Sandia National Laboratories has the expertise to analyze the failure of a product, component, or process by using advanced materials characterization and chemical analysis equipment and techniques. With techniques such as metallography, image analysis, scanning electron microscopy (SEM), fractography, electron-probe microanalysis (EPMA), chemical analysis, surface analysis, and x-ray diffraction, Sandia failure analysts not only determine the cause of failure, but also provide recommendations for preventing future problems.
Microstructural and Chemical Analysis: Sandia's expertise in materials characterization and analysis provides unique capabilities for failure analysis. A typical case involves low- and high-magnification analysis using light microscopy and SEM to characterize the general appearance of the failed component. Identifying deformation, corrosion product, wear marks, cracks, or other markings is an important step in diagnosing the cause of failure.
The Material Characterization Department has a diverse set of instrumentation and capabilities for materials characterization.
Based on initial observations and background information about the component, our experts in metallurgy, ceramics, polymers, corrosion, chemical analysis, and materials characterization can decide what further analysis is necessary. Particular regions or subcomponents may be analyzed at higher magnification. Advanced metallographic techniques can help determine the cause of failure as improper processing or heat treatment, improper manufacturing techniques, or inappropriate service conditions for particular materials.
SEM investigation of fracture surfaces can reveal the mode of failure, i.e., fatigue, creep, shear overload, tensile overload, or other complex failure modes. In addition, other tests may be performed, including chemical analysis, x-ray diffraction, or surface analysis, to identify species such as second phases or corrosion products.
In analyses of glass and ceramics, identification of characteristic fracture features aids in determining the magnitude and direction of applied stress and whether fracture occurred rapidly or slowly. As an example, fracture markings on the glass in the figure on the reverse show that the fracture initiated due to interfacial separation between the glass case and epoxy end-cap.
This type of forensic information provides the basis to identify and recommend changes in design, processing, and fabrication to eliminate fractures in devices that contain glass and ceramic members.
Identification of Failure Mechanism and Root Cause: When all the analyses are combined, a picture of the failure mechanism emerges. For example, the results may show the failure mechanism to be fatigue fracture. However, the next critical step is to identify the root cause, which may have been improper material selection, excessive vibration, or a pre-existing flaw in the material that eventually initiated the fatigue crack. In addition, once the root cause is identified, it is important to make recommendations concerning the future service of similar components. The failure analyst, working with other Sandia experts, will specify courses of action, such as a change in material, design, or environment, or other possibilities to help prevent future failures.