Ultrasonic Polishing Research Articles

Multiscale model of material removal for ultrasonic assisted polishing of cylindrical surfaces

Ultrasonic assisted polishing is an effective and precise method in engineering production that applies in finishing surface. A multiscale model was developed which is able to forecast the surface micromorphology and material removal rate. Process factors were considered include polishing force, grain diameter, ultrasonic amplitude and so on in this model at different scales. The impact of various process factors on surface roughness and material removal rate were analyzed by orthogonal experimental table. The perfect combination of process parameters was identified, and its effectiveness was verified through both simulations and experimental analysis, with an error rate below 9.43%. To provide a mechanism study of ultrasonic polishing of curved surfaces and optimization of process parameters by this theoretical model.

Acceleration mechanism of abrasive particle in ultrasonic polishing under synergistic physical vibration and cavitation: Numerical study

Ultrasonic technology is widely applied in the engineering ceramic polishing processes without the limitation of material properties and ideally integrated into computer numerical control system. Ultrasonic-induced cavitation and mechanical vibration effect could accelerate the motion of solid abrasives. The individual behaviors of microjet/shockwave of ultrasonic cavitation in gases and liquids, and micro-abrasives with simple harmonic vibrations in solids and liquids has been extensively studied. To conduct a systematic and integrated study of abrasives behavior in the polishing contact region involving abrasive, surround-workpiece wall, ultrasonic physical vibration, and ultrasonic cavitation impact, a novel model integrating the free abrasive motion velocity and fixed abrasive indentation depth under multi-scale contact was proposed according to Hertzian contact theory, Greenwood-Williamson model, indentation deformation theory, the basic equations of cavitation bubble dynamics, cavitation impact control equations, and Newton's law of motion equation. The effects of ultrasonic amplitude, ultrasonic frequency, preloading force and particle size on the proposed model were investigated by theoretical analysis and numerical simulations. Ultrasonic physical vibration mainly influences the dynamic gap and further influence the number of different abrasives. Furthermore, the indentation depth of fixed abrasive depends mainly on the abrasive geometry. As the contact gap and abrasive size decrease, the indentation depth gradually decreases. Under the synergistic effect of cavitation-induced shock wave and microjet, the velocity of free abrasive in this paper is generally 0–150 m/s, and the kinetic energy of free abrasive increases roughly linearly with increasing frequency and approximately as a quadratic function with increasing particle size. Increasing the preloading force leads to a reduction in the abrasive kinetic energy. Besides, the kinetic energy induced by the shock wave has a cliff-like increment at an amplitude of 0.7–0.8 μm. It is revealed that the abrasive kinetic energy is suppressed by the cavitation bubble expansion and collapse at smaller ultrasonic pressure amplitude and surround-wall distance. This research provides a theoretical reference for the modeling of potential defects and material removal on the workpiece surface caused by abrasive motion during polishing, and reduces the trial cost for parameter optimization in actual polishing processing.

Multi-Objective Optimization in Ultrasonic Polishing of Silicon Carbide via Taguchi Method and Grey Relational Analysis.

As high-level equipment and advanced technologies continue toward sophistication, ultrasonic technology is extensively used in the polishing process of difficult-to-process materials to achieve efficiently smooth surfaces with nanometer roughness. The polishing of silicon carbide, an indispensable difficult-to-machine optical material, is extremely challenging due to its high hardness and good wear resistance. To overcome the current silicon carbide (SiC) ultrasonic polishing (UP) process deficiencies and strengthen the competitiveness of the UP industry, the multi-objective optimization based on the Taguchi-GRA method for the UP process with SiC ceramic to obtain the optimal process parameter combination is a vital and urgently demanded task. The orthogonal experiment, analysis of variance, grey relational analysis (GRA), and validation were performed to optimize the UP schemes. For a single objective of roughness and removal rate, the influence degree is abrasive size > preloading force > abrasive content > spindle speed > feed rate, and spindle speed > abrasive size > feed rate > preloading force > abrasive content, respectively. Moreover, the optimal process combination integrating these two objectives is an abrasive content of 14 wt%, abrasive size of 2.5 μm, preloading force of 80 N, spindle speed of 8000 rpm, and feed rate of 1 mm/s. The optimized workpiece surface morphology is better, and the roughness and removal rate are increased by 7.14% and 28.34%, respectively, compared to the best orthogonal group. The Taguchi-GRA method provides a more scientific approach for evaluating the comprehensive performance of polishing. The optimized process parameters have essential relevance for the ultrasonic polishing of SiC materials.

