(V) Powerful Systematic Methodological Fractographic Analysis at the Macro, Mezzo and Micro Scales

This three step method of performing fractography is more powerful than the classical two step method. Since a true answer to the question "Why did it break?" is always "Because the (local) stress exceeded the (local) strength," it behooves us to start with an analysis of the stresses. Since the stresses themselves are invisible, we need to take a step back and imagine the loading geometry, based on the part shape and our knowledge of its use. The loading geometry is (often, at least in simply shaped components) immediately discernible in the form of the fragment shape. Specifically, we need to determine the orientation of the fracture surface with respect to the original part surface features. However, in some cases, the answer might not be unique, and thus we also need to go a step further along the decision tree. In either case, we need to classify the material behavior during the fracture event itself as either ductile or brittle. Before moving on, we need to ask if the crack is at its expected location. That is macro-fractography. Then we move to mezzo-fractography, where we interpret steps, ridges, coloration, texture, and other features commonly described in the classical fractography literature. Finally, micro-fractography, often with the aid of a scanning electron microscope, and focusing on the suspected initiation and final separation areas, as determined in the mezzo stage, lets us understand how the stresses and environment interacted with the microstructure of the material. Using this three step method of fractographic inspection and analysis is inherently epistemologically confidence inspiring, and when correctly performed, gives the practitioner a rightful claim to having practiced one of the major foundations of skillful thinking. Use of this methodology allows all FA practitioners to communicate their findings to non-materials scientists in a clear and concise manner.