Search

SiCp/Al composites are widely used in the aerospace field due to their excellent properties. However, the huge difference in the properties of silicon carbide and aluminum matrix materials can easily lead to machining defects. Ultrasonic vibration-assisted machining is an effective method to deal with difficult-to-machine materials. In this study, ultrasonic elliptical vibration is applied to the helical milling of SiCp/Al composites. Firstly, the ultrasonic elliptical vibration-assisted helical milling (UEVHM) cutting-edge trajectory is modeled, and the equation of the UEVHM tool-chip separation condition is established, which lays a foundation for the analysis of the cutting mechanism. Then, the influence of ultrasonic elliptical vibration on the removal mechanism of SiCp/Al composites was investigated by finite element simulation. It was found that UEVHM can reduce the tearing of aluminum matrix and reduce the hole damage by changing the direction of the cutting velocity and the relative position of the cutting edge and particles. Finally, the single-factor experiment was carried out, and the surface morphology and roughness of HM and UEVHM were compared. The influence of process parameters on the surface roughness of UEVHM was analyzed. The experimental results show that compared with HM, UEVHM can reduce surface defects and exit damage, to obtain better surface roughness and exit edge quality. The increase in cutting speed can reduce the roughness, and the increase in pitch and revolution speed will increase the surface roughness. [ABSTRACT FROM AUTHOR]

Freeform micro-structures can exhibit advanced and useful functions of optical components by guiding beam path. Growing interest has been shown in fabricating large-scale 3D freeform micro-structures on hard-to-cut materials as mould for mass production. Currently, ultrasonic vibration-assisted diamond turning is a feasible and efficient technique to fabricate these structures made of steel. However, the tool path linear error increases significantly with the increase in workpiece dimension in fast tool/slow slide servo diamond turning of microstructures with sharp edges. In this research, using Mirrax 40 steel as the mould material and applying a high-frequency ultrasonic tooling system (UTS2) to ease the machining of steel workpiece. To reduce linear error in machining large-scale 3D microstructures, diamond sculpturing instead of diamond turning was applied. This machining technology is called ultrasonic vibration-assisted sculpturing (UVAS). The principle of UVAS, tool path determination, surface generation, tool parameter selection as well as linear error of the tool path and form error induced by ultrasonic vibration kinematics, were comprehensively investigated, in order to fabricate an aspheric microlens array and a freeform microlens array with small theoretical error and reliable slide dynamic response. Furthermore, a large-scale freeform microlens array was fabricated and a measurement method was used to evaluate the machining accuracy. UVAS achieved a form error of less than 0.5 μm and an arithmetic surface roughness Sa of 5 nm for the large-scale freeform microlens array. • Ultrasonic vibration-assisted diamond sculpturing was used to reduce linear error in machining large-scale microstructures. • Form error induced by kinematical overcut in ultrasonic vibration-assisted sculpturing was theoretically clarified. • Tool vibration was eliminated to cut aspheric and freeform microlens arrays by various tool path modification methods. • A method based on finding structural peaks was used to evaluate 3D global form accuracy of large-scale 3D microstructures. [ABSTRACT FROM AUTHOR]

The surface roughness of mechanical parts plays an important role in evaluating the machining performance. However, achieving fine surface finishes on small-diameter shafts through traditional lathes poses challenges due to low cutting speed and workpiece stiffness. To address this issue, in the present work, we applied ultrasonic-assisted vibration aligned with the cutting speed direction to enhance the turning process of small shafts made of C40 Carbon steel or 201 stainless steel. The workpieces were machined by Ultrasonic Assisted Turning (UAT) at three different cutting speeds, ranging from 15 to 36 m/min, while maintaining a constant feed rate and depth of cut. To facilitate comparison with conventional turning (CT), the cutting parameters remained consistent, and both methods were performed for the same duration. UAT necessitates the use of a specialized turning inserts' fixture known as a horn to transmit ultrasonic vibrations from the generator to the tooltip. This study also presents the design methodology and the performance evaluation of the horn. Surface roughness was assessed using the arithmetical mean height, Ra. In UAT, the roughness Ra exhibited the most significant reduction for C40 Carbon steel, reaching a decrease of 308% at a cutting speed of 15 m/min, whereas for 201 stainless steel, Ra did not vary by more than 23% across different cutting speeds. [ABSTRACT FROM AUTHOR]

Exploring advanced green processing technology is the way to achieve efficient precision manufacturing of difficult-to-machine materials and carbon-neutral development. Thus, the design and manufacture of a large-amplitude longitudinal ultrasonic vibration-assisted milling (LALUVAM) toolholder is conducted in this work. For validation of the developed toolholder a TC4 titanium alloy milling experiment is carried out. Multifaceted analysis are presented in terms of milling force, surface roughness, and residual stress. The results indicate that the LALUVAM toolholder exhibits excellent performance in milling TC4 materials. What's more, the disordered tool feed trajectory is eliminated when using the LALUVAM toolholder in milling TC4. Moreover, resultant forces F is reduced 36.61%. The minimum surface roughness and a smaller range of compressive residual stress can be obtained under LALUVAM condition. Meanwhile, a scaled texture can be generated on the surface of TC4 by using harmonic movement of end mill. In the future, LALUVAM toolholder will be able to meet the 10 μm to 20 μm ultrasonic machining and provide better results in terms of reduced milling forces and surface roughness. [ABSTRACT FROM AUTHOR]

