Ultrasonic Grinding Research Articles

Visualization of Stress Distribution by Photoelastic Method Under Ultrasonic Grinding Condition

This study investigates phenomena in ultrasonic vibration-assisted grinding. The appropriateness of a stress visualization method is proven through comparison of a Hertzian contact stress analysis using finite element methods. The stress distribution on soda-lime glass caused by a 3-mm-diameter diamond electro-deposited wheel is visualized using a photo-elasticity method. The study compares the local stress concentrations caused by grains with and without ultrasonic wheel vibration. The global reaction force is measured by a dynamometer. The ultrasonic vibration leads to a reduced fluctuation of force, as well as a reduced time-averaged force. It is thought that the ultrasonic vibration causes a smaller local stress beneath the grains, which generates chips. In contrast, typical photo-elasticity methods are applicable for plane stress conditions. However, the stress distribution in a workpiece under a face grinding condition is distributed three-dimensionally, and the stress distribution cannot be recognized directly from the phase difference. Assuming that the stress distribution is sufficiently stable in a wheel rotation, continuously-captured images can be reconstructed to produce a 3D stress distribution, using computed tomography. The experimental tomographic images show a spatially-dispersed phase difference image caused by the electro-deposited wheel, with several discontinuous diamond grains on the end face of the wheel.

System design and experimental research on ultrasonic assisted elliptical vibration grinding of Nano-ZrO2 ceramics

Aiming at the low toughness, high hardness and difficult machining of hard and brittle materials such as Nano-ZrO2 ceramics, a new type of ultrasonic assisted elliptical vibration grinding (UAEVG) system was designed to improve its machinability and grinding quality. The overall frequency equation of the ultrasonic grinding cup-shaped tool transformer (UGCTT) was derived by the integrated nonresonant design method and the length of the conical horn was optimized. The trajectory of abrasive particles was simulated by finite element software and verified by ultrasonic resonance test. Finally, through the experiment of UAEVG Nano-ZrO2 ceramics, the effects of UAEVG method on its surface morphology, roughness and residual stress were explored. The results showed that when the length of the horn was 65 mm after optimization, the transformer had good vibration mode. Simulation and ultrasonic resonance test results showed that the abrasive particles periodically moved in an elliptical shape in the longitudinal radial plane, and the radial and longitudinal amplitude were AR = 7.5 μm and AL = 3.1 μm. The grinding experiments of Nano-ZrO2 ceramics showed that UAEVG could change the grinding mechanism of conventional grinding (CG), reduce the generation of grinding debris and material fracture. When the grinding depth was increased, the plastic processing ratio of the material under UAEVG was significantly larger than that of CG, which could form a better surface topography. The surface roughness increased with the increase of the grinding depth and feed rate, and the surface compressive stress decreased with the increase of grinding depth. UAEVG could reduce the surface roughness by about 30% and increase the residual compressive stress by about 20% compared with CG, which could achieve better grinding surface quality. Therefore, it can be concluded that UAEVG could expand the plastic processing domain, improve the surface integrity and fatigue strength of Nano-ZrO2 ceramics to some extent.

Investigation on grinding force and machining quality during rotary ultrasonic grinding deep-small hole of fluorophlogopite ceramics

Fluorophlogopite ceramics is widely used in the fields of aerospace and biomedicine, and the machining of deep-small hole for fluorophlogopite ceramics is a focus in the field of precision and ultra-precision machining. In this work, the trajectory and brittle-to-ductile transition depth of single abrasive during rotary ultrasonic grinding process were analyzed. The rotary ultrasonic grinding and common grinding tests of deep-small holes for fluorophlogopite ceramics were performed on an ultrasonic vibration and precision machining center. The axial grinding force was obtained by wavelet denoising, the roundness deviation was calculated by using Canny and gray level detection methods, and the internal surface roughness was measured by using laser scanning confocal microscopy. The experimental results indicated that compared with the common grinding, rotary ultrasonic grinding could effectively decrease the grinding force, roundness deviation, and the value of surface roughness. In addition, the grinding force, roundness deviation, and the value of surface roughness decreased as the spindle speed and ultrasonic power increased, and they increased as the feed speed increased. This work was of significance for realizing the high efficiency and precision machining of deep-small holes of the hard-brittle materials.

