Elliptical Vibration Research Articles

Compensating varying size effect in diamond cutting of SiCp/Al by ultrasonic elliptical vibration

The heterogeneous mechanical properties of individual phases in SiCp/Al result in significant varying size effect (SE) existed in its deformation process. And modulating the varying SE is crucial for improving the machined surface finish of SiCp/Al in mechanical machining. In this study, we elucidate the mechanisms governing the varying SE in conventional cutting and ultrasonic elliptical vibration-assisted cutting (UEVC) of SiCp/Al using diamond tools by theoretical analysis, numerical simulations and experiments. Specifically, the impact of cutting tool-workpiece contact states in UEVC on the fundamental cutting behavior of SiCp/Al, in terms of microscopic deformation modes and their correlations with machining force variation, machined surface morphology and chip profile, is evaluated. Subsequently, ultrasonic elliptical vibration-assisted diamond turning of SiCp/Al is performed to achieve a surface roughness of 20 nm accompanied with significantly suppressed tool wear. Finally, the compensation effect on the varying SE in SiCp/Al cutting by ultrasonic elliptical vibration of cutting tool is discovered, which leads to decreased brittle fracture and improved surface integrity. The research findings provide a theoretical support for understanding the machining mechanisms of UEVC of SiCp/Al, as well as proposing new perspectives for improving the machinability of SiCp/Al composite accompanied by suppressed varying SE.

Locus control based on microtexturing model in the elliptical vibration-assisted turning

Elliptical vibration-assisted cutting (EVC) is an efficient cutting process in the fabrication of microtextures. In this paper, a novel locus control method for EVC is proposed to fabricate intricate surface textures. First, the mechanism of the EVC microtexturing process is analyzed. Then the detailed ideas and mapping process of the locus control method of EVC according to the model of microtexture are investigated. To realize the mapping process of the locus control, the relationship between the elliptical vibration locus and the discrete points of the microtexturing model is established, while the generation algorithm of excitation inputs for the actual elliptical vibration exciter is developed. A series of EVC microtexturing turning experiments are performed while microtexturing simulation experiments are also conducted. The test results between microtexturing turning and simulation experiments show that the proposed locus control method is satisfactory and can be used to fabricate differently shaped microtextures.

Investigation of ultrasonic mechanism and development of tool wear model in ultrasonic elliptic vibration assisted cutting of stainless steel

By analyzing the kinematics and dynamics of ultrasonic vibration under various conditions, the tool wear mechanism in Ultrasonic Elliptic Vibration-Assisted Cutting (UEVAC) were investigated. Two distinct mechanisms for mitigating tool wear emerge: In non-separated UEVAC, the pivotal factor is the reduction of material yield stress through the acoustic softening effect. Conversely, in separated UEVAC, tool wear reduction is attributed to the decrease in average contact stress via stress superposition and the hammer effect. These findings highlight the effectiveness of aligning ultrasonic energy field action times and intensity to reduce stainless steel tool wear rates in non-separated UEVAC. Furthermore, the proposed tool wear model demonstrates robust reliability for separated UEVAC processes.

Cutting depth-oriented ductile machining of infrared micro-lens arrays by elliptical vibration cutting.

Infrared micro-lens arrays (MLAs) are widely used in advanced optical systems due to their advantages such as low focusing depth and high sensitivity. Elliptical vibration cutting (EVC) is a promising approach for the fabrication of MLAs on infrared brittle materials. However, the mechanism of ductile machining of MLAs prepared by EVC has not been fully elucidated so far. In this paper, based on the vibration intermittent cutting characteristics and the transient material removal state, a ductile machining model of MLAs on brittle material by EVC was established. This model effectively calculates the subsurface damage of the machined surface and realizes the prediction of the critical depth for ductile machining of MLAs. Furthermore, the concave micro-lenses were prepared on single crystal silicon by EVC and ordinary cutting (OC) to verify this model. The results demonstrated that EVC could significantly enhance the critical depth by approximately 4.3 times compared to OC. Microstructural surface damage predominantly occurs at the exit side of the tool cutting. This proposed model accurately predicts the actual critical depth, with an average error of about 7.5%. Additionally, elevating the amplitude in the depth of cut direction could increase the critical depth, but a larger amplitude would inhibit the increase of the critical depth. This study contributes to a better understanding of ductile machining of microstructure on brittle materials and facilitates the process optimization of MLAs fabrication using EVC.

