Surface Discontinuities and Fatigue Performance
We all know that surface conditions and discontinuities can affect fatigue performance. And certainly, not all surface discontinuities (or materials) are equal with respect to fatigue performance. However, in our experience, metallurgists and other failure analysts often ignore the big picture in a failure investigation and focus on the microscopic. This presentation reviews the fundamentals of fatigue, surface analysis, stress concentration and fatigue sensitivity, and fracture mechanics and stress analysis, and aims to provide failure analysts with tools by which to better evaluate the effects of varying surface conditions, discontinuities, and actual defects on the fatigue performance of engineering components as part of a failure analysis investigation. Lastly, we provide a case study that uses these tools to help evaluate the effect of machining marks on the fatigue fracture of an orthopedic implant.