model is not limited exclusively to the prediction of the resulting forces. It is also supposed to be able to qualitatively predict the expected resulting surface of the workpiece. Hence, this paper will focus on the topographic characteristics that can occur in the scratch test due to different cooling lubricants and scratching speeds.Based on real experiments on a test rig for such scratch tests, it has been shown that different scratch speeds have a negligible influence on the topographical nature and expression of a scratch. In contrast, however, there is a direct influence of cooling lubricants on the topographic properties. This effect is additionally influenced by the viscosity of the cooling lubricant used.

A PRACTICE-ORIENTED METHOD FOR ESTIMATING THE SPECIFIC ENERGY OF DESTRUCTION OF CERAMIC COMPOSITIONS OF THE ABRASIVE GRAIN–CERAMIC BINDER–PORES SYSTEM

The article is devoted to the development of an original production method for estimating the specific energy of destruction of ceramic compositions of the “abrasive grain–ceramic binder–pores” system. The results of experimental studies and theoretical calculations that form the basis of the proposed method. Recommendations for its use are given.

Investigation of force modeling in ultrasonic vibration-assisted drilling SiCf/SiC ceramic matrix composites

Due to their exceptional high-temperature and rust resilience, SiCf/SiC ceramic matrix composites have been regarded as potential high-temperature components. For application, to overcome issues resulting from the high hardness and brittleness, the ultrasonic vibration-assisted machining technique is primarily adopted in the machining of SiCf/SiC ceramic matrix composites. It is essential to develop a force model for a better understanding of the material removal and cutting processes by applying ultrasonic vibration. As a result, studies on force modeling during ultrasonic vibration-assisted drilling of SiCf/SiC ceramic matrix composites have been conducted in this study, taking into account the trajectory of the drilling tool, the tool-workpiece contact state, and the material removal mode. Based on the coefficient calibration experiment and least square method, the irregular coefficient of abrasive grains, the crack growth parameters of materials, and the mechanical parameters that are difficult to be measured were determined. After that, the drilling parameters and vibration parameters were merged to build the analytical force model, and the parameter influence rules on the force was also studied. The suggested drilling force model concurred well with tests under the highest relative error of 17.34 %, according to the findings of the confirmation experiments.

INFLUENCE OF THE METHOD OF ELECTROLYTIC POLISHING, MECHANICAL TREATMENT AND PURITY OF THE BASE METAL SURFACE ON THE STRENGTH OF BONDING BY ELECTROLYTIC DEPOSITS OF IRON

In the present work, the influence of the composition of the electrolyte and the duration of electropolishing of the base metal on the strength of adhesion to iron deposits was studied, and the method of mechanical treatment before applying electrolytic coatings was shown to determine not only the microgeometry of the surface, but also the physicochemical state of the metal in the surface layer, thereby affecting the protective properties. oxide film. On the other hand, the type of machining affects the cost of restoring and coating parts. Therefore, it is practically important to determine the effect of the method of machining and the surface finish of the base metal on the adhesion strength with electrolytic iron deposits. Along with mechanical action, chemical processes play an important role in polishing. The surface of the metal is covered with thin, invisible oxide or salt films under the influence of the environment and the chemically active substances contained in the polishing pastes. When polishing, the film is removed, but on the exposed areas of the metal it is formed again. The hardness of abrasive grains during polishing is not as important as during grinding, since in the first case the abrasive removes a thin film that is less durable than metal. In the process of manufacturing parts by mechanical polishing, traces of processing in the form of small irregularities remain on their surface. The magnitude of these microroughness’s determines the surface finish of the parts. This characteristic has a great influence on the quality of the finish and the performance properties of the products. The smoother the metal surface, the better it resists corrosion. Improving the surface finish increases the wear resistance of the parts. Obtaining shiny surfaces is also associated with the need to remove microroughness. It has been determined that the cleanliness of the surface treatment of parts before electroplating is determined by their purpose and type of coating. Surface cleanliness depends on how the parts are prepared before electroplating. Polishing products with a lower initial surface finish significantly increases the processing time, which reduces the productivity of the equipment. It has been established that electrochemical and chemical polishing have several advantages over mechanical polishing. They do not require the physical effort of the worker, which reduces the complexity of finishing operations. Many products of various shapes and sizes can be processed simultaneously, which is not feasible when polishing with circles. Electrochemical polishing has become more widespread in industry. With its help, a greater smoothing and more intense gloss of the metal surface is achieved than with chemical polishing. The use of this process in preparation for electroplating reduces the number of operations and transitions and improves product quality by increasing the adhesion strength of the coating to the base metal. Keywords: Machining, surface finish, electropolishing, electrolyte, roughness, adhesive strength, iron precipitation, iron plating.

