Rotary Ultrasonic Machining Research Articles

Investigations on the critical feed rate guaranteeing the effectiveness of rotary ultrasonic machining

Rotary ultrasonic machining (RUM) is a well-known and efficient method for manufacturing holes in brittle materials. RUM is characterized by improved material removal rates, reduced cutting forces and reduced edge chipping sizes at the hole exit. The aim of this study is to investigate the critical feed rate to guarantee the effectiveness of RUM. Experimental results on quartz glass and sapphire specimens show that when the feed rate exceeds a critical value, the cutting force increases abruptly, accompanied by a significant decrease of ultrasonic amplitude. An analytical model for the prediction of critical feed rates is presented, based on indentation fracture mechanic and the theory of impact of vibrating systems. This model establishes the theoretical relationships between the critical feed rate, idling resonant ultrasonic amplitude and spindle speed. The results predicted by the analytical model were in good agreement with the experimental results.

Drilling induced tearing defects in rotary ultrasonic machining of C/SiC composites

Drilling induced tearing defects at the hole exit restrict the reliability of C/SiC production. In this study, the drilling induced tearing defects in rotary ultrasonic machining of C/SiC composites were investigated quantitatively. The mechanism of tearing defect formation was studied through the detailed observation of thrust force. Experimental results indicate a positive dependence of tearing defect on the thrust force. A larger thrust force corresponds to a larger drill displacement during the formation process of tearing defect, resulting in larger tearing defect. RUM can averagely reduce the tearing defect at the hole exit more than 60%. Tearing defects can be further reduced by increasing the spindle speed and the ultrasonic amplitude, or decreasing the feed rate.

Surface grinding of carbon fiber–reinforced plastic composites using rotary ultrasonic machining: Effects of tool variables

Carbon fiber–reinforced plastic composites have many superior properties, including low density, high strength-to-weight ratio, and good durability, which make them attractive in many industries. However, due to anisotropic properties, high stiffness, and high abrasiveness of carbon fibers in carbon fiber–reinforced plastic, high cutting force, high tool wear, and high surface roughness are always caused in conventional machining processes. This article reports an investigation using rotary ultrasonic machining in surface grinding of carbon fiber–reinforced plastic composites in order to develop an effective and high-quality surface grinding process. In rotary ultrasonic machining surface grinding of carbon fiber–reinforced plastic composites, tool selection is of great importance since tool variables will significantly affect output variables. In this work, the effects of tool variables, including abrasive size, abrasive concentration, number of slots, and tool end geometry, on machining performances, including the cutting force, torque, and surface roughness, are experimentally studied. The results show that lower cutting forces and torque are generated by the tool with higher abrasive size, lower abrasive concentration, and two slots. Lower surface roughness is generated by the tool with smaller abrasive size, smaller abrasive concentration, two slots, and convex end geometry. This investigation will provide guides for tool selections during rotary ultrasonic machining surface grinding of carbon fiber–reinforced plastic composites.

An experimental study on rotary ultrasonic machining of Macor ceramic

Macor ceramic has been well recognized as an eminent engineering material which possesses enlarged industrial usage owing to its excellent and versatile properties. However, its fruitful and economic processing is still unanswered. This article has targeted to experimentally investigate the influence of numerous process variables on machining characteristics in rotary ultrasonic machining of Macor ceramic. The impact of different input factors, namely, spindle speed, feed rate, coolant pressure, and ultrasonic power has been appraised on process responses of interest, that is, material removal rate and chipping size. The experimental plan was designed by employing response surface methodology through central composite rotatable design. The variance analysis test has also been performed with a view to observe the significance of considered parameters. Microstructure of machined samples has also been evaluated and analyzed using scanning electron microscope. This analysis has revealed and confirmed the presence of dominated brittle fracture that caused removal of material along with the thin plastic deformation in rotary ultrasonic machining of Macor ceramic. The reliability and competence of the developed mathematical model have been established with test results. The multi-response optimization of machining responses has also been done by utilizing desirability approach, and at optimized parametric setting, the obtained experimental values for material removal rate and chipping size are 0.4762 mm3/s and 0.3718 mm, respectively, with the combined desirability index value of 0.937.