Wear study of CBN tools in laser ultrasonic composite cutting of cemented carbide

The laser ultrasonic composite cutting (LUCC) process was proposed by combining laser heating-assisted cutting (LHAC) and elliptical ultrasonic vibration cutting (UVC). In the process of cutting experiment, cubic boron nitride (CBN) is selected as the tool’s material. The wear morphology and wear appearance of the tools were observed by super depth-of-field microscopy and scanning electron microscopy (SEM) to research the wear characteristics and wear mechanism of CBN tools during LUCC of cemented carbide. Compared with conventional cutting (CC), UVC and LHAC, during LUCC of cemented carbide with CBN tools the tool wear are significantly reduced by 45.11%, 28.92%, and 17.39% respectively, the cutting force are decreased by 61%, 44%, and 46% respectively, and the surface roughness are lowered by 77%, 55%, and 62% respectively, therefore the tool life is obviously lengthened. Moreover, the tool flank wears model of during LUCC of cemented carbide was established and verified by the tool flank face wear test. The results show that when the CBN tool is used for LUCC of cemented carbide, the wear band on the tool’s rake face is basically parallel to the cutting edge and is in the shape of a long strip, and the wear band on the tool’s flank face shows a triangular-shaped wear band accompanied by shallow pits and grooves; In the process of the LUCC of cemented carbide, the main causes of CBN tool wear include adhesive wear, oxidation wear and abrasive wear are the main causes of CBN tool wear during LUCC of cemented carbide; The faster the cutting speed, the bigger the error among the experimental value with the calculated value, and the wear of tool’s flank face during LUCC of cemented carbide gradually increased.

Surface/subsurface formation mechanism of tungsten during ultrasonic elliptical vibration cutting

The ultrasonic elliptical vibration cutting (UEVC) has been proved to be a valid method to improve surface quality and reduce subsurface damage of tungsten. However, it is still a huge challenge to elucidate the surface/subsurface formation mechanism of tungsten during UEVC. Hence, molecular dynamics simulations were employed to reveal the formation mechanism of surface/subsurface during UEVC of tungsten from the atomic level, and the effects of ultrasonic amplitude and frequency on the surface/subsurface formation were explored. The results showed that compared with general cutting (GC), the improved surface quality was attributed to the smaller actual cutting depth and more amorphous tungsten in chips caused by cyclic loading-unloading during UEVC. Moreover, the reversing friction direction facilitated the formation of surface chips during UEVC as well. The thermal-activated dislocations caused by high transient cutting temperature could result in the wide distribution of subsurface dislocations, and the dislocations were usually expanded by the way of crystal plane slip to suppress generation of long slip plane, which could reduce the subsurface damage of tungsten during UEVC. In comparison with ultrasonic amplitude in cutting depth direction, elevated ultrasonic amplitude in cutting speed direction or ultrasonic frequency could reduce depth of subsurface damage layer, surface roughness, and dislocation density, which derived from the small transient cutting force and stress as well as high strain rate. This study provides a new insight into the surface/subsurface formation mechanism of tungsten during UEVC, which can offer a theoretical basis on the selection of ultrasonic parameters for achieving high surface/subsurface quality for tungsten and other materials machined by UEVC.

Effect of longitudinal-bending elliptical ultrasonic vibration assistance on electrosurgical cutting and hemostasis

Electrosurgical devices are widely used for tissue cutting and hemostasis in minimally invasive surgery (MIS) for their high precision and low trauma. However, tissue adhesion and the resulting thermal injury can cause infection and impede the wound-healing process. This paper proposes a longitudinal-bending elliptical ultrasonic vibration-assisted (EUV-A) electrosurgical cutting system that incorporates an ultrasonic vibration in the direction of the cut by introducing an elliptical motion of the surgical tip. Compared with a solely longitudinal ultrasonic vibration-assisted (UV-A) electrosurgical device, the EUV-A electrode contacts the tissue intermittently, thus allowing for a cooler cut and preventing tissue accumulation. The experimental results reveal that the EUV-A electrode demonstrates better performance than the UV-A electrode for both anti-adhesion and thermal injury through in vitro experiments in porcine samples. The tissue removal mechanism of EUV-A electrosurgical cutting is modeled to investigate its anti-adhesion effect. In addition, lower adhesion, lower temperature, and faster cutting are demonstrated through in vivo experiments in rabbit samples. Results show that the EUV-A electrode causes lower thermal injury, indicative of faster postoperative healing. Finally, efficacy of the hemostatic effect of the EUV-A electrode is demonstrated in vivo for vessels up to 3.5 mm (equivalent to that of electrocautery). The study reveals that the EUV-A electrosurgical cutting system can achieve safe tissue incision and hemostasis.

