Holographic assessment of surface crack depths in rectangular bars

Abstract

It is shown that a partially-clamped, nondefective bar under an end load is characterized by a linear relationship between two normalized parameters which are related to the fringe order and the fringe location. That this linearity is perturbed due to the presence of a surface crack subsequently forms the basis for unambiguous detection of normal and inclined transverse cracks on the bar. This paper also demonstrates that the defective bar may be modeled as a partially-clamped stepped bar whose cross-sectional change is related to the geometry and depth of the crack. Furthermore, with the present method of analysis, the change in the fringe pattern with optical arrangement during constructing and reconstructing the hologram is easily taken care of.