High-volume fraction silicon carbide particle-reinforced aluminum (SiCp/Al) has a promising application for its high specific strength, wear resistance, and thermal conductivity. However, SiCp/Al components with a high-volume fraction are prone to poor surface quality and defects such as fractures, cracks, and micro-pits. It has been reported that ultrasonic-assisted grinding machining (UAG) helps to improve the quality of SiCp/Al machined surfaces. However, the differences between SiCp/Al with different volume fractions obtained by UAG machining are not clear. Therefore, a comparative study of surface roughness, morphology, and cutting force was carried out by UAG machining on SiCp/Al samples with volume fractions of 45% and 60%. Compared to the 45% volume fraction SiCp/Al, the 60% volume fraction SiCp/Al has a higher cutting force and roughness under the same machining parameters. In addition, experiments have shown that cutting forces and surface roughness can be reduced by increasing the tool speed or decreasing the feed rate. UAG machining with an ultrasonic amplitude within 4 μm can also reduce cutting forces and surface roughness. However, more than 6 μm ultrasonic amplitude may lead to an increase in roughness. This study contributes to reasonable parameter settings in ultrasonically-assisted grinding of SiCp/Al with different volume fractions. [ABSTRACT FROM AUTHOR]

SiCf/SiC ceramic matrix composites are widely used in high-tech fields such as aerospace and usually processed by grinding methods. In the conventional machining (CON-M), the cutting force during machining is increased due to the hard and brittle characteristics of the material, which affects the surface topography after machining. As a new machining method, longitudinal-torsional coupled rotary ultrasonic machining (LTC-RUM) can effectively reduce the cutting force and improve the surface topography after machining. The machining characteristics of SiCf/SiC ceramic matrix composites in LTC-RUM was investigated to improve the service performance of the material, and reduce the energy consumption. However, relatively few studies have been performed on the machinability of SiCf/SiC ceramic matrix composites by LTC-RUM. This paper studies the cutting force and surface topography during machining by experimental methods. Firstly, the motion characteristics of a single abrasive grain during LTC-RUM are analyzed, and the cutting characteristics of the abrasive grain under the both machining conditions are obtained. Secondly, the effects of spindle speed, feed rate, cutting depth, and ultrasonic amplitude on cutting force and surface roughness were obtained by experimental exploration of CON-M and LTC-RUM. Compared with CON-M, the cutting force is reduced by 64.4%, the surface roughness is reduced by 44.5% under LTC-RUM, and the surface topography is significantly improved. The results of this study provide a theoretical and experimental basis for machining SiCf/SiC ceramic matrix composites. [ABSTRACT FROM AUTHOR]

Rotary Ultrasonic Machining (RUM) stands as a crucial method for machining hard and brittle materials. However, for machining hard-to-machine metal, it continues to face many challenges due to the complex vibration of the milling tool. Flank milling is an efficient method for machining complex parts, such as blisks and impellers, which have been widely used in aerospace field. However, current research is more focused on rotary ultrasonic end milling. In this context, we will study the surface integrity of rotary ultrasonic flank milling 40Cr steel using a self-developed RUM system. We delve into exploring the impacts of tool vibration on surface morphology, residual stress, and micro-hardness of the workpiece under various process parameters. The experimental findings reveal that rotary ultrasonic flank milling, in contrast to traditional flank milling techniques, significantly diminishes the surface roughness by about 40%. The reasons for the reduction of surface roughness are analyzed from the point of view of the cutting force. The surface roughness appears to be notably linked to both the average cutting force and the frequency domain characteristics. In addition, the experimental results indicate that rotary ultrasonic flank milling demonstrates the capacity to elevate the micro-hardness of the machined surface. [ABSTRACT FROM AUTHOR]

Micro-hole is widely used in various fields, and common machining methods of micro-hole in factories are drilling and electrical discharge machining (EDM), but because of low machining efficiency, these methods cannot meet requirements. Therefore, it is urgent to investigate a high efficient micro-hole machining technology to meet the demands of micro-hole machining in factory. Over past few decades, ultrasonic machining technology has developed rapidly and achieved good results in solving many critical machining problems in field of difficult-to-cut materials. Therefore, this paper builds an ultrasonic vibration-assisted drilling (UAD) experiments platform to combine micro-fine small hole drilling with ultrasonic machining technology for micro-hole multi-factor experimental research. Results show that UAD machining of micro-hole below diameter 0.5 mm is comparable to conventional drilling machining because of its high-frequency pulse intermittent cutting process, stable change in machining diameter, good stability of parameters such as shape tolerance roundness and cylindricity, small cutting force during cutting, small tool wear, and small surface roughness of inner wall of micro-hole. Compared with EDM, UAD has high efficiency and good stability of parameters such as diameter and roundness of shape tolerance. Comprehensive analysis of UAD can be used as an alternative technology solution for machining small holes in non-special requirements of metal materials in factory and has technical feasibility of stable batch production. [ABSTRACT FROM AUTHOR]

The increase in demand for aerospace parts leads to a need for effective and efficient machining methods to enhance the machinability of titanium alloys. This research investigates the effect of ultrasonic-assisted turning (UAT) on aerospace titanium alloy Ti-6Al-4V by varying cutting parameters. Ultrasonic turning experiments were conducted to investigate the reduction in cutting forces and tool wear at different cutting parameters with wear and surface roughness analysis. Consequently, a finite element model is used to simulate the ultrasonic turning of titanium to have a better understanding of the effect of UAT on stresses and temperature profiles in the process and help explain the results found experimentally. Separation time between the tool and chip was found to be inversely proportional to the cutting speed and the depth of cut with a reduction in cutting forces and surface roughness of up to 42.5% and 61.4%, respectively, for low cutting speed and depth of cut. Tool wear is also shown to decrease in the ultrasonic machining where adhesion-diffusion wear is reduced on the rake face due to separation in the tool-chip interface. The chip temperature was found to increase while the tool temperature is found to decrease with the motion of the tool. [ABSTRACT FROM AUTHOR]