Design and optimization of a single excitation elliptical vibration system

Design and optimization of a single excitation elliptical vibration system

Analytical modeling of subsurface damage and material removal energy in elliptical vibration cutting of micro-structures on brittle materials

Elliptical vibration cutting (EVC) is a promising technique for the fabrication of micro-structures on brittle materials. In this work, the surface quality and material removal energy in ultra-precision machining of micro-structures on brittle materials by EVC were investigated. Theoretical models were first established for predicting subsurface damage and specific cutting energy (SCE) based on the intermittent material removal characteristics of EVC. The models correlated cutting parameters with the tool vibration trajectory parameters, target surface geometry parameters, and material removal modes. Furthermore, the material removal behaviors in the nominal cutting direction and the feeding direction were comprehensively considered. To verify the model, the experiments of EVC and ordinary cutting (OC) were performed on single crystal silicon, and the surface morphology and cutting force were characterized. The results indicated that, compared with OC, the maximum subsurface damage depth is reduced by 61.82% and the SCE stability value is reduced to 45.87% by applying EVC to fabricate micro-structures. EVC could significantly improve the machining quality and reduce energy consumption. In addition, increasing the vibration amplitude in the depth of cut direction could further save energy, but a larger amplitude would increase subsurface damage. This work not only promotes the recognition of the material removal mechanism of EVC, but also presents effective guidance for achieving high-quality and sustainable machining of micro-structured surfaces.

Cutting Chatter in Ultrasonic Elliptical Vibration Cutting and Its Influence on Surface Roughness and Tool Wear

Ultrasonic elliptical vibration cutting has a wide range of applications in the field of precision cutting of difficult-to-machine metal materials. However, due to its intermittent cutting characteristics and the weak rigidity of the horn, cutting chatter is prone to occur during its cutting process, which has an important impact on cutting surface quality and tool wear. In this paper, the rigid/viscoplastic rod model is used to simulate the horn in the ultrasonic elliptical vibration cutting device, and the influence factors of the amplitude-frequency response of the horn are analyzed. The influence of cutting speed and cutting depth on cutting chatter was studied by ultrasonic elliptical vibration cutting experiment of tungsten heavy alloy, and the influence of cutting chatter on cutting surface morphology and diamond tool wear was studied. The research shows that cutting speed will change the excitation frequency of the horn, and reasonable cutting speed can inhibit the occurrence of cutting chatter and avoid resonance of the horn. The cutting depth will affect the excitation amplitude and amplify the vibration amplitude when chatter or resonance occurs. The experimental results show that in ultrasonic elliptical vibration cutting of heavy tungsten alloy, chatter suppression can significantly improve the quality of the cutting surface and reduce the wear of diamond tools.

Development of a novel piezoelectric-driven non-resonant elliptical vibrator with adjustable characteristics.

Aiming at the fabrication of a micro-textured surface, a novel piezoelectric-driven non-resonant elliptical vibrator is proposed in this paper; the output characteristics could be adjusted by the length change of the tool holder. The flexible mechanism is the primary structure of the vibrator, which includes a lever type mechanism, an enhanced Scott-Russell mechanism, and a T-shaped mechanism. The former two mechanisms are used to enlarge the output of the piezoelectric actuator, and the T-shaped mechanism is applied to transfer the parallel movements to the elliptical trajectory. The theoretical models including the elliptical trajectory, output stiffness, and resonant frequencies are established to investigate the impacts of the tool holder and controlling signals on the output characteristics of the vibrator, which are further validated using the finite element analysis method. A prototype is developed by integrating the non-resonant elliptical vibrator assembly and controlling system. Some experiments are carried out to verify the basic performance and the adjustable properties of the vibrator.

An analytical cutting force model for elliptical vibration texturing of nano-grating surfaces

Although the direct texturing processes using dynamic cutting depth modulation have been widely demonstrated for generating micro/nano-structured surfaces, the material shearing removal dominates the surface topography generation that inevitably inhibits the machining feasibility of high-aspect textures. This paper proposes a novel nano-grating generation mechanism governed by the combined effect of shearing-based material removal and compressive forming-based deformation in elliptical vibration texturing. A newly dynamic cutting force model is established to reveal its transient cutting mechanics that incorporating the process elastic rebounding behaviors and essential local cutting characteristics in three deformation zones. The model fully considers the complex transient shear angle variation, friction reversal phenomenon on tool-chip interface as well as the unique flank-waviness interaction. A series of texturing experiments are delicately designed to modulate the contribution of material shearing removal and flank compressive forming on nano-grating generation mechanism. The measured dynamic cutting force show good agreements with the simulated results, based on which the model accuracy and main process assumptions are well validated. Furthermore, the relationship between the cutting force characteristics and nano-grating topography is analyzed to guide the optimal elliptical trajectory designs for simultaneously achieving high-quality nano-gratings and smaller dynamic cutting forces. The outcomes of this paper not only lay the scientific foundations for machining capability extension of direct texturing processes, but also contribute to the understandings of combined surface generation mechanisms of other intermittent cutting processes in nano-scale domain.

