Saeid Amini

Effect of Ultrasonic Vibrations on Chip–Tool Contact Zone in Turning of AISI304

In this paper, primary and secondary deformation zone of chips produced by vibration turning (VT) and ordinary turning (OT) are investigated and compared with each other to study seizure length and shear angle. To do this, it is required to quickly stop moving chips on the surface of vibrating tools. A fixture with the ability to quickly stop vibrating tool was designed and manufactured. Workpieces were tubular and made of AISI304, and cutting tools were DCMW11T308. Orthogonal cutting tests were performed by VT and the process was stopped quickly while chip moving on tool surface; then, shear angle and seizure length were measured by an optical microscope. Based on the achieved results, applying ultrasonic vibrations to turning process can increase shear angle and decrease seizure length.

Experimental and numerical study of ultrasonically-assisted drilling

Highlights3D finite element simulation of ultrasonically‐assisted drilling is represented.Influence of harmonic movement of drill bit on built‐up edge formation is evaluated.Analysis of heat generation affected by ultrasonic vibrations is carried out.Forces are smaller in ultrasonic assisted drilling compared to the conventional one.Modification of continuous chip to segmented chip in UAD is happened by increase of deformed chip curling. ABSTRACT In this study, 3D finite element simulation of ultrasonically‐assisted drilling is carried out to analyze the effect of ultrasonic vibrations on common difficulties existed in conventional drilling. Influence of harmonic movement of drill bit on the formation of built‐up edge is experimentally evaluated and also discussed by investigation of heat generation on the tool faces in simulation. At the end, it was revealed that intermittent movement of drill bit in vibration method causes the total time of heat transfer between workpiece and drill bit to be reduced resulting lower built‐up edge formation compared to conventional drilling. Moreover, linear motion of cutting tool in the feed direction results in the increase of chip strain and consequently damage value which causes to generation of broken chips.

Effect of longitudinal−torsional vibration in ultrasonic-assisted drilling

ABSTRACT In general, drilling of aeronautical materials is faced with some difficulties. To improve this process, a variety of methods have been presented by researchers. One of these methods is ultrasonic-assisted drilling (UAD). In this study, performance of longitudinal−torsional (L-T) vibration in UAD of Al 7075-T6 with HSS tool is investigated. Accordingly, a vibration tool with ability of producing L-T vibration was designed. After modal analysis and achievement of desired resonance frequency, it was fabricated and some experimental tests were conducted. A dynamometer with six degrees of freedom was utilized to measure torque and thrust force during the cutting process. As a result, it was revealed that this kind of vibration significantly reduces cutting forces compared with the conventional drilling (CD). Furthermore, this reduction was clarified by investigation of generated chips and tool rake angle. Moreover, effect of ultrasonic vibration on drill skidding and surface quality has been studied.

Effect of ultrasonic vibration on frictional behavior of tool–chip interface: Finite element analysis and experimental study:

Ultrasonic-assisted machining is an advanced method which allows significant improvements in processing of materials. In this study, a finite element model is developed to study the effect of ultrasonic vibration on machinability of AISI 304 stainless steel in which the results are compared with conventional cutting process. A pneumatic quick-stop device and an optical microscope are applied to validate the simulation results by measuring shear angle and sticky region experimentally. As a result, the analysis of heat generation in primary and secondary deformation zones shows that temperature increases in the primary zone when ultrasonic vibration is used, while a significant reduction in temperature is seen in the tool–chip contact zone. This area is considerably effective on the length of sticky region. Moreover, the influence of cutting speed and feed rate on tool–chip engagement time is investigated by the analysis of cutting force profile.

Built-up edge reduction in drilling of AISI 1045 steel

ABSTRACT In this study, a combined drilling method consists of ultrasonic-assisted drilling (UAD) under the presence of minimum quantity lubrication (MQL), is evaluated. Effect of this method on machinability factors is investigated by implementation of a dynamometer and a vision-measuring microscope. Then the results are compared with the values obtained in conventional drilling, and separately UAD and MQL-drilling. As a result, it was revealed that the output parameters were significantly improved when combined MQL–UAD method was exerted. In particular, built-up edge and drill skidding have almost been eliminated. Moreover, it was shown that increase of tool rake angle and producing broken chips caused thrust force and surface roughness to be reduced in UAD and UAD–MQL. In the combined strategy, burr-less hole has been achieved due to the formation of solid burr at the exit surface of drilled hole.