Effects and mechanisms of different types of surfactants on sapphire ultrasonic polishing

The effects of three different types of surfactants, including cationic surfactant cetyltrimethylammonium bromide (CTAB), anionic surfactant sodium dodecyl benzene sulfonate (SDBS), and nonionic surfactant fatty alcohol polyoxyethylene ether (AEO), on sapphire ultrasonic polishing (UV-CMP) were studied. Through XPS, SEM, surface tension, zeta potential and particle size analysis, the implications of surfactants on the chemical products, abrasive adsorption, and material removal rate (MRR) of sapphire surface were investigated. The findings indicate that AEO and SDBS result in a certain degree of abrasive agglomeration and slight particle size increase due to hydrogen bonding and electrostatic repulsion respectively. The cationic surfactant CTAB exhibits significant agglomeration of abrasive particles due to electrostatic attraction, and causes the increase in particle size. The slurry’s surface tension is directly proportional to sapphire MRR within a certain range. The polishing effects are the best when 0.10% CTAB is added. Sapphire MRR is 80.50 nm/min, which is nearly twice as much as that of the slurry without surfactants. The surface roughness is 0.200 nm after polishing.

Profile prediction for ultrasonic vibration polishing of alumina ceramics

Ultrasonic-assisted polishing methods are widely used for the precision processing of hard and brittle materials such as glass and ceramics due to their excellent polishing performance. Most research has been focused on basic removal mechanisms of ultrasonic-assisted polished materials. Some investigators have studied the profile of surfaces after conventional mechanical polishing, but less research has been done on the profile of faces after axial ultrasonically assisted polishing. This paper has established a novel force prediction model for the ultrasonically assisted polishing, which is critical for geometrical accuracy and surface finish. Also a material removal model has been developed for this process using a spherical polishing head at different tilt angles. Pressure and velocity distributions have been calculated for multi-position contact areas. The experimental study of multiple trajectory polishing of alumina ceramics showed a good correlation between the experimental and simulated surface profiles. The ultrasonic polishing process parameters were optimized by applying the gray correlation analysis. The obtained results can be used not only select ultrasonic assisted polishing process parameters but also provide theoretical underpinning for surface polishing trajectory planning.

Preliminary DOE Analysis of the Polishing Process of AISI P20 Mould Steel by Ultrasonic Erosion, Using Alumina and Diamond Hard Particles

The present work examines the surface finishing of AISI P20 tool steel, average hardness of 31.5 HRc, in the polishing process by ultrasonic erosion by loose abrasive particles. The study was performed in laboratory equipment, using various alumina and diamond hard particle sizes, ultrasonic frequencies and times. P20 steel is widely employed in the fabrication of polymer injection mould cavities due to its good machinability, homogeneous microstructure, hardness, corrosion and abrasion wear resistance. Mould cavity polishing processes represents the second longest manufacturing process time required to achieve the mould surface finish for good quality polymer parts. This time-consuming and largely artisanal polishing process contributes to high mould costs. Thus, several studies have been carried out in the literature to automate the mould polishing process, aiming to reducing surface roughness and polishing time. Present investigation was carried out in a surface cleaning equipment by the ultrasonic technique with commercial paste of abrasive hard particles used in mould polishing. Three factors were investigated: abrasive particle size, ultrasonic frequency and polishing time. The investigated alumina particle sizes were 0.05, 0.3, and 1.0 micron and the diamond particle size was 1.5 micron, which are the common sizes available in commercial paste for polishing metallography samples. The studied frequencies of the ultrasonic polishing process were 28 and 40 kHz, and the times of polishing process were 15, 30, and 45 minutes. Analysis of variance (ANOVA) of factor effects and two types of DOE analysis were employed to obtain the roughness Ra outcomes by empirical response surface modelling: 3x3 partial factorial design and 4x2 factorial design were used to investigate the surface roughness. The response surface modelling results indicate that the minimum surface roughness Ra of 0.21 micron obtained by ultrasonic polishing correspond to the frequency of 40 kHz, 20 minutes of polishing and alumina particle size of 0.7 microns.