Experimental investigation of machining characteristics in rotary ultrasonic machining of quartz ceramic

Quartz ceramic has been well observed as one of the highly demanded advanced ceramics which is receiving enlarging industrial approbation owing to its excellent and superior properties. However, its fruitful processing with traditional and non-traditional machining methods is still a challenge. The current article has aimed to experimentally investigate the influence of several process variables, namely, spindle speed, feed rate, coolant pressure, and ultrasonic power on machining characteristics of interest, i.e. chipping size, and material removal rate in rotary ultrasonic machining of quartz ceramic. Response surface methodology has been employed to design the experiments and the variance analysis test has also been performed with a view to observe the significance of considered parameters. Microstructure of machined samples has also been evaluated and analyzed using scanning electron microscope. This analysis has revealed and confirmed the presence of dominating brittle fracture that caused removal of material along with the slighter plastic deformation in rotary ultrasonic machining of quartz ceramic. The soundness and competence of the developed mathematical model have been established with test results. The multi-response optimization of machining responses has also been done by utilizing desirability approach, and at optimized parametric setting, the obtained experimental values for material removal rate and chipping size are, 0.6437 mm3/s and 1.3326 mm, respectively, with the combined desirability index value of 0.949.

Rotary ultrasonic face grinding of carbon fiber reinforced plastic (CFRP): a study on cutting force model

Carbon fiber reinforced plastic (CFRP) offers excellent mechanical properties, such as high strength, light weight, which makes it widely used in aerospace, transportation, machineries, and industrial applications. However, because of its anisotropic mechanical properties, high hardness, high strength, and poor thermal conductivity, the traditional processing methods are gradually unable to meet the processing needs. Except delamination, glitches, and tearing during processing, there are also other defects, like severe tool wear, larger cutting force, and higher cutting temperature, which make the tool life shortened. The machinability of CFRP materials using conventional machining (CM) techniques has seen a limited improvement over the years. Rotary ultrasonic machining (RUM) is an advanced machining process, which has shown to have specific advantages especially in the machining of CFRP. Many experimental investigations on cutting force in RUM of CFRP have been reported. However, in the literature, there are no reports on the development of a cutting force model for flat surface rotary ultrasonic machining, i.e., rotary ultrasonic face grinding (RUFG). In order to reveal the mechanism of grinding force reduction in RUFG of CFRP, based on material properties of CFRP, the brittle fracture theory approach was adopted and a cutting force model was developed for CFRP in RUFG process. The experiments were carried out and found the affect of the input variables for the cutting force in RUFG. The results were analyzed and discussed. The trends of predicted effects of input variables on cutting force agree well with the trends determined experimentally. Compared with the experimental results, the developed cutting force model was regarded as reasonable.

Investigation on the surface morphology of Si3N4 ceramics by a new fractal dimension calculation method

Rotary ultrasonic grinding machining (RUGM) has been employed in Si3N4 ceramics parts machining widely, and the surface morphology is related with surface friction and wear properties directly. It is necessary to investigation on the surface morphology characterization to improve surface quality. Surface morphology of Si3N4 ceramics for rotary ultrasonic grinding machining was investigated based on fractal theory in the paper. The fractal features of surface morphology have been proved with qualitative and quantitative investigation. Differential box-counting method and peleg-blanket method was applied to calculate fractal dimension, but low calculation accuracy was found. So a new fractal dimension calculation method called perimeter-volume method has been proposed. The results show that the calculation deviation rate of morphology fractal dimension is only 2.5%. Meanwhile, the influence of spindle speed, cutting depth, feed rate and cutting force on fractal dimension has also been investigated. The investigation results provide the support for surface morphology optimization.

Experimental study on rotary ultrasonic machining of alumina ceramic: Microstructure analysis and multi-response optimization

Excellent and superior properties of alumina ceramic make it a one of the highly demanded advanced ceramics in the present competitive scenario of manufacturing and industrial applications. However, its effective and economic processing is still a challenge. The present article has targeted to experimentally investigate the influence of several process variables, namely spindle speed, feed rate, coolant pressure, and ultrasonic power on different machining performances, i.e. surface roughness, and chipping thickness. Response surface methodology has been employed to design the experiments. Microstructure of the machined samples has been evaluated and analyzed through scanning electron microscope. This analysis has revealed and confirmed the presence of plastic deformation of work surface that caused the material removal along with the dominated brittle fracture in the processing of alumina ceramic with rotary ultrasonic machining. The multi-response optimization of machining responses has been done by using desirability approach. At the optimized parametric setting, the obtained experimental values for surface roughness and chipping thickness are found to be 0.215 µm and 0.159 mm, respectively.

