Scribe Marks at Fuselage Joints: Determination of Residual Stress and Effects of Fatigue Loading Using Nanoindentation and Snychrotron X-Ray Diffraction

Empirical understanding of fatigue crack growth from small defects is of tremendous importance and of significant concern for structural integrity of aerospace structures. In fatigue, a crack initiates from a stress concentration location and causes premature failure. In principle fatigue life for scribes and scratches is function of the stress concentration around the root which depends upon the depth and root radius of the scribe, the associated microstructure, the residual stress field, work hardening from plastic deformation during scribing and relaxation or redistribution of these residual stresses in fatigue. The scope of the present work is on determination of the residual stress field around scribe marks of different geometries and the effect of fatigue loading on the residual stress field. The determination of a local residual stress field in a small area of 100 μm x 100 μm around shallow scribes (