Grinding Mechanism Research Articles

Experimental analysis and low-damage machining strategy for composite ultrasonic vibration-assisted grinding of silicon carbide based on DA-MLP-NSGA-II algorithm

At present, because of the lack of ultrasonic composite vibration assisted grinding mechanism, neural network optimization algorithm (NNOA) is used to optimize the processing results. In NNOA, multi-layer perceptron (MLP) neural network model and non-dominated sorting genetic algorithm-II (NSGA-II) are very efficient and accurate methods. In this paper, based on the measurement and analysis of the specific ultrasonic vibration device, the CUVAG experiments on silicon carbide (SiC) ceramic were carried out to investigate the influence of processing parameters on the grinding forces, the ground surface roughness and morphology, and the subsurface damage. Then, the brittle-ductile removal behavior of hard-and-brittle materials could be revealed according to the above analysis. After that, MLP model and NSGA-II were utilized to predict and optimize the processing results in CUVAG. The results show that the grinding forces are basically constant, the surface quality deteriorates, and the subsurface damage increases with increased axial vibration amplitude and workpiece infeed speed, but all fluctuate with enlarged wheel speed, and turns at the inflection point of brittle-ductile transition with increased elliptic vibration amplitude. The fitting goodness R2 of the established MLP neural network prediction model is between 0.94 and 0.975, and the process parameters calculated by the NSGA-II optimization algorithm are verified. With optimized processing parameters, the grinding forces are reduced by about 13 %, the surface roughness is reduced to Ra0.037 μm (by 29 %), and the depth of subsurface damage is reduced by 68 %.

Experimental Investigation of Cr12 Steel Under Electrostatic Minimum Quantity Lubrication During Grinding

In this work, electrostatic minimum quantity lubrication (EMQL) has been applied in grinding. When the droplets were charged, it could promote penetrability in the processing area. The electric field formed between the charged droplets and the surface of Cr12 die steel could affect the hardness of the workpiece surface. The grinding mechanism of EMQL has been revealed under different charging voltage by analyzing the wetting angle of droplets and the hardness of Cr12 surface. The reduction of grinding force (11.5% to 49%), surface roughness (10% to 22.1%), and the increase in grinding ratio (1.9% to 27.3%) and surface quality of EMQL under various charging voltages were studied. The results showed that the wetting angle decreased when the droplets were charged. Compared to MQL, the charged lubricant droplets with better penetrability are easier to penetrate and spread on the contact surface between the grinding wheel and the workpiece, thereby improving the lubrication of the friction interface and obtaining better grinding performance. Moreover, we also found that the positively charged EMQL not only effectively improves the penetrability of droplets but reduces the hardness of the Cr12 surface. Thus, the grinding performances under positively charged EMQL are always better than these under negatively charged when grinding Cr12.

Atomic-scale insights into the microstructure and interface evolution mechanism of copper/tantalum nanofilms during ultra-precision grinding

The copper (Cu)/tantalum (Ta) nanofilms are the vital component in the through silicon via (TSV) wafer. However, the current lack of research on the ultra-precision machining of Cu/Ta nanofilms limits the development of TSV-based 3D integration technologies. In this work, molecular dynamics simulations are conducted to reveal the microstructure and interface evolution mechanism of Cu/Ta nanofilms during nano-grinding under various grinding depths. The results show that the material removal mode differs between the Cu and Ta layers, and the thickness of the subsurface damage layer of the Cu layer is greater than that of the Ta layer. The Cu/Ta interface is well stabilized, and small amounts of micro-defects appear only at larger grinding depths after grinding. The lattice mismatch of the constituent layers and the hindering role by the interface lead to stress concentration at the interface, and it is more obvious with increasing grinding depth. Nevertheless, there is a significant stress release after grinding. Our computations indicate that the competition between the evolution of interfacial structures and discrepancies in the physical properties of constituent layers leads to an increase in grinding forces at the interface. Furthermore, the heat transfer is obstructed by the Cu/Ta interface. This study provides valuable insights into the grinding mechanisms of Cu/Ta nanofilms, which is conducive to further improving the manufacturing process of the TSV wafer and enhancing the performance of microelectronic devices.