Investigation of Material Removal Distributions and Surface Morphology Evolution in Non-Contact Ultrasonic Abrasive Machining (NUAM) of BK7 Optical Glasses.

A non-contact ultrasonic abrasive machining approach provides a potential solution to overcome the challenges of machining efficiency in the high-precision polishing of optical components. Accurately modeling the material removal distribution (removal function (RF)) and surface morphology is very important in establishing this new computer-controlled deterministic polishing technique. However, it is a challenging task due to the absence of an in-depth understanding of the evolution mechanism of the material removal distribution and the knowledge of the evolution law of the microscopic surface morphology under the complex action of ultrasonic polishing while submerged in liquid. In this study, the formation of the RF and the surface morphology were modeled by investigating the cavitation density distribution and conducting experiments. The research results showed that the material removal caused by cavitation bubble explosions was uniformly distributed across the entire working surface and had a 0.25 mm edge influence range. The flow scour removal was mainly concentrated in the high-velocity flow zone around the machining area. The roughness of the machined surface increased linearly with an increase in the amplitude and gap. Increasing the particle concentration significantly improved the material removal rate, and the generated surface exhibited better removal uniformity and lower surface roughness.

Synthesis and polishing characteristics of a novel green GO/diamond hybrid slurry under ultrasonic technology

Ultrasonic polishing (UP), as an efficient and clean precision machining process, is increasingly applied in the hard and brittle material processing. To minimize the surface damage and polishing expenses, this paper aims to prepare novel graphene oxide/diamond hybrid slurries (GDS) by ultrasonication, and to investigate the UP mechanisms for silicon carbide (SiC) ceramics on UP and tribological experiments. Findings showed that GDS exhibited superior polishing performance compared to diamond polishing slurries. Moreover, the promotion effect of GDS was more obvious under UP. The surface roughness was improved by 31.62% after UP using GDS with a graphene oxide (GO) content of 0.1 wt%. On the one hand, the lubrication of GO reduce the wear and coefficient of friction. On the other hand, ultrasonic vibration induces stronger impact kinetic energy of abrasives to remove material and allows for a better uniform distribution of GDS to further enhance the lubrication characteristics of GO nanosheets. The application of GO in UP is a processing technology penetrating the manufacturing industry and even human life, laying the foundation for SiC nano-polishing.

Electrorheological fluid–assisted ultrasonic polishing for IN625 additively manufactured surfaces

Electrorheological fluid–assisted ultrasonic polishing for IN625 additively manufactured surfaces

Development of Ultrasonic Vibration-Assisted Magnetic Compound Fluid (MCF) Polishing Technology

This study investigates the development of an ultrasonic vibration-assisted magnetic compound fluid (MCF) polishing technology for final polishing. The fabrication of an experimental apparatus entails an ultrasonic polishing unit, and the experimental investigation of its performance in surface polishing is described. In addition, ultrasonic vibration-assisted MCF polishing under different applied methods of ultrasonic vibration is studied. The experimental results indicate that applying ultrasonic vibration to the workpiece improves the surface roughness and material removal rate when the ultrasonic vibrations are changed. In addition, across the range of polishing conditions employed in this study, the precision surface roughness and high material removal rate can be easily obtained on the acrylic plate by applying an elliptical vibration to the ultrasonic vibration.