Rotary ultrasonic machining of macor ceramic: An experimental investigation and microstructure analysis

ABSTRACTMacor ceramic has been well recognized as a classic engineering material that possesses wide industrial usage owing to its excellent and versatile properties. However, its fruitful and productive processing is still unanswered. The present article attempts to experimentally investigate the influence of numerous process variables on machining characteristics in rotary ultrasonic machining of macor ceramic. The impact of different input factors, namely spindle speed, feed rate, coolant pressure, and ultrasonic power, has been evaluated on the process responses of interest, i.e., surface roughness (SR) and chipping thickness (CT). The experiments are designed by utilizing response surface methodology (RSM) through a central composite rotatable design. The variance analysis test was performed with a view to observe the significance of the considered parameters. Microstructure analysis of the machined samples revealed and confirmed the presence of dominating brittle fracture that caused the removal of material along with a slight plastic deformation of the work surface. The multi-response optimization of machining responses was carried out by utilizing the desirability approach. At optimized parametric setting, the obtained experimental values for SR and CT were found to be 0.523 µm and 0.156 mm, respectively.

Investigations on the edge-chipping reduction in rotary ultrasonic machining using a conical drill

The edge chipping of holes, which is induced by mechanical machining, restricts the applications of brittle materials. Rotary ultrasonic machining is considered a suitable approach to machine holes in brittle materials with a smaller edge-chipping size. However, obvious edge chipping at the hole exit in rotary ultrasonic machining remains observable. In this study, conical diamond core drills with various characteristic angles ( θ) were designed to further reduce the edge-chipping size for rotary ultrasonic machining. Machining tests on quartz glass were conducted to evaluate the effectiveness of this new type of drill. Experimental results show that the conical drill can obviously reduce the edge-chipping size only when certain conditions are satisfied. The mechanism of edge-chipping reduction using a conical drill was revealed by the theoretical analysis and detailed observation of the thrust force and obtained cylinder. To guarantee the feasibility of the conical drill, its characteristic angle should exceed a critical value at a certain feed rate. A higher feed rate requires a higher critical characteristic angle. The other advantage of the conical drill is its ability to suppress the bad effects of increasing the feed rate on the stability of ultrasonic vibration.

Improving hole exit quality in rotary ultrasonic machining of ceramic matrix composites using a compound step-taper drill

Mechanical-machining-induced tearing defects at hole exits restrict the application of C/SiC composites. Rotary ultrasonic machining (RUM) is suitable for hole manufacture in brittle composites, providing reduced tearing size as compared with conventional grinding. Even so, substantial tearing defects at the hole exit remain with RUM. In this study, a novel compound step-taper diamond core drill for RUM of C/SiC was developed to further improve the hole exit quality. Contrastive machining tests were conducted to evaluate the effectiveness of the new type drill. Experimental results show that the compound drill can help reduce the tearing size by 30% on average. Results of variance analysis indicate that there is little dependency of tearing size on processing variables with the compound drill, whereas the common drill shows substantial dependence. Detailed observation of the thrust force reveals that the tearing size reduction using the compound drill is due to the reprocessing effects of its taper face. In the reprocessing process of the taper face, the thrust force gradually decreases at the hole exit. Increasing the ultrasonic amplitude can help further improve the hole exit quality when using our compound drill.