Research on microscopic fracture mechanism of glass-ceramics grinding surface based on progressive scratch test

Progressive scratch test was carried out on the glass-ceramics to study the continuous micro-fracture mechanism of its surface, which provided an important basis for the research on the grinding mechanism of glass-ceramics. By microimaging of scratch, the continuous material removal process of glass-ceramics from ductility to ductile brittleness to brittleness was observed in micro-view, confirming that there was a ductile brittleness between ductility and brittleness on the surface of glass-ceramics. The critical point for breaking from ductility to ductile brittleness and the critical point for breaking from ductile brittleness to brittleness were measured. The machined critical depth hc1 of the composite domain of ductility and ductile brittleness and the machined critical depth hc2 of the composite domain of ductile brittleness and brittleness for glass-ceramics were further obtained by computational analysis. This study provides valuable insights into the surface machining forming and surface microstructure generating of glass-ceramics material. The research results can also provide reference on determining the critical grinding parameters of glass-ceramics material.

A distinctive material removal mechanism in the diamond grinding of (0001)-oriented single crystal gallium nitride and its implications in substrate manufacturing of brittle materials

Single crystal gallium nitride (GaN) substrates are highly demanded for fabricating advanced optoelectronic devices. It is thus essential to develop high efficiency machining technologies for this difficult-to-machine material, which in turn necessitates a thorough understanding of its deformation mechanism. In this study, the deformation and removal characteristics of (0001)-oriented single crystal GaN involved in diamond grinding were systematically investigated. The material removal exhibited a brittle mode when using relatively coarse diamond abrasives of 2000 in mesh size, while ductile removal was achieved when diamond abrasives of 6000 in mesh size were utilized. A novel peeling phenomenon was observed along (0001) lattice plane (c-plane) in the coarse grinding, as the crystal has a hexagonal crystal structure with c-planes serving as the preferable slip/cracking planes. Peeling observed in material removal agrees well with the findings that lateral planar defects were prone to initiate in nanoscratching in comparison to nanoindentation in the ductile regime, indicating that the effect of tangential grinding force is significant. The application of Molecular dynamics (MD) simulations, employing smaller indentation/scratching models, provided additional confirmation of the crucial role played by lateral force in initiating planar defects on c-planes. Furthermore, larger-scale MD scratching models substantiated the occurrence of peeling in the deformation process on c-plane, a finding corroborated by scratching experiments conducted in the brittle regime. Conversely, such peeling is absent on m- and a-planes. Complementary to the simulations, specifically designed grinding experiments were conducted to empirically demonstrate that peeling phenomena were intensified with elevated rotational wheel speeds. This enhancement was attributed to the increased tangential grinding force associated with higher speeds. These findings contribute to a comprehensive understanding of the intricate relationship between rotational wheel speed, tangential grinding force, and the observed peeling mechanisms in the context of single crystal GaN machining.

Singularity-free practical finite-time force control for a compliant grinding mechanism subject to hysteresis nonlinearity and asymmetric time-varying air pressure constraints

Singularity-free practical finite-time force control for a compliant grinding mechanism subject to hysteresis nonlinearity and asymmetric time-varying air pressure constraints

Mechanism of three-body abrasive grain grinding on GaN textured surfaces under uniform acceleration and variable depth

In this study, molecular dynamics (MD) was used to simulate the three-body grinding process on the textured surfaces of gallium nitride (GaN) and to investigate the effect of the processing parameters during the grinding process on the quality of the process and the removal mechanism of the material. The results show that the friction coefficient, normal force, tangential force, grinding temperature and potential energy increase with the increase of the accelerated interval segment, while the stress, subsurface damage depth and dislocation length decrease. Overall, higher speed value classes in the GaN grinding process are favorable for improving the surface finish quality. In addition, under the conditions of variable depth machining, with the increase of rising speed, the coefficient of friction, the tangential force, the normal force, the potential energy increase, the grinding temperature increases, the stress decreases, and the subsurface damage of the workpiece and the nucleation of dislocations are also significantly reduced, and the surface finish quality and the surface integrity of the workpiece are improved. The textured surfaces is an innovation in GaN processing.