Study of the Transcription Effects of Pressing Dies with Ultrasonic Polishing on Glass Molding

The micro lens array (MLA) has played an important role in optical systems for the past few years, and the precision of pressing dies has dominated the quality of MLAs in glass molding. Few studies have covered the transcription effects on surface roughness of pressing dies for this technology. Therefore, this research utilized pressing dies to produce a sine-wave lens array on glass molding, to transform the Gauss-distributed spotlight into a uniform straight one and then characterize the transcription effects of these lenses. Pressing dies with a sine-wave shape were firstly cut by wire electrical discharge machining (WEDM), and then ultrasonic polishing using diamond abrasives was applied to finish the sine-wave surface with an original roughness of 0.2 μm Ra. Next, the sine-wave lens arrays were pressed by glass molding at the appropriate pressure and temperature, before evaluating the transcription effects of transforming the Gauss-distributed spotlight into a uniform straight one. The result showed that the sine-wave lens array stuck easily to the pressing die and then ruptured during glass molding due to the poor surface roughness of pressing tool. However, the diamond abrasive with appropriate sizes could establish good surface roughness on pressing dies via ultrasonic polishing, and the pressing die with a low surface roughness of 0.08 μm Ra was able to successfully perform MLA in the glass molding. However, only pressing dies with a surface roughness smaller than 0.023 μm Ra could produce precision glass lenses to transform the Gauss-distributed spotlight into a uniform straight one.

Ultrasonic dispersion method used in glass polishing experiment

To solve the problems of low processing efficiency and poor glass surface quality when using rare earth polishing powder to grind super-hard K9 glass. The potential, phase structure, surface morphology, and particle size distribution of the nano-rare earth polishing powder were characterized. Compare the evaluation indexes such as polishing efficiency, surface morphology, and contact angle after the polishing process is changed. The results of the comparative study show that the average surface roughness of the glass after heating ultrasonic polishing process is 0.9064 nm, the polishing rate reaches 0.748 μm/min, the average surface roughness of the glass without heating ultrasonic polishing process is 1.3175 nm, and the polishing rate reaches 0.586 μm/min, the ultrasonic assisted polishing process is superior to the conventional polishing process. The heating ultrasonic method provides experimental basis for precise and rapid processing.

Assessment of trapped powder removal and inspection strategies for powder bed fusion techniques

The issue of trapped powder within a part made using powder bed fusion additive manufacturing (AM) is one of the ‘dirty secrets’ of AM, yet it has not received significant attention by the research community. Trapped powders limit the application of AM for complex geometries, including heat exchangers and dies with conformal cooling channels. Being able to detect and remove trapped powder from the build is a necessary step to avoid downstream processing and performance challenges. In this work, ‘powder challenge geometries’ with complex internal features were fabricated via laser powder bed fusion (L-PBF) and electron beam selective melting (EBSM) and were used to assess the effectiveness of several powder removal and inspection methods. Hand-held ultrasonic polishing was explored as a powder removal technique and was shown to effectively clear extremely elongated channels that grit-blasting (the current industry standard) cannot clear. X-ray computed tomography (XCT) and weighing were used to inspect and quantitatively assess the effectiveness of powder removal techniques on the challenge geometries. Using the lesser known ‘vacuum boiling’ powder removal process and the more common ultrasonic bathing process, trapped L-PBF powder was easily removed from the deep channels. Conversely, trapped EBSM powder was difficult to remove using ultrasonic polishing as the powder was sintered inside the channels. It was shown that the powder recovered by the ultrasonic polishing process had size distributions, surface chemistry, morphology and porosity similar to the virgin powder. It is suggested, on these bases, that the recovered powder could likely be recycled without detrimental effects on the process operation.

