Heat treatment, surface roughness and corrosion effects on the damage mechanism of mechanical components in the very high cycle fatigue regime

Many engineering components are subjected to combined torsion and axial loading in their working conditions, and the cyclic combined loading can result in fatigue fracture after a very long life fatigue regime. The present investigation extends over a wider range of test conditions involving surface treatment and manufacturing effects such as machining, so as to understand the fatigue properties and damage mechanisms of the material beyond 109 cycles. This work reviews the effect of surface conditions on the fatigue behaviour of mechanical components in the gigacycle regime. Evidently, surface conditions can be variable and are due to very different reasons such as manufacturing effects like machining or final surface processes on the parts, heat treatment before and after manufacturing or environmental conditions like corrosion. In fact, this is a detailed comparative study based on the results of experiments carried out by our research team working in this domain. For this reason, it reveals a continuous decrease of the fatigue strength in the VHCF domain for the investigated materials under different surface conditions as important information for design engineers. Experimental investigation on the test specimens was performed at a frequency of 20 kHz with different stress ratios varying between R = -1 and R = 0.7 at room temperature. All of the fatigue tests were carried out up to 10(10) cycles. The damage mechanism was evaluated by Scanning Electron Microscopy (SEM). (C) 2009 Elsevier Ltd. All rights reserved.