Parametric study and multicharacteristic optimization of rotary turning process assisted by longitudinal ultrasonic vibration

Turning with rotary tool is a newly developed alternative of the conventional turning process in which cutting edge of a round insert rotates about its axis, so that a continuously indexed cutting edge is fed into the cutting zone. In the present study, a longitudinal high-frequency vibration was superimposed to the rotary tool to analyze the cutting force and surface roughness of AA7075 during orthogonal cutting. However, due to contribution of wide ranges of factors in the vibratory-rotary turning process, the selection of optimal parameter setting is a challenge that is faced with this process. In the present work, an attempt was made to simultaneously minimize machining force (Fz) and surface roughness (Ra) through selection of the optimal setting of cutting velocity, feed rate, tool rotary speed in rotary turning, and vibratory-rotary turning operations. Here, grey relational analysis was used to find the optimal parameter setting in rotary turning and vibratory-rotary turning processes, separately. Then the obtained solutions were compared. Results indicated that applying axial vibration to the rotary tool turning significantly reduced both surface roughness and cutting force. From the optimization by the grey relational analysis method, it was obtained that for both rotary turning and vibratory-rotary turning operations, setting of 4 m/min cutting velocity, 220 r/min tool rotary speed, 0.08 mm/rev feed rate, and 0.3 mm depth of cut are the most-optimal solutions that causes minimum Fz and Ra, simultaneously. Also, the vibratory-rotary turning process had higher values of grey relational grade than the rotary turning process that implies outperformance of the vibratory-rotary turning with respect to the rotary turning process. The obtained results were then verified, compared, and discussed based on the mechanics of turning process.

Elliptical ultrasonic–assisted turning tool with longitudinal and bending vibration modes

Ultrasonic-assisted turning is a machining process in which a vibrational displacement (usually in ultrasonic frequencies) is superimposed with the machining displacements in the cutting direction (one-dimensional ultrasonic-assisted turning) or in the cutting direction along with the radial direction (two-dimensional ultrasonic-assisted turning or elliptical ultrasonic–assisted turning). In this research, an elliptical ultrasonic–assisted turning tool is designed in ABAQUS software, in which the longitudinal and bending vibration modes have the minimum resonance frequency difference, so that the resonance of both the vibration modes can be achieved in a definite frequency. A set of half-ring piezoelectric stacks is employed for excitement of the bending mode, and a set of ring-shaped piezoelectric stacks is used for the excitement of the longitudinal mode. There is a phase shift with the amount of π/2 between the longitudinal and bending vibration modes to produce an elliptical vibration. The manufactured tool is employed for machining of copper, which resulted in better surface finish and lower cutting forces.

Characterization of various coatings on wear suppression in turning of Inconel 625: A three-dimensional numerical simulation

Applying cutting tool with longer functioning time is a vital issue in machining of the nickel-based super alloys. However, the experimental analysis of this problem is quite expensive. Thus, three-dimensional numerical simulation of tool wear propagation in turning of Inconel 625 super alloy is taken into account, in this study. The cutting insert with complex geometry is modeled by using a reverse engineering method. Based on the cutting tool and workpiece material, Usui wear rate model is exerted to estimate the tool wear rate. In the first section, characterization of TiAlN-coated carbide tool, which is suggested by catalogue, on wear resistance is evaluated and then simulation results are validated with experiments. As a result, increment of depth of cut is the most effective factor on the generation of temperature and stresses on the tool faces resulting in wear rate acceleration. In the second section, different commercial coatings with multicompositions are applied in the simulation to find the best performance against wear. Finally, TiCN coating outperformed other coatings in turning of Inconel 625.

Investigation of the ultrasonic vibration effect in incremental sheet metal forming process

The mechanism of incremental sheet metal forming is based on plastic and localized deformation of sheet metal. The sheet metal is formed using a hemispherical-head tool in accordance with the path programmed into the computer numerical control milling machine controller. Experimental and numerical analyses have been performed previously on the application of ultrasonic vibration to various metal forming processes. However, thus far, the effects of ultrasonic vibration on incremental sheet metal forming have not been investigated. This article presents the process of design, analysis, manufacture and testing of a vibrating forming tool for the development of ultrasonic vibration–assisted incremental sheet metal forming. The results obtained from modal analysis and natural frequency measurement of the vibrating tool confirmed the emergence of a longitudinal vibration mode and resonance phenomenon in the forming tool. Then, the effect of ultrasonic vibration on incremental sheet metal forming was studied. The obtained experimental results from the straight groove test on Al 1050-O sheet metals showed that ultrasonic vibration led to decrease in the following parameters as compared with conventional incremental sheet metal forming: applied force on forming tool axis, spring-back and surface roughness of formed sample.

Improvement of Near-Dry Machining and Its Effect on Tool Wear in Turning of AISI 4142

In this study, improvement of near-dry machining (NDM) and its effect on tool wear in turning of AISI 4142 by carbide tool (DNMG 150608-PM) is investigated. First, the preparation of experimental setup was carried out, and then, some experiments to study the process were performed. Surface roughness was used as the criterion of finding the optimal conditions of fluid flow rate and frequency, and position and angle of nozzle. After optimization of the process, some experiments were performed to study tool life. Machining force, roughness, and tool wear were chosen as the criteria to determine the tool life. Obtained results show that the tool life in NDM is longer than that in dry machining.