Development of a micro-beam method to investigate the fatigue crack growth mechanisms of submicron-scale cracks

In this paper, we propose a new experimental method to investigate the fatigue crack growth mechanisms of submicron-scale cracks by using freestanding single edge notched micro-beams that are fabricated on the surfaces of conventional bending specimens with the focused ion beam technique. Three dimensional FEM simulations in conjugate with LEFM fracture analysis were carried out to correlate the applied far field stresses with the local crack-tip driving force. For the validation of the new method, micro-beam experiments were conducted on 4340 low alloy steels and the results showed the similar findings compared to those in the literature while revealed undiscovered fatigue damage mechanisms that took place at the submicron and nanometer scales.Department of Mechanical Engineerin