Single Diamond Grain Research Articles

Experimental Study on the Crushing Strength of Diamond Grains

This study investigates the crushing strength of single diamond grains of varying grades and particle sizes using the WDW-100 electronic universal testing machine. The research aims to understand the mechanical properties of diamond particles, which are critical for optimizing the performance of diamond tools in industrial grinding processes. High-grade diamond particles, characterized by their regular polyhedral shapes and minimal impurities, exhibit higher and more stable maximum load forces compared to medium- and low-grade particles. Medium-grade particles show a balance between strength and brittleness, while low-grade particles display significant variability in their structural integrity due to higher impurity levels and defects. The study also reveals that larger diamond particles tend to have lower average maximum load forces, attributed to increased crystal defects and pronounced grain boundary effects. These findings underscore the importance of considering both the grade and particle size of diamond grains in applications requiring high mechanical strength. The insights gained from this research are essential for improving the design and durability of diamond tools, ensuring their efficiency and longevity in industrial applications.

Retention and interfacial failure mechanism of single diamond grains in resin-bonded grinding tools

Abrasive grains and the associated bonding agent are the two significant components in the manufacturing of fixed abrasive machining tools. The material properties and interfacial bonding behavior between the grains and the bonding matrix determine machining performance. In precision machining processes with diamond abrasives, the primary failure modes of fixed abrasive tools are grain dislodgement and premature loss, leading to abrupt change in machining load and ultimately causing inaccurate and inefficient machining performance. This study develops a comprehensive model for understanding abrasive grain retention and interfacial failure mechanisms in resin-bonded diamond tools. Finite element analysis of a single diamond grain embedded in a resin matrix was conducted to examine the influence of the grain shape, protruding height, and orientation angle on critical interfacial failure force. A series of single diamond scratching experiments validated the model, revealing that the maximum retention force reached 43.56 N for grains with a 0.9 mm protruding height and a 60° orientation angle. The results also show that, within a specific grain size range, grain shape—quantified by the sphere deviation coefficient proposed in this paper, has the greatest impact on retention and failure behavior. Protruding height plays a secondary role, while the contribution of orientation angle is minimal. These findings provide valuable insights for the design, manufacture, and optimization of precision abrasive machining tools, particularly for applications requiring high precision and reliability.

Material removal characterization during axial ultrasonic vibration grinding SiCp/Al composites with a single diamond grain

Material removal characterization during axial ultrasonic vibration grinding SiCp/Al composites with a single diamond grain

Study on the grindability and removal mechanism of high volume fraction SiCp/Al composites based on single diamond grain grinding

Study on the grindability and removal mechanism of high volume fraction SiCp/Al composites based on single diamond grain grinding

Investigation of Single Grain Grinding of Titanium Alloy Using Diamond Abrasive Grain with Positive Rake Angle

Traditional grinding, which is predominantly performed with a negative rake angle (NRA), can be transformed into grinding with a positive rake angle (PRA) by employing femtosecond pulsed laser technology to modify the apex angle of the grains to be less than 90°. This innovative approach aims to reduce grinding forces and grinding temperatures while improving the surface quality of typical hard-to-machine materials. To assess the performance of PRA single grain grinding and to investigate the underlying mechanisms, the finite element simulation software ABAQUS 6.14 was employed to model the grinding of Ti6Al4V titanium alloy with a single diamond abrasive grain. The dependence of grinding force and temperature in single grain grinding with a PRA or an NRA under different grinding parameters was studied and compared. PRA and NRA single diamond grain grinding experiments on Ti6Al4V alloy were carried out, with grinding forces measured using a dynamometer and compared with the simulation results. The grinding surface morphology and surface roughness were observed and measured, and a comparison was made between PRA and NRA grinding. The results indicated that in single diamond grain grinding, transforming to a PRA significantly enhances grinding performance, as evidenced by reduced grinding forces, lower temperatures, improved surface morphology, and decreased surface roughness. These findings suggest that PRA single diamond grain grinding offers substantial benefits for the precision machining of hard-to-machine materials, marking a step forward in optimizing surface finishes.

