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In this article, the effect of vibration amplitude during ultrasonic elliptical vibration–assisted turning on cutting tool flank wear ( VBmax) and tool diffusion wear mechanism has been experimentally studied in machining of AISI 4140 hardened steel. To achieve this goal, an ultrasonic elliptical vibration–assisted turning setup was designed and manufactured. This device was then used in both ultrasonic-assisted tuning and ultrasonic elliptical vibration–assisted turning tests (i.e. one-dimensional and two-dimensional ultrasonic-assisted machining). According to the achieved results, ultrasonic elliptical vibration–assisted turning is more effective than ultrasonic-assisted tuning in reducing tool flank wear; at an amplitude of 13 μm, work velocity of 180 mm/s and feed of 0.09 mm/rev, VBmax were decreased 30.3% and 54.3%, respectively, in case of ultrasonic-assisted tuning and ultrasonic elliptical vibration–assisted turning. It was also observed that increasing the amplitude of ultrasonic vibrations reduces VBmax; at work velocity of 180 mm/s and feed of 0.09 mm/rev, the reduction of VBmax in ultrasonic elliptical vibration–assisted turning with amplitudes of 5 and 13 μm is, respectively, 39.3% and 54.3%, compared with that of conventional machining. The results also show that the application of ultrasonic vibrations weakens the cutting tool diffusion wear mechanism. This attenuation is much higher for ultrasonic elliptical vibration–assisted turning in comparison to ultrasonic-assisted tuning. Besides, the amount of attenuation in cutting tool diffusion wear mechanism decreases with increasing vibration amplitude.

This article summarizes the results of theoretical and experimental studies of average tool temperature in ultrasonic-assisted turning of aerospace aluminum using Al 2 O 3 -coated tools. In theoretical study, thermal modeling of heat source at the tool-work interface and the temperature distribution in the cutting tool are presented. To determine the actual performance, the sticking and slipping tool-chip contact lengths (l c and l s ) are experimentally measured and then heat source at the tool-work interface is modeled according to the analogy between shear stress distribution and heat source distribution on the rake face. Then, with respect to the kinematics of the process, the cutting velocity model is presented. The velocity model is used to define the heat flux equation and shear strain rate in ultrasonic-assisted turning. Using heat flux function and Johnson-Cook model, the temperature distribution in a semi-infinite rectangular corner, as a function of time and distance from tool tip, is presented. The analysis results are compared with experimental measurements of average cutting temperature from ultrasonic-assisted turning tests on 7075 aluminum using K-type Testo 735 thermocouple. On the other hand, results show that ultrasonic-assisted turning does not necessarily lower the average cutting temperature in all cases. The effectiveness of the technique is highly dependent on the value of vibration amplitude, work velocity, and feed rate. At low feed rates and amplitudes, the average tool temperature for ultrasonic-assisted turning is 60% of the conventional turning value while growing with an increase in feed rate and amplitude.

One of the major problems encountered in hardened components such as roller bearings, which work under fatigue loading conditions, is that the requirement of higher surface finishes (≈0.15 µm Ra) cannot be achieved by the sequential hard turning and ball burnishing processes. Such high surface qualities can be generated by additional finishing operations such as grinding. However, despite the improvement in the surface roughness, the grinding process increases both the tensile surface residual stresses and crack initiation sites on the ground surface; therefore, the fatigue behavior of the component may deteriorate. In this study, the effects of adding a grinding operation before the ball burnishing process on the fatigue behavior of AISI 4130 steel were experimentally studied. According to the achieved results, the burnished pre-ground samples show a considerable reduction in the final surface roughness and, at the same time, higher microhardness, higher endurance limit, and smaller area of the fatigue cracking zone. The burnished pre-turned and burnished pre-ground samples showed 4.24% and 10.95% improvements in the endurance limit compared to that of the turned samples, respectively.

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