Abrasive Shape Research Articles

Development of classification system by abrasive grain shape using deep learning

Development of classification system by abrasive grain shape using deep learning

Influence of Abrasive Shape on the Abrasion and Phase Transformation of Monocrystalline Silicon

The effect of abrasive shape on the three-body abrasion behaviors of monocrystalline silicon was investigated via molecular dynamics. The axial ratio of abrasive particle varied from 1.00 to 0.40 to mimic abrasive shape. It has been observed that the particle’s movement became sliding instead of rolling when the axial ratio was smaller than a critical value 0.46. In the abrasion process, the friction force and normal force showed an approximately sinusoid-like fluctuation for the rolling ellipsoidal particles, while the front cutting of particle caused that friction force increased and became larger than normal force for sliding particles. The phase transformation process was tracked under different particle’ movement patterns. The Si-II and Bct5 phase producing in loading process can partially transform to Si-III/Si-XII phase, and backtrack to original crystal silicon under pressure release, which also occurred in the abrasion process. The secondary phase transformation showed difference for particles’ rolling and sliding movements after three-body abrasion. The rolling of particle induced the periodical and inhomogeneous deformation of substrates, while the sliding benefited producing high-quality surface in chemical mechanical polishing (CMP) process. This study aimed to construct a more precise model to understand the wear mechanism benefits evaluating the micro-electro-mechanical systems (MEMS) wear and CMP process of crystal materials.

Classifying diamond abrasive grain shape by image processing

Classifying diamond abrasive grain shape by image processing

Predicting Microscale Cross-Hatched Surface Texture in Engine Cylinder Bore

Cross-hatched texture is the essential surface feature in cylinder bore generated from honing process. The interconnected grooves of the surface texture provide storage space and diffusion channels for the lubrication oil. Thus, it is widely used to reduce contact friction, lubrication oil consumption and improve the wear resistance of piston-ring contact pairs in automotive engine. The surface texture was simulated by various analytical methods in literatures. However, the mechanism of generation of surface texture stays a black box and poses a challenge to further control engine quality. This study presents a new kinematic model to simulate the generation of cross-hatched surface texture in the honing process of engine cylinder bore. It formulates the process motions based on honing operations in automotive industry. And a microscale model is established to simulate honing stone surface topography with randomly distributed abrasive particle sizes, postures and distributions obtained by a modified Poisson disk sampling algorithm. The kinematic simulation is performed by moving the honing stone surface topography along the motion trajectory. Abrasive particles interact with cylinder surface and generate texture grooves as honing stones feed. Using this method, honing surface texture is demonstrated with cross-hatched feature at microscale level, and the difference of cross-hatched texture is revealed visibly and quantitively as roughness corresponding to honing stones with different abrasive particle shapes, wear conditions and position distributions in height direction.

Diamond Wire Sawing of Solar Silicon Wafers: A Sustainable Manufacturing Alternative to Loose Abrasive Slurry Sawing

Slicing silicon wafers for solar cells and micro-electronic applications by diamond wire sawing has emerged as a sustainable manufacturing process with higher productivity, reduced kerf-loss, thinner substrates that save material, and reduced environmental impact through the use of water-based cutting fluids, compared to the conventional loose abrasive slurry sawing process. This paper reviews recent research on diamond wire sawing of photovoltaic silicon wafers and compares it with the loose abrasive wire sawing process from a standpoint of sustainable manufacturing. Various aspects of the diamond wire sawing process including surface morphology, total thickness variation (TTV), surface and subsurface damage, fracture strength, residual stress, stress induced phase transformation, effect of microstructure and abrasive grit shape are critically reviewed and areas of future need are identified.

An experimental study of the effects of dressing parameters on the topography of grinding wheels during roller dressing

Vitreous-bonded grinding wheels are widely used for machining features on aerospace components achieving high material removal rates under high pressure coolant. Dressing is a vital stage in the grinding process to ensure a consistent wheel topography and performance. However, the effects of roller dressing on functional performance of vitreous grinding wheels as well as its influence on different abrasive grit morphologies have not been fully characterised. This paper studies the influence of dressing parameters on the topography, morphology and characteristics of the surface of different vitrified abrasive wheels in order to better understand the process and therefore optimise the preparation of grinding wheels for industrial machining. Alumina grinding wheels with conventional and engineered grit shapes were dressed at two different infeed rates over a range of seven different speed ratios (from −0.8 to +1). An experimental methodology has been developed incorporating a range of known techniques to define the abrasive wheel condition including measured power consumption and ground graphite coupons as well as using optical microscopes to measure grain fracture flats, peak density and abrasive grain shape. It has been found that power consumption of the grinding wheel spindle increases at higher infeed rates and speed ratios. This leads to increased fracturing of the grains and whole-grain pull out. According to the results the infeed rate has a more substantial effect on wheel topography than speed ratio and the response of engineered grit morphologies to dressing is dependent on grit orientation.