Investigation of machining characteristics in rotary ultrasonic machining of alumina ceramic

ABSTRACTAlumina ceramic is well documented as a much-demanded advanced ceramic in the present competitive structure of manufacturing and industrial applications owing to its excellent and superior properties. The current article aimed to experimentally investigate the influence of several process variables, namely: spindle speed, feed rate, coolant pressure, and ultrasonic power, on considered machining characteristics of interest, i.e., chipping size and material removal rate in the rotary ultrasonic machining of alumina ceramic. Response surface methodology has been employed in the form of a central composite rotatable design to design the experiments. Variance analysis testing has also been performed with a view to observing the consequence of the considered parameters. The microstructure of machined rod samples was evaluated and analyzed using a scanning electron microscope. This analysis has revealed and confirmed the presence of plastic deformation that caused removal of material along with brittle fractures in rotary ultrasonic machining of alumina ceramic. The validity and competence of the developed mathematical model have been verified with test results. The multi-response optimization of machining responses (material removal rate and chipping size) has also been attempted by employing a desirability approach, and at an optimized parametric setting the obtained experimental values for material removal rate and chipping size were 0.4166 mm3/s and 0.5134 mm, respectively, with a combined desirability index value of 0.849.

Reduction of edge chipping in rotary ultrasonic machining by using step drill: a feasibility study

The mechanical machining induced edge chipping at hole exit restricts the applications of brittle materials. Rotary ultrasonic machining (RUM) is regarded as a suitable approach for the holes-manufacturing of brittle materials with reduced edge chipping, comparing with conventional grinding. However, obvious edge chipping can still be observed in RUM. In this research, a novel step diamond core drill for RUM was designed to further reduce the edge-chipping size. RUM tests on both quartz glass and sapphire were conducted to evaluate the effectiveness of this new type drill. Experimental results show that the step drill can reduce the edge-chipping size by approximately 60 % without bringing obvious bad influences on the tool life. The mechanism of edge-chipping reduction was revealed by the detailed observation of thrust force and theoretical analysis. In order to guarantee the effectiveness of step drill, the step thickness should be smaller than the thickness of drill end face and the step height should exceed a critical value.

Investigation on surface residual stress distribution and evaluation of engineering ceramics in rotary ultrasonic grinding machining

Residual stress of engineering ceramics is one of surface integrity evaluation indexes affecting the parts’ strength properties. Rotary ultrasonic grinding machining is the most powerful machining method for engineering ceramics with better surface integrity. The residual stress field distribution is changed due to micro cracks which are inevitable in the process. A residual stress distribution model of machined surface micro crack tip has been established in the paper. And the experimental results enable us to obtain surface residual stress distribution of engineering ceramics in rotary ultrasonic grinding machining. Then, we propose an evaluation parameter called confidence stress tolerance to evaluate surface residual stress characteristic. Preliminary results indicate that surface residual stress distribution is in line with the normal distribution. Confidence stress tolerance is an effective parameter to improve the evaluation reliability. Furthermore, precision and affecting factors of confidence stress tolerance evaluation have also been investigated.

Modeling Analysis of Contactless Power Transfer System for Rotary Ultrasonic Machining

In rotary ultrasonic machining (RUM), the traditional power transfer method was achieved by slip ring that cannot cope with high-speed rotary of the tool, which limits the machine potential of RUM. Based on the principle of electromagnetic mutual inductance and the technology of loosely coupled inductively power transfer (LCIPT), a contactless power transfer system (rotary transformer) is built for RUM to achieve its power transfer goal. Resonant Compensation technology is used to enhance the efficiency of the rotary transformer. And the performance of the rotary transformer is validated on Maxwell platform.

Influence of Machining Parameters on Surface Topography of Cubic Boron Nitride at Rotary Ultrasonic Machining

Poly-crystalline cubic boron nitride (PCBN) is one of the hardest known material. Therefore only advanced methods are able to treat such material. Advanced machining methods, proper for machining of hard and brittle materials (such as glass and ceramics) include rotary ultrasonic machining (RUM). This method should achieve high precision and low surface roughness (at least during machining of materials such as ceramics). Achievable roughness is affected by machined material and machining parameters. This contribution investigates influence of machining parameters, such as cutting speed and feed rate, on resultant surface roughness during machining of PCBN by rotary ultrasonic machining.

Influence of Machining Parameters on Machine Tool Loads at Rotary Ultrasonic Machining of Cubic Boron Nitride

Poly-crystalline cubic boron nitride (PCBN) is one of the hardest known material. Therefore only advanced methods are able to treat such material. Advanced machining methods, proper for machining of hard and brittle materials (such as glass and ceramics) include rotary ultrasonic machining (RUM). However, high hardness of workpiece cause higher loads and it could negatively affect achievable accuracy and surface topography. Machine loads are affected by both: machined material and machining parameters. This contribution investigates influence of machining parameters, such as spindle speed, feed rate and depth of cut, on loads of machine tool during machining of PCBN by rotary ultrasonic machining.

