Papers by Author: Stefano Cavalleri

Abstract: This work focuses on the fatigue behaviour of notched Ti-6Al-4V titanium alloy in inert environment. V-notched flat samples were cycled under axial fatigue (R = 0.1) under inert conditions by immersion in paraffin oil. A step-loading technique was used to determine the fatigue limit at the complete fracture for a constant fatigue life of 2×10⁵ load cycles. The results were compared with previous data obtained with tests carried out in air and 3.5 wt.% NaCl solution. Fracture surfaces were examined under stereoscopic microscope.

Abstract: In this work the rolling contact fatigue (RCF) behaviour of WC/C PVD-coated and uncoated case hardened transmission gears for competition motorcycles was studied both numerically and experimentally. Finite element models of the gears were processed and a theoretical-numerical procedure was applied to the numerical results to predict their RCF life. The presence of the coating and the residual stress fields induced by the surface treatments were simulated. Besides 16NiCr11, which is the actual material of the gears analyzed, the Ti-6Al-4V alloy was also considered with the numerical models. Preliminary RCF tests were carried in both dry and lubricated condition to observe the damage on the tooth flanks with and without the presence of the coating.

Abstract: The aim of this work is to investigate the (rolling) contact fatigue behaviour of transmission spur gears coated with PVD (Physical Vapour deposition) thin hard films. Numerical models of coated steel and titanium spur gears were developed. The effect of the residual stress gradient induced by the coating deposition process was considered in the calculations. A theoretical-numerical procedure was arranged to foresee the crack propagation direction. Such a procedure could represent a powerful tool to predict the (rolling) contact fatigue resistance of PVD-coated gears.

Abstract: In this paper the influence of DCT (Deep Cryogenic Treatment) and a CrN arc-deposited PVD (Physical Vapor Deposition) coating on the fatigue behaviour of AISI 302 stainless steel was studied. Rotating bending tests were carried out on standard specimens to evaluate the fatigue limit at 300000 load cycles. The single and the combined effects of the two treatments were investigated by addressing untreated, PVD-coated and both PVD-coated and DC-treated specimens to the tests. All the series of specimens were also tested statically and laboratory analyses including fracture surface SEM observations and hardness measurements were performed.