Microtexturing of industrial surfaces via radial ultrasonic vibration-assisted machining: An analytical model and experimental validation

Abstract

The aim of this paper is to develop an analytical model to predict different texture patterns obtained with Radial Ultrasonic Vibration Assisted Machining (RUVAM) and estimate the dimensions of their characteristic features. It is also validated experimentally by performing advanced surface metrology on C45 specimens. The model is based on considering the machining of craters along radial tracks as the main texturing mechanism due to the change in the effective depth of cut provoked by the ultrasonic vibration of the insert. Mathematical formulae composing the model are then developed by considering how the machined craters in those tracks interact radially and axially, describing the final texture as the result of a multidirectional geometrical interaction. To predict how those interactions take place depending on the manufacturing parameters chosen, threshold values for the feed rate and the depth of cut are proposed. They also allow the validation of the formulae that estimate the different geometrical descriptors of craters (radial and axial heights and widths). According to the different combinations of parameters, the model succeeds in proposing diverse potential texturing scenarios. In the second part of this paper, a full factorial design is planned and applied on C45 specimens to validate the results with a RUVAM tool of 40 kHz and a 1 μm-amplitude. The plan includes three factors (insert nose radius, depth of cut and feed rate). Their levels are defined according to the threshold values for feed and depth of cut defined by the model to reproduce different textures. Results prove that the proposed threshold values allow a very good assessment of the resulting microtexturing structures on the surfaces. The measured values of widths and heights are in agreement with the values predicted by the model. With this technique, the heights of the textured surfaces span from 5 to 400 μm and widths from 45 to 720 μm, depending on the selected parameters. In the radial direction, the vibratory motion of the insert is robustly imprinted on the material, with radial heights and widths of around 2 μm and 39.6 μm, agreeing with the model. In overall, errors comparing the experimental measurements and the values predicted by the model rise up to 9%, although this error can reach 15% at some cases on radial descriptors because of their higher sensitivity to the F-filtering. A last texturing mechanism can be attributed to RUVAM related to the shaping of craters, as different oval permeters can be obtained by combining the parameters adequately. All these results lead to potential future studies related with the functional implications of all the detected textures.