In this study, an ultrasonic-assisted electrochemical grinding (UAECG) system was designed to improve the low efficiency and tool wear in conventional grinding of hard and tough materials. In this system, multiple-field energy consisting of ultrasonic, electrochemical and mechanical grinding was used. The processing mechanism was investigated to determine the interaction mechanism between ultrasonic, grinding and electrochemical processing. The established theoretical model showed that the processing efficiency was affected by the ultrasonic amplitude, ultrasonic frequency, electrolyte conductivity and other parameters. In verifying the feasibility of UAECG machining and the effect of machining elements on machining, a series of corresponding machining experiments was conducted. Experiments showed that the machining efficiency can be improved by machining through the UAECG system. The material removal rate of W18Cr4V machining was 2.7 times higher than that of conventional grinding and 1.7 times higher than UAG. The processing efficiency of YT15 was increased by 3.2 times when the processing voltage increased from 2 to 6 V. The surface shape and roughness were also affected by these parameters. The surface roughness of the SiCp/Al workpiece reached the best level at 4 V as the machining voltage increased from 2 to 6 V. However, the surface roughness increased significantly when the voltage increased to 6 V. Thus, parameters such as machining voltage must be optimised for efficient and precise machining in practice. [ABSTRACT FROM AUTHOR]

To achieve high precision, stability, and good surface quality when producing micro-dimple arrays on cylindrical surfaces, we propose a new processing method known as radial ultrasonic rolling electrochemical micromachining (RUREMM) in this study. This method is based on the electrochemical micromachining (EMM) and ultrasonic machining principle. The relevant simulation model was created, and ANSYS researched the flow field characteristics of the electrolyte between the array electrodes and the workpiece. Micro-dimple arrays were created on a SS304 cylindrical surface with the consideration of the effects of the machining parameters, including ultrasonic amplitude and applied pulse voltage. Compared with the EMM, the average width of the micro-dimples is reduced by 24.5%, the aspect ratio of the dimple is increased by 108.0%, and the surface roughness of micro-dimples is decreased by 59.7%. In addition, the localization and the surface quality of micro-dimples by RUREMM can be improved when using appropriate machining parameters. [ABSTRACT FROM AUTHOR]

Thin-walled structures have many applications in the aerospace industry. An important feature of them is their high strength to weight. When milling the thin-walled part, the thickness decreases step by step by cutting, which causes the process to be complex and dependent on process parameters. In the present study, thin-walled aluminum structures are investigated using conventional and ultrasonic milling processes, and distortion, surface roughness, surface texture, and average thin-wall forces are also investigated. Therefore, 18 tests are performed on parts made of 7075T6 aluminum alloy using various feeds, spindle speeds, and machining modes. The results showed that the machining type and spindle speed had 47% and 33% effect on distortion, respectively. In addition, the results showed that by applying vibrations to the milling, the amount of distortion can be reduced by up to 30% and effectively optimized. This technique is suitable for manufacturing industries that require high dimensional accuracy. Also, the surface texture and burr formation are investigated. In particular, the surface roughness in ultrasonic milling decreased compared to conventional milling. [ABSTRACT FROM AUTHOR]

Conventional surface grinding can be divided into up grinding and down grinding according to rotation direction of spindle. Nevertheless, the effects and differences of ultrasonic vibration on the two machining methods have been less reported. The influence of ultrasonic vibration amplitude on cutting force, surface roughness and surface topography were investigated in this paper by conducting tangential and radial ultrasonic vibration assisted down/up grinding comparison experiments on SiC. The results showed that the grinding force of down grinding was less than that of up grinding in conventional grinding, while the surface roughness was greater than that of up grinding. The grinding forces of both down grinding and up grinding were reduced to different ratios after applying different ultrasonic vibration, while the surface roughness increased. The grinding force of up grinding decreased and then increased with the increase of amplitude, while the grinding force of down grinding kept decreasing and the surface roughness decreased. The reasons for the differences in cutting forces and surface quality between the two grinding methods after the application of ultrasonic vibration are discussed. By observing the surface morphology, the percentage of ductile area on the machined surface decreases and then increases with the increase of amplitude. [ABSTRACT FROM AUTHOR]

The paper presents the fixtures with movably mounted turning and drilling cutting tools. The fixtures were developed on the principle of oscillating tooltip similar to the principle of the ultrasonic vibration-assisted machining process. However, presented fixtures do not need an electricity source and utilize mainly forced and self-excited oscillations. In general, the tool vibrations during the cutting process are recognized as a negative phenomenon as it causes a shortening of the tool life and worsens the roughness of the machined surfaces. However, a deeper understanding of the cutting process proposes possible positive effects of tool vibration in terms of chip shapes, flank wear, chip volume coefficient, and quality of the machined surface. Experimentally obtained dependence of mentioned quantities is provided in the paper. [ABSTRACT FROM AUTHOR]

