Applicability of white light scanning interferometry for high-resolution characterization of surface defects

Current requirements for structural integrity, product safety, process feedback control and smart structures require methods for monitoring material properties and component performance to improve quality control and decrease maintenance costs. In most applications the onset of damage occurs at the component surface due to plastic deformation, fretting, corrosion, or crack nucleation. Therefore, the first step in nondestructive evaluation of a component is a thorough evaluation of the surface conditions. White light interferometry provides a fast, non- contact method of characterizing the 3D surface topography with a 3 nm vertical resolution. Thus far, white light interferometry has not been widely utilized as a nondestructive inspection tool. In this paper, the applicability of white light interferometry for monitoring damage progression for applications that are surface condition sensitive will be examined. These applications include corrosion initiation and progression, fretting damage characterization, combustion byproduct characterization and surface crack detection. For each application, a method for obtaining a quantitative measure of damage and a metric that can be used to determine remaining component life will be discussed.