Experimental study and smoothed particle hydrodynamics simulation of synthetic diamond grit scratching on steel

Superabrasives like synthetic diamonds are indispensable in today’s construction industry, particularly for core drilling applications in reinforced concrete. The increase of the cutting efficiency of such core bits strongly depends on the material removal behavior of single diamond grains placed in a diamond segment acting as cutting elements. Therefore, this paper presents a newly developed experimental setup for a 3-mm single diamond grain scratch test, as well as the application of a Smoothed Particle Hydrodynamics (SPH) method to model single diamond grains scratching a rebar base material at operational parameters. Diamonds in two main different crystallographic and geometric orientations are tested and investigated with respect to their forces and temperatures at the cutting edge. Furthermore, the chip formation and different material removal mechanisms are analyzed for each orientation and compared with the model output. Validation tests and sensitivity analyses are performed in 3D and high resolution, thanks to the runtime acceleration of SPH through parallel computing on the graphics card. The results indicate: 1) A significantly different material removal behavior as a result of changing the diamond orientation; 2) The capability and high efficiency of SPH for modeling single grain scratch tests.

АНАЛІЗ ФОРМОУТВОРЕННЯ ПОВЕРХНІ ПРИ ЕЛЕКТРОЕРОЗІЙНОМУ АЛМАЗНОМУ ШЛІФУВАННІ ЗІ ЗМІННОЮ ПОЛЯРНІСТЮ ЕЛЕКТРОДІВ

The paper presents the methodology of the process of surface shaping based on mathematical modeling, the nature of the interaction of the cutting relief of the circle with the material being processed. This made it possible to reveal the regularities of the configuration of the physical and technological characteristics of the process and their relationship with the productivity and wear of the wheels in different criteria for electroerosive diamond grinding. It is shown that the process of electroerosive diamond grinding provides a stable state of the diamond wheel relief, stable conditions for the interaction of its working surface with the material being processed. This made it possible, using a mathematical model, to establish the relationship of factors and optimize the parameters, guarantee the reliability and reproducibility of the results. To create an adequate model, a scheme of the grinding process is considered, which takes into account that diamond grains do not have a regular geometry, located on the working surface of the tool at different levels, wear out and break during operation. On the basis of the considered scheme of the electroerosive grinding process, dependences were developed for calculating the probability of material removal at any point of the contact zone, taking into account several shaping processes occurring simultaneously. They allow predicting the removal of material, differentially assessing the influence of individual factors on the quality parameters of the part and the speed of the process. The open structure of the model makes it possible to improve it as the parameters included in it are refined. A dynamic theoretical-probabilistic model of surface shaping during electroerosive diamond grinding with changing electrode polarity has been developed. This model takes into account erosion processes that affect the material being processed. When constructing, the dimensional wear of the wheel, the processes of chipping and pulling out of single diamond grains from the wheel bond, the size of the wear areas and the actual depth of microcutting are taken into account. For the direct use of the obtained theoretical results, experimental studies are needed to determine the parameters that make up the model.

Study on subsurface damage and recrystallization of single crystal superalloy in scratching with single diamond grain

Single crystal superalloy has gradually become the primary manufacturing material of advanced aero-engine turbine blades. However, it is easy to introduce subsurface damage and recrystallization in the precision machining process of this kind of material, and hence to worsen the high-temperature service performance of the parts. To explore its damage mechanism and influencing factors, a series of scratching experiments of single crystal superalloy with single diamond grain were conducted in this work. The examined results of the machined sample section by using a scanning electron microscope indicated that the subsurface damages include metallographic plastic deformation, slip band and transverse crack before heat treatment. Furthermore, cellular recrystallization observed in the surface layer mainly occurred in the metallographic plastic deformation zone after heat treatment. The experimental results revealed that the recrystallization depth increased with a rise in tool dimension and normal components of the scratching force. When the normal force is less than 20 N, the recrystallization depth scratched by the 80° tool is less than the critical safety value of 15 μm. Further analytical results indicated that improving the tool cutting performance and reducing the cutting force are beneficial to reduce the degree of recrystallization and subsurface damages. The research finding of this work is expected to provide a theoretical basis for the high efficiency and low damage machining of single crystal superalloy.

