Enhancing surface finish through ultrasonic vibration in machining of hardened Mo40 steel

Analysis of forces in ultrasonically assisted turning

This paper presents finite-element modeling and experimental study of the main cutting force in ultrasonic assisted turning (UAT) of Aerospace Aluminum using multicoated carbide inserts. At first, mathematical models were developed to investigate the effects of tool coating, rake angle, cutting speed, and feed rate on the friction coefficient. Then, with respect to the kinematics of the process, the cutting velocity model is presented. This velocity model is used in combination with mathematical models to define the friction coefficient during UAT. The mentioned frictional model is used to write a user subroutine to incorporate the effect of friction coefficient as a function of cutting parameters in the finite-element software Abaqus. Then, 2D finite-element modeling (FEM) models are developed for simulation of conventional turning (CT) and UAT with multilayer cutting tools. The models are used to investigate the effect of vibration amplitude, work velocity, feed rate, rake angle, and multicoated tool on the main cutting force during both CT and UAT. Finally, the results of FEM are compared with experimental measurements of the main cutting force. The results show that UAT is able to lower the main cutting force, by about 29%, in low feed rates (≈0.14 mm/rev), with vibration amplitude of ≈10 µm and work velocity of ≈0.5 m/s.

Nickel-based superalloys are widely used in the aerospace, automotive, marine and medical sectors, owing to their high mechanical strength and corrosion resistance. However, they exhibit poor machinability due to low thermal conductivity, high shear modulus, strain hardening, etc. Various modifications have been incorporated into existing machining techniques to address these issues. One such modification is the incorporation of ultrasonic assistance to turning operations. The assisted process is popularly known as ultrasonic assisted turning (UAT), and uses ultrasonic vibration to the processing zone to cut the material. The present article investigates the effect of ultrasonic vibration on coated carbide tool wear for machining Nimonic-90 under dry and wet conditions. UAT and conventional turning (CT) were performed at constant cutting speed, feed rate and depth of cut. The results show that the main wear mechanisms were abrasion, chipping, notch wear and adhesion of the built-up edge in both processes. However, by using a coolant, the formation of the built-up edge was reduced. CT and UAT under dry conditions showed an approximate reduction of 20% in the width of flank wear compared to CT and UAT under wet conditions. UAT showed approximate reductions of 6–20% in cutting force and 13–27% in feed force compared to the CT process. The chips formed during UAT were thinner, smoother and shorter than those formed during CT.

Ultrasonically assisted turning (UAT) is a novel material-processing technology, where high frequency vibration (frequency f ≈ 20kHz, amplitude a ≈15μm) is superimposed on the movement of the cutting tool. Advantages of UAT have been demonstrated for a broad spectrum of applications. Compared to conventional turning (CT), this technique allows significant improvements in processing intractable materials, such as high-strength aerospace alloys, composites and ceramics. Superimposed ultrasonic vibration yields a noticeable decrease in cutting forces, as well as a superior surface finish. A vibro-impact interaction between the tool and workpiece in UAT in the process of continuous chip formation leads to a dynamically changing stress distribution in the process zone as compared to the quasistatic one in CT. The paper presents a three-dimensional, fully thermomechanically coupled computational model of UAT incorporating a non-linear elasto-plastic material model with strain-rate sensitivity and contact interaction with friction at the chip–tool interface. 3D stress distributions in the cutting region are analysed for a representative cycle of ultrasonic vibration. The dependence of various process parameters, such as shear stresses and cutting forces on vibration frequency and amplitude is also studied.

Ultrasonically assisted turning (UAT) is a novel material-processing technology, where high frequency vibration (frequency f ≈ 20kHz, amplitude a ≈15μm) is superimposed on the movement of the cutting tool. Advantages of UAT have been demonstrated for a broad spectrum of applications. Compared to conventional turning (CT), this technique allows significant improvements in processing intractable materials, such as high-strength aerospace alloys, composites and ceramics. Superimposed ultrasonic vibration yields a noticeable decrease in cutting forces, as well as a superior surface finish. A vibro-impact interaction between the tool and workpiece in UAT in the process of continuous chip formation leads to a dynamically changing stress distribution in the process zone as compared to the quasistatic one in CT. The paper presents a three-dimensional, fully thermomechanically coupled computational model of UAT incorporating a non-linear elasto-plastic material model with strain-rate sensitivity and contact interaction with friction at the chip–tool interface. 3D stress distributions in the cutting region are analysed for a representative cycle of ultrasonic vibration. The dependence of various process parameters, such as shear stresses and cutting forces on vibration frequency and amplitude is also studied.

The surface integrity of machined sample has detrimental effects on the product’s life. The machining parameters have been found to significantly affect the surface integrity during the turning operation. Surface roughness, residual stresses and microhardness are the most commonly used parameters to study the surface integrity. In this chapter, an attempt has been made to present a comparative analysis of conventional turning (CT) and ultrasonically assisted turning (UAT) processes with plain and textured cutting tools. The effect of ultrasonic power (measured in terms of amplitude) on surface roughness has been studied during UAT process. An increase in the amplitude improved the surface finish of the machined specimen, significantly. The surface residual stresses generated in the machined part during UAT have been compared for plain and self-lubricating cutting inserts using XRD analysis. An attempt has been made to evaluate the residual stresses generated during the process by using commercially available finite element method package, ANSYS. The generation of a large compressive residual stresses during UAT process with self-lubricating cutting inserts signifies better fatigue life of the component. The microhardness measurements are used to demarcate the Machine Affected Zone (MAZ) for UAT and CT process. A comparative analysis between CT and UAT has also been presented in terms of surface integrity to demonstrate better machining regime found in UAT using self-lubricating cutting inserts.