Automated instrument for assessing abrasives

An automated instrument for monitoring the destructive compressive load on abrasive grains (measuring 400–1250 μm) between two rotating rollers has been developed. A modernized version of the instrument also permits determination of the grain size, shape, and microgeometric and topographic characteristics of abrasives. Equipped with a photometric unit and a module for processing numerical information, the modernized instrument permits multiple recording of each particle by six cameras (in both directions along three orthogonal axes), with assessment of the microgeometry. Such information regarding the grains, along with identification of their shape (plates, needles, isometric form, etc.), permits their quality assessment; their subsequent separation on vibrational sorters; and their most effective use in the abrasive machining of materials characterized by different hardness, brittleness, and composition, including composites.

Microabrasion of three experimental cobalt-chromium alloys: Wear rates and wear mechanisms

Cobalt-chromium alloys are known for their excellent wear resistance. Many studies on the wear behavior of these alloys were reported in literature. Nevertheless, microabrasive wear still lacks extensively investigation. Microabrasive wear behavior, of three experimental cobalt alloys, was investigated: Alloy 1 similar to Stellite 250, 48wt% Co, 29wt% Cr, 19wt% Fe; Alloy 2 similar to Stellite 6, 64wt% Co, 24wt% Cr, 4.2wt%W, 2,3wt% and Alloy 3 similar to Tribaloy – T400, 56wt% Co, 8.5wt% Cr, 29wt% Mo, 3.3wt% Si. These alloys are being used for manufacturing guides for hot rolling seamless steel pipes. Alloy 2 and Alloy 3 are being tested as wear segments used inside a 2nd generation ethanol reactor. Tests were performed using three 0.1g/cm3 slurries composed by SiO2, Al2O3, and SiC particles, in a distilled water suspension. A load of 0.3N was applied, the rotational speed was 20rpm and the total sliding distance 48m. Analysis of the alloys' tribosurfaces – by Optical Microscopy, Scanning Electron Microscopy and Contact Stylus Profilometry – showed abrasive size, shape and hardness may influence wear coefficients significantly. Tests performed with SiC and Al2O3 slurries resulted in greater wear rates than those with SiO2 slurry. Alloy 1 showed the greatest wear coefficient, in comparison with the other two experimental alloys, due to the absence of hard second phase precipitates in its microstructure. The variation of the wear coefficients as a function of abrasive hardness (Ha) and the compound alloy hardness (Hs) showed a linear correlation (R2 = 0.73). Two-body abrasion (grooving wear) was the dominant wear micro-mechanism observed for all tests. Alloy 2, containing Laves phase showed a transition from ductile to brittle wear mechanism when tested with alumina slurries. The SiC slurry gave the highest worn volume among the three tested slurries.

Modeling surface roughness for polishing process based on abrasive cutting and probability theory

ABSTRACTThe surface roughness is a variable used to describe the quality of polished surface. This article presents a surface roughness model based on abrasive cutting and probability theory, which considers the effects of abrasive grain shape, grit and distribution feature, pressure on surface roughness. The abrasive grain protrusion heights are thought to close to Gaussian distribution, and then the relationship between the indentation depth and the pressure based on Hertz contact theory is obtained. Surface roughness prediction model is established by calculating indentation depth of the abrasive grains on workpiece surface. The maximum surface profile height (Ry) is approximately equal to the maximum indentation depth of the abrasive grain. The arithmetic average surface roughness (Ra) is equal to the average indentation depth of the abrasive grain. The effects of process parameters such as pressure and grit on Ry and Ra were simulated and analyzed in detail.

A scratching force model of diamond abrasive particles in wire sawing of single crystal SiC

The wire sawing process for single crystal SiC can be regarded as nano and micro scratching on the work-piece with diamond abrasives. The surface/subsurface quality of wafers is affected by the forces in scratching. In this paper, a theoretical force model for nano and micro scratching in wire sawing of single crystal SiC at arbitrary scratching angle is proposed. The geometrical shape of diamond abrasives is discussed and simplified. Then, a primary force model for the simplified abrasive is established considering the interfacial friction coefficient between the abrasive and work-piece. Indention size effect based on strain gradient plasticity theory and elastic recovery are included in this model. Finally, the influences of input variables on the theoretical force under the actual machined depth in wire sawing are discussed. The validity of this model is verified through nano and micro scratching tests in literatures, and the theoretical model matches well with the experimental results.