Investigation of Indentation Zone on K9 Glass under Ultrasonic Vibration Condition Using an Equivalent Mean Contact Pressure

Ultrasonic vibration-assisted grinding (UVAG) is a promising processing method for parts made of hard-brittle material, as a green machining. The material removal mechanism of hard-brittle material in UVAG is not yet fully understood. The mean contact pressure in the mechanical model of material deformation/fracture that is induced by abrasive grit reveals the deformation/fracture level during the material removal of the indentation of hard-brittle material. To investigate the material removal mechanism of K9 glass in UVAG, a new variable, namely, the equivalent mean contact pressure (EMCP) of glass indentation under ultrasonic vibration was proposed as a corresponding variable for mean contact pressure. A series of indentation experiments with/without ultrasonic vibration was carried out to analyze the material fracture of glass as induced by single random-shaped diamond grits. To obtain the EMCP, an equivalent characteristic size of ultrasonic vibration indentation of K9 glass was defined and measured in the experiments. The vertical load, EMCP and the profile features of the indentation zone, such as the equivalent characteristic size and indentation depth, were investigated in the indentation experiments. Subsurface damage of the K9 glass was also investigated by using UVAG and traditional grinding experiments to analyze the significance of the EMCP on material fracture during machining. The experimental results show the EMCP correlated better with the subsurface damage from UVAG than vertical load. Therefore, compared with the load, the EMCP is a better variable to reveal the difference of material removal mechanism between the UVAG and traditional grinding of glasses.

Study on key factors influencing the surface generation in rotary ultrasonic grinding for hard and brittle materials

Rotary ultrasonic grinding (RUG) provides effective solutions for hard and brittle materials processing, but the surface generating mechanism is still unclear. This paper presented a fundamental research for surface forming in RUG processing hard and brittle materials. A new method is pointed out for surface morphology regulating and predicting in engineering ceramics machining. According to the kinematics analysis and fracture mechanics of brittle materials, the surface forming model is developed step by step. The grinding force and material removal rate are discussed for evaluated the RUG process. Depend on the mathematical models, the dynamic association between ultrasonic energy, grinding parameters and surface micro structure were revealed and presented. The surface topography can be simulated and regulated by ultrasonic energy control or grinding parameters adjustment. Micro structure design and high precision machined surface can be realized through theory calculation. Due to the fundamental analysis, a series of simulation and experiment were executed for verify the theory deduction. This model can be served as a fundamental principle for surface topography modification and machining efficiency improvement in RUG.

Research on the matching relationship between ultrasonic-assisted grinding parameters and workpiece surface roughness

As a nontraditional type of processing technology, ultrasonic-assisted grinding (UAG) can effectively improve the surface integrity. A considerable research effort has been devoted to investigate the impact of various processing parameters on surface roughness. However, few studies have been conducted on the effects of matching relationship between different parameters. In this study, the numerical model of a dressed grinding wheel is constructed using a measured diamond pen. Based on the grinding kinematics, the micro surface topography of the workpiece is generated. The relationship between surface roughness and three main processing parameters is studied, and the concept of critical ultrasonic amplitude is proposed. It is found that the ultrasonic grinding can effectively weaken the deterioration of the roughness by increasing the depth of cut, and then, the relationship between the critical ultrasonic amplitude and the depth of cut is obtained. Furthermore, the coupling relation is explained from the angle of a single abrasive grain. Finally, the accuracy of the findings is verified by the experimental results, which may serve as an effective method or reference for the setting of ultrasonic grinding parameters.

The preparation and research of reduced graphene oxide/glass composite fiber

In this article, reduced graphene oxide/glass composite fiber was prepared from mixing graphene oxide and glass powder by ultrasonic dispersion, planetary grinding, high-temperature sintering, and melting wire drawing. The effects of reduced graphene oxide content on the mechanical and electrical properties of the fiber were investigated. Thermal gravimetric analyzer, differential scanning calorimeter, x-ray diffraction, and energy-dispersive x-ray spectroscopy analysis revealed that the graphene oxide was reduced to reduced graphene oxide in the sintering process and the performances of the composite fiber were improved. The tensile strength of reduced graphene oxide/glass composite fiber was 20% higher than the pristine glass fibers by the addition of 0.5 wt% of reduced graphene oxide. Reduced graphene oxide content was positively correlated with composites conductivity, and according to the percolation theory, the percolation threshold of reduced graphene oxide/glass composite fiber was about 0.5 wt%, and the conductivity of the composite fibers was increased by four orders of magnitude compared to the pristine glass fibers when the content of reduced graphene oxide was 0.5 wt%.

Study on grinding force model in ultrasonic vibration-assisted grinding of alloy structural steel

Based on the micro-removal mechanism of the ultrasonic vibration-assisted grinding (UVAG), a new prediction model of alloy structural steel is proposed in this paper. In the grinding process, the abrasive grains mainly go through two stages: plowing stage and chip forming stage. Then, grinding force model of single grain under different material removal modes is established. The thickness of the abrasive grain, the number of grains involved in grinding, and the interference between the abrasive grains are essential factors that affect the grinding force. Considering the influence of ultrasonic vibration on these factors, the grinding force model of the grinding wheel is developed. The ultrasonic grinding experiments are conducted to validate this model. Findings show that the theoretically predicted results are consistent with the experimental results.