This study investigates ultrasonic-assisted turning (UAT) of hardened 4340 steel, analyzing the effects of cutting speed, vibration amplitude, and feed rate on cutting forces and surface finish compared to conventional turning (CT). Results demonstrate that UAT reduces cutting forces significantly through impulse cutting, which lowers the friction coefficient by transitioning from quasi-static to dynamic contact. However, higher cutting speeds diminish this benefit by prolonging tool-workpiece contact. Optimal surface roughness is achieved by increasing vibration amplitude while reducing cutting speed. The findings highlight UAT’s potential to enhance machining efficiency in hard-turning applications, offering improved surface quality and reduced cutting forces. The study underscores the importance of parameter optimization to maximize UAT’s advantages, particularly for challenging materials like hardened steel.

Ultrasonically assisted turning (UAT) is a progressive machining method in which vibration is applied to the cutting insert in the direction of the cutting tool velocity to reduce the cutting forces, significantly and increase the surface finish noticeably. However, the key question about the tool damage caused by the vibration and its effect on the cutting forces, surface roughness and process zone temperature is still unknown in UAT.This paper presents experimental analysis of the effect of worn tool in UAT and conventional-turning (CT) of β-Ti-15V-3Al-3Cr-3Sn (Ti-15333) alloy on surface quality of a machined surface, temperature of the process zone and cutting forces using KC5510 (PVD TiAlN) and CP500 (PVD (Ti,Al)N-TiN) cutting inserts. In UAT, the tool edge damages in CP500 inserts increased with tested machining time resulted a growth of 8 N and 10 N in tangential force component in CT and UAT, respectively. Similarly, with the progression of tool edge damage, a growth of 1.7% and 9.3% in process zone temperature was observed in CT and UAT, respectively. The surface roughness results revealed a gradual degradation with machining time, however, the results UAT with a worn tool was significantly better when compared to CT, with a virgin tool.

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.

3D finite element analysis of ultrasonically assisted turning

Thermomechanical finite element simulations of ultrasonically assisted turning

GH4068 superalloy is a new type of nickel-based superalloy in the aerospace field. It is an important alloy material for the manufacture of aircraft tubular components and aero-engine hot-end components. These components need to be machined with good surface quality to meet their use requirements. New hybrid machining processes can improve the quality of surface finish compared to conventional machines. In this paper, ultrasonic assisted turning (UAT) technology was applied to the machining of GH4068 superalloy. The experimental system of UAT was established. Experiments of UAT and conventional turning (CT) of GH4068 superalloy were carried out to study the effects of cutting speed, feed speed, cutting depth and vibration amplitude on cutting force and surface roughness. The surface morphology of the workpiece and chip were observed. The experimental results show that Fx and Fy can be reduced by a maximum of 44% and 63%, respectively, and the surface roughness can be reduced by a maximum of 31% after adding ultrasonic vibration. Compared with CT, the UAT has a better machining quality, a more obvious chip-breaking effect, and a smaller chip bending radius, which guides the high-quality processing of the GH4068 superalloy.

Many techniques have been developed to improve the machinability of aeronautical materials titanium and nickel-based alloys such as ultrasonic-assisted turning, laser-assisted turning, and cryogenic-assisted turning. This collaborative scientific investigation presents the steps taken to gain insight into the phenomena of machining Nimonic 90 (a nickel-based alloy) alloy using ultrasonically assisted turning. The cutting speed, feed rate, depth of cut, and frequency are taken as input parameters and average surface roughness (Ra), power consumption (P), and chip formation are considered as output parameters. The experiments are carried out with the full factorial design. The UAT (ultrasonically assisted turning) process gives a significant improvement in average surface roughness and power consumption because of the intermittent cutting action of the cutting tool. UAT process shows a 70–80% reduction in average surface roughness (Ra) and a 6–15% reduction in power consumption as compared with CT (conventional turning) process. Ultrasonically assisted turning also resulted in the thin and smoother chips as compared with CT process which helps to achieve a more superior machining effect. Finite element modeling shows that the quasi-static nature of the stress induced in the UAT process leads to lower force and ultimately lower power generation. Moreover, a sustainability assessment model is implemented to investigate the effect of UAT in terms of machining performance as well as sustainability effectiveness in a single integrated approach. The novelty of this work lies in providing an integrated concept that combines experimental analysis and sustainability assessment when using ultrasonic vibrational energy during turning of Nimonic 90.

Ultrasonically assisted turning of micro-SiCp/Al 2124 composite

Aerospace-grade Ni-based alloys such as Inconel 718 and 625 are widely used in the airspace industry thanks to their excellent mechanical properties at high temperatures. However, these materials are classified as ‘difficult-to-machine’ because of their high shear strength, low thermal conductivity, tendency to work-harden and presence of carbide particles in their microstructure, which lead to rapid tool wear. Machining-induced residual stresses in a machined part is an important parameter which is assessed since it can be used to evaluate overall structural resilience of the component and its propensity to fatigue failure in-service. Ultrasonically assisted turning (UAT) is a hybrid machining technique, in which tool-workpiece contact conditions are altered by imposing ultrasonic vibration (typical frequency ~ 20 kHz) on a tool’s movement in a cutting process. Several studies demonstrated successfully the resulting improvements in cutting forces and surface topography. However, a thorough study of UAT-induced residual stresses is missing. In this study, experimental results are presented for machining Inconel 718 and 625 using both conventional turning (CT) and UAT with different machining parameters to investigate the effect on cutting forces, surface roughness and residual stresses in the machined parts. The study indicates that UAT leads to significant cutting force reductions and improved surface roughness in comparison to CT for cutting speeds below a critical level. The residual stresses in machined workpiece show that UAT generates more compressive stresses when compared to those in CT. Thus, UAT demonstrates an overall improvement in machinability of Inconel alloys.