Abrasive size and load effects on the wear of a 19.9% chromium and 2.9% carbon cast iron

The effects of applied loads and abrasive sizes on the wear of a 2.9% carbon and 19.9% chromium martensitic white cast iron were investigated. Abrasive wear tests using a pin test on silica and garnet papers (ASTM G132) were carried out using three different abrasive average sizes: 67μm, 149μm and 177μm and two applied normal load: 5N and 10N. A modified rubber wheel abrasion test (ASTM G65) was carried out using three abrasive average sizes - 90μm, 115μm and 170μm quartz sand - and three applied normal loads: 44N, 80N and 130N. The abrasive shape and the wear surface of the specimens were examined using a scanning electron microscope (SEM). The worn surfaces topography was obtained with a Taylor Hobson 3-D surface analyser. In the pin test with silica paper, a change in the magnitude of the volume loss was observed as a result of increasing the applied load from 5N to 10N. In the rubber wheel abrasion tests the mass loss increased with the increase of particle size until a critical particle size was reached. In general, the mass loss increased with the increase of the applied load and the abrasive size. For the lower load and the smallest abrasive size wear grooves were observed only in the martensitic matrix while the carbides remained intact. With higher loads and larger abrasives, scratching was observed also in the carbides. A wear map is proposed with a ‘wear rate’ parameter developed in this work plotted against abrasive sizes.

Influence of Abrasive Grain Geometrical Characteristics on the Grinding Quality

In the engineering industry grinding is mostly the final operation of the production process, therefore it should provide for the necessary surface quality, dimensional accuracy, and the required geometric shape of a product. This paper reveals how raw material grit, abrasive grains shape, ordering of grains influence the efficiency of the grinding wheels. The implemented research let us conclude that the shape of the grain has a significant influence on performance characteristics of abrasive tools. The choice of a certain shape and orientation of grains depends on the particular task and the desirable result of the process.

Investigation of cBN Electroplated End-Mill Shape for CFRP Machining

Currently, carbon fiber reinforced plastics (CFRP) are being increasingly adopted in various fields. Thus, machining CFRP with high accuracy and high efficiency is required. In addition, machining stack materials composed of CFRP and titanium alloys is required. Therefore, in this study, a novel end-mill electroplated with a cubic boron nitride (cBN) abrasive, which has high thermal resistance, is proposed. In order to evaluate the influence of the base metal shape of the proposed end-mill on the machining process, several cBN-electroplated end-mills with different rake angles or chamfers were fabricated and used to cut CFRP. In addition, in order to evaluate the abrasive shape, a blocky abrasive was also electroplated on the end-mill. The results indicate that the negative rake angle is useful to restrain the progression of tool wear. However, in order to obtain the element of cutting and grinding, it is required that the rake angle should be positive. Moreover, the reasonable width of chamfer is effective for restraining the increase in CFRP temperature. Further, a sharp shaped abrasive can more effectively generate a CFRP with a sharp edge compared with a blocky shape abrasive.

Single-asperity contributions to multi-asperity wear simulated with molecular dynamics

We use a molecular dynamics approach to simulate the wear of a rough ferrite surface due to multiple hard, abrasive particles under variation of normal pressure, grinding direction, and particle geometry. By employing a clustering algorithm that incorporates some knowledge about the grinding process such as the main grinding direction, we can break down the total wear volume into contributions from the individual abrasive particles in a time-resolved fashion. The resulting analysis of the simulated grinding process allows statements on wear particle generation, distribution, and stability depending on the initial topography, the grinding angle, the normal pressure, as well as the abrasive shape and orientation with respect to the surface.

Comparative evaluation of tooth substance loss and its correlation with the abrasivity and chemical composition of different dentifrices.

In India, teeth cleaning with tooth powder is common in rural and semi-urban areas. These dentifrices may contain low-quality abrasives, which may have a deleterious effect on dental hard tissues. This study aims to evaluate the tooth substance loss caused by different dentifrices and to correlate it with chemical composition, size, and shape of abrasives used. An indigenously made automated machine was used for brushing the specimens. Sixty-four freshly extracted premolars were allocated to eight groups (n = 8). Colgate toothpaste was used as the control group. Each specimen was brushed in a vertical motion for 2½ h at 200 strokes/min with a constant applied load of 200 g corresponding to 6-month brushing. The difference in weight (pre- and post-brushing) was determined by an analytical weighing machine. Chemical analysis was done to determine the presence of iron oxide by Inductively Coupled Plasma Mass Spectrometry method. Shape and size of the abrasive particles was evaluated under scanning electron microscopy (SEM). One-way analysis of variance and Paired t-test were used to analyze the data. Tooth substance loss was maximum in the group brushed with red tooth powder, which was shown to contain the highest amount of iron oxide and also exhibited large, irregularly shaped abrasive particles under SEM. Tooth substance loss was documented to be correlated with chemical composition (iron oxide) and the size and shape of abrasive particles used in dentifrices.