Feasibility study on the rotary ultrasonic elliptical machining for countersinking of carbon fiber–reinforced plastics

Carbon fiber–reinforced plastics have been widely applied in aerospace industry as aircraft structural components due to their excellent mechanical and physical properties. The countersinking process of the carbon fiber–reinforced plastic hole is indispensable for the assembly of countersunk head screw. In conventional countersinking process of carbon fiber–reinforced plastics, it is prone to produce the delamination, fiber pullout, poor surface levelness and dimensional accuracy of countersunk hole. As a new technology, the rotary ultrasonic elliptical machining for countersinking of carbon fiber–reinforced plastics is employed, which is a non-traditional process that can effectively improve the surface levelness, surface integrity and machining accuracy of carbon fiber–reinforced plastic countersunk hole. This article reported a feasibility study on the rotary ultrasonic elliptical machining for countersinking of carbon fiber–reinforced plastics without coolant for the first time. The processing principle of rotary ultrasonic elliptical machining for countersinking was illustrated according to the countersinking models and the equations of motion locus. Based on the principle analysis, the surface levelness, tool blades’ path and countersunk hole surface morphology in rotary ultrasonic elliptical machining of the separated and unseparated types were analyzed compared to that in conventional countersinking. In addition, the rotary ultrasonic elliptical vibration transducer was designed and fabricated, as well as the experimental platform was set up. The experimental results demonstrated that the rotary ultrasonic elliptical machining achieved much better results than that in conventional countersinking, such as lower thrust force, torque, cutting temperature, better surface levelness, hole dimensional accuracy, surface integrity and chip-removal effect. The experimental results also verified the feasibility of rotary ultrasonic elliptical machining for countersinking of carbon fiber–reinforced plastics.

Subsurface damage depth and distribution in rotary ultrasonic machining and conventional grinding of glass BK7

The morphology, depth, and distribution of subsurface damage (SSD) on glass BK7 specimens produced in rotary ultrasonic machining (RUM) and conventional grinding (CG) processes with three diamond tools were investigated. The ultrasonic effects on the SSD characteristics were also explored with respect to the material removal mechanisms and the specific kinematics principles of the abrasives. The experimental results demonstrated that the increased cutting velocity would improve the subsurface qualities, while the increased feed speed and cutting depth would deteriorate SSD depth of the RUM/CG specimens. Superimposition with the ultrasonic vibration increased the maximum cutting depth of each abrasive by an amplitude and also resulted in the cyclical variation in abrasive trajectories, hereby worsening the SSD depth of the final RUM surfaces. A large amount of incipient cracks which pulverized the material were just concentrated on the top RUM surface, thus increasing the subsurface crack distributions. With the abrasive moving ahead, these incipient cracks would propagate forward, hereby hindering the nucleation of the fresh cracks, and decreasing the subsurface crack obscurations of the RUM surface at a local level. Some rogue cracks were occasionally found to be located in deeper subsurface of the RUM/CG specimens, and the mutual interactions between the adjacent abrasive indentations would promote the propagations of the subsurface cracks, which gave rise to the nucleation of these rogue cracks.

Simulation and Optimization of Contactless Power Transfer System for Rotary Ultrasonic Machining

In today’s rotary ultrasonic machining (RUM), the power transfer system is based on a contactless power system (rotary transformer) rather than the slip ring that cannot cope with high-speed rotary of the tool. The efficiency of the rotary transformer is vital to the whole rotary ultrasonic machine. This paper focused on simulation of the rotary transformer and enhancing the efficiency of the rotary transformer by optimizing three main factors that influence its efficiency, including the gap between the two ferrite cores, the ratio of length and width of the ferrite core and the thickness of ferrite. The finite element model of rotary transformer was built on Maxwell platform. Simulation and optimization work was based on the finite element model. The optimization results compared with the initial simulation result showed an approximate 18% enhancement in terms of efficiency, from 77.69% to 95.2%.