#### Vol. 1, No. 4, 2006

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So\dots is this a surface-breaking crack?

### Milan Poznic and Claudio Pecorari

Vol. 1 (2006), No. 4, 743–762
##### Abstract

An inspection technique used to assess the structural integrity of critical components in a nuclear power plant must be able to discern surface-breaking cracks from subsurface cracks. This work proposes an ultrasonic method to provide that information and presents a theoretical investigation into it. The main assumption of the model is that water carried by pressurized pipes infiltrates and fills a surface-breaking crack, while a subsurface crack is dry. The model simulates an inspection in which the modulation technique is employed and the surface hosting the crack is not accessible. A ratio, $R$, constructed with signals recorded in backscattering configuration during a modulation cycle, is examined and shown to provide a clear criterion allowing subsurface cracks to be distinguished from surface-breaking cracks when a shear vertical wave at 45 degree incidence is employed as a probe.

##### Keywords
partially closed cracks, modulation, wave scattering stress-corrosion
##### Milestones
Received: 15 December 2005
Revised: 7 February 2006
Accepted: 30 March 2006
Published: 1 August 2006
##### Authors
 Milan Poznic Marcus Wallenberg Laboratory Department of Aeronautical and Vehicle Engineering Royal Institute of Technology SE 10044 Stockholm Sweden Claudio Pecorari Marcus Wallenberg Laboratory Department of Aeronautical and Vehicle Engineering Royal Institute of Technology SE 10044 Stockholm Sweden