Search Results (28)

The surface quality of diamond wire sawing (DWS) wafers directly affects the efficiency and yield of subsequent processing steps. This paper investigates the motion trajectory of abrasives in ultrasonic-assisted diamond wire sawing (UADWS) and its mechanism for improving surface quality. The influence of ultrasonic vibration on the cutting arc length, cutting depth, and interference of multi-abrasive trajectories was analyzed through the establishment of an abrasive motion trajectory model. The ultrasonic vibration transforms the abrasive trajectory from linear to sinusoidal, thereby increasing the cutting arc length while reducing the cutting depth. A lower wire speed was found to be more conducive to exploiting the advantages of ultrasonic vibration. Furthermore, the intersecting interference of multi-abrasive trajectories contributes to enhanced surface quality. Experimental studies were conducted on monocrystalline silicon (mono-Si) to verify the effectiveness of ultrasonic vibration in improving surface morphology and reducing wire marks during the sawing process. The experimental results demonstrate that, compared with DWS, UADWS achieves a significantly lower surface roughness Ra and generates micro-pits. The ultrasonic vibration induces a micro-grinding effect on both peaks and valleys of wire marks, effectively reducing their peak–valley (PV) height. This study provides a theoretical basis for optimizing UADWS process parameters and holds significant implications for improving surface quality in mono-Si wafer slicing. Full article

The fir-tree blade tenon is an important connection part of the turbine blade; its machining quality directly affects the life and power of the aeroengine. At present, the machining of the blade tenon requires multiple profile grinding processes. This study highlights the whole profile of the grinding processes of K4002 nickel-based superalloy blade tenons in ultrasonic vibration-assisted grinding (UVG). A probability superposition method was utilized to calculate the undeformed chip thickness and contact rate considering the random distribution of the abrasive grains and the overlap of the grinding trajectories. Subsequently, the grinding force, grinding temperature and surface integrity of the blade tenons in conventional grinding (CG) and UVG were investigated. The results indicate that the ultrasonic vibration causes intermittent cutting behavior which can reduce the contact rate to 0.6 at most. The grinding force, grinding temperature and surface integrity are deeply affected by the fir-tree shape of the blade tenon. The maximum grinding force occurs at the start of the full contact stage; surface burnout easily occurs in the middle top area of the blade tenon. Compared to CG, the use of UVG leads to an average reduction in the grinding force and temperature by 20% and 23%, respectively, improving the surface burnout of the K4002 superalloy. Full article

Aluminum matrix composites reinforced with silicon carbide particles (SiCp/Al) are widely used in aerospace fields with excellent properties, such as high specific strength, high specific stiffness, and high thermal conductivity. Due to the heterogeneous structure, its microstructure is one of the determinants of workpiece life, and ultrasonic vibration can improve the surface quality after grinding. Therefore, in this study, ultrasonic vibration-assisted grinding (UVAG) orthogonal tests were designed to study the surface morphology of SiCp/Al and the form of SiC particle removal under different machining parameters based on the SEM observation of the material surface, and to analyze the percentage of different kinds of grinding forces. The results show that the existence of particle fracture force depends on the relative sizes of the maximum undeformed chip thickness and the critical chip thickness. Through surface roughness testing and analysis, the influence of processing parameters on the surface roughness of the material is explored, and it is found that the application of ultrasound reduces the surface roughness of the material, which can be used as a guideline for the surface quality of the grinding process and the optimization of the process parameters. Full article

Ultrasonic vibration-assisted grinding (UVAG) has proven to be beneficial for grinding difficult-to-machine materials. This work attempts to enhance the grinding performance of Inconel 718 through a comprehensive study of UVAG characteristics. Grinding experiments were performed in both dry and Minimum Quantity Lubrication (MQL) environments, and assessment of the grinding forces, specific energy, residual stress, and surface topography was done. A substantial reduction of both surface roughness and grinding force components was observed in UVAG compared to conventional grinding (CG). Utilizing UVAG with MQL at the maximum vibration amplitude led to a 64% reduction in tangential grinding force and a 51% decrease in roughness parameter, R_a, when compared to CG conducted in a dry environment. The high-frequency indentations of the abrasives in UVAG generated compressive residual stresses on the ground surface. Surface parameters pointed to uniform texture and SEM images showed widening of abrasive grain tracks on the workpiece surface during UVAG. The utilization of UVAG under MQL produced a synergistic impact and resulted in the lowest grinding forces, specific energy, and optimal surface quality among all the grinding conditions investigated. Overall analysis of the results indicated that the axial configuration of the vibration set-up is favorable for UVAG, and the high-frequency periodic separation-cutting characteristic of the process improves lubricating efficiency and grinding performance. Full article