Modeling and investigation of minimum chip thickness for silicon carbide during quasi-intermittent vibration–assisted swing cutting

In micromachining, the quasi-intermittent vibration—assisted swing cutting technology alleviates the residual height problem of elliptical vibration–assisted cutting (EVC) and inherits its intermittent machining characteristics. The minimum chip thickness has a significant impact on cutting forces, tool wear, and process stability when working with difficult-to-machine materials. This study thoroughly examines the impact of cutting parameters and tool parameters on the quality of the workpiece during machining in order to better understand the time-varying characteristics of the quasi-intermittent vibration–assisted swing cutting (QVASC) machining process and the size effect on micro-cutting of silicon carbide crystal. This paper created the minimum chip thickness prediction model suited to QVASC machining process. The effects of variables such as cutting velocity and tool inclination on the minimum chip thickness were discussed as well as the scribing tests that were conducted on such challenging materials as silicon carbide. The research findings shown that during the machining process, the critical undeformed chip thickness of silicon carbide decreased continuously as the cutting velocity sequentially increased (1.51 mm/min, 1.88 mm/min, 2.26 mm/min); under the down inclination angle (0–10°), the critical undeformed chip thickness also continuously decreased. These results confirm that cutting too fast reduces the instantaneous undeformed chip thickness, which is not conducive to ductile removal.

Random spherical microlens array fabricated by elliptical vibration diamond cutting and molding.

Microlens arrays (MLAs) are widely used in homogenized laser beams due to excellent optical properties. However, the interference effect generated in traditional MLA (tMLA) homogenization will reduce the quality of the homogenized spot. Hence, the random MLA (rMLA) was proposed to reduce the interference effect in the homogenization process. To achieve mass production of these high-quality optical homogenization components, the rMLA with randomness in both period and sag height was proposed first. Subsequently, MLA molds were ultra-precision machined on S316 molding steel by elliptical vibration diamond cutting. Furthermore, the rMLA components were precisely fabricated by applying molding technology. Finally, Zemax simulation and homogenization experiments were carried out to verify the advantage of the designed rMLA.

Microstructure evolution mechanism of tungsten induced by ultrasonic elliptical vibration cutting at atomic/nano scale

Ultrasonic elliptical vibration cutting (UEVC) technology has been utilized for ultra-precision machining of difficult-to-machine metal materials such as tungsten. Nevertheless, the microstructure evolution mechanism of tungsten under the synergistic effect of ultrasonic and mechanical loads remains unclear, particularly at the atomic/nano scale. Additionally, the plastic deformation mechanism of tungsten differs from that of other metallic materials due to its low dislocation mobility (brittle at room temperature). Hence, the molecular dynamics simulation of UEVC for single crystal tungsten was established to study its mechanisms in plastic deformation and microstructure evolution under stress induction in this study. The results indicated that the main plastic deformation mechanisms including dislocation slip, amorphous phase transformation and nanocrystal were found during the tungsten removal, and accompanied by some extent of lattice distortion. The instantaneous shear stress of UEVC reached 16.88 GPa. Compared with common cutting (CC), the formation of nanocrystals mainly occurred in UEVC because the instantaneous shear stress exceeded the critical shear stress of multiple slip systems during cutting. Similarly, the high dislocation density and high plastic deformation degree of the machined zone in UEVC were also attributed to the high shear stress. The dynamic recrystallization of tungsten induced by UEVC was realized from dislocation slip to the formation of dense dislocation walls, followed by the formation of sub-grain boundaries, and finally to the formation of nanocrystals.

Experimental Investigation of Material Removal in Elliptical Vibration Cutting of Cortical Bone

To benefit tissue removal and postoperative rehabilitation, increased efficiency and accuracy and reduced operating force are strongly required in the osteotomy. A novel elliptical vibration cutting (EVC) has been introduced for bone cutting compared with conventional cutting (CC) in this paper. With the assistance of high-speed microscope imaging and the dynamometer, the material removals of cortical bone and their cutting forces from two cutting regimes were recorded and analysed comprehensively, which clearly demonstrated the chip morphology improvement and the average cutting force reduction in the EVC process. It also revealed that the elliptical vibration of the cutting tool could promote fracture propagation along the shear direction. These new findings will be of important theoretical and practical values to apply the innovative EVC process to the surgical procedures of the osteotomy.