Study on ultrasonic elliptical vibration-assisted grinding mechanism and surface quality of C/SiC composite material

2.5D C/SiC composites have excellent mechanical properties and broad application prospects in the aerospace field. This study investigates the ultrasonic elliptical vibration-assisted grinding mechanism of 2.5D C/SiC composites in different structural directions. A surface roughness prediction model considering abrasive grain protrusion height, brittle-plastic transition of materials and the influence of ultrasonic vibration is established. Experimental results show that material removal involves matrix and fiber fracture, fiber pullout and interface debonding. Ultrasonic vibration causes intermittent cutting, producing finer chip particles and numerous cross microgrooves, reducing subsurface damage. The roughness prediction model is in good agreement with the experimental trend. When the grinding speed is increased from 1 m/s to 8.9 m/s, the surface roughness Ra is reduced by 30.1 %. When the feed speed is increased from 50 mm/min to 650 mm/min, the surface roughness Ra is increased by 47.6 %. When the grinding depth is increased from 0.01 mm to 0.04 mm, the surface roughness Ra is increased by 53.2 %. This study provides a reference for efficient and low-damage processing of fiber-reinforced ceramic matrix composites.

Experimental study on grinding process of Al-Mg2Si aluminum matrix composites

As an aluminum-based reinforcement, Mg2Si particles have excellent properties such as high hardness, high melting point, and high elastic modulus compared with other reinforcements and are widely used in aerospace and automobile fields. However, there is little research on the cutting mechanism of this material. In order to explore the surface grinding mechanism of Mg2Si/Al composites, Grinding simulation of low-volume fraction Mg2Si/Al composites was carried out by ABAQUS, and the influence of different positions of matrix and particle removal on the surface quality of Mg2Si/Al composites was expounded. The plane reverse grinding test was carried out by using CBN (boron nitride) grinding wheel. The L16(43) orthogonal test and three groups of single factor tests were designed. The orthogonal results show that the linear velocity of the grinding wheel has the greatest influence on the surface roughness, and the feed rate and grinding depth are significantly smaller. The range analysis shows that the optimal grinding parameters are: vs = 35 m/s, vw = 0.75 m/min, ap = 0.015 mm. The regression equation for surface roughness was established by using MATLAB. The single factor results show that the surface quality is obviously improved by increasing the linear velocity of the grinding wheel and reducing the feed rate and grinding depth through the observation of the morphology of the processed specimen. The analysis results show that defects such as pits, protrusions, burrs, and a small amount of fish-scale-like on the machined surface are mainly caused by the linear velocity of the grinding wheel, the pulling force of the grinding wheel, and the adhesion of the debris. The defects such as particle micro-cracks, particle pull-out, and matrix cracking on the subsurface, are mainly caused by the compressive stress of the grinding wheel and the stress concentration of the particles. The research results have guiding significance for future composite material cutting research and actual cutting processing.

Brittle-ductile transition mechanism during grinding 4H-SiC wafer considering laminated structure

4H-SiC wafer with alloy backside layer is gradually applied in power devices. However, the laminated structure presents various challenges in manufacturing. In this study, a model for brittle-ductile transition in grinding of laminated materials is established and verified by grinding experiment to ensure the complete removal of the alloy backside layer while achieving ductile removal of the 4H-SiC layer. In the modeling process, the maximum unreformed chip thickness and brittle-ductile transition critical depth of each-layer in the laminated material is deriving, taking into account the laminated structure. Consider the variability in proportion of dynamic active grits during grinding, set operation is introduced to analyze the relationship between sets maximum unreformed chip thickness and brittle-ductile transition critical depth, and to predict the removal mechanism of the 4H-SiC layer. Comparing the predicted results with experimental grinding data, found that under the conditions of grinding wheel with average size of abrasive 10 μm, grinding wheel speed vs of 74 m/s, grinding depth ap of 10 μm, and feeding speed vw of 2 mm/s, the alloy backside layer can complete removal while achieving ductile removal of the 4H-SiC layer. This study provides a new method for predicting removal mechanism in grinding of laminated material and theoretical guidance for optimizing machining parameters of 4H-SiC wafer with alloy backside layer.