Glassy phase influence on the optical finishing of sintered silicon carbide with Al2O3 and Y2O3

Developing low-roughness silicon carbide (SiC) mirror surfaces for aerospace applications is challenging due to their extreme hardness and brittle nature. In this work, liquid phase sintered silicon carbide (LPS-SiC) substrates were machined at different feed rates. The influence of the glassy phase on the final finishing process was evaluated. An innovative thermo-chemical etching was proposed to evince the glassy phase. X-ray diffraction (XRD) analysis revealed the change of crystal structure from β-SiC to α-SiC in addition to the presence of YAP and YAG phases, constituents of the glassy phase. Vickers microhardness and scratch tests simulating the action of a single diamond grain on the surface of the substrates with and without the glassy phase showed that the hardness of the SiC grain and its fracture resistance exceeded the values obtained for the substrate with the glassy phase by 110% and 170% respectively. Reducing the feed rate decreased the damage to the surface of the substrate with the glassy phase by 25% and to the SiC matrix by 90%.

Microstructure and properties at bonds of diamond grains and Ni[sbnd]Cr filler alloy by fiber laser brazing

Advanced laser technology has been used in laser brazing to bond diamond grains in metal matrix to achieve some distinctive advantages such as high protrusion heights and large gaps of diamond grains. However, laser brazing has not been widely adopted as expected to produce various diamond tools since that bonding mechanisms, microstructures and characteristics of bonded interfaces have not fully investigated. In this paper, the experimental study was performed for using fiber laser brazing to bond diamond grains on steel substrate with NiCr filler alloy. Microstructures, graphitization, and shear force at the bonded interface were especially analyzed. The experiments led to the following outcomes: (1) the interface of diamond grains and NiCr alloy was a wavy surface with an average thickness of 7 μm. (2) Two types of carbide, i.e., Cr3C2 and Cr7C3, were generated on the brazed surface; Cr3C2 was lath-shaped and generated at first, and Cr7C3 was prismatic and built upon Cr3C2. (3) The interface of diamond grains and NiCr alloy was rough and accompanied by graphitization. (4) The shearing test showed that an average force of 138 N was applied to debone single diamond grain from filler metal.

Investigation on abrasive wear mechanism of single diamond grain in flexible scribing titanium alloy

Abrasive belt grinding technique has been gradually used in precision machining those attractive materials of aerospace field. The excellent performance of rigid-flexible composited diamond belt shows great application prospect while its abrasive wear mechanism is deeply revealed. Therefore, a series of theoretical and experimental studies are performed to explore the wear mechanism of single diamond grain in flexible scribing titanium alloy in this work. Three-dimensional finite element simulation model was built to investigate the elastic frictional wear process between a diamond grain and the titanium alloy sample under different combinations of processing parameters. The simulation results showed that the normal force and grain size contributed much to frictional stress and the friction speed had the greatest effect on the frictional temperature. On this basis, the flexible scribing experiments of titanium alloy sample by using single diamond grain were conducted to verify the effect of scribing parameters on diamond grain wear. Raman scattering analysis, chemical thermodynamic calculation and X-ray photoelectron spectroscopy analysis methods were proposed to further research the essential wear of diamond grain at elevated temperature. The results indicated that the physical wear caused by higher scribing force was the main pattern at lower temperature. When the temperature reached up to 1100 K, Raman shifts peak of graphite corresponding to 1544 cm−1 was detected to illustrate the graphite transformation of diamond crystal structure, and the existence of TiO2 and CO bond were confirmed to explain the oxidation wear of diamond grain at the atmosphere of air medium. This research work provides an important theoretical basis for restraining the diamond belt wear in precision grinding operation of titanium alloys.