Ultrasonic vibration-assisted grinding is a critical method for machining ultra-hard optical molds. However, current ultrasonic-assisted grinding spindles, as essential foundational equipment, face limitations in maintaining ultra-high rotational speed, high precision, and a compact structure during ultrasonic operation. This study presents a novel ultra-precision ultrasonic-assisted high-speed aerostatic spindle for grinding ultra-hard optical molds, developed through theoretical calculations, FEM, and CFD simulations. The spindle features a simple and compact design (φ60 mm outer diameter × 194 mm length), operates at an ultrasonic frequency of 41.23 kHz, and is driven by an impulse turbine providing torque up to 50.4 N•mm, achieving speeds exceeding 40,000 r/min. Aerostatic bearings provide axial and radial load capacities of 89 N and 220 N, respectively. The results demonstrate that the proposed high-speed precision ultrasonic spindle exhibits both feasibility and potential for practical application. Full article

Aluminium nitride (AlN) materials are widely used in heat-dissipation substrates and electronic device packages. However, the application of aluminium nitride ceramics is hindered by the obvious anisotropy and high brittleness of its crystals, leading to poor material surface integrity and high grinding force. With the rapid development of microelectronics, the requirements for the material’s dimensional accuracy, machining efficiency, and surface accuracy are increasing. Therefore, a new machining process is proposed, combining laser and ultrasonic vibration with grinding. The laser–ultrasonic-assisted grinding (LUAG) of aluminium nitride is simulated by molecular dynamics (MD). Meanwhile, the effects of different processing techniques on grinding force, stress distribution, matrix damage mechanism, and subsurface damage depth are systematically investigated and verified by experiments. The results show that laser–ultrasonic-assisted grinding produces 50% lower grinding forces compared to traditional grinding (TG). The microhardness of AlN can reach more than 1200 HV, and the coefficient of friction and wear is reduced by 42.6%. The dislocation lines of the AlN substrate under this process are short but interlaced, making the material prone to phase transformation. Moreover, the subsurface damage depth is low, realising the substrate’s material hardening and wear resistance. These studies not only enhance the comprehension of material build-up and stress damage under the synergistic impact of laser, ultrasonic, and abrasive processing but also indicate that the proposed method can facilitate and realise high-performance machining of aluminium nitride substrate surfaces. Full article

Machining characteristics were applied to topology optimization for machine tool structure design improvement in this study, and the goals of lightweight and high rigidity of the structure were achieved. Firstly, an ultrasonic-assisted grinding experiment was carried out on zirconia to investigate the surface roughness, surface morphology, grinding vibration, and forces. Then, the topology optimization analysis was conducted for structure design improvement, in which the magnitude of the grinding vibration was utilized as the reference for selecting the topology subsystems and the grinding force was used as the boundary conditions of the static analysis in the topology optimization. Hence, columns, bases, and saddles were redesigned for structure stiffness improvement, and the variations in the effective stress, natural frequency, weight, and stiffness of the whole machine tool were compared accordingly. The results showed that the deduced topological shape (model) can make the natural frequency and stiffness of the whole machine tool tend to be stable and convergent with a weight retention rate more than 75% as the design constraint. The subsystem structures with larger effective stress distributions were designated for stiffness improvement in the design. At the same time, the topological shape (model) was also employed in the design for weight reduction, focusing on minimizing redundant materials within the structure. In contrast to the consistency of the modal shapes before and after topological analysis, the sequential number of the modal mode of the machine tool model after topological analysis was advanced by two modes relative to those of the original situation, which means the original machine tool may be out of its inherently resonant frequency range. Also, the natural frequencies corresponding to each mode had an increasing tendency, and the maximum increase was 110.28%. Furthermore, the stiffness of the machine tool also increased significantly, with a maximum of 355.97%, leading to minor changes of the machine tool’s weight. These results confirm that the topology optimization based on machining characteristics proposed in this study for structure redesign improvement and stiffness enhancement is effective and feasible. Full article