Theoretical and experimental study of 3D ultrasonic vibration-assisted turning driven by two actuators

Ultrasonic vibration-assisted turning techniques can be used to reduce the roughness of the output surface and also to obtain special texture structures. This paper introduced an adjustable 3D ultrasonic vibration-assisted turning device, which has two operating modes, one for reducing the roughness of the output surface, and the other for constructing special textures with hydrophobic properties. Theoretical calculations, geometric modeling, finite element simulation and harmonic response analysis were used to guide the design process, and finally experimental verification was performed. The amplitude calibration results show that a 3D spatial elliptical vibration pattern of the turning tool can be realized. The experimental results indicate that a small cutting speed and a low feed rate help to reduce the roughness of the finished surface, while a large cutting speed and a large feed rate are good for increasing the contact angle of the output surface.

Tool–workpiece separation characteristic and surface generation in ultrasonic assisted milling

Ultrasonic assisted machining is an eco-friendly surface texture fabrication method with low machining cost, high-accuracy precision, and efficiency. This study analyzes the surface texture formation in feed direction ultrasonic vibration assisted milling (FUVAM) and elliptical ultrasonic vibration assisted milling (EUVAM). The trajectories of the single and adjacent tool tips in FUVAM are analyzed. Furthermore, the tool–workpiece separation mechanism in EUVAM is discussed. Moreover, a 3D surface topography model of EUVAM is applied to study the influences of machining parameters on the ultrasonic machining topography. The experiments of conventional milling (CM) and EUVAM are carried out and different types of surface textures are successfully fabricated on Ti-6Al-4V using EUVAM. The results of the response surface indicate that the surface roughness shows an increasing trend with higher spindle speed, but decreases with improved feed speed and cutting depth. Compared with CM, the chips generated in EUVAM have the characteristics of small width and low bending degree. This work is expected to provide some guidance for the selection of machining and vibration parameters during ultrasonic assisted milling.

Structural coloration with two-dimensional nanostructures fabricated by elliptical vibration nanoindentation

Structural color stemming from the two-dimensional (2D) nanostructures that induced light interference attracts more attention than 1D grating due to its higher design flexibility. However, the fast and cost-effective fabrication of pixel-by-pixel 2D nanostructures is challenging. This study prompts nanoindentation as a promising technique for fabricating 2D nanostructure on metallic surfaces by adding an ultrafast elliptical vibration on the nanoindenter. First, the elliptical vibration nanoindentation (EVN) process principle is analyzed. Next, an ultrafast elliptical vibration nanoindentation tool (UEVNT) with a maximum working frequency of 2 kHz is developed. Then, machining experiments were conducted on aluminum to evaluate the performance of EVN, whose results demonstrate the successful fabrication of pyramid-type nanostructures with a depth of hundreds of nanometers and a spacing of 1–3 μm. Based on the unique spatial diffraction characteristic of 2D nanostructures, a high-decoupling optical variable device has also been fabricated on the aluminum surface by rendering two images into two orthogonal observation directions. Finally, the 2D nanostructures on a metallic surface were transferred to the flexible polymer to fabricate a structural color-based bidirectional strain sensor. Stretching tests have been performed with results verifying the potential application of 2D nanostructures-induced structural color in the wireless measurement of mechanical deformation.

Numerical study on flow-induced vibration of LBE-cooled wire-wrapped rod bundle

Flow-induced vibration (FIV) characteristics of LBE-cooled wire-wrapped rod bundle are crucial to the wire-to-cladding fretting. In the present study, numerical simulation on FIV of wire-wrapped rod bundle in LBE flow was performed using a fluid–structure interaction methodology based on the coupling between fluid and solid domains. The effects of geometry parameters on the FIV of wire-wrapped single rod and rod bundle were obtained. The results show that the circumferential force of coolant on the single fuel rod was uneven, which made the fuel rod undergo elliptical and off-axis periodic vibration. The variations of structure parameters of wire spacers had weak effects on the vibration of the single rod, while significant effects on the vibration trajectory of rod bundle. The vibration characteristics of border rods were more sensitive to the variations of transverse flow, while the center fuel rods were more sensitive to the difference in support constraint.