Multivariate Modelling of Effectiveness of Lubrication of Ti-6al-4v Titanium Alloy Sheet using Vegetable Oil-Based Lubricants

Abstract

The article presents the results of modelling the friction phenomenon using artificial neural networks and analysis of variance. The test material was composed of strip specimens made of 0.5-mm-thick alpha-beta Grade 5 (Ti-6Al-4V) titanium alloy sheet. A special tribotester was used in the tests to simulate the friction conditions between the punch and the sheet metal in the sheet metal forming process. A test called the strip drawing test has been conducted in conditions in which the sheet surface is lubricated with six environmentally friendly oils (palm, coconut, olive, sunflower, soybean and linseed). Based on the results of the strip drawing test, a regression model and an artificial neural network model were built to determine the complex interactions between the process parameters and the friction coefficient. A multilayer perceptron with one hidden layer and eight neurons in this layer showed the best fit to the training data. The network training was conducted using three algorithms, i.e. Levenberg-Marquardt, back propagation and quasi-Newton. Taking into consideration both the coefficient of determination R2 (0.962) and S.D. ratio (0.272), the best regression characteristics were presented by the network trained using the Levenberg-Marquardt algorithm. From the response surfaces of the quadratic regression model it was found that an increase in the density of lubricant at a specific pressure causes a reduction in the coefficient of friction. Low density and high kinematic viscosity of the oil leads to a high coefficient of friction.

Mechanical Properties of Titanium Grade 1 After Laser Shock Wave Treatment

“…Under these irradiation conditions, a shock wave is generated near the surface of the sample, the front propagation of which changes the properties of the material [18,19]. In experiments with a laser shockwave, which differs from other methods of generating shockwaves, it is fundamentally simplified to obtain the shape of the wavefront -flat, cylindrical, spherical, as well as the number of shock pulses, since the first of them depends only on the shape of the absorbing surface, and the second one on the selection and adjustment of the optical emitter and modulator of the Q factor [20][21][22]. Nanosecond laser treatment of titanium has found its application in medicine and dentistry.…”