Research on Cloud-Edge-Device Collaborative Intelligent Monitoring System of Grinding Wheel Wear State for High-Speed Cylindrical Grinding of Bearing Rings

Aiming at the problems of grinding wheel wear during high-speed cylindrical grinding, communication delays, and slow response during data acquisition, processing, and system operation, an intelligent online monitoring technology frame for CNC manufacturing units is proposed, incorporating a real-time-perception grinding mechanism and a cloud-edge device. Based on the grinding data and grinding wheel wear mechanism, a monitoring model using multi-sensor information fusion is constructed to assess the grinding wheel wear state. In addition, edge data acquisition and online monitoring software have been developed to improve the speed of data transmission and processing. Finally, based on the proposed framework, a cloud-edge device collaborative intelligent monitoring system for assessing grinding wheel wear during high-speed cylindrical grinding of bearing rings is constructed. It improves the grinding quality and efficiency, reduces the grinding cost, and incorporates remote control functionality.

Material Removal Mechanisms of Polycrystalline Silicon Carbide Ceramic Cut by a Diamond Wire Saw.

Polycrystalline silicon carbide (SiC) is a highly valuable material with crucial applications across various industries. Despite its benefits, processing this brittle material efficiently and with high quality presents significant challenges. A thorough understanding of the mechanisms involved in processing and removing SiC is essential for optimizing its production. In this study, we investigated the sawing characteristics and material removal mechanisms of polycrystalline silicon carbide (SiC) ceramic using a diamond wire saw. Experiments were conducted with high wire speeds of 30 m/s and a maximum feed rate of 2.0 mm/min. The coarseness value (Ra) increased slightly with the feed rate. Changes in the diamond wire during the grinding process and their effects on the grinding surface were analyzed using scanning electron microscopy (SEM), laser confocal microscopy, and focused ion beam (FIB)-transmission electron microscopy (TEM). The findings provide insights into the grinding mechanisms. The presence of ductile grinding zones and brittle fracture areas on the ground surface reveals that external forces induce dislocation and amorphization within the grain structure, which are key factors in material removal during grinding.

Chemical mechanical planarization of nanotwinned copper/polyimide for low temperature hybrid bonding

In this study, fully cured low-temperature polyimide (PI) films and 〈111〉, 〈110〉, 〈200〉, and 〈211〉-oriented Cu films on Si wafers were chosen to investigate the grinding effect on Cu/PI pattern wafers. PI is chemically inert and low cost with good mechanical properties, which is a promising material for hybrid bonding. However, it is challenging to remove PI during chemical mechanical planarization (CMP) process. The removal rate of PI is dominated by the abrasive grinding mechanism. By adjusting the mechanical parameters (abrasive type, size, dose, and platen velocity), we explored the desorption/adsorption (Kpad) and repulsion (Krep) coefficients using a modified Langmuir adsorption model. Such a tool enables us to predict and discover the optimal PI grinding interval. Additionally, results showed that the hardness of Cu with different orientations varied and was inversely proportional to the removal rate. It was found that the 〈111〉-oriented nanotwinned Cu (NT-Cu) possessed high surface hardness and low polishing rate, which benefited the CMP process of Cu/PI hybrid joints. The optimal height profile of NT-Cu/PI was adjusted by abrasives and pad types. PI recess was achieved while Cu was protected from further dishing under harsh grinding environment. As characterized by atomic force microscopy, Cu protrusion of 200 nm was obtained, achieving excellent bonding interfaces for the NT-Cu/PI hybrid bonding under a thermal compression bonding (TCB) process at 220 ℃ for 1 h with 8.3 MPa.

Multi-Step Two-Dimensional Ultrasonic-Assisted Grinding of Silicon Carbide: An Experimental Study on Surface Topography and Roughness.

