Macro- & Micro-Fractographic Characterization
All metallic fracture surfaces leave a “signature” that can be discerned using the proper tools, techniques, and expertise. For fractographic analysis at the macro-level, stereomicroscopes are most commonly employed; at the micro-level, a combination of scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) is used – the latter is especially used when corrosion involvement is suspected.
For many failure investigations, such analyses provide the means by which many of the potential failure modes can be quickly eliminated and the primary mode can be determined for constructing the most probable root cause failure cascade (RCFC).
Advanced fractographic analysis of fatigue fractures can be used to determine the time-to-fracture initiation, from which key parameters, such as safe life and maintenance intervals, may be deduced. The determination of site(s) of fracture initiation can also provide critical information with respect to relatively simple and practical mitigation measures. For example, a determination that fracture initiation was associated with surface grinding marks or a sharp transition radius would turn the focus on blending and shot peening for significant increases in component life.
At DTB, we have the tools, techniques, and proven expertise to perform highly complex fractographic analyses. We have used such analyses to construct RCFCs for over 150 investigations. We have additionally performed hundreds of fractographic analyses to confirm or deny various assumed failure modes.