МАТЕМАТИЧНЕ МОДЕЛЮВАННЯ СТАНУ ІНСТРУМЕНТУ ПРИ ЕЛЕКТРОЕРОЗІЙНОМУ АЛМАЗНОМУ ШЛІФУВАННІ

The methodology of forecasting of indicators of a condition of the tool on the basis of mathematical modeling of character of interaction of a cutting relief of a circle with the processed material is resulted in work. This revealed the patterns of changes in physical and technological parameters of the process and their relationship with the productivity and wear of the wheels in different conditions of EDM diamond grinding. It is shown that the process of EDM diamond grinding provides a stable state of relief of the diamond wheel, stable conditions of interaction of its working surface with the processed material. This allowed using a mathematical model to establish the relationship of factors and optimize the parameters, to ensure the reliability and reproducibility of the results. To create an adequate model, the scheme of the grinding process is considered, which takes into account that diamond grains do not have a regular geometry, are located on the working surface of the tool at different levels, wear and break during operation. When analyzing the grinding process, it is taken into account that the radius vectors of the tool and the workpiece are random, and their centers of rotation are shifted relative to each other not only due to the presence of feeds, but also temperature, elastic deformations. Based on the considered scheme of the grinding process, dependences are developed to calculate the probability of material removal at any point of the contact zone, taking into account several simultaneously occurring molding processes. They allow you to predict the removal of material, differentiated to assess the impact of individual factors on the quality parameters of the part and the speed of the process. The open structure of the model makes it possible to improve it as you refine the incoming dependencies that are part of it. A dynamic theoretical–probabilistic model of wear of an abrasive–diamond tool taking into account the erosion processes affecting the wheel connection has been developed. The construction takes into account the dimensional wear of the circle, the processes of chipping and uprooting of single diamond grains from the bond, the size of the wear areas and the actual depth of microcutting. For direct use of the received theoretical results experimental researches on definition of the parameters which are a part of model are necessary.

Theoretical modeling and experimental analysis of single-grain scratching mechanism of fused quartz glass

Abstract Surface and subsurface damage, including cracks, scratches, microcracks, and residual stress, is inevitable when fabricating fused quartz glass because of their high brittleness and low fracture toughness. Single-grain scratching mechanism of fused quartz glass is examined using smoothed particle hydrodynamics (SPH) to clarify the mechanisms of material removal and produce crack-free optical surfaces. Single diamond grain experiments were conducted to validate the proposed SPH model, which predicts the critical depth of approximately 0.20 μm for ductile–brittle transition in fused quartz glass. Both simulation and experimental results indicate that three removal regimes, namely, complete ductile, ductile–brittle transform, and complete brittle modes, are involved in the material removal process. SPH simulation helps identify the location of crack formation and morphology of crack propagation during scratching. Thus, the SPH model is used to simulate the single grain scratching process under different conditions. Simulation results reflect that changing the scratching speed will lead to a remarkably different mechanism of crack initiation and propagation compared with changing the scratching depth. Effects of scratching depth and speed on scratching force and residual stress are also discussed thoroughly in the simulation analysis.

Mechanics analysis and predictive force models for the single-diamond grain grinding of carbon fiber reinforced polymers using CNT nano-lubricant

