Ultrasonic Vibration-assisted Milling Research Articles

Tool wear rate prediction in ultrasonic vibration-assisted milling

In the current study, a predictive model on tool flank wear rate during ultrasonic vibration-assisted milling is proposed. One benefit of ultrasonic vibration is the frequent separation between tool and workpiece as the cutting time is reduced. In order to account for this effect, three types of tool–workpiece separation criteria are checked based on the tool center instantaneous position and velocity. Type I criterion examines the instantaneous velocity of tool center under feed movement and vibration. If the tool is moving away from workpiece, there is no contact. Type II criterion examines the position of tool center. If the tool center is far from the uncut workpiece surface, there is no contact even though the tool is getting closer. Type III criterion describes the smaller chip size due to the overlaps between current and previous tool paths as a result of vibration. If any criterion is satisfied, the tool flank wear rate is zero. Otherwise, the flank wear rate is predicted considering abrasion, adhesion and diffusion. The proposed predictive tool flank wear rate model is validated through comparison to experimental measurements on SKD 61 steel with uncoated carbide tool. The proposed predictive model is able to match the measured tool flank wear rate with high accuracy of 10.9% average percentage error. In addition, based on the sensitivity analysis, smaller axial depth of milling, larger feed per tooth or higher cutting speed will result in higher flank wear rate. And the effect of vibration parameters is less significant.

Tool wear mechanisms in axial ultrasonic vibration assisted milling in-situ TiB2/7050Al metal matrix composites

The in-situ TiB2 particle reinforced aluminum matrix composites are materials that are difficult to machine, owing to hard ceramic particles in the matrix. In the milling process, the polycrystalline diamond (PCD) tools are used for machining these materials instead of carbide cutting tools, which significantly increase the machining cost. In this study, ultrasonic vibration method was applied for milling in-situ TiB2/7050Al metal matrix composites using a TiAlN coated carbide end milling tool. To completely understand the tool wear mechanism in ultrasonic-vibration assisted milling (UAM), the relative motion of the cutting tool and interaction of workpiece-tool-chip contact interface was analyzed in detail. Additionally, a comparative experimental study with and without ultrasonic vibration was carried out to investigate the influences of ultrasonic vibration and cutting parameters on the cutting force, tool life and tool wear mechanism. The results show that the motion of the cutting tool relative to the chip changes periodically in the helical direction and the separation of tool and chip occurs in the transverse direction in one vibration period, in ultrasonic vibration assisted cutting. Large instantaneous acceleration can be obtained in axial ultrasonic vibration milling. The cutting force in axial direction is significantly reduced by 42%–57%, 40%–57% and 44%–54%, at different cutting speeds, feed rates and cutting depths, respectively, compared with that in conventional milling. Additionally, the tool life is prolonged approximately 2–5 times when the ultrasonic vibration method is applied. The tool wear pattern micro-cracks are only found in UAM. These might be of great importance for future research in order to understand the cutting mechanisms in UAM of in-situ TiB2/7050Al metal matrix composites.

Experimental study on tool wear in ultrasonic vibration–assisted milling of C/SiC composites

Carbon-fiber reinforced silicon carbide matrix (C/SiC) composites are typical difficult-to-cut materials due to high hardness and brittleness. Aiming at the problem of the serious tool wear in conventional milling (CM) C/SiC composite process, ultrasonic vibration–assisted milling (UVAM) and conventional milling tests with a diamond-coated milling cutter were conducted. Theoretical and experimental research on the cutting force during the ultrasonic vibration milling process of C/SiC composites is carried out. Based on the kinematics analysis of tool path during ultrasonic vibration milling process, the cutting force model of ultrasonic vibration milling is established, and the influence mechanism of ultrasonic vibration on the cutting force is revealed. Based on the analysis of the evolution law of tool wear profile and wear curve during the traditional milling and ultrasonic vibration milling of C/SiC, the tool wear forms and mechanism of diamond-coated milling cutters in two processing modes and the influence mechanism of ultrasonic vibration on tool wear are revealed. It is found that the main wear mechanism of the diamond-coated milling cutter is abrasive wear, and the main wear form is the coating peeling. Compared with the traditional milling, the tool wear can be reduced by the ultrasonic vibration milling in machining process. In the range of test parameters, the tool wear decreases first and then increases with the increase of ultrasonic amplitude.

