Full definition
Failure analysis is a critical process in engineering that investigates components or systems that fail before their expected service life. This systematic examination employs various engineering tools and methodologies to identify the failure mode, mechanism, and root cause. The primary goal is to gather evidence that can inform corrective measures to prevent future occurrences of similar failures. The process typically begins with preserving and documenting the failed component, which includes photographing the item in its original position, collecting all fragments, and recording the operational and maintenance history. This information serves as a foundation for the subsequent steps.
A visual examination follows, where engineers analyze fracture surface features to glean insights about the failure type. Characteristics such as beach marks indicate fatigue, while dimpled ruptures suggest ductile overload, and cleavage patterns may reveal brittle fractures. Additionally, intergranular fractures often signal issues like corrosion or creep. Non-destructive testing (NDT) techniques, such as dye penetrant, magnetic particle, ultrasonic, or X-ray testing, are then employed to detect any subsurface defects that may not be visible to the naked eye.
If necessary, destructive testing is carried out to further investigate the material properties. This includes metallography, where cross-section microstructures are examined, along with hardness testing and chemical analyses to verify material grades. Scanning Electron Microscopy (SEM) combined with Energy Dispersive Spectroscopy (EDS) can reveal specific fracture surface morphologies and elemental compositions. Mechanical testing, including tensile, impact, and fatigue tests on similar material samples, is also crucial for understanding the mechanical limits of the material involved in the failure.
The final step is determining the root cause by correlating the findings from all the analyses with the recorded operating conditions. This thorough investigation is guided by standards such as ASTM E2332, which provides a comprehensive methodology for conducting failure analysis, and API 579, which addresses fitness-for-service assessments. In the case of rubber products, specific failure patterns like flex cracking, ozone cracking, chemical attack, heat degradation, and mechanical damage are analyzed, and tests such as hardness, tensile, compression set, and Fourier Transform Infrared Spectroscopy (FTIR) can be performed to identify the compound composition.