Abstract Machining of carbon fiber-reinforced polymer (CFRP) with less damage remains to be a challenge because of anisotropy and inhomogeneity issues. Flood cooling will reduce the mechanical properties of CFRPs due to its hygroscopicity, however, dry grinding will result in thermal damage and deterioration of surface integrity, which cause it not suitable in aeroengine and aerostructure applications. Aiming to resolve the above gaps, the grinding mechanics for a single grain of CFRPs involving CNT nano-lubricant minimum quantity lubrication (MQL) is explored. To reveal the various fundamental mechanisms in machining CFRP of special transversal grinding and lubrication conditions, four sub-models were developed based on the unique geometries of grain and fiber in contact due to the random fiber arrangements and grain edge shapes under different undeformed chip thicknesses. Specifically, the models account ⅰ) the contact force model between the grain tip and fibers, ⅱ) the local contact stress model of elliptical region between the spherical grain edge and cylindrical fiber, ⅲ) the tensile fracture force model of single fiber regarded as an bending beam fixed at both ends and constrained on the elastic foundation, and ⅳ) the extrusion and shearing force model on the cut fiber section at the grinding groove. Furthermore, the grinding force model is obtained by integrating these sub-models, in which the grain-fiber friction coefficient and grinding mechanics are accurately introduced. Finally, the model is numerically simulated and the trend of force along the entire grinding arc length is obtained. Experimental verifications demonstrate the approach for predicting the grinding force have acceptable accuracy and can successfully capture the mechanics of CFRPs. The model reveals that the tensile fracture force of single fiber has the most contributions to the grinding force.

Laser-dressing topography and quality of resin-bonded diamond grinding wheels

Laser dressing technology has shown extremely outstanding advantages and broad application prospects in dressing of superabrasive grinding wheels. However, this technology is currently facing bottlenecks that the generation mechanism of the metamorphic layer on the surface of the grinding wheel is unclear, and the influence rule of the heat accumulation effect on the removal threshold of the grain is not mastered. In this paper, the laser cutting experiment of single diamond grain, and the laser ablation experiment and dressing experiment of resin-bonded diamond grinding wheels were systematically carried out, and the effects of process parameters on the topography and quality of nanosecond laser dressing were comprehensively explored by means of SEM, Raman, EDS, XRD and other detection methods. The mechanism of generation and removal of the graphite layer on the surface of diamond grains during profiling was revealed. It was found for the first time that there was a clear interface between the graphite layer and diamond, and the increase of the finishing time was beneficial to reduce the degree of graphitization of profiled diamond grains. The influence rule of the heat accumulation effect on the removal energy threshold of diamond grain during the sharpening process was first clarified. It was found that the removal energy threshold of diamond grain decreased first and then stabilized with the increase of the spot overlap ratio. The pyrolysis process and phase transformation of resin bond during laser dressing were innovatively explored. It was found that the proportion of C element increased and the proportion of O element decreased in the bond, while the composition and content of the auxiliary materials in the bond changed little. Finally, the comprehensive optimization of laser dressing parameters was completed, and low damage and ultra-precision dressing of resin-bonded diamond grinding wheels were achieved.

Modeling and evaluation in grinding of SiCp/Al composites with single diamond grain

In this paper, the theoretical model of grinding force and the finite element simulation model of single diamond grain grinding SiCp/Al aluminum matrix composites were established, and the material removal mechanism was studied, including grinding force, stress distribution and material removal behavior of SiC reinforced particles. The validity of the theoretical model and the finite element model are proved by experiments. The results show that the maximum stress displays smoothly during the removal process of the aluminum matrix, while during the removal process of SiC particles, it fluctuates greatly. Material removal is divided into four stages: plastic removal of aluminum matrix, crack initiation of SiC particles, crack growth of SiC particles, and brittle fracture of SiC particles. The surface defects of grinding SiCp/Al with single diamond grain mainly include voids, microcracks and aluminum matrix delamination. According to the current experimental results, compared to the grinding wheel speed, the undeformed chip thickness (UCT) has more significant influence on the machined surface/subsurface quality. In addition, the removal modes of the SiC particle can be divided into ductile removal, ductile-brittle removal and brittle removal.