Study on the effects of temperature on the equivalent circuit parameters of ultrasonic grinding transducer

The variation characteristics of the ultrasonic grinding transducer equivalent circuit parameters under the effect of temperature were studied in this paper. An ultrasonic grinding transducer equivalent circuit model was established. Then an experimental platform was set up to test the variation regularity of the ultrasonic grinding transducer equivalent circuit parameters at different temperatures. The results have important guiding significance for the control and process design of the ultrasonic grinding.

Semiconductor Quantum Dots as Materials for Lasers Based on Them

Quantum dots (QDs) today belong to the central research objects of many scientific groups. The study of theproperties of structures of small size is important both for the further development of electronics, and for theimprovement of existing semiconductor devices. At present, there are many methods of obtaining QDsobtainingunder the laboratory conditions: the method of ultrasonic grinding, molecular beam epitaxy, pulsed laser ablation,as well as using such methods of chemical synthesis as organometall synthesis, synthesis in reverse micelles,electrothermal synthesis, sol-gel synthesis, synthesis using thiol stabilizers, synthesis in a non-aqueous medium.Nowadays, the most promising methods are based on the use of the phenomenon of self-organization. These aremolecular-beam epitaxy and colloidal chemistry methods, and the latter are used for synthesisof nanosizedcrystals.The band gap width and the energy of luminescence peak are determined by the size of the particles.

Grinding, Machining Morphological Studies on C/SiC Composites

C/SiC composite is a typical material difficult to machine. It is hard and brittle. In machining, the cutting force is large, the material removal rate is low, the edge is prone to collapse, and the tool wear is serious. In this paper, the grinding of C/Si composites material along the direction of fiber distribution is studied respectively. The surface microstructure and mechanical properties of C/SiC composites processed by ultrasonic machining were evaluated. The change of surface quality with the change of processing parameters has also been studied. By comparing the performances of conventional grinding and ultrasonic grinding, the surface roughness and functional characteristics of the material can be improved by optimizing the processing parameters.

Experimental investigations into electric discharge grinding and ultrasonic vibration-assisted electric discharge grinding of Inconel 601

ABSTRACTThe paper presents experimental investigations into electric discharge grinding (EDG) and ultrasonic vibration-assisted electric discharge grinding (UVAEDG) of Inconel 601. The process parameters selected for both processes were duty cycle, discharge current, pulse on time, grinding wheel speed, work speed, and speed ratio to study their influence on responses like surface roughness (Ra) and material removal rate (MRR). It was found that duty cycle, wheel speed, work speed, discharge current, speed ratio, and pulse duration significantly influenced MRR and Ra. It was inferred that MRR increased with increase in duty cycle, wheel speed, current, work speed, and pulse duration in both EDG and UVAEDG processes. It was also inferred that Ra increased with rise in duty factor, pulse on time, and discharge current in EDG and UVAEDG processes.

Removal mechanism of ultrasonic vibration and ELID composite plane grinding based on ultrasonic vibration of nano-ceramic workpiece

To realize the high efficiency mirror surface grinding of hard brittle materials (such as nano-ceramic material), this work firstly constructs an experimental platform for workpiece ultrasonic vibration and ELID combined plane grinding according to the processing mechanism of ultrasonic vibration assisted grinding and ELID grinding; then, based on the removal mechanism of hard brittle material, this work analyzes the kinematics of single abrasive grit with workpiece ultrasonic vibration plane grinding, and studies the effect of ELID plane grinding on the grinding depth; finally, based on the above work, this work proposes the mathematical model of material removal rate for the workpiece ultrasonic vibration and ELID combined plane grinding. Experimental results show that the material removal rate of combined plane grinding increases with the increase of the cutting depth and workpiece speed, the material removal rate of ultrasonic vibration and ELID combined grinding is higher than that of ELID grinding under the same conditions.

Study of temperature field for UVAG of CFRP based on FBG

Ultrasonic vibration-assisted grinding (UVAG) is an effective method for processing carbon-fiber-reinforced plastics (CFRP); on the other hand, how to lower the grinding temperature is always a burning question; thus, it is of great significance to further study the temperature field distribution for processing CFRP. As for UVAG of CFRP, temperature may be measured by the method (multi-point and multi-level layout of FBGs) to study temperature field distribution of CFRP workpieces and corresponding influencing factors and provide a reference basis for improvement of CFRP nondestructive monitoring technology and optimization of UVAG process parameters. A comparison of simulation and experimental results indicates that the weak thermal conductivity and anisotropy of CFRP lead to the elliptical temperature distribution in the same section; what is more, the grinding parameters have great influence on the distribution of temperature except the granularity of the tool.