Investigations on torsional fretting wear properties of CuAlNi processed by ultrasonic vibration-assisted milling

This paper investigates the effects of parameters of ultrasonic vibration-assisted milling (UVAM) on torsional fretting wear properties of CuAlNi. Surface texture is processed on CuAlNi surfaces by the UVAM method. Fretting wear experiments on the CuAlNi surfaces are carried out by the torsional wear test rig. Further surface topography measurements using three-dimensional (3D) surface profiler, relationships between the UVAM parameters and the fretting properties of UVAM-processed samples were established. The results indicated that the UVAM-processed samples showed excellent antiwear and antifriction properties in comparison with untreated CuAlNi; this improvement is mainly due to the enhancement on abilities of storing lubricated oil and catching wear debris during the fretting wear process, as well as the increased hardness.

Study on effect of vibration amplitude on cutting performance of SiCp/Al composites during ultrasonic vibration–assisted milling

Silicon carbide particulate reinforced aluminum (SiCp/Al) matrix composites play an important role in aviation, aerospace, electronics, automobile, and other fields due to their outstanding mechanical properties. However, the existence of reinforcing SiC particles leads to poor cutting performance, terrible surface quality, and severe tool wear of SiCp/Al composites. In this study, a series of experiments were carried out with an ultrasonic vibration–assisted milling (UVAM) experimental device to study the effect of amplitude on the machinability of 20% SiCp/Al composites from four aspects: cutting force, surface roughness, surface morphology, and chip morphology. The results showed that it had a great influence on cutting force, surface roughness, surface morphology, and chips when the amplitude increased to 3 μm. The surface of workpiece material deteriorated rapidly and presented the fragmentation. In addition, a large number of micro-cracks and particle bulges appeared on the machined surface. It was suggested that the amplitude below 5 μm had a negative impact on the milling surface quality of 20% SiCp/Al composites, and the amplitude of 3 μm was considered as a critical value.

Investigation on machining characteristics of TC4 alloy by simultaneous application of ultrasonic vibration assisted milling (UVAM) and economical-environmental MQL technology

Abstract The optimization of machining methods is one of important guiding principles for achieving high-quality, cost saving and environmental protection machining of difficult-to-machine materials in modern manufacturing. Considering the principles and advantages of ultrasonic machining (UM) method and minimum quantity lubrication (MQL) technique, the simultaneous application of UM and MQL methods is anticipated to further improve machining performance in terms of cutting force, surface quality and chip morphology. Theoretical analysis indicates that the MQL system in UVAM could provide enhanced lubrication and cooling performance because of the separate-type cutting mechanism, the surface acoustic and the cavitation phenomenon of resonant workpiece in UM. Conventional milling (CM) trials, general UVAM trials and combined UVAM&MQL trials were conducted to investigate the effect of UVAM and MQL methods on machining performance of TC4 alloy, where the results of CM and general UVAM could provide indispensable reference. Multifaceted comparisons are presented in machining results of CM, UVAM and UVAM&MQL trials in terms of time-domain analysis and frequency-domain analysis of milling force, average cutting force, surface topography, surface profile and surface roughness. The results show that cutting force features could be significantly affected under UVAM and UVAM&MQL condition compared with that in general milling due to intermittent cutting mechanism and the coupling effect of UVAM and MQL methods. The uniform micro-textured surfaces with improved profile fluctuations could be obtained when applying the UVAM&MQL strategy. Compared with surface roughness in CM and UVAM, the surface roughness in UVAM&MQL is improved by about 30–50% and about 20–30%, respectively. The excellent machining performance demonstrates the feasibility and effectiveness of simultaneously applying UVAM and MQL methods.