Material Removal in Ultrasonic Abrasive Polishing of Additive Manufactured Components

Powder-based layered Additive Manufacturing (AM) techniques lead to high surface roughness, due to the balling and partial melting of powders, which cannot satisfy the requirements of design and practical use. Consequently, until there is a significant step-change in the resolution of AM technology, finishing processes will be a necessary step in the additive manufacturing process. In this work, ultrasonic abrasive polishing experiments are conducted with the aim of improving the surface quality of additive manufactured components. The roles of cavitation bubbles and abrasive particles in material removal are discussed. The impact action of abrasive particles is simulated using the Smoothed Particle Hydrodynamics (SPH) method. The effects of ultrasonic output power and the concentration of abrasive suspension on machining characteristics are also examined. It is found that the cavitation bubble collapse in ultrasonic polishing can remove the partially melted structures efficiently, and further roughness improvement could be obtained using the micro-cut and impact of abrasive particles in the slurry. An increase in the ultrasonic output power and abrasive concentration within a certain range lead to a more desirable polishing effect.

Role of a nanoparticle on ultrasonic cavitation in nanofluids

Ultrasonic cavitation in nanofluids improves material removal rate and surface quality. Ultrasonic cavitation in nanofluids was investigated using molecular dynamics simulations. The formation and growth of nanobubbles were promoted, by nanoparticles in water systems. Three distinct impact stages were observed which were caused by the impact of the shock wave, nanojet and nanoparticle. These differed in the system without a nanoparticle. The material removal rate was primarily caused by the nanoparticle hit, a result of the nanobubble collapsing during the third impact. A mechanism of material removal in ultrasonic polishing is discussed at a nanometric level.

Effects of the ultrasonic vibration field on polishing process of nickel-based alloy Inconel718

In view of the hard machinability of nickel-based alloy Inconel718, an axial ultrasonic vibration assisted polishing method was proposed in this paper with the purpose of improving its surface quality and processing efficiency simultaneously. First of all, an ultrasonic polishing experimental platform was built up. The ultrasonic polishing experiments were accomplished on Inconel718 to study the influence of ultrasonic vibration field on polishing quality. The effects of ultrasonic vibration field on the polishing process were investigated by modeling the motion equation and conducting the trajectory simulation of the abrasive particles in polishing fluid. The corresponding analyses results indicate that the introducing of ultrasonic vibration field changes the motion state and trajectory of the embedded and free abrasive particles, thus effectively improving the polishing quality compared with conventional polishing. Furthermore, a correlation coefficient M was put forward to understand the effects of ultrasonic vibration field on the polishing process in detail. The validation experiments indicate that the correlation coefficient M can qualitatively reflect the relation between the strength of ultrasonic vibration and the polishing quality. Meanwhile, the experiments results are highly consistent with the analytic results of the abrasive particles’ motion and trajectory simulation. The correlation coefficient M could be applied to evaluate and direct the ultrasonic vibration assisted polishing process for Inconel718.

Experimental and simulation studies of abrasive particles impacting monocrystalline silicon in suspension thin film flow field of ultrasonic polishing

In ultrasonic polishing (USP), when the gap between the polishing tool and workpiece is small enough, the suspension seeped into it can be considered as suspension thin film (STF). STF flow field provides a periodic oscillation condition for abrasive particles, which can improve abrasive particle cutting performance by changing its behavior. It is very effective for improving the polishing efficiency and surface quality of hard-to-machine materials. However, the interaction behavior of target material, STF flow field, and abrasive particle in USP has rarely been studied. In this paper, to fulfill a fundamental understanding of this field, the behavior of abrasive particles impacting monocrystalline silicon in STF flow field is investigated by experimental and simulation methods. At macro-level, through the study of ultrasonic amplitude, abrasive particle size, and polishing tool rotational speed in USP experiments, the positive role of STF flow field has been revealed, and the change characteristic of surface roughness is obtained. The computational fluid dynamics (CFD) simulation results show that strong transverse shear flow is formed in STF, which plays a major role in material removal. At micro-level, novel mathematical models of plastic deformation and brittleness removal and material removal mechanism of STF flow field are proposed. Comprehensive analysis of blunt and sharp abrasive particles impacting monocrystalline silicon is implemented through finite element method (FEM), which includes the effect of abrasive particle size on material removal rate (MRR), kinetic energy change of abrasive particle, force analysis of impact, the effect of impact angle, and polishing tool rotation on MRR. The final results show FEM simulation results are consistent with that of CFD simulation and experiments, which is of great significance to reveal the behavior principle of abrasive particles in STF and guide the actual production.

