Grinding Direction Research Articles

Online Orientation Recognition of Single-Crystal Diamond Tools in the Process of Indexing Grinding Based on HMM and Multi-Information Fusion

Single-crystal diamond tools occupy an important position in the field of optical processing as the basis and key to advanced optical manufacturing technology, such as grating manufacturing and optical mirror-turning processing. Single-crystal diamond tools have become the cornerstone of the development of related industries. This paper takes a single-crystal diamond arc tool as the research object. Sound signal analysis technology and vibration signal analysis technology are comprehensively applied to the online orientation identification of a single-crystal diamond tool in the indexing grinding process. The online orientation method of the tool is explored, the sound signal and the vibration signal are taken as the characteristic signals, and a wavelet algorithm (WT) is used to reduce the noise of the vibration signal and sound signal. The kurtosis of the sound signal and the kurtosis and skewness of the vibration signal in the high-order statistics strongly related to the grinding direction of a single-crystal diamond are used as the characteristic parameters, and the online direction recognition model of the tool is established using the Hidden Markov Method (HMM). The above characteristic parameters are used as model input for multi-information fusion. The mapping relationship between the characteristic parameters of the characteristic signal and the crystal orientation of the single-crystal diamond crystal face is obtained, and then the online orientation method of the single-crystal diamond arc tool in the process of indexing grinding is formed. The effectiveness of the method is verified by experiments, and effective orientation information is provided for research on the positioning control strategy of the tool grinding process to ensure the efficiency of grinding and improve the manufacturing level of the tool.

Understanding machinability improvements and removal mechanism of ceramic matrix composites during laser-ablating assisted grinding

Ceramic matrix composites are advanced high-temperature materials for aerospace equipment, but they are also known as hard-to-machine materials. This study introduced laser-ablating assisted grinding (LAAG), and analyzed the complex physicochemical transformations of Cf/SiC composites during picosecond-laser ablating, then systematically explored the grinding characteristics, damage behavior, removal mechanism, and abrasive wear. It was revealed that Cf/SiC composites occurred sublimation and oxidation reactions during laser ablating, resulting in SiO2 ablation products with a loose microstructure. Grinding force, temperature and diamond wear remarkably decreased through LAAG. Besides, surface roughness was observably reduced, and the surface morphology of Cf/SiC composites was primarily shown as micro fracture and ductile removal. Furthermore, subsurface damages, including fiber pulling-out and interface debonding, were almost invisible after LAAG. More importantly, the graphite crystallites of carbon fibers near the ground surface became disordered, and an amorphous structure layer was first found on the micro-fractured carbon fibers. The grinding chips generated in LAAG were lamellar-fractured ablated materials rather than uncharacteristically-fractured fiber bundle, indicating the anisotropy removal behavior of Cf/SiC composites was decreased. The machinability improvements were especially significant when the laser scanning interval was small and the scanning direction was perpendicular to the grinding feed direction.

Study on the dynamic influence of the distribution of cutting depth on the ground surface quality in a precision grinding process

Focusing on the excitation mechanisms of self-excited vibration and forced vibration, a time-delay differential model of the radial cutting depth of a single active abrasive grit is presented. Based on the principle of the layered superposition characteristics of each component of radial cutting depth, a full discrete simulation technology is used to analyze the dynamic mechanisms of different vibration excitations on the grinding characteristics. The reliability of the dynamic mechanisms is verified by the corresponding grinding experiments. The verification results demonstrate that static and dynamic components in the grinding dynamics, including radial cutting depth, grinding force, surface roughness and surface morphology of workpiece are greatly influenced by total material removal rate, followed by speed ratio and grinding directions. With the increase of cutting depth, the variation amplitude of grinding process influenced by forced-vibration mechanism are nearly twice larger than those influenced by self-excited vibration mechanism. When speed ratio reduces to a half, surface roughness of workpiece improves by nearly 33 %. The stability of machining process and finish surface of workpiece during up-grinding are better than those during down-grinding, where force reduction by up to 10 % and surface finish improvement by 37 %.

