<title>Amendment in observation of cracklike defects in metal plates with new instrumentation by utilizing holographic interferometry as NDT method</title>

Abstract

In holographic interferometry an object must be irritated in order to make material defects or displacements of the object visible. In solids an elastic wave is a reliable source of this irritation for holographic interferometry purposes. The nature of the elastic wave is quite essential when studying crack-like defects in metal plates. A high quality CO<SUB>2</SUB>-pistol can establish an impact velocity of over 100 m/s and adequate stability in a long series of impacts can be generated by the pistol's bullet. In this paper a new instrumentation for external impact on the object in holographic interferometry is described. Interferograms are recorded by a double-pulsed ruby laser synchronized with the external impact. Some interferograms of a 10 mm thick iron plate are studied. In these interferograms the crack-like defects are clearly observable.