Zirconia (ZrO 2) ceramics, as advanced structural ceramics, are gradually used in manufacturing, aerospace and other fields due to their excellent properties. However, it is problematic to process the ZrO 2 ceramics by conventional machining. This study adopted the longitudinal-torsional coupled rotary ultrasonic machining to process the ZrO 2 ceramics. Firstly, the material removal mechanism was clarified in the view of a single abrasive particle. Then, the longitudinal-torsional coupled rotary ultrasonic machining experiment was conducted to explore the effect of processing parameters on the cutting force, hole surface roughness, surface morphology, and single abrasive particle wear with those in the conventional machining. It was found that the cutting force reduced with the spindle speed and ultrasonic power, growing with the feed rate. The hole surface roughness declined with spindle speed, enhanced with feed rate, and decreased first and then increased with ultrasonic power. Compared with the conventional machining, both the cutting force and surface roughness were significantly reduced in the longitudinal-torsional coupled rotary ultrasonic machining. The test results proved that the hole surface quality was improved, and the single abrasive particle wear was reduced in the longitudinal-torsional coupled rotary ultrasonic machining. This study's results are considered instrumental in the longitudinal-torsional coupled rotary ultrasonic machining processing of hard and brittle materials. [ABSTRACT FROM AUTHOR]

Copyright of China Mechanical Engineering is the property of Editorial Board of China Mechanical Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Machining of hard workpieces is one of the most important challenges of the manufacturing industry. Hence, new methods were added to traditional machining. Ultrasonic vibration machining is one of these methods. The advantages of using ultrasonic vibrations compared to traditional machining include reducing machining forces, reducing tool wear and friction, increasing tool life, creating intermittent cutting conditions, increasing surface quality, and so on. To vibrate the tool, a horn with a resonant frequency of 20,633 Hz was analyzed by Abacus software. In this study, the effects of cutting speed, feed rate, conventional machining conditions, and vibration machining conditions at three different hardness of 15, 30, and 45 Rockwell C for the workpiece on surface roughness and tool wear were evaluated. The experiments were designed at full factorial, and a total of 54 experiments were performed. The results showed that at higher workpiece hardness by applying vibration the surface roughness was reduced. The surface roughness (Ra) in machining by means of ultrasonic vibrations is up to about 36% less than conventional machining in various machining parameters. In addition, the temperature in vibration machining is lower about 15% at higher stiffness of the workpiece. Also, with the increase in the hardness of the workpiece, the tool wear was increased, which is less by applying ultrasonic vibrations. Also, by applying vibrations, tool wear was reduced in total, which can be minimized by selecting cermet tools and applying vibrations in 4140 AISI steel machining. [ABSTRACT FROM AUTHOR]

The paper deals with the main nonconventional hybrid micro-machining processes with ultrasonic assistance, starting from basic nonconventional technologies. In introduction, some hybrid processes were presented, like vibration, laser, fluid, magnetic and external electric fields, or carbon nanofibre assisted micro-machining. The study details the means of ultrasonic vibrations were applied, i.e., by vibrating the tool, workpiece or working fluid, and also the effect on output (technological) process parameters, mainly the machinability and removal rate for specific machined material. A comparison was made between the results obtained using classic electrical discharge machining (EDM) and ultrasonically aided EDM (EDM+US). In this case, the surface roughness, the machining rate, and the volumetric relative wear were studied. Finally, the advantages and disadvantages were exposed, and some solutions of output technological parameters for further improvement. [ABSTRACT FROM AUTHOR]

The ultrasonic transducer employing helical slots to generate longitudinal-torsional (L&T) ultrasonic vibration is popular in the field of hard and brittle material machining. However, the design approach for this type of L&T ultrasonic transducer is not well established. An improved design model combining equivalent circuit theory and material parameter equivalent method based on stiffness variation was proposed in this study. The structure parameters of the transducer can be obtained according to given resonance frequency and nodal position. The model can further predict electrical characteristics and mechanical responses under specific excitation. For the preliminary verification of this theoretical model and the optimization of the transducer, finite element analyses were carried out to investigate the influences of slot structure parameters on dynamic performances in terms of resonance frequency, frequency separation, and amplitude of L&T vibration. After that, a prototype was manufactured according to the design results, and the measurements of impedance curve and vibration amplitude were conducted. The experimental results indicate that this prototype resonates at 24,920 Hz with an effective electromechanical coupling coefficient of 0.19. Meanwhile, the vibration amplitude in longitudinal direction is 8.1 μm and that in tangential direction is 5.6 μm under 70-V sinusoidal voltage excitation, which are consistent with the theoretical design and simulation results. Furthermore, machining tests demonstrate that surface roughness reduction and surface quality improvement can be gained by adopting this L&T ultrasonic transducer, compared to using the longitudinal vibration transducer. The proposed design approach was validated and this study can provide guidelines for the design of L&T ultrasonic transducer for rotary ultrasonic machining (RUM). [ABSTRACT FROM AUTHOR]