Early wetting and interfacial behavior of Sn-based solder on copper substrates with different roughness

Purpose This paper aims to investigate the effect of solder composition and roughness on early wetting behavior and interfacial reaction under atmospheric conditions. Design/methodology/approach High-speed photography is used to observe the early wetting and spreading process of the solder on the substrate in real time. The morphology of intermetallic compounds (IMCs) was observed by scanning electron microscopy, and the composition of IMCs micro bumps was determined by energy dispersive spectroscopy. Findings With a roughness range of 0.320–0.539 µm, the solder is distributed in an elliptical trilinear pattern along the grinding direction. With a roughness range of 0.029–0.031 µm, the solder spreads in the direction of grinding and perpendicular, forming a perfect circle (except in the case of Sn63Pb37 solder). The effect of three types of solder on early wettability is Sn63Pb37 > Sn96.5Ag3Cu0.5 > Sn. The wetting behavior is consistent with the Rn∼t model. The rapid spreading stage (Stage I) is controlled by the interfacial reaction with n1 values between 2.4 and 4. The slow spreading stage (stage II) is controlled by diffusion with n2 values between 4 and 6.7. The size of Cu6Sn5 formed on a rough substrate is greater than that produced on a smooth substrate. Originality/value Investigating the effect of solder composition and roughness on early wettability. This will provide a powerful guide in the field of soft brazing.

Investigation of friction and scuffing during loss of lubrication on a high velocity twin-disc test rig

Increasing demands on gear components such as high-pressure and high speeds are aggravated by weight saving strategies eliminating an optional secondary lubrication system during negative g operations or windmilling, which result in loss of lubrication conditions (LOL) and scuffing. In order to understand gear design options able to withstand LOL at high velocities, systematic, fundamental studies on model test-rigs, e.g. twin-disc rigs, are required. For this purpose, a twin-disc rig was designed which is able to perform test at high entrainment velocities of up to 80 m/s and high lubricant injection temperatures. Systematic studies have been carried out in continuous lubrication and LOL condition and evaluated in terms of friction and time-of failure (TOF). A mixed EHL model complemented the experimental matrix for wider range of temperatures and additionally compared the influence of the grinding direction on the lubricant gap.Entrainment velocity showed to have the most prominent influence on friction in continuous mode, mostly for the increase from 8 m/s to 23 m/s, followed by minor changes upon further increase to 30 m/s. The influence of injection temperature was mostly prominent at high entrainment velocities. Contact pressure had the strongest influence on TOF. Comparisons with superfinished disc surfaces exhibited a high increase in TOF and significantly less scuffing damage fractures on the runway.

Detrimental Effect of Surface Mechanical Grinding on Stress Corrosion Behavior of Monel 400 Alloy in Hydrofluoric Acid Vapor

Surface finish or integrity is always an important problem threatening the safety service of components. In this study, the stress corrosion cracking (SCC) and crack initiation behavior of Monel 400 alloy with different surface working treatments (mechanical grinding TD specimen [the grinding direction is perpendicular to the loading direction] and PD specimen [the grinding direction is parallel to the loading direction]) and electrolytic polishing [EP specimen]) in hydrofluoric acid (HF) vapor were compared by conducting slow strain rate test (SSRT) and constant loading test (CLT). Although SSRT can evaluate the enhancement effect of mechanical grinding on SCC susceptibility, it cannot quantify its contribution to the crack initiation stage. The CLT shows the cracking initiation rate of different specimens in order of: EP specimen < TD specimen < PD specimen. For mechanical grinding specimens, local corrosion and cracks are inclined to nucleate at the groove shoulder zone rather groove bottom, which is mainly ascribed to the accumulation of higher corrosion degradation and higher defects at the groove shoulder. As the shoulder edge on the PD specimen is less constrained, it is easier to induce cracking under the synergistic action of stress concentration and preferential corrosion dissolution. The shoulder edge of the TD specimen is not a stress concentration position under tensile loading, and the microcracks formed by grinding are parallel to the loading direction, which is not conducive to the development of microcracks. Therefore, the crack initiation sensitivity of the TD specimen is lower than that of the PD specimen.