Distributed capacitance effects on the transmission performance of contactless power transfer for rotary ultrasonic grinding

The contactless rotary transformer has been widely used in rotary ultrasonic machining because of less heat, less vibration, no friction and higher revolving speed. However, the power transfer efficiency of the rotary transformer is rather low. So it is necessary to adopt the method of capacitance compensation to maximum transfer efficiency, and more accurate compensation model will achieve better transmission performance. However, distributed capacitance existing in the primary and secondary winding current compensation models, which will seriously effect accuracy of capacitance compensation. In this study, a new mathematical model of four circuit compensation topologies is proposed, which takes distributed capacitance into consideration. Moreover, a series of experiments are conducted, which focus on the transmission efficiency and output power. The results of experiments have a good consistency with the new model and show higher accuracy compared with the previous models. In addition, the effect of distributed capacitance at different frequencies is also researched.

Simulation investigation into mechanics behaviour in material removal process of ultrasonic assisted grinding of silicon carbide ceramics

Grinding force and stress in the ultrasonic assisted grinding (UAG) influence on the material removal behaviour. In this study, the simulation investigation of the material removal process, by ultrasonic assisted scratching (UAS) of silicon carbide using a single abrasive grain in UAG was conducted, to reveal the grinding force and stress variation behaviour. Conventional scratching (CS) without ultrasonic vibration was also carried out on the same condition for comparison. The results showed that: 1) the cutting forces in UAS undergo a periodic sinusoidal change, whereas those in CS are basically stabilised to a certain level after the tool cuts into the workpiece completely; 2) the stress distribution fields on the cross and top surfaces along the cutting direction become wider in UAS than in CS; 3) the kinetic energy of the grain consumed in UAS is bigger than that in CS, leading to the impact of the grain on the workpiece.

Effect of single grit impacts on initiation and propagation of cracks in ultrasonic assisted grinding of ceramics by using SPH method

In order to investigate the material removal mechanism in vertical ultrasonic assisted grinding (VUAG) of ceramics, single-grit impact simulation is performed by using smoothed particle hydrodynamics (SPH) method. The initiation and propagation of cracks in grinding of Al2O3 ceramics are analysed. In this simulation, the grit is modelled as a rectangular pyramid diamond indenter and the process of grit impacting on workpiece under different impact speeds is simulated. The critical depth of initiation and propagation of lateral crack is observed. The results show that within a certain range of impact speed, the critical depth of lateral crack decreases with the increasing of impact speed. This means that the brittle fractures are more prone to occur in VUAG. Considering that the material micro-fracture is the main mode in ceramics material grinding under ordinary processing conditions, the material removal rate in VUAG can be improved. Moreover, by observing the surface topography, it can be found that the surface roughness becomes smaller when the impact speed increases.

3D surface roughness evaluation of surface topography in ultrasonic vibration assisted end grinding of SiCp/Al composites

In order to investigate the effect of ultrasonic vibration and cutting conditions on surface quality accurately, the grinding experiments of SiCp/Al composites were carried out. And a comprehensive analysis to characterise the machined surface topography with 3D roughness such as amplitude parameters and spatial parameters was presented. The experimental results indicate that the machined surface of ultrasonic vibration assisted end grinding is filled with peaks and dales and the surface texture is almost isotropic. Ultrasonic vibration can tremendously improve the machined surface performance, comparing with conditional grinding. And low surface roughness value can be obtained in the conditions of high spindle speed, large vibration amplitude, low feed rate and small cutting depth.

Calculation and Experimental Study on Residual Stress in Axial Ultrasonic Dry Grinding of 12CrNi4A Material

Calculation and Experimental Study on Residual Stress in Axial Ultrasonic Dry Grinding of 12CrNi4A Material

Design and Simulation of Ultrasonic Horns in Ultrasonic Vibration Machining

Ultrasonic horns are also called ultrasonic shift levers. They magnify ultrasonic vibration amplitude to meet the requirements of ultrasonic machining. To improve the efficiency of ultrasonic grinding, reduce the connecting parts of the lever, and reduce internal stress, the amplitude of the ultrasonic vibration process is defined in this study. The amplitude of the stress and modal simulation was determined using ANSYS was used as the simulation system for ultrasonic horn deformation. The stress and displacement at the end of the ultrasonic horns are the highest; however, the displacement at the node position of the flange is almost zero. The maximum displacement is 14.893 µm, and the minimum displacement is close to zero. Ultrasonic horns in ultrasonic vibration machining meet the requirements of use. It is proved in theory that the performance of the ultrasonic system is reliable and the design is reasonable.