Fractal characterization of surface microtexture of Ti6Al4V subjected to ultrasonic vibration assisted milling

The high-frequency tool vibration occurring during ultrasonic vibration cutting results in a formation of unique micromorphology of the machined surface. Different microtextures are known to have a substantial effect on the workpiece service performance. In this study, an attempt is made to assess this effect quantitatively for a more accurate characterization of the processed surface. The dependence between the contour root mean square deviation and fractal dimension is derived via the fractal theory. The concept of characteristic fractal dimension is proposed and successfully applied to Ti6Al4V surfaces subjected to ultrasonic vibration assisted milling (UVAM) with various spindle rotation speeds and vibration amplitudes. The experimental results obtained strongly indicate that smaller characteristic fractal dimensions correspond to more regular surface microtextures and contour curves, which proves the validity of the characteristic fractal dimension representation. Besides, the lower the characteristic fractal dimension of the surface, the shorter the time to reach the stable friction phase during dry friction.

Comparative investigation of tool wear mechanism and corresponding machined surface characterization in feed-direction ultrasonic vibration assisted milling of Ti–6Al–4V from dynamic view

This paper mainly investigated the wear mechanism of universal coated carbide tools in feed-direction ultrasonic vibration-assisted milling (UVAM) of Ti–6Al–4V alloy through theorical analysis and experimental approaches, where the external ultrasonic vibration excitation was imposed on the workpiece. The rapid intermittent machining features, the generation mechanism of ultrasonic-frequency pulse cutting force and alternating friction, ultrasonic-frequency dynamic impact effect of resonant workpiece and considerable changes in tool trajectory and relative cutting speed in UVAM were analyzed from perspective of tool-workpiece dynamics and kinematics. Due to the ultrasonic-frequency friction between the tool and the workpiece, the minimum quantity lubrication (MQL) with biodegradable cutting fluid was firstly introduced in UVAM to improve the lubrication/cooling performance between tool and workpiece/chips interfaces. Three different machining methods, general milling, feed-direction UVAM and feed-direction UVAM&MQL, were sequentially carried out to comparatively investigate the tool wear mechanism and characterize tool wear and machined surface features. The corresponding machined surface quality including surface topography, surface profile and surface roughness under different tool wear states were presented to evaluate the tool wear condition. The results indicated that the tool wear mechanism in workpiece feed-direction UVAM system was dominated by ultrasonic-frequency dynamic load, where ultrasonic-frequency cutting force, ultrasonic-frequency friction, ultrasonic-frequency vibration impact and cutting inflection points of tool-tip trajectory worked together on the cutting edges. And the tool wear morphology in feed-direction UVAM was mainly characterized by tool-tip fracture, impact crack, friction traces and fatigue crack. The results of machined surfaces indicated that compared with the surfaces obtained in CM and general UVAM, the UVAM&MQL method could significantly improve the finished surface quality, which can also improve the tool wear to a certain extent.

Investigations of micro-textured surface generation mechanism and tribological properties in ultrasonic vibration-assisted milling of Ti–6Al–4V

Ultrasonic machining (UM) as a non-traditional manufacturing technology has been recognized as an effective machining method for improving surface topography and surface quality. Although substantial experiment studies have been conducted and reported, the generation mechanism of textured surfaces in UM is still ambiguous, in which trajectories of tool-tips is not equal to actual cutting path due to separate-type cutting mechanism. Besides, the influence of ultrasonic vibration texture on tribological performance of machined surfaces is uncertain. This paper focuses on investigating the micro-texture generation mechanism and the effect of textured surface characteristics on tribological properties of machined surfaces in ultrasonic vibration-assisted milling (UVAM) process. Firstly, based on detailed analysis of tool-tips trajectories and rapid separate-type cutting process in UVAM, the generation mechanism of micro-texture was theoretically studied and the visualization of intermittent cutting process was given. Secondly, both conventional milling (CM) and UVAM experiments on Ti–6Al–4V were conducted to distinguish surface morphology features between CM and UVAM surfaces. Thirdly, the characterization methods of surface morphology, roughness parameters etc. were employed to characterize textured surfaces by comparing with CM surfaces. Finally, friction experiments were carried out to investigate influence of micro-texture on surface tribological properties, which was of great significance to functional property, wear property and service life of components. Experiment results showed that compared to common surfaces, uniform micro-texture could significantly improve surface morphology and surface quality. Friction test results also verified that micro-vibration-texture had a significant influence on improving tribological properties by reducing friction coefficients and its fluctuations.