Surface integrity and acoustic emission characteristics during slot milling 3D carbon/carbon composites using superabrasive diamond grinding point

This study mainly investigated the effect of machining parameters on surface morphology and defects in three-dimensional carbon/carbon ceramic matrix composites during slotting with superabrasive diamond grinding points. Specifically, it discussed the mechanisms of burr and uncut fiber formation based on the relationship between grinding and fiber directions. The experimental work was conducted under different spindle speeds and feed speeds, revealing that the poor machining surfaces and severe defects occurred at the minimum spindle speed (2000 rpm) with maximum feed speed (160 mm/min), and most uncut fiber defects occurred when the fiber cutting angle exceeded 90°. Acoustic emission (AE) signals were analyzed via signal processing techniques to capture the energy and frequency characteristics of slotting process under various machining parameters. Results indicated that spindle speed had a significant impact on the frequency band distribution of AE signals, while feed speed primarily influenced the stability of signal profiles. The material removal and tool wear mechanisms were examined through SEM micrographs of machined surfaces and grinding points, revealing that fiber debonding and fracture were the primary material removal mechanisms, and were highly dependent on the fiber cutting angle. Abrasive particles with relatively lower cutting velocity at the center of the grinding tool suffered severe damage/wear.

A modified infrared emissivity model accurately determining dynamic temperatures for belt grinding Inconel 718

The temperature of belt grinding significantly influences the quality of Inconel 718 workpieces that are widely used in the aerospace and energy fields. The single-color infrared radiation (IR) camera is frequently used to measure grinding temperatures, where material-surface emissivity is a key parameter. However, accurately calculating surface emissivity in a simple and fast way is still a challenge at present. In this study, a modified fourth-power-law model (MFM), which considers the effects of radiation waveband and background radiation, and takes the ambient temperature, the temperature under emissivity of 1 and the reference temperature as inputs, is proposed to calculate the dynamic surface emissivity in a simple and fast way. The MFM clarifies the physical relationship among the input temperatures, surface emissivity and grinding temperatures. The results of dry, constant-force belt grinding Inconel 718 that was processed by forging and isothermally annealing show that the MFM-determined dynamic surface emissivity and grinding temperatures have relative errors of below 0.5 % and 2.1 %, respectively, which are one or even two orders of magnitude lower than those produced by previous methods. The relevant finite element analysis (FEA) model confirms the elliptical temperature distribution with the largest temperature change rate along the grinding direction on the grinding surface. The established MFM provides a simple and fast way to accurately calculate the dynamic surface emissivity and temperatures for belt grinding Inconel 718, and could be applied in other machining practices.

Multi-classification recognition and quantitative characterization of surface defects in belt grinding based on YOLOv7

Due to the complex and varied surface defects of the belt grinding, the automatic recognition and quantitative characterization of the surface defects is still an issue that needs to be resolved. To characterize surface defects in belt grinding, this study proposed a multi-classification recognition and quantification method. The YOLOv7 algorithm was utilized to detect defects, which would obtain classification and location information of defects. Aiming at the defects with continuous geometric boundaries, an object detection strategy based on Hough straight-line image correction was designed to quantitatively describe the characteristics of the defects in the grinding direction. In order to capture the quantitative information of burn defects without continuous geometric boundaries, an adaptive threshold segmentation approach with correction factors was developed. The results demonstrated that the YOLOv7 performance on our dataset reaches the mAP of 0.907. The suggested quantitative characterization method can effectively quantitatively characterize and analyze the defects.

Rolling contact fatigue resistance and damage evolution of carburized bearing steel treated by surface ultrasonic rolling process (SURP)

The impacts of the surface ultrasonic rolling process (SURP) on the surface morphology, surface microstructure, residual stress distribution, and rolling contact fatigue (RCF) properties of G20Cr2Ni4A carburized bearing steel were studied in this research. The results show that when the RCF rolling direction is perpendicular to the grinding direction, the fatigue peeling of the raceway surface is more serious. SURP not only reduces surface roughness but also enhances the residual compressive stress and hardness of the surface layer, allowing it to resist the initiation and propagation of surface cracks and enhancing RCF life. Fatigue cracks are easily formed between the ground layer and the matrix, according to microscopic analyses of fatigue crack initiation and propagation on the original sample surface. These cracks have the potential to spread down the ground layer, causing the shallow layer of approximately 1 μm to spall off. They also promote crack propagation into the matrix and shorten fatigue life. SURP can cause the ground layer to peel off, making fatigue cracks on the surface more difficult to form and enhancing contact fatigue life.