Machining of aluminium nitride ceramic with a hAJM process using SiC abrasives: Experiments and simulation

Extreme hardness makes aluminium nitride (AlN) ceramic machining costly. Hot abrasive jet machining (hAJM) erodes a target profile by indentation of an air-hot abrasive stream comprising fine hot SiC grains for cutting AlN ceramic materials without thermal deformation. This study is intended to analyze the material removal rate (MRR) in the hAJM process of AlN ceramic. The Box-Behnken design of experiments was used to test 15 sets of machining limitations (abrasive temperature, compressed air pressure, and nozzle angle) (BBDOE). Computational fluid dynamics (CFD) modeling was used to establish a relationship between machined profile shape and erosive flow. Hot abrasives in hAJM improved material removal efficiency. SEM investigation of the machined surface indicated fracture initiation, propagation, and erodent particle embedment. Depending on the percentage concentration and mesh size of the abrasive grains, they are dispersed randomly throughout the medium. The predicted results from simulation and those obtained from experimental observation are compared to describe the relative importance of hAJM constraints. Moreover, the analysis revealed that abrasive temperature, nozzle angle, and air pressure significantly influenced the machined surface profile and material erosion. Improved hole quality, material erosion, and impact collision of abrasives were obtained under machining with the vertically positioned nozzle.

Force of cutting by a single abrasive grain

This paper investigates the cutting forces arising when using a single abrasive grain. Analytical studies were carried out using a model of a single abrasive grain in the form of a rod with a radiused apex acting on the workpiece material. The slip-line method (method of characteristics) was used to calculate the deformation intensity of a plastically edged workpiece material under the action of a single grain. Mathematical models were developed for the following factors: plastic deformation of the material, edging of the stagnated zone and its friction against the grain surface when moved upwards in the form of chippings, grain friction against the plastically deformed material, and the action of the dynamic component of plastic deformation. The significance of the dynamic component in the overall balance of forces related to plastic deformation was established by determining the ratio of dynamic stress on the break line and shear yield point. This dependence calculated for D16T and 30HGSA materials showed the feasibility of accounting for the dynamic component of the cutting force under the velocity of a single grain impacting the workpiece surface of above 50 m/s. Graphs depicting the relative grain force and the relative depth of grain penetration are given. The proposed calculation method for cutting forces using a single grain can be used to determine the total force of interaction between the single grain and the work-piece material. In order to adopt the defined processing method and the workpiece material, the number of grains in contact, the contact duration, and the cutting speed should be found. On this basis, the process performance and the quality of the workpiece surface can be calculated.

INVESTIGATION ON PERFORMANCE OF EXTRUSION HONING PROCESS ON QUALITY OF SURFACE TEXTURE

The EH approach overcomes this limitation of conventional finishing method. The present study focus on the impact of number of passes at the specimen's entry and exit sides of the carrier media. The improvements in surface finish (Ra) on both side i.e entry and exit are evaluated as well. A dimensionless expression for Ra is also developed. The relation is implemented using Buckingham’s π theorem and comparison of developed model is performed with experimental results. SEM analysis is made to portray surface texture produced by selected process parameters such as number of passes, volume fraction and grit size of abrasive grains.

Conical Grinding Wheel Ultrasonic-Assisted Grinding Micro-Texture Surface Formation Mechanism

The rotating ultrasonic-assisted grinding (RUAG) experiment of the conical grinding wheel generated the intermittent pit-shaped micro-texture on the surface of the workpiece, reducing thermal damage and improving the lubrication characteristics compared with conventional grinding (CG). To further optimize the surface properties, this paper studied the formation mechanism of micro-texture. This study used as basis the theory that micro-debris volume equals the macroscopic material removal one to establish the mathematical equation of grinding depth. Thereafter, formulas of micro-texture feature parameters, including pit length, pit depth, and texture spacing were deduced. The solved microscopic grinding depth was alternatingly positive and negative, indicating that the alternating separation between the grinding grain and workpiece caused intermittent pits in the grinding. Through response surface analysis (RSA), this paper analyzed the relationships among macroscopic grinding depth, micro-texture feature parameters, and machining parameters (i.e., amplitude, feed rate, and rotational speed). Single-factor experiments of machining parameters, with finite element simulation and experiment methods, were performed to verify the theoretical micro-texture features. The simulated program formed three-dimensional surfaces with micro-textures. Their measurement results were consistent with the theoretical ones. Experimental results proved that the range of pit length covers the theoretical ones, further verifying the accuracy of the grinding depth model. For this grinding wheel, the 8–10 μm amplitude was optimal for better roughness, lubrication, and thermal damage. Roughness was improved when increasing the rotational speed or reducing the feed rate based on the experiment. If the rotational speed and feed rate exceed the limiting values, then continuous grinding will break down the abrasive grains and even damage the cubic boron nitride (CBN) coating. Experimental results likewise showed that the pit shape was closely related to the surface properties, which deserves further investigation.