Surface microstructure of titanium alloy thin-walled parts at ultrasonic vibration-assisted milling

Milling of the titanium alloy thin-walled workpiece is a critical challenging task and the machining vibration is a major effect on the accuracy of the final part due to difficult machining properties and low stiffness. The common milling (CM) is very hard for titanium alloy thin-walled parts to get high-quality machined surface microstructure, so finding an effective way of processing to obtain better surface microstructure is particularly important. In this article, the longitudinal-torsional composite ultrasonic vibration-assisted milling (LTCUVM) is proposed to overcome the problems of the common milling. The cutting method of the high-frequency vibration separation of a workpiece and the tool reduces an average cutting force. Thereby suppressing the tool relieving and further providing a good machined surface. In this study, firstly, the kinematic model of LTCUVM was established and the variations of the movement of the cutting edge flank with the spindle speed change were analyzed. Then the finite element model (FEM) of the two processing methods was developed and significant differences between the CM and LTCUVM in the micro-milling were revealed. Further, related experiments were designed and conducted. Finally, the experimental analysis showed that the LTCUVM effectively reduced an average cutting force, and further reduced surface roughness and height of chatter marks compared to the CM with the same processing parameters.

Friction and wear on titanium alloy surface machined by ultrasonic vibration-assisted milling

With the development of the feasibility study on ultrasonic vibration-assisted machining in difficult cutting materials, its surface microstructure and the use performance get more and more attention. In this paper, the 3D roughness and surface residual stress are analyzed based on the experiments of common milling (CM) and ultrasonic vibration-assisted milling (UVAM) TC4 titanium alloy. Besides, the surface friction and wear properties machined by CM and UVAM are compared. The results show that, although arithmetic average deviation ($${s_\mathrm{a}}$$) and root-mean-square deviation ($${s_\mathrm{q}}$$) increase slightly because of the high-frequency vibration, the uniformity and consistency of the surface texture improve obviously. Moreover, the surface residual compressive stress increases with the increasing of the ultrasonic current. Additional, the friction coefficient and wear volume are reduced obviously by the surface microstructure machined by UVAM under oil lubrication. Because there are many continuous pits distribution on the surface, which can not only store the debris but also generate the hydrodynamic effect. However, there is no obvious difference in surface tribological properties machined by CM and UVAM under dry friction, due to the disappearance of hydrodynamic effect.

Analytical modeling of tool-workpiece contact rate and experimental study in ultrasonic vibration-assisted milling of Ti–6Al–4V

Ultrasonic machining (UM) method is characterized by separate-type cutting that the tool and workpiece will undergo numerous times of separation and contact in machining process. Based on intermittent machining mechanism in UM, this paper presented an analytical model for calculating the tool-workpiece contact rate (TWCR) in ultrasonic vibration assisted milling (UVAM). The non-periodic distribution of contact and separation points between the tool and workpiece, which is caused by continuous change of critical velocity, greatly increases the complexity of intermittent machining in UVAM. According to the proposed TWCR theoretical model in UVAM, the nominal cutting speed, vibration frequency, vibration amplitude and rotation angle are four key parameters affecting TWCR. Since machining parameters are closely related to the TWCR, so a series of ordinary milling and UVAM experiments were conducted to study the effect of machining parameters on machining performance of Ti–6Al–4V. Experimental results showed that UVAM method had obvious technical advantages in reducing cutting force, improving finished surface quality, suppressing burrs and optimizing chip formation. In this paper, the advantages of ultrasonic machining mechanism were explained from the perspective of TWCR. The oscillation characteristics, amplitude reduction characteristics and FFT spectrum characteristics of original cutting force signal in UVAM were analyzed. Moreover, the effect of machining parameters on surface roughness and topography in UVAM was investigated. And the influence mechanism of ultrasonic vibration on burr suppression and chip formation was also introduced and studied. Experiment results verified the superior of UVAM method compared to ordinary milling under the same cutting condition.