Fatigue failure mechanism analysis of 1Cr17Ni2 stainless steel blades ground by an abrasive belt

Fatigue failure, as the main failure form of aero-engine blades, has a direct impact on the reliability and service life of aviation equipment. In order to improve the service performance of machined blades, it is necessary to understand the failure process and failure mechanism of blades and then optimize the grinding process. This paper takes abrasive belt grinding of an 1Cr17Ni2 stainless steel blade as the research object and analyzes the fatigue failure mechanism by characterizing the surface morphology, cross-sectional microstructure, and cross-sectional characteristics of the fatigue failure blade. The results show that cracks are prone to propagate in carbon-rich areas with poor mechanical properties inside the material, and the accumulation of large-size carbon-rich areas leads to continuous cracks easily and accelerates crack growth. The grinding process promotes the migration and consumption of surface carbon elements and forms a carbon consumption layer on the surface of the material, which can inhibit the initiation of fatigue cracks. The point-like pits on the ground surface have an adverse effect on the fatigue life and play a role in the initiation of fatigue crack enhancement. The direction of material research and development to homogenize the structure of the material and the direction of anti-fatigue grinding to increase the thickness of the carbon consumption layer on the ground surface and avoid the damage of micro-pits are proposed. The research has important guiding significance for anti-fatigue machining of key components.

An experimental study on the creep feed grinding of laser macro-structured alumina considering constant material removal volume

Engineering ceramics such as alumina have found special applications in aerospace, electronics, and automotive industries due to their superior mechanical and thermal properties. Among these properties, chemical stability at high temperatures, high strength to weight ratio, hardness, strength, wear, and corrosion resistance are of prime importance. Due to these superior properties, processing of these ceramics encounters some difficulties and requires special machining processes such as diamond grinding; in addition to high manufacturing costs, this technique suffers from noticeable challenges such as high grinding forces and temperatures which may lead to serious surface damages. To overcome these challenges, in recent years, laser-assisted grinding has been introduced; in this process, laser source is used to preheat or structuring the workpiece surface in order to reduce grinding forces and temperatures. In this research, first four different patterns were created on alumina using a pulsed laser. Then, these weakened structures were machined using creep feed grinding. In order to provide a better understanding from the effect of each pattern, the volume of the material that can be removed was kept constant in all four patterns. Finally, the effect of created patterns on grinding forces and surface roughness has been studied. Besides, scanning electron microscopy has been used to investigate possible surface damages. The results showed that the normal and tangential forces in the non-structured case were 2 and 2.7 times higher than the forces recorded in the best patterned samples. However, no significant effect of the created patterns on the surface roughness was observed. Furthermore, serious heat damage and cracks were not observed in the structured workpieces, but non-structured workpieces were crushed during operation. Among the created patterns, pattern with perpendicular grooves to the grinding direction was introduced as the best.

Microstructure, interfacial characteristics, and wear performances of Cu–Fe–SiC cermet composites

AbstractThe Cu–Fe metal‐based ceramic grinding wheel material with SiC as abrasive was prepared by the powder metallurgy process of ball milling and hot pressing sintering. Cu–Fe–SiC cermets with Cu:Fe mass ratios of 4:1, 1:1, and 1:4 were designed by changing the composition of metal binder. The phase composition, microstructure, mechanical properties, and grinding properties of Cu–Fe–SiC cermets were systematically studied. The effect of Cu–Fe binder ratio on the microstructure and properties of cermets was analyzed. The results show that with the increase of Fe content, the density and hardness of cermets increase gradually, indicating that the mechanical properties are improved. Because the Fe in the adhesive can react with the abrasive SiC to form the reaction bonding interface, the Cu–80Fe–SiC cermets with higher Fe content have better adherence. The grinding test results of Cu–80Fe–SiC cermet show that the friction coefficient is .341, the surface roughness is 6.64 μm, the residual stresses parallel to the grinding direction are 353.3 MPa, and the residual stresses perpendicular to the grinding direction are 140.9 MPa. With the increase of Fe content, the wear mechanism changes from ploughing and cutting to friction.

