Understanding the Surface Features of Fatigue Fractures: How They Describe the Failure Cause and the Failure History

Most of us have been exposed to fatigue failures since we first started looking at broken pieces. In many cases, the first explanation of a failure began with a well-intentioned person explaining that a component had "crystallized" because it was a piece of defective steel. However, as we know, virtually all structural metals are crystalline, and after working with fatigue analysis for a while, it becomes apparent that defective materials are not common failure causes. Additionally we learn that the fracture face can provide a wealth of information about the causes. It can show the type and direction of the forces acting on the part, the magnitude and fluctuations of these forces, and can give a general indication of the length of time from initiation to final fracture. This paper is a review of a selection of fracture faces and the descriptions of how to interpret some of the details on these faces.