Estimation of workpiece-temperature during ultrasonic-vibration assisted milling considering acoustic softening

Ultrasonic-vibration assisted milling (UAM) process is one of the most recent advancements in the area of milling. In UAM, milling cutter vibrates with ultrasonic frequency and small amplitude during cutting. The assistance of ultrasonic-vibration during milling operation improves surface roughness, dimensional accuracy and tool life. Due to these benefits UAM finds application in precision manufacturing. Thermal aspect in machining plays a significant role in the dimensional accuracy of the products. Therefore, in this work analytical and experimental studies were carried out to model the temperature rise in workpiece during UAM process (with axial vibration). For analytical modelling, a process physics based equation was developed to predict the temperature rise in workpiece, considering acoustic softening. A setup was developed for performing UAM experiments. A statistical model was developed to estimate the temperature rise in workpiece during UAM. The predictions from physics-based and statistical models were in good agreement with experimental results.

Generation of functional surfaces by using a simulation tool for surface prediction and micro structuring of cold-working steel with ultrasonic vibration assisted face milling

The industrial production of technical systems is characterized by increasing demands on performance sustainability, resource efficiency and manufacturing costs. As a result, surfaces with special properties become more important. Therefore, their functionalisation is subject of many fields of research. Typical application ranges are improving haptics, the generation of optical effects or the reduction of friction in mechanical as well as fluidic systems. Furthermore, functional surfaces can contribute to an increase of the adhesive strength of coatings and coating systems, respectively. This can extend the implementation possibilities for the substrate material. Due to its defined cutting edge geometry and kinematics, the ultrasonic vibration assisted milling (UVAM) represents a suitable method for a reproducible generation of a defined micro structure. Accordingly, an ultrasonic vibration system was implemented in a high precision machining centre and initial experimental investigations were carried out. Moreover, a surface simulation tool was developed and used for the structure design and modelling, which predicts a virtual micro structure using the relevant parameters. In the first tests, a high degree of conformity with the machined surfaces could already be achieved. Thus, a possibility for economic micro structuring of components made of steel was developed.

Research on Milling Deformation in Ultrasonic Vibration Assisted End Milling of Titanium Alloy Thin-Walled Parts

The hard machinability of titanium alloy material and the poor stiffness of thin-walled parts hindered the extensive application of titanium alloy thin-walled components in aerospace engineering. In order to heighten the geometric accuracy in the processing, the ultrasonic vibration assisted (UVA) end milling technology with workpiece vibrating in feed direction was put forward in this paper, and characteristics of the milling deformation in UVA milling of titanium alloy TC4 thin-walled workpieces were researched. Through the theoretical analysis, the cutting force and deformation characteristics in UVA milling were clarified. Based on the range analysis of orthogonal experiment, the effects of milling parameters and ultrasonic amplitude on the deflection displacement and the milling deformation of workpieces are obtained. Research results show that the deflection displacement in the process of UVA milling affects the thickness error of the thin wall. Ultrasonic parameters as well as milling parameters should be optimized to obtain higher machining accuracy. The research provides a certain reference for the precision milling of titanium alloy thin-walled parts.

Research on Milling Force in Ultrasonic Assisted End Milling of Titanium Alloy Thin-Walled Parts

Hard machinability of titanium alloy material and poor stiffness of thin-walled part restricted the extensive applications of titanium alloy thin-walled component in aerospace engineering. In order to increase geometric accuracy, a method of ultrasonic vibration assisted (UVA) end milling technology with workpiece vibrating in feeding direction was put forward in this paper, and the corresponding milling force characteristics in UVA milling of titanium alloy TC4 thin-walled workpiece were researched. Through theoretical analysis, the path of cutter tooth in UVA milling was analyzed. The important factors that affect milling force are obtained with the signal to noise ratio analysis. Results show that the radial cutting force in UVA milling is smaller than that in traditional milling. Cutting force fluctuate in high frequency when treated ultrasonic vibration. And the axial cutting feed is the core factor that affects the milling force. The research provides a certain reference for the precision milling of titanium alloy thin-walled parts.

