Fatigue Crack Prognostics by Optical Quantification of Surface Roughness

Reliable and operationally simple methods that can be used in the field are needed for observationally-based prognosis of remaining fatigue life. Previous work in the fatigue literature and at MetroLaser has shown that surface roughness can be a key indicator of the fatigue state of a component and that light scattering measurement is a convenient method for characterizing this roughness. However, there still exists a significant gap in the modeling capability due to the relative novelty of this technique. During Phase I, we showed the feasibility of developing a framework for interfacing between the sensed data and remaining life prediction in addition to showing the feasibility of integrating the sensor with different fatigue monitoring methods. With the basic feasibility of this prognostic paradigm demonstrated, the Phase I results can be used in the subsequent Phase II effort to refine the sensor design and develop remaining life models. The ultimate result will be a complete prognosis solution for structural health monitoring. Such a complete solution for sensing and prognostics would enable substantial cost savings in defense and commercial aircraft maintenance particularly. The compactness and low cost of the sensor technology makes it especially attractive.