Two-dimensional ultrasonic-assisted grinding (2D-UAG) has exhibited advantages in improving the machining quality of hard and brittle materials. However, the grinding mechanism in this process has not been thoroughly revealed due to the complicated material removal behaviors. In this study, multi-step 2D-UAG experiments of silicon carbide are conducted to investigate the effects of machining parameters on surface quality. The experimental results demonstrate that the tool amplitude and the workpiece amplitude have similar effects on surface roughness. In the rough grinding stage, the surface roughness decreases continuously with increasing ultrasonic amplitudes and the material is mainly removed by brittle fracture with different surface defects. Under semi-finishing and finishing grinding steps, the surface roughness first declines and then increases as the tool amplitude or workpiece amplitude grows from 0 μm to 8 μm and the inflection point appears around 4 μm. The surface damage contains small-sized pits with band-like distribution and localized grooves. Furthermore, the influences of cutting parameters on surface quality are similar to those in conventional grinding. Discussions of the underlying mechanisms for the experimental phenomena are also provided based on kinematic analysis. The conclusions gained in this study can provide references for the optimization of machining parameters in 2D-UAG of hard and brittle materials.

Study on the grinding surface quality of CNTs/2009AL composite material based on minimum quantity lubrication

Carbon nanotube aluminum matrix (CNTs/AL) composites are ideal lightweight and high-strength materials due to their excellent properties. However, the research on CNTs/AL composites only stays in the simulation and preparation stages, and no grinding research has been carried out. Revealing the grinding mechanism of CNTs/AL composites has far-reaching significance for the development of high-end equipment industries such as aerospace. Taking CNTs/2009AL composites as the research object, a minimum quantity lubrication (MQL) flat grinding platform was built for comparing the surface quality and defects of dry grinding and MQL grinding. The experimental results show that grinding wheel velocity was the grinding parameter that had the greatest influence on surface roughness in dry grinding and MQL grinding. The subsurface defects of dry grinding mainly included microcracks, burrs, pits, coatings, cavities, etc., and the rebound phenomenon of agglomerated carbon nanotubes. The subsurface defects of MQL grinding were only burrs and pits. The surface coating phenomenon of dry grinding increased with the increase in grinding wheel velocity, and the surface quality was improved. MQL grinding could significantly reduce grinding heat, reduce friction, and make the machined surface smoother. In dry grinding and MQL grinding, the subsurface damage depth decreased obviously with the increase in grinding wheel velocity. When the grinding wheel velocity was 30 m/s, the minimum subsurface damage depth of dry grinding and MQL grinding was 40.091 and 26.906 μm, respectively. Mastering the grinding mechanism of grinding CNTs/AL composites and the influence of grinding parameters on surface quality provides a basis for the selection of parameters and methods in grinding in industry. MQL grinding of CNTs/AL composites reduces the formation of many surface defects and improves the surface quality of the workpiece. It is an efficient, clean, and environmentally friendly processing method.

Model for surface topography prediction in the ultra-precision grinding of silicon wafers considering volumetric errors

Ultra-precision grinding machine is widely used for thinning silicon wafers. The wafer surface quality is considerably affected by volumetric errors at the functional point of the ultra-precision grinding machine. Therefore, a volumetric error model is established based on the homogeneous transformation matrix (HTM) method. The model is, then, optimized by considering Abbe and Bryan errors induced volumetric errors during the error measurements process. A prediction model for the wafer surface topography is established by combining the manufacturing mechanism of the ultra-precision grinding and the optimized volumetric error model of the ultra-precision grinding machine. Volumetric errors are detected using an author’s group developed laser measurement system and a commercial spindle error analyzer. The model enables to predict the topography and total thickness variation (TTV) of the wafer surface. A group of grinding experiments are performed to verify the effectiveness of the proposed models.

Fracture mechanism of ultrasound-assisted scratching 2D-SiCf/SiC composite fibers with different fiber orientations

The aim of this paper is to investigate the grinding characteristics and mechanism of 2D- SiC/SiC composites with 0°/90° orthogonal anisotropic structured surfaces under different scratching fiber angles (angle between scratch direction and fiber orientation, SFA). A series of surface single abrasive scratching tests were conducted. The effects of the scratch fiber angle on the grinding force, surface morphology and roughness were investigated. The results show that the scratch force and surface roughness at different scratch fiber angles are in the order of 0° > 30°> 45°; SFA also has an important effect on the surface microstructure. The grinding mechanism of 2D-SiCf/SiC composites was analyzed by single-particle scratching test. The results of the scratch force and surface morphology provide strong evidence of the differences produced during the grinding process. The advantages of ultrasonic vibration over conventional machining were further identified by comparing specific scratch energies. This study elucidates the damage behavior of 2D-Sicf/sic composites in correlation with the influence of angle, and these results provide a new guideline for ultrasonic vibratory grinding of woven fiber-reinforced ceramic matrix composites for machining quality.