A New Vibration Device Applied for Two-Dimensional Ultrasonic Polishing of Biomaterials

For the research of the performance of two-dimensional ultrasonic polishing (TDUP) on the biomaterials, a new vibration device was designed. Meanwhile, our aim is to study the mechanism of multiangle polishing to cope with the complex structure of biomaterials. The device is composed of piezoelectric rings, asymmetric transformer, ultrasonic generator, and so on. The structural dimension parameters were optimized by finite element analysis, and especially the groove size on the transformer was discussed in detail. Two kinds of experiments had been conducted to test the performance of the proposed device, including impedance analysis experiments and amplitudes measurement experiments. Furthermore, a mechanical model to explain the principle of the multiangle polishing was set up, which could assist to analyze the influence of different polishing angles in terms of machining. Finally, the machining experiments and multiangle polishing experiments were carried out to verify the effectiveness of the device. Compared with traditional mechanical polishing, the surface roughness is reduced from 235 nm to 140 nm. The results of multiangle polishing experiments indicate that the surface quality of biomaterials will be prominently affected by different polishing angles. In addition, the polishing mechanism will transform owing to the inversion of the normal velocity during the polishing process with the angle increasing. The surface morphology will also be affected. It has been proven that the experimental results agree with the model well.

CFD simulation and experimental studies of suspension flow field in ultrasonic polishing

With the rapid development of science and technology, hard and brittle materials with high performance have been widely used. Meanwhile, it necessitates the development of compatible machining techniques. As the final processing step of precision component, polishing plays a decisive role. Ultrasonic polishing is a powerful method for improving polishing efficiency and surface quality, especially for hard and brittle materials. In this paper, effects of ultrasonic vibration on suspension flow field have been specifically studied in ultrasonic polishing. At micro level, a mathematical model for analyzing the effects of ultrasonic vibration on the velocity and stress of the inner microelement in polishing suspension flow filed was established. CFD simulation was adopted to study the behavior of polishing suspension flow filed under the action of ultrasonic vibration. It was proved that periodic dynamic changes occur and turbulence form in suspension flow field which are positive for polishing, suspension flow field velocity in x direction near workpiece surface could reach a maximum of about 2.3 m/s, while that in z direction is 0.13 m/s. Material removal thus mainly depends on generated transverse shear flow. And a surface rough change rule was summarized. At macro level, monocrystalline silicon polishing experiments have verified the positive role of ultrasonic vibration, within the same polishing time and polishing head rotation velocity, the surface roughness without ultrasonic vibration reduced from 102 nm to 15 nm, while that with ultrasonic vibration reduced from 109 nm to a minimum of 4 nm, only with ultrasonic amplitude of 15 μm, surface roughness reduced from 98 nm to 27 nm, with the rotation of polishing head and ultrasonic amplitude of 9 μm, 15 μm and 21 μm respectively, the surface roughness reduced to 6 μm, 4 μm and 4 μm respectively. The changes of surface roughness in all experiments were consistent with the summarized rule.

Mechanical Vibration Mechanism Motion Simulation of Ultrasonic Composite Vibration Polishing Equipment

In order to design a kind of mechanical vibration part with stable motion in ultrasonic composite vibration polishing equipment. firstly, the main working principle of ultrasonic composite vibration polishing equipment is briefly introduced. Secondly, the mechanical vibration structure of the design is analyzed theoretically, again, using ADAMS software to simulate the crankshaft connecting rod piston mechanism. When the crankshaft speed is 750r/min, the stroke of the piston is 90mm, which is similar to the theoretical analysis value. Finally, using ANSYS Workbench software to analyze the crankshaft statics. The analysis shows that the design of the mechanical vibration structure is reasonable, which provides a theoretical basis for the study of the mechanical vibration structure of ultrasonic composite vibration polishing equipment.