THEORETICAL AND EXPERIMENTAL RECOMMENDATIONS FOR THE ELIMINATION OF GRINDING CRACKS DURING THE PROCESSINGOF PERMANENT MAGNETS

The manufacturing technology of permanent magnets has high precision characteristics and is based on extreme dependencies of physical and mechanical properties of magnets from the contents of the alloy, crystalline structure and temperature and force factors during their processing. Grinding of magnets in high-coercivity state relates to low productivity and relatively high flaw regarding cracks and scratches. Quality analysis of the preliminary and terminal size processing of permanent magnets shows that the main defects of the magnets are microcracks, surface cracks, chips. Their appearance during the grinding of the magnets is the consequence of relatively low mechanical characteristics of the alloys, wrong choice of characteristics of the grinding wheel, breaking proper grinding modes, presence of the defects that were formed during the previous technological stages of permanent magnets manufacturing. The objective of this research is the development of theoretical and experimental recommendations for eliminating grinding cracks during permanent magnets processing. The mechanism of grinding cracks appearance was considered regarding to the influence of geometry of structural components and their orientation related to the direction of grinding of the magnets in high-coercivity state. The problem of defining stress-strain state of the surface layer of the grinded magnets in high-coercivity state weakened by the system of foreign inclusions was solved. Analytical balance conditions of the structural defects of hard magnet alloys depending on the coefficient of crack resistance and the value of the contact temperature of grinding which is defined by the technological parameters were discovered. These technological parameters make possible the building of the algorithm for choosing technological parameters that provide the required quality of the processed surfaces. Technological backgrounds for controlling quality characteristics of the parts being grinded using the criteria of maximum allowable temperatures of grinding, heat flow, size of structural parameters, cutting forces, crack resistance coefficients were developed.

Titanium alloys surface integrity of belt grinding considering different machining trajectory direction

The interplay of abrasive grains and materials complicates the grinding of titanium alloys by abrasive belts. Notably, the influence relationship of surface generation for complex curved workpieces such as hollow blades needs to be clarified, making precise control of the surface integrity of complex surfaces difficult in abrasive belt grinding applications. This paper thus proposes a trajectory planning method based on the direction of interaction between grinding grains and materials to reveal its influence law on the surface integrity of complex curved surfaces of titanium alloy with unevenly distributed machining allowances. First, a machining trajectory with different angles between the grinding direction and feed direction is proposed. In order to determine the corresponding experimental scheme for titanium alloy hollow blades. Experimental results are used to analyze the influence of different grinding trajectory directions on the surface roughness, residual stress, surface topography, and accuracy of the contours. The results show that different grinding trajectory directions significantly affect the workpiece’s surface integrity. By varying the grinding trajectory direction, it is possible to reduce the surface roughness of titanium alloy workpieces by approximately 40%, increase the surface residual compressive stress by approximately 50%, provide a finer workpiece surface and improve the consistency of the surface texture. This work is expected to guide the efficient and high-quality machining of complex curved parts such as titanium alloy hollow blades.

Up/down processing modes effects on residual stress for belt grinding

ABSTRACT Belt grinding is increasingly being used to process complex parts because of its ability to achieve flexible, form-following machining. Although the choice between down-grinding or up-grinding is one of the most common issues in process decisions, the influences of the differences in material removal mechanisms remain unclear, especially on surface residual stresses (RS). Thus, this paper focuses on the different grinding direction’s influence on residual stress distribution, followed by a causal analysis of the abrasive cutting mechanism. The results suggest that the up-grinding surface is more prone to compressive RS of σ a due to the different material flow directions close to the machined surface, and has stronger stress amplitudes of σ t due to the increased belt wear caused by the grits entering from the hardened machined surfaces. For both down- and up-grinding, σ a along the grinding trace’s cross-section is symmetrically distributed in a peaked pattern, but σ t is closer to a uniform distribution. One possible reason is that the contact wheel dissipates heat more quickly on both sides than in the center. Besides, the consistency of the RS distribution is better for up-grinding both within the same grinding trace and among different grinding traces.