Building a model of the abrasion grinding mechanism in a tumbling mill based on data visualization

The object of this study is the grinding process in a tumbling mill when the mechanism of destruction by abrasion is implemented, which is caused by the mechanism of shear loading. The abrasive effect due to the impulse interaction during the mutual chaotic movement of granular particles in the shear layer of loading, characterized by the granular temperature, is taken into account. The task solved was determining the parameters of the shear interaction, which is caused by the difficulties of modeling and complexity of the hardware analysis of behavior of the internal loading in the mill. A mathematical model was built based on data visualization for the abrasion grinding mechanism. The power of the shear interaction forces was taken as an analog of the grinding performance. The initial shear characteristic was considered to be the average value of the shear velocity gradient in the central averaged normal section of the shear layer. The impact on productivity of the granular temperature and mass fraction of the shear layer and loading turnover was taken into account. The effect of rotation speed on performance was evaluated by experimental modeling at a chamber filling degree of 0.45 and a relative particle size of 0.0104. The maximum value of the energy and productivity of grinding by abrasion was established at the relative speed of rotation ψω=0.55–0.6. The results have made it possible to establish a rational speed when grinding by abrasion, ψω=0.5–0.6. This value is smaller in comparison with grinding by crushing ψω=0.55–0.65 and breaking ψω=0.75–0.9. The established effect is explained by the detected activation of the chaotic quasi-thermodynamic movement of particles of the shear layer at slow rotation. The model built makes it possible to predict rational technological parameters of the energy-saving process of fine grinding in a tumbling mill by abrasion

Study on nickel-based single crystal superalloy DD6 subsurface damage of belt grinding with a large cutting depth of one pass

Single crystal superalloy has been widely utilized as a crucial manufacturing material for aeroengine turbine blades due to its excellent properties. However, machining this alloy is easy to cause subsurface damage, resulting in the engineering failure of blades. To explore a large cutting depth and low damage processing method, this paper established a grinding depth analytical model for the abrasive belt. The model provides insights into the material removal behavior mechanism during belt grinding and predicts the impact of process parameters on the grinding depth. Subsequently, the grinding experiments of this alloy with different abrasive belts were conducted. The experimental results showed that grinding depth increased as normal force amplified and exhibited a nonlinear growth pattern with the reduction of feed velocity. This preliminary verified the prediction model of grinding depth. The material removal properties of the pyramid, diamond, and hollow-sphere belts were analyzed, and the ratio of material removal capacity for the three was found to be 12:8:5. Based on the analysis of the topography and roughness of the grinding surface, the study examined the influence mechanism of grinding force, feed velocity and abrasive grain morphology on grinding depth and surface quality. The subsurface damage behavior mechanism and recrystallization depth change law of belt grinding were revealed. The grinding depth of the pyramid and diamond belts could exceed 160 μm and the recrystallization depth was less than 5 μm. To achieve efficient and low-damage machining, it is recommended to reduce the feed velocity rather than increase the grinding normal force. It is important to note that the feed velocity should not exceed 10 mm/s. This study is to furnish a theoretical groundwork and offer engineering technical recommendations for achieving large grinding depth and low damage machining of single crystal superalloy.

Grinding mechanism and surface quality evaluation strategy of single crystal 4H-SiC

This paper investigated the removal mechanism and surface quality of single crystal 4 H-SiC during the grinding process, as well as the impact of the measurement area on surface roughness (Sa) during surface morphology detection. This problem is relatively unexplored. Experimental findings suggest that when the measurement area is below 400 µm², there is a greater error in Sa. Conversely, when the measurement area exceeds 400 µm², the error in Sa values is relatively small and stable. The surface quality increases with the increase of wheel speed (vs) and decreases with the increase of workpiece feed rate (vw) and grinding depth (ap). This study finds that the material removal of monocrystalline single crystal 4 H-SiC during the grinding process occurs primarily through plastic deformation, accompanied by brittle fracture.