• A new ultrasonic vibration-assisted machining process for SiCp/Al composites is proposed. • The friction characteristics between tool-workpiece-chip during multidimensional ultrasonic vibratory machining are analyzed. • The coefficient of friction during three-dimensional ultrasonic vibration-assisted milling was experimentally investigated. • The effect of friction coefficient on milling force and surface roughness was investigated. Silicon carbide particle reinforced aluminum matrix composites (SiCp/Al) have excellent mechanical and physical properties and are widely used in the defense and military industry, aerospace, and so on. However, when machining SiCp/Al, due to the large difference in cutting properties between the particles and the base material, the compression and friction on the tool may cause fluctuations in the cutting force, resulting in poor machined surface quality. Therefore, the study of friction characteristics during machining is necessary and of great significance to improve the machining quality of SiCp/Al. A three-dimensional milling processing method with the help of ultrasonic vibration is proposed in this study. The friction-reducing effect of the processing method is then demonstrated by analyzing the friction characteristics of the tool-workpiece and the friction forms of the aluminum matrix and particles when extruded on each cutter surface. Also, four different volume fractions of SiCp/Al, namely 15, 25, 45 and 60%, were machined by milling to investigate the effect of different ultrasonic amplitudes on the friction coefficient, as well as to study the effect of friction coefficient on the milling force and the machined surface. The results show that the larger the volume fraction, the larger the friction coefficient and milling force. Moreover, an increase in amplitude leads to an increase and then a decrease in the friction coefficient. The friction coefficient is reduced by up to 83% compared to conventional milling, and an increase or decrease in the friction coefficient leads to an increase or decrease in the milling force and the roughness of the machined surface. [ABSTRACT FROM AUTHOR]

When processing difficult-to-cut materials, conventional turning (CT) typically suffers from the problems of large cutting force, difficult chip removal, and serious tool wear, resulting in deteriorated processing quality, reduced processing efficiency, and increased processing costs. In addition, special-purpose machine tools used for ultrasonic machining exhibit disadvantages, such as narrow application scope, high manufacturing cost, and poor universality; thus, they are not conducive to being popular in actual production and processing. Accordingly, this study analyzed the characteristics of ultrasonic wave, the mechanism of ultrasonic vibration-assisted turning (UAT), and the formation of a machined surface in UAT. Moreover, the machining system of UAT was established. This system applied an ultrasonic wave vibration device to an engine lathe to meet the requirements of vibration cutting in actual production. Simultaneously, Inconel 718, a typical and widely used difficult-to-cut material, was selected for the experimental study. The machining effect of UAT was analyzed in detail, including surface roughness, surface topography, and chip shape. Results indicated that ultrasonic amplitude, cutting speed, depth of cut, and feed rate exert considerable influences on the machining effect. UAT can achieve this effect, which is difficult to realize via CT, under the condition of a reasonable selection of technological parameters. This research can provide theoretical support and experimental basis for the development and practical application of UAT. [ABSTRACT FROM AUTHOR]

Aluminium 8112 alloy has become a leading material in the aluminium family and currently used in the aerospace and automobile industries due to its excellent chemical and mechanical properties. However, during machining of aluminium alloy, one of the challenges faced by the manufacturing industry is the material adhesion, which increases the rate of chips discontinuity at the machining region and leads to a high surface roughness of the workpiece. The focus of this research is to proffer solutions to this material adhesion by implementing vegetable oil that is copra oil-lubricant, titanium dioxide (TiO2) and multi-walled carbon nanotube (MWCNTs) nano-lubricants during end-milling of AA8112 alloy. Also, using quadratic rotatable central composite design (QRCCD) to study the effects of the machining parameters under minimum quantity lubrication condition, this research used the two-step method to synthesise the nano-lubricants and carried out the homogenisation using the magnetic stirrer and ultrasonic cleaner machine. The study considered five machining factors, including spindle speed, feed rate, length of cut, depth of cut and helix angle. The result from the surface roughness shows that the TiO2 nano-lubricant reduces the surface roughness with 10% and 17% when compared with the MWCNTs nano-lubricant and copra oil. The minimum surface roughness of 1.15 μm, 1.16 μm and 1.35 μm, for the three machining environments, was achieved, respectively. Spindle speed is the most influential machining parameter, followed by the feed rate. The result of this study will aid the manufacturing industry to produce an excellent quality product for a cleaner manufacturing system. [ABSTRACT FROM AUTHOR]

Pocket milling has been regarded as one of the most widely used operations in machining. The surface quality of the machined pockets is an essential aspect of any engineering and medical applications. In the current study, rotary ultrasonic machining (RUM) was applied for milling micro-pockets on alumina (Al2O3) ceramic. The objective of this research was to analyze the effect of the tool overlapping parameters on the surface roughness, surface morphology and the profiles of the machined pockets. Subsequently, the effect of different tool path strategies was analyzed on the surface quality and the material removal rate (MRR) of the machined pockets. A scanning electron microscope is used for analyzing the tool wear mechanisms. The experimental results provide evidence that the surface roughness, surface morphology and the MRR have been significantly affected by the considered tool overlapping and the tool path strategies. Furthermore, among the selected tool overlapping parameters (5–25%) and the tool path strategies, the best surface roughness (Ra = 0.155 μm and Rt = 1.432 µm) of the machined pockets can be found at 20% of the tool overlapping with a mix of uni-directional and zigzag tool path strategy. [ABSTRACT FROM AUTHOR]