The effect of tooth cusp morphology and grinding direction on TMJ loading during bruxism

Increased mechanical loading of the temporomandibular joint (TMJ) is often connected with the onset and progression of temporomandibular joint disorders (TMD). The potential role of occlusal factors and sleep bruxism in the onset of TMD are a highly debated topic in literature, but ethical considerations limit in vivo examinations of this problem. The study aims to use an innovative in silico modeling approach to thoroughly investigate the connection between morphological parameters, bruxing direction and TMJ stress. A forward-dynamics tracking approach was used to simulate laterotrusive and mediotrusive tooth grinding for 3 tooth positions, 5 lateral inclination angles, 5 sagittal tilt angles and 3 force levels, giving a total of 450 simulations. Muscle activation patterns, TMJ disc von Mises stress as well as correlations between mean muscle activations and TMJ disc stress are reported. Computed muscle activation patterns agree well with previous literature. The results suggest that tooth inclination and grinding position, to a smaller degree, have an effect on TMJ loading. Mediotrusive bruxing computed higher loads compared to laterotrusive simulations. The strongest correlation was found for TMJ stress and mean activation of the superficial masseter. Overall, our results provide in silico evidence that TMJ disc stress is related to tooth morphology.

Evaluation of Surface Roughness Parameters of HDF for Finishing under Industrial Conditions.

One of the most important properties of the surface of wood-based panels is their roughness. This property determines the way of working with the material in the processes of gluing and surface varnishing. The aim of this study was to determine the effect of various sanding belt configurations and the feeding speed of the conveyor belt during grinding on the surface roughness of high-density fiberboards (HDF). The research material was prepared under industrial conditions. Three types of boards were selected for the tests. After grinding, the roughness parameters were measured both transversely and longitudinally relative to the grinding direction, using a Mitutoyo SJ-210 profilometer and the optical method. Based on ANOVA analysis of the data, it was found that the type of HDF boards used and the configuration of the abrasive belts had a statistically significant impact on the roughness. The samples for which the grinding process was performed with sanding belts of the highest grain size had the lowest roughness. For the amplitude roughness parameters, the direction of roughness measurement had a significant influence. These results may provide valuable guidance for the furniture industry in the preparation of HDF for furniture production.

Surface topography modeling and analysis of camshaft generated by swing grinding process

In conventional grinding (CG), camshafts with wide profiles suffer from poor quality and low efficiency because the large contact area between the grinding wheel and camshaft profile limits the diffusion of grinding temperature, leading to burning defects. Swing grinding (SG) can mitigate these problems as it involves a reciprocating motion along the axis of the grinding wheel; however, the lack of understanding of machined surface topography has restricted its application. Therefore, in this study, a surface topography prediction model was proposed that based on the distribution, shape, and trajectory of grains. The model was verified through experiments, and the mean error was 12% for Rax and 9% for Ray; the roughness along the grinding direction was Rax, and the roughness along the vertical grinding direction was Ray. Compared to CG, SG has a 3% lower Ray. The influence of the wheel speed and feed rate in SG is consistent with that in CG. Rax exhibited a periodic trend with an increase in the swing amplitude and a monotonically decreasing trend with an increase in the swing frequency. The variation trend of Ray with the swing amplitude was the same as that of Rax. Furthermore, Ray exhibited a nonlinear increasing trend with an increase in swing frequency.

A theoretical model to predict the anisotropic characteristics in grinding of diamond conical indenter

Mechanical grinding of a high-precision diamond conical indenter is difficult due to the strong grinding removal rate anisotropy. In the existing literature, theoretical models have been established to predict the strength anisotropy of diamond on the (100), (110) and (111) planes, which provide a theoretical basis for the fabrication of pyramid diamond indenters, such as Berkovich, Vickers or Knoop indenters. However, investigations on the anisotropic characteristics in processing of diamond curved surface are rarely carried out. To solve the anisotropy problem in grinding of diamond conical indenter, this work contributes a theoretical model to predict the anisotropic characteristics in grinding of diamond cone face, and provides an effective method to optimize the grinding direction for enhancing the fabrication precision. Based on a proposed grinding-ability factor model, a general method is developed to analyze the grinding ability along different directions according to the formation process of the cone face. The results suggest that the optimized mechanical grinding direction can be determined by minimizing the standard deviation of the grinding-ability factors of the crystal planes. The proposed method is validated by grinding experiments on indenters, with the <100> or <111> orientation along the indenter axis. The experimental observations confirm that the optimized grinding direction can weaken the pyramid phenomenon, yielding a roundness error of 0.12 μm. In addition, the grinding removal rate-dependent roughness petal phenomenon is suppressed, which considerably enhances the conical surface quality.