Ductile Mode Behavior of Silicon During Scribing by Spherical Abrasive Particles

Reducing surface and subsurface damage in cutting brittle materials using fixed abrasive processes like wire sawing is an important challenge. This paper investigates the effect of size and shape of abrasives on ductile mode cutting of single crystal silicon. Diamond and tungsten carbide abrasives of different shapes (irregular and spherical) deposited on a steel surface are used to scribe silicon and the material removal mode is analyzed. Experiments show that spherical abrasives enhance ductile mode cutting when compared to irregular shapes, yielding a smoother surface and significantly fewer micro-cracks.

研削砥石作業面トポグラフィのステレオ視法援用機上3次元計測システムに関する研究

The abrasive grain shape and its distribution in the grinding wheel have an influence on the grinding characteristic of the wheel. Therefore, we aim to develop the on-machine 3D measurement system by binocular stereopsis for abrasive grain shape and its distribution in the grinding wheel. In this paper, the 3D shape measurement is carried out using the omnifocal images. Comparing between the ratios of outlier by use of optical filters, we aim to improve the stereo pair images by decrease the outlier of matching. Thereafter, we analyzed the grinding wheel surface 3D topography and the abrasive behavior by performing tracking observation of the grinding wheel working surface in the grinding process by using this system.

Experimental Investigation on Rotary Ultrasonic Face Grinding of SiCp/Al Composites

SiCp/Al composites have been widely used in many fields such as aerospace, automobile, advanced weapon system, etc. But this kind of material, especially with high volume fraction, is difficult to machine due to the reinforced particles existing in matrix, which has limited its further application. Rotary ultrasonic machining (RUM) has many excellent features and it has never been used to machine SiCp/Al composites. In order to improve the machinability and application of SiCp/Al composites, the rotary ultrasonic face grinding experiments of SiCp/Al composites reinforced with 45% volume SiC particles were carried out to investigate cutting force, surface quality, tool wear, and abrasive chip shapes. The experimental results indicate that ultrasonic vibration could reduce cutting force, surface roughness, surface defects, and increase plastic removal ratio. The cutting force could be lowered by an average of 13.86% and the surface roughness could be lowered by an average of 11.53%. The examined results of tool wear patterns suggest that tool wear is mainly caused by grain breakage and grain fall-off. Grinding wheel blockage and grinding burn were not observed in machining process.

Characterization of irregularly micro-structured surfaces related to their wetting properties

It is difficult to control a surface wetting due to the random surface texture, but its fabrication is easy. Hence, the volume ratio is proposed through the 3D characterization of micro-structured surface in contrast to traditional roughness factor, fractal dimension and aspect ratio through 2D characterization. The objective is to investigate the wetting properties related to the characterization of irregularly micro-structured surface. First, the irregularly micro-structured Si surfaces with 0.22–3.58μm in depth were machined by the rubbing, the polishing and the grinding with different diamond abrasive grain size and random abrasive grain shape, respectively; secondly, the surface wetting properties were investigated with regard to the characterized parameters of measured micro-topographic surfaces; finally, the irregular wetting model was constructed by using volume ratio on the base of non-composite wetting. It is shown that the contact angle increases with increasing roughness factor and aspect ratio and decreasing fractal dimension on the irregularly micro-structured surfaces, but it is different from the prediction of non-composite wetting model. Moreover, the irregularly micro-structured surfaces without anisotropic properties produce smaller contact angles than regularly micro-structured surfaces with anisotropic properties. The experimental results show that an increase in volume ratio leads to a decrease in contact angle. It is identical to the predictions of the proposed model. This is because the volume ratio precisely illustrates 3D contact information between the liquid and solid interfaces. It is confirmed that the volume ratio may be utilized to predict and control the wetting of irregularly micro-structured surface.

A molecular-scale analytic model to evaluate material removal rate in chemical mechanical planarization considering the abrasive shape

This paper presents a theoretical model of material removal rate (MRR) in the process of chemical mechanical planarization (CMP), in which the morphology effect of abrasive particles is taken into account using a shape factor. In contrast to previous models based on the continuum material removal mechanism, the physical basis of the current model is that the wafer material is primarily removed by de-bonding the chemistry-weakened surface molecules. It is shown that a non-linear relationship between the shape factor and the MRR is given rise to by two opposite effects. On one hand, the increase in the shape factor results in the decrease in the number of the effective particles participating in the material removal, and subsequently contributing to the decrease in the MRR. On the other hand, the particle/wafer contact diameter is enhanced with the increase in shape factor, leading to the increase in the MRR. The simulation results match well with the published experimental data in the range of low polishing pressure conditions. With further increase in the pressure, the effect of the shape factor on the MRR becomes significantly pronounced, which might be ascribed to the influence of the abrasive shape on the micro-contact state of the pad/abrasive/wafer. In addition to the shape factor, most variables involved in the CMP process, such as processing conditions (velocity, pressure), pad properties (modulus, hardness and asperity size) abrasive characteristics (size, concentration and distribution) and wafer hardness, were also addressed in the present model.