doi:10.1088/0957-0233/25/11/115601engPech-May,N. W.Oleaga, AMendioroz, AOmella, A. J.Celorrio, R.Salazar, A.Vertical cracks characterization using lock-in thermography: I infinite cracksART-2014-91883Early detection of cracks is a challenging task to prevent failures in working structures. In the last decades the ‘flying spot’ method, based on heating the sample with a moving laser spot and detecting the surface temperature with an infrared detector, has been developed to detect cracks in a fast manner. The aim of this work is to measure the width of an infinite vertical crack using lock-in thermography. An analytical solution for the surface temperature of a sample containing such a crack when the surface is illuminated by a modulated laser beam focused at a fixed spot close to the crack is obtained. Measurements on samples containing calibrated cracks have been performed using an infrared camera. A least square fit of the amplitude and phase of the surface temperature is used to retrieve the thickness of the crack. A very good agreement between the nominal and retrieved thicknesses of fissure is found, even for widths down to 1 µm, confirming the validity of the model.2014http://zaguan.unizar.es/record/16949310.1088/0957-0233/25/11/115601http://zaguan.unizar.es/record/169493oai:zaguan.unizar.es:169493MEASUREMENT SCIENCE & TECHNOLOGY 25, 11 (2014), 115601 [11 pp.]by-nc-ndhttps://creativecommons.org/licenses/by-nc-nd/4.0/deed.esinfo:eu-repo/semantics/openAccess