A new theoretical model for surface roughness prediction in rotational abrasive finishing process

Rotational abrasive finishing (RAF) is a new nano-finishing technique in which the finishing forces are applied to the workpiece by the opposite rotations of a stirring-blades and the workpiece. The RAF process allows for finishing the inner and outer surfaces of workpieces, particularly complex ones with axial symmetry. The present study aims to propose a new theoretical model to obtain deeper insights into the material removal mechanism, surface roughness prediction, and forces in RAF process. Since the abrasive-workpiece interaction is random and complex in nature in the RAF, some initial assumptions were considered. To validate the repeatability of the experimental results, the experiments were designed based on the Response surface method (RSM). To validate the new proposed theoretical model, a number of influential parameters were investigated. It was found that the stirring-blade speed (S), working gap (W), and abrasive grain size (A) had significant effects on Ra. The minimum surface roughness (Ra) was obtained to be 46.87 nm at a rotational speed of 600 rpm, a working gap of 1 mm, and grain size of 18 μm. The experimental results were relatively in good agreement with the theoretical results so that the maximum error was about 24%. This can be assumed that the most important explanation for the difference between the theoretical and experimental results can be attributed to the initial theoretical assumptions.

Analytical grinding force prediction with random abrasive grains of grinding wheels

A reliable prediction of grinding forces and surface morphology is critically important to the design of a grinding process. However, due to the complex microstructure of a grinding wheel which contains randomly-sized and randomly-distributed abrasive grains, a practical prediction model has been unavailable. This paper aims to develop a novel stochastic model to take into account the random nature of the abrasive grain size and their distribution in a grinding wheel, and hence to predict grinding forces more accurately. In addition, the evolution of the ground surface morphology, the real-time undeformed chip thickness, the interactions between the abrasive grains and the grain-workpiece contact mechanics are integrated into the modelling. Nanoindentation and tribology experiments were conducted to determine the micromechanical properties of the workpiece and abrasive grain. Grinding experiments were then performed to validate the predictions of the model. It was found, both theoretically and experimentally, that the stochastic model thus established can reliably predict grinding forces. It was also demonstrated that the proposed model can be effectively used to reveal the underlying mechanisms of grinding processes.

New Calculation Methodology of the Operations Number of Cold Rolling Rolls Fine Grinding

This article considers the methods of calculating the number of operations for the fine grinding of cold rolling rolls which allows one to ensure the least labor-intensive processing of the part. Based on the analysis of the patterns in the operation of single abrasive grains, the dependence of the productivity of the fine-grinding process on the grain size of the wheel, the grinding allowance, the grinding mode, the size of the workpiece, and the wheel, is proposed. To analyze the productivity of the finishing grinding processes, a productivity indicator, independent of the size of the wheel and the workpiece, is analyzed, and the impact on the productivity indicator of the number of finishing grinding operations, as well as the following sequence of their optimization, is established. To simplify the calculation of the optimal number of operations, graphs and a nomogram are constructed. According to the proposed methodology, the calculation of the number of finishing operations of cold rolling rolls of various sizes was carried out. Experimental verification of the proposed theoretical dependencies and methods for calculating the optimal number of grinding operations was also carried out.

Study of the Impact of Coals and Claystones on Wear-Resistant Steels

This paper discusses the impact of coal abrasive materials of varied petrographic composition and claystones containing admixtures of coal matter on the surface wear of wear-resistant martensitic steels. Wear tests were conducted at a test stand for three petrographic varieties of hard coal: vitrinite, clarinite, and durinite, and five samples of claystone. These tests revealed no significant effect of the type of coal abrasive used on the value of mass loss from the surface of the wear-resistant steel samples. The reason behind the foregoing is the observed tendency of coal abrasives, irrespective of their petrographic variety, to penetrate surface irregularities, especially those attributable to previous surface treatment of the samples and the impact of wear products. The dominant forms of surface damage were surface fatigue chipping and scratches caused by the particles which detached themselves from the surface of the steel samples, as observed for all the analysed coal variants. On the surfaces of the samples seasoned in the presence of claystones, highly varied forms of damage were observed: microcutting, scaly surface cracks, delamination, and deep cracks. In these cases, it was possible that the abrasive grains had been pressed into the steel surface irregularities, but no layered forms of the pressed-in abrasive material were observed to have developed. The paper also presents a model for the formation of coal films and discusses their possible effect on wear minimisation.