The ultrasonic-assisted drilling (UAD) process is a technology that applies ultrasonic vibrations in the feed direction of the drill to improve drilling conditions and productivity. In recent years, UAD has been the subject of extensive research due to its advantages over the conventional drilling (CD) process, these being reported as thrust force and torque reduction, burr height reduction, improvements in surface roughness, and hole accuracy. The results of the research also showed that these benefits do not necessarily equally occur for all drilling conditions but can vary with machining and ultrasonic conditions. In particular, it is found that the drill vibration amplitude is a key factor in determining UAD benefits. However, a critical difficulty is that the all-important matter of the drill vibration amplitude at the point of material engagement, the so-called "down-the-hole" amplitude, is not known due to inaccessibility. This difficulty, not faced, for example by the ultrasonic-assisted turning (UAT) process due to its visual access, has prevented measurement of load effects on UAD, as well as verification of analytical models of the process. In this study, a technique to measure the effect of load on drill vibration amplitude during UAD is presented. The technique is based on examining the surface of the drilled hole, where minute, oscillatory traces of the vibrating drill tip are found that correspond to drill tip vibrational amplitude. This data, when coupled with in-process laser vibration measurements at the drill chuck, as well as no load amplitude measurements, permit the effects of load on vibration amplitude to be determined. Results have shown that drilling loads cause measurable reductions in drill vibration amplitude and must be accounted for in UAD procedures. [ABSTRACT FROM AUTHOR]

Ultrasonic machining (USM) is known for its ability of processing brittle and hard materials such as silicon, glass and quartz. Usually, material removal in conventional USM is in brittle mode. The machined surface is covered with sharp tips and edges. In micro USM, the size of machined feature is less than 1 mm. Different from the conventional USM, in micro USM, it was found that the machined surface is flat and smooth under certain machining conditions. This indicates that the ductile material removal mode exists in micro USM. Based on the experimental observation, the surface roughness, Rpk, is used to identify the existence of ductile material removal mode in micro USM. The impact force of a single abrasive particle is calculated based on the elastic theory and crack generation. In this paper, 3D micro cavities were machined in quartz by micro USM under different machining conditions. Machined bottom surfaces were measured. Experimental results indicate that the brittle and ductile material removal modes are achievable by controlling the static load of micro USM. [ABSTRACT FROM AUTHOR]

Small-diameter CFRP holes have a number of applications such as aerospace structures, circuit boards and rehabilitation medical equipments. High quality hole-making technology for the small-diameter CFRP holes is urgently needed due to various mechanical damages in twist drilling and chip removal clog in core drilling. In order to improve the hole quality, rotary ultrasonic helical machining (RUHM) was developed for machining small-diameter CFRP holes in this paper. The trajectory of cutting edge in RUHM was modelled and the intermittent cutting mode in RUHM was analyzed. Afterwards, the comparison experiments were conducted between RUHM and conventional grinding (CG). The results shows that compared to CG, both thrust force and transverse force were remarkably reduced in RUHM with a maximum decrement of 71.3% and 61.5%, respectively. Meanwhile, both the hole edge quality and surface integrity were significantly improved in RUHM. Compared to CG, delamination factor at hole exit was reduced by 12.8–25.7% and surface roughness for hole inner surface was reduced by 51.9%–53.2% for Ra value in RUHM. Moreover, the mechanisms of cutting force reduction, delamination formation and suppression, and surface roughness improvement in RUHM were also analyzed. The results suggest that RUHM is a promising processing strategy for machining small-diameter CFRP holes. [ABSTRACT FROM AUTHOR]

Highlights • Novel evaluation method of surface roughness based on sampling array. • Mean value and standard deviation of S a on base of Gaussian fitting are applied. • The spatial distribution of S a across the machined surface is presented. • Fracture mechanism of reinforcement fibers mainly depends upon cutting angle. Abstract This paper focuses on the evaluation of surface roughness of carbon fiber reinforced polymer (CFRP) composites after rotary ultrasonic machining. The carried out research involved a novel evaluation method based on sampling array, in which N × N samples are averagely distributed over machined surface. Surface topography of each sample was measured by a white light interferometer and quantitatively characterized by arithmetical mean height (S a). Frequency histogram of S a in sampling array was fitted with Gaussian function. The mean value and standard deviation of Gaussian function were applied to evaluate surface quality of machined surface. The conducted research shows that the critical sampling number is 13 × 13 and the relative error has found to be less than 1%. Moreover, the spatial distribution of S a across the surface has been analyzed innovatively and found that small value of S a takes a large proportion while large one presents strip spatial distribution along feed direction. Fracture mechanism of reinforcement fibers accounts for this phenomenon. This research work provides a foundation for surface quality evaluation of composites and has applications for precision manufacturing industry. [ABSTRACT FROM AUTHOR]

Electrical discharge turning is an emerging modification of die sinking electrical discharge machining process that enables to machine the difficult-to-cut round cylindrical bars. In the present study, the machinability of AISI D2 workpiece was studied while the tool electrode has high-frequency longitudinal vibration. Here, a series of experiments has been carried out taking into account the effect of ultrasonic power, spindle speed, discharge current, pulse on time, and pulse off time to study material removal rate (MRR), surface roughness (Ra), and residual stress (RS). The process has been studied through Taguchi orthogonal design through conducting of 27 experiments. Analysis of variances has also been carried out to find which factor has the greatest effect on process performance. Results indicated that among the factors, pulse current and workpiece rotation have the greatest effect on MRR and SR while the pulse on time is most influential on RS. [ABSTRACT FROM AUTHOR]