Mathematical model for cutting force in ultrasonic-assisted milling of soda-lime glass

Ultrasonic-assisted milling (UAM) has an outstanding performance in machining hard and brittle materials, such as glass. The cutting force which has been investigated both experimentally and theoretically is the key factor that affects the machined surface quality. This paper presents a mechanistic mathematical model for the axial cutting force in UAM of soda-lime glass. This model is based on the process mechanism of material removal and can be used to predict the cutting force without the need of performing actual experiments. The mathematical model is proposed taking into consideration two different material removal mechanisms, that directly affect the final material removed volume for the brittle material. The first model is the ductile model which is described by the ductile mechanism where the material is removed by the plastic flow, while the other is the brittle model described by the brittle mechanism where the material is removed due to the crack formation that cause material fracture. In the present models, the effects of both the rotation and ultrasonic vibration motion of the cutting tool were taken into consideration through their effects on the indentation volume, by each diamond grain, into the workpiece. The development of the model started by the analysis of the behaviour of a single diamond grain and obtaining the cutting force for an individual diamond grain first. The total cutting force then was derived by summing up the forces caused by all diamond grains taking part in the cutting process. From the developed models results, the trends of the predicted results from the ductile model agree well with the results determined experimentally at low feed rates and low depths of cut. However, the predicted results from the brittle model agree well with the results determined experimentally at high feed rates and high depths of cut. These results explain that the ductile mode of the material removal is occurring at low feed rates and low depths of cut. Then it changes to the brittle mode of material removal by further increasing of the feed rate and depth of cut.

Predictive model for minimum chip thickness and size effect in single diamond grain grinding of zirconia ceramics under different lubricating conditions

Abstract To address the current bottleneck of debris formation mechanism in plastic removal for hard-brittle materials, a minimum chip thickness ( h min ) model that considers lubrication conditions (represented by frictional angle β ) is developed according to strain gradient, as well as geometry and kinematics analyses. Model results show that h min decreases with increasing β . Furthermore, grinding experiments using single diamond grain under different lubricating conditions are carried out to verify the model. With increasing β , h min values are 71.6, 57.8, 52.0, 50.7, 45.6, 39.7, and 32.4 nm, thereby verifying the trend of h min decreasing with increasing β . Furthermore, the location of size effect occurs is determined according to the variation trend of single abrasive particle specific energy and unit grinding force curves. The size effect occurs in the border area of ploughing, the cutting region, and mainly, in the ploughing region. Theoretical analysis results are consistent with experimental results with a model error of 6.06%, thereby confirming the validity of the theoretical model.

Deformation induced complete amorphization at nanoscale in a bulk silicon

Solid state amorphization is induced by shock, irradiation and deformation, while deformation induced complete amorphization remains a challenge in a bulk solid. Brittle-to-ductile transition (BDT) mechanism is elusive at loading speeds of m/s at nanoscale depth of cut. Existing formula has no effects of shape and radius of cutting edges on the critical depth of cut at BDT. In this study, a new route of deformation induced complete amorphization at nanoscale is proposed in a bulk solid confirmed by transmission electron microscopy (TEM). This is performed by a novel approach of ultraprecision grinding, conducted on a specially designed setup. The grinding is carried out by a developed single diamond grain with a cutting edge radius of 2.5 μm, at depth of cut of 24 nm under a loading speed of 40 m/s. BDT takes place at depth of cut of 419 and 172 nm for Si (100) respectively, ground by single diamond grains with tip radii of 5 and 2.5 μm correspondingly. A new model is suggested for BDT, considering the effects of radius and shape of cutting edges. The findings provide new insights for design and fabrication of high performance devices used in flexible electronics, nanodevices, microelectronics and optoelectronics.

Study on the material removal mechanism of glass in single diamond grain grinding with ultrasonic vibration assisted

The ultrasonic vibration assisted grinding is widely used in machining of hard and brittle material. This paper presents a study on the material removal mechanism in ultrasonic vibration assisted grinding of glass. The single diamond grain grinding experiments were performed with and without ultrasonic vibration assisted. The grinding force and acoustic emission signal were measured and analysed, and the ground groove morphology was observed and analysed in detail. The following conclusions can be obtained: 1) the material removal mechanism is changed from continuous crack propagation in conventional grinding to micro crack breakage in ultrasonic vibration assisted grinding; 2) the addition of ultrasonic vibration in grinding of brittle material can reduce the crack propagation distance; 3) compared with the conventional grinding, the energy distribution of acoustic emission signal in ultrasonic vibration assisted grinding is more concentrated.