An Investigation of Finite Element Analysis (FEA) on Piezoelectric Compliance in Ultrasonic Vibration Assisted Milling (UVAM)

Finite element analysis for piezoelectric actuator has been developed in Ansys Software which are a program that can analyses and simulate the dynamic behaviour of piezoelectric. The Ultrasonic Vibration assisted Milling (UVAM) experimental having a difficulty to investigate the effect of vibration mechanism where existence of error in material, mechanism and attachment of piezoelectric thus affect the amplitude and frequency of mechanical compliance during the machining of UVAM. This paper will investigate the modelling of piezoelectric compliance and follow the procedures of FEA to accurately predict the dynamic behaviour of compliance. The parameters for simulation of piezoelectric are voltage, electromechanical coupling and frequency. The compliance mechanism is model by using SolidWorks 2014 and imported to Ansys Mechanical APDL Software were the piezoelectric are embedded on the mechanism. Modal analysis and harmonic analysis has been used in order to obtain the mode shape and displacement. The displacement of the compliance mechanism will be compare between simulation and experimental. The dynamic behaviour was discussed in simulation to study the reliability of the compliance mechanism before it safely used in UVAM.

Influence of the surface microstructure on the adhesion of a CVD-diamond coating on steel with a CrN interlayer

forming tool coating. Most of the forming tools are made of steel, so that especially the coatability of steel by a polycrystalline diamond coating would rise the range of fields of application. The polycrystalline CVD-diamond coatings are deposited by a laser induced plasma CVD process, without a vacuum chamber. Various surface microstructures were investigated regarding their influence on the residual stresses to prevent a flaking of the coating: on the one hand, deterministic structures generated by ultrasonic vibration assisted milling (UVAM) and on the other hand, stochastic structures manufactured by blasting and polishing processes. For the UVAM, a surface prediction tool was used to design the surface microstructure beforehand. All steel substrates (material no. 1.2379) were coated in one batch by high-power impulse magnetron sputtering with a chromium nitride coating with a thickness of 2.4 μm. The specimens were analysed by laser microscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy and Raman spectroscopy. None of the microstructures investigated in this study was able to prevent delamination of the coating entirely. It could be shown that a roughness higher than Sa 0.1μm supports the interlocking between coating and surface as well as that sharp peaks inhibit a homogenous diamond coating deposition.

Modeling of static machining force in axial ultrasonic-vibration assisted milling considering acoustic softening

Ultrasonic-vibration assisted milling (UAM) process is one of the most recent advancements in the area of milling. In axial UAM process, milling cutter is rotated and vibrated in axial direction simultaneously with high frequency and small amplitude. Experimental studies showed that superposition of axial ultrasonic vibrations in milling operation improved the process by reducing cutting forces and enhancing surface finish. This study is focused on analytical study of the UAM process with axial vibration of end milling tool. A process physics-based model was developed to evaluate the cutting forces in axial ultrasonic assisted milling process. The developed model included acoustic softening, intermittent cutting and end mill helix angle effects. For validation of the developed model an experimental setup was developed. Axial UAM of Al6063 alloy workpiece was carried out with a high speed steel end milling tool. The predicted values and trend were found in good agreement with experimental results.

Study of milling force variation in ultrasonic vibration-assisted end milling

ABSTRACTUltrasonic vibration cutting has been proved to be an effective cutting technology for its excellent cutting performance and has been widely applied in turning and drilling process. However, this kind of technology is rarely tried in milling process. In cutting process, cutting force is an important process parameter, which affects surface finish and tool wear. This paper investigates the milling force variation in ultrasonic vibration-assisted end milling process through a series of slot-milling experiments. The main research contents include two parts, one is the effect of the externally excited vibration on milling force in milling process, and the other is the influence of milling and vibrating parameters matching on milling force value. Experimental results show that ultrasonic vibration can change traditional milling conditions, realize separate-type milling, obtain similar pulse-like profiles of cutting forces, reduce average cutting force value; and the peak value of the feed direction cutting force can also be greatly decreased by adopting reasonable vibration amplitude, an optimal combination of machining parameters is of great benefit to achieving small cutting force. According to the experimental findings, ultrasonic vibration-assisted milling is a prospective technology to achieve precision milling of small part.