Highlights • Ultrasonic machining induced micro-cracks can be completely healed by laser irradiation. • Periodic dimple-like micro-structures were generated as a result of the combined influences of USM and laser irradiation. • Combination of micro-USM and laser irradiation presents a potential for efficient machining of complex micro-optics. Abstract In ultrasonic machining (USM), a mirror-like surface cannot be readily obtained on hard and brittle materials owing to easily generated microcracks. This drawback greatly limits the utilisation of USM as a finish machining technology. Therefore, minimizing the crack size or even eliminating the cracks is necessary to improve surface quality. In this study, fine abrasive particles are first applied to minimize the crack size during USM. Material removal efficiency and surface quality are then evaluated. However, crack formation during this process is unavoidable, and microcracks left on the machined surface cannot be completely removed by merely decreasing the particle size. In addition, minimizing the particle size is not beneficial to maintaining a desired machining rate. Therefore, a new method to repair the cracks by laser irradiation is proposed. The USM machined surfaces of glass plates are irradiated by a carbon dioxide laser at a wavelength of 10.6 μm to repair the cracks because glass has a high absorption coefficient at this wavelength. The temperature field generated during this process is evaluated using the finite element method. Simulation and experimental results demonstrate that the scanning speed of the laser beam has a considerable effect on the temperature increase, thereby influencing the repair result accordingly. Finally, a smoothed surface without cracks is obtained under a scanning speed of 300 mm/min and 5 W power. The combination of micro-USM and laser irradiation exhibits great potential for fabricating various micro-shapes and structures on hard and brittle materials, such as glass with high efficiency, high form precision and high surface quality. [ABSTRACT FROM AUTHOR]

Ceramic materials have tremendous demand in manufacturing sectors. However, poor machinability impedes their widespread applications on an industrial scale. BK-7 falls in the same category and is normally processed by ultrasonic machining. But nowadays rotary ultrasonic machining is overtaking the ultrasonic machining for processing difficult to cut materials because of its superlative material removal mechanism. Current study aims to improve the surface quality of BK7 by studying the effect of input factors on surface roughness during rotary ultrasonic machining. Response surface methodology has been used to observe the effect of input variables ― spindle speed, feed rate and ultrasonic power ― on surface roughness (SR). Thereafter, central composite design was employed to estimate the regression coefficients of quadratic model for surface roughness. Fitness of developed quadratic model was checked by ANOVA test, which also revealed that all the model terms of input factors were significant except feed and speed interaction. Feed has the maximum impact over surface roughness descended by moderate impact of power and spindle speed. The study was further reinforced on observing the surface integrity of processed surfaces using scanning electron microscopic images. Mixed flow of material was observed to occur at lower feed rate and higher levels of rpm and ultrasonic power. [ABSTRACT FROM AUTHOR]

Ultrasonic-assisted machining, which is the application of ultrasonic vibrations to standard or "conventional" machine tools for processes such as drilling, milling, and turning, is a rapidly developing technology aimed at increasing the productivity of machining processes. While a solid foundation is being established through laboratory-based research studies, typically these processes have not yet progressed to fulfill the demanding requirements of the factory floor. The objective of the current work is to transition the ultrasonic-assisted drilling (UAD) process from the laboratory to a production system compatible with automated machining systems. This work details the design and development of an ultrasonic drilling module that has sufficient strength, stiffness, and accuracy for production demands, while maintaining powerful levels of ultrasonic vibrations that result in lowered drilling forces and faster feed rates. In addition, this work will review prior work in UAD, including the development of a module based on a vibration-isolating case using a standard tool holder. Performance of the system is shown to provide thrust force reductions, while maintaining or improving surface finish and drilling accuracy. The results from drilling several materials are presented. [ABSTRACT FROM AUTHOR]

In order to further improve the processing performance of rotary ultrasonic machining (RUM), a novel longitudinal-torsional-coupled (LTC) vibration was applied to the RUM. An experimental study on quartz glass was performed to access the feasibility of the LTC-RUM of a brittle material. The LTC-RUM was executed through the addition of helical flutes on the tool of conventional longitudinal RUM (Con-RUM). The experimental results demonstrated that the LTC-RUM could reduce the cutting force by 55% and the edge chipping size at the hole exit by 45% on an average, compared to the Con-RUM. Moreover, the LTC-RUM could also improve the quality of the hole wall through the reduction of surface roughness, in particular, when the spindle speed was relatively low. The mechanism of superior processing performance of LTC-RUM involved the corresponding specific moving trajectory of diamond abrasives, along with higher lengths of lateral cracks produced during the abrasives indentation on the workpiece material. The higher edge chipping size at the hole entrance of LTC-RUM indicated a higher length of lateral cracks in LTC-RUM, due to the increase in the maximum cutting speed. Furthermore, the effect of spindle speed on the cutting force and surface roughness variations verified the important role of the moving trajectory of the diamond abrasive in the superior processing performance mechanism of LTC-RUM. [ABSTRACT FROM AUTHOR]

Ultrasonic-assisted machining is a machining operation based on the intermittent cutting of material which is obtained through vibrations generated by an ultrasonic system. This method utilizes low-amplitude vibrations with high frequency to prevent continuous contact between a cutting tool and a workpiece. Hot machining is another method for machining materials which are difficult to cut. The basic principle of this method is that the surface of the workpiece is heated to a specific temperature below the recrystallization temperature of the material. This heating operation can be applied before or during the machining process. Both of these operations improve machining operations in terms of workpiece-cutting tool characteristics. In this study, a novel hybrid machining method called hot ultrasonic-assisted turning (HUAT) is proposed for the machinability of Hastelloy-X material. This new technique combines ultrasonic-assisted turning (UAT) and hot turning methods to take advantage of both machining methods in terms of machining characteristics, such as surface roughness, stable cutting depths, and cutting tool temperature. In order to observe the effect of the HUAT method, Hastelloy-X alloy was selected as the workpiece. Experiments on conventional turning (CT), UAT, and HUAT operations were carried out for Hastelloy-X alloy, changing the cutting speed and cutting tool overhang lengths. Chip morphology was also observed. In addition, modal and sound tests were performed to investigate the modal and stability characteristics of the machining. The analysis of variance (ANOVA) method was performed to find the effect of the cutting speed, tool overhang length, and machining techniques (CT, UAT, HUAT) on surface roughness, stable cutting depths, and cutting tool temperature. The results show both ultrasonic vibration and heat improve the machining of Hastelloy-X. A decrease in surface roughness and an increase in stable cutting depths were observed, and higher cutting tool temperatures were obtained in UAT and HUAT compared to CT. According to the ANOVA results, tool overhang length, cutting speed, and machining techniques were effective parameters for surface roughness and stable cutting depths at a 1% significance level (p ≤ 0.01). In addition, cutting speed and machining techniques have an influence on cutting tool temperature at a 1% significance level (p ≤ 0.01). During chip analysis, serrated chips were observed in UAT and HUAT. [ABSTRACT FROM AUTHOR]