WC-10Co-4Cr coating is highly valued for its corrosion resistance and wear resistance when applied using the high-velocity oxy-fuel (HVOF) spraying method. However, conventional grinding (CG) of this coating presents challenges, including substantial grinding forces and elevated surface temperatures. To address these concerns, our study proposed the utilization of ultrasonic vibration-assisted grinding (UVAG) as a means to enhance the machining properties of HVOF-sprayed WC-10Co-4Cr coatings. Comparative experiments were conducted to analyze the impacts of various factors on the grinding forces and surface roughness in UVAG and CG processes. Additionally, the topography of the ground surfaces was examined to gain insights into the material removal mechanism in UVAG. The experimental outcomes reveal significant reductions in tangential and normal grinding forces, amounting to 15.47% and 22.23%, respectively, in UVAG when compared with CG. Furthermore, UVAG led to a roughly 29.14% decrease in ground surface roughness compared with CG. Microscopic analysis of the ground surfaces using scanning electron microscopy (SEM) indicated that ductile removal was the predominant material removal mode in UVAG. Overall, UVAG was found to be effective in diminishing grinding forces, improving ground surface roughness, and enhancing surface integrity when contrasted with CG. These findings introduce a novel approach for processing WC-10Co-4Cr coatings. Full article

Ultrasonic-assisted grinding (UAG) is widely used in the manufacture of hard and brittle materials. However, the process removal mechanism was never elucidated and its potential is yet to be fully exploited. In this paper, the mechanism of material removal is analyzed by ultrasonic-assisted scratching. Three distinct surfaces (S1, S2, and S3) were selected on the basis of the braided and laminated structure of fiber bundles. The ultrasonic-assisted scratching experiment is carried out under different conditions, and the scratching force (SF) of the tested surface will fluctuate periodically. Under the conditions of different feed speeds, depths, and ultrasonic amplitudes, the normal scratching force (SF_n) is greater than the tangential scratching force (SF_t), and the average scratching force on the three surfaces is generally S3 > S2 >S1. Among the three processing parameters, the speed has the most significant influence on the scratching force, while the scratching depth has little influence on the scratching force. Under the same conditions and surface cutting mode, the ultrasonic vibration-assisted scratching force is slightly lower than the conventional scratching force. The scratching force decreases first and then increases with the amplitude of ultrasonic vibration. Because the fiber undergoes a brittle fracture in the ultrasonic-assisted scratching process, the matrix is torn, and the surface residues are discharged in time; therefore, the surface roughness is improved. Full article

This study proposes the mechanism of two-dimensional ultrasonic assisted grinding- electrolysis-discharge generating machining (2UG-E-DM). It analyzed the influence of vibration directions on grinding characteristics and surface morphology through the motion simulation of an abrasive. Comparative experiments with different vibration directions verified the effect of ultrasonic assistance on the weakening of the grinding force, the widening of the surface pits, and the leveling of the surface morphology of SiC_p/Al composites. Simulation analysis of a single abrasive particle verified the test results. The results of machining tests at different amplitudes showed that as the workpiece and tool amplitude increased, the grinding force of the normal force decreased faster than that of the tangential force. The effect of surface electrolysis discharge machining was significant, and the number of exposed particles increased, but the residual height of the surface and the surface roughness were reduced by vibration grinding. When the two-dimensional amplitude was increased to 5 μm, the axial and tangential vibrations increased the grinding domain, and the dragging and rolling of the reinforced particles significantly reduced the surface roughness, which obtained good surface quality. Full article

During the process of internal cylindrical ultrasonic-assisted electrochemical grinding (ICUAECG), both the workpiece and the conductive grinding wheel are rotating, the machining space is closed and narrow, the electrolyte is difficult to spray into the machining area, and the insulation between the workpiece and the machine bed is challenging. According to the machining characteristics of ICUAECG, the structure of a special machine tool was designed to mitigate these problems. In particular, the rotation, electrolyte supply, electric connection, and insulation modes of the workpiece clamping parts were studied, yielding a novel workpiece clamping- and rotating-device design. This structure can fully use the internal space of the hollow spindle of the machine tool, effectively reduce the external moving parts, and achieve the appropriate liquid injection angle of the electrolyte. The ultrasonic vibration system and its installation mechanism, the dressing device of the conductive grinding wheel, and the electric grinding spindle-mounting and -fixing device were analyzed in detail. Then, a special machine tool for ICUAECG was designed, the operability and feasibility of which were verified by experiments involving conductive grinding wheel dressing and ICUAECG. Full article