In the present competitive structure of manufacturing and industrial applications, alumina ceramic has been well observed as one of the highly demanded advanced ceramics owing to its excellent and superior properties. The objective of this articleis to experimentally investigate the influence of several process variables, namely, spindle speed, feed rate, coolant pressure, and ultrasonic power on different machining performances, that is, 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. The existence of plastic deformation has also been observed along with the dominated brittle fracturein rotary ultrasonic machining of alumina ceramic. Feed rate and spindle speed have been observed as the most influential parameters that govern the deformation mode in alumina ceramic. The optimization of machining responses has also been conducted by employing desirability theory, and at an optimized parametric setting, the obtained experimental values for surface roughness and chipping thickness are 0.134 μm and 0.073 mm, respectively. [ABSTRACT FROM AUTHOR]

The carbon fibers fracture mechanism depending on fiber orientation significantly affects the machined surface quality of C/SiC composites. The rotary ultrasonic machining (RUM) has been proved to be a beneficial method for C/SiC composites drilling with minor tearing defects at the hole exits. In contrast, the effects of tool vibration on surface topography in RUM of C/SiC composites considering fiber orientation have not been reported. In order for a unique evaluation of surface generating mechanism in RUM of C/SiC composites, several RUM experiments were conducted on 2D-C/SiC composites. The micro structural characteristics of the hole surfaces under various fiber directions, ultrasonic amplitudes and spindle speeds were analyzed. The fiber fracture mechanism in RUM of C/SiC was discovered through theoretical analysis. The results displayed that both fiber cutting direction and cutting speeds significantly affect the surface topography in RUM and CG of C/SiC composites. The tool ultrasonic vibration could contribute to the hole surface quality improvement in RUM of C/SiC composites by the fiber fracture mechanism alteration. With the ultrasonic vibration contribution, the fiber cutting direction tended towards 90° and the cutting speeds were increased. In contrast, due to the non-monotonic effect of the cutting speed on the surface roughness, only when the spindle speeds were relatively low, the higher ultrasonic amplitude apparently contributed to the hole surface quality further improvement. [ABSTRACT FROM AUTHOR]

Electron beam melting (EBM), an additive method and rotary ultrasonic machining (RUM), a subtractive technique have been in great demand owing to their innumerable benefits. These techniques can manufacture components from titanium alloys (such as Ti-6Al-4 V) for industries such as aerospace, medical, and automotive, etc. However, these techniques have their own limitations since they are not yet fully developed for many materials including Ti-6Al-4 V. For example, the RUM involves high machining time due to the extremely low MRR while EBM suffers with poor surface quality of final parts. Therefore, in this work, an attempt has been made to combine the additive (EBM) and subtractive (RUM) techniques. The two techniques have been integrated to overcome the limitations of one over the other. In fact, this research has aimed to minimize the surface roughness of EBM fabricated parts using RUM. The design of experiment (DOE) has been adopted to get the best combination of RUM parameters which produce a high surface finish for EBM parts. Moreover, the artificial neural network (ANN) model has been developed to predict the surface roughness effectively. The machining parameters such as coolant pressure, frequency, spindle speed, depth of cut, feed rate, and power supply of RUM have been investigated for better surface finish. It has been confirmed from this study that the surfaces with R value less than 0.3 μm can be achieved using the proposed methodology. [ABSTRACT FROM AUTHOR]

Un-deformed chip thickness is a critical parameter in machining processes. Measuring un-deformed chip thickness experimentally is a complicated process, especially in micro machining and may not even be measured accurately. The un-deformed chip thickness has an influence on material removal rate, cutting forces, specific energy and surface finish etc. In ceramic machining, it is also an indication of material removal mode such as ductile or brittle fracture. In the present study, an effort is made to model undeformed chip thickness, cutting forces and specific cutting energy in rotary ultrasonic machining (RUM) applied to the side milling operation. RUM may be considered as super-imposition of ultrasonic vibrations on the grinding process. The kinematics of ultrasonic motion has been applied to the grinding for the development of the RUM process models. To validate the models, machining experiments have been performed on borosilicate glass in RUM and grinding modes. Percentage of ductile mode of fracture for the machined surfaces has been evaluated using SEM images. Surface roughness values have also been compared for the same material removal rate conditions to ascertain fracture mode. Developed models have been verified and found that ductile mode of fracture as well as surface finish were higher in RUM as compared to grinding process for same material removal rate. RUM process for six aerospace grade materials has also been tried using micro and macro tools and size effects studied. [ABSTRACT FROM AUTHOR]