The grinding force is an important index during the grinding process, which affects the surface quality and other aspects after machining. However, the research on the grinding force of ceramic matrix composites assisted by two-dimensional ultrasonic vibration-assisted grinding is very weak. In this paper, the impact of the relationship between the critical cutting depth and the maximum undeformed chip thickness on the removal mode of ceramic matrix composites was analyzed. On this basis, the grinding force model of two-dimensional ultrasonic vibration-assisted grinding were developed for ductile removal and brittle removal, respectively. Finally, the correctness of the model was verified, and the impact of grinding parameters on the grinding force was analyzed. The experimental results show that compared with the conventional grinding force, the two-dimensional ultrasonic vibration assisted grinding force decreases obviously. When the feed rate and grinding depth increase, the grinding force increases. When the grinding velocity and ultrasonic amplitude increase, the grinding force decreases. Compared with the experimental value, the average relative error of normal grinding force is 8.49%, and the average relative error of tangential grinding force is 13.59%. The experimental and theoretical values of the grinding force have a good fitting relationship. Full article

C/SiC composites are the preferred materials for high temperature resistant (usually above 1500 °C) structural parts in aerospace, aviation, shipbuilding, and other industries. When this kind of material component is processed efficiently by grinding, the damage forms of fiber step brittle fracture and fiber pulling out are often produced on the machined surface/subsurface. The existence of these damage forms deteriorates the quality of the machine surface and may reduce the bending strength of materials to a certain extent. Therefore, it is very important to study the mechanism and the damage law of ordinary grinding and ultrasonic vibration-assisted grinding and take reasonable measures to restrain the machining damage. In this paper, the typical damage forms of C/SiC composites during the end and side grinding are explored. The surface and subsurface damage degree of C/SiC composites during grinding and ultrasonic vibration-assisted grinding were compared. The effects of different process parameters on material damage were compared and analyzed. The results show that the damage forms of ordinary grinding and ultrasonic grinding are basically the same. Compared with ordinary grinding, ultrasonic-assisted grinding can reduce surface damage to a certain extent and subsurface damage significantly. Full article

In the grinding process, the friction energy generated by grains and the workpiece in the grinding zone will affect the service life of the grinding wheel. Ultrasonic-vibration-assisted grinding (UVAG) can reduce the friction force and reduce the generation of friction energy during grinding. In this work, the wear mechanism of grinding wheels in UVAG is discussed in detail from the perspective of the grain grinding trajectory and tribology. The results show that UVAG has a smaller friction force than conventional grinding (CG). Furthermore, when the initial included angles of grains are 90° and 150°, the friction energy of a single grinding surface in UVAG is reduced by 24% and 37% compared with that of CG, respectively. In UVAG, the grains are prone to microfractures, and the self-sharpening ability of the grinding wheel is enhanced, which can obtain a lower grinding force and better grinding surface quality. Full article

This study used a forming grinding wheel to machine an involute spur gear with ultrasonic vibration applied to the gear in order to improve the gear processing technology and enhance the gear processing effect. Conventional grinding and ultrasonic vibration-assisted forming grinding gear (TUVA-FGG) tests were carried out. The effects of grinding parameters, such as spindle speed, feed rate, radial grinding depth, and ultrasonic amplitude, on grinding force, grinding temperature, residual stress, surface roughness, and surface morphology were analyzed. The TUVA-FGG significantly improved processing efficiency. With the increase in spindle speed, the maximum reductions in the normal and tangential grinding forces, grinding temperature, and surface roughness reached 33.6, 24.5, 23.9, and 21.6%, respectively. With the increase in feed rate, the respective maximum reductions were 21.4, 19.7, 20.3, and 16.1%. With the increase in radial grinding depth, these values attained 24.6, 20.3, 21.5, and 17.6%, respectively. Finally, with the increase in ultrasonic amplitude, these reductions reached 21.4, 19.7, 21.5, and 19.4%. The maximum residual compressive stress grew by 30.3, 27.5, 30.9, and 27.5% with the increase of wheel rotation speed, feed speed, radial grinding depth, and ultrasonic amplitude, respectively. TUVA-FGG changed the conventional continuous cutting mechanism between the abrasive grain and workpiece into intermittent cutting, reducing grinding forces, grinding temperature, and surface roughness. Moreover, it increased residual compressive stress and improved the micromorphology of the tooth surface, thus enhancing gear machining efficiency. Full article