Nonlinear frequency-mixing photoacoustic imaging of a crack: Theory

Abstract

This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitation.aip.org/termsconditions. Downloaded to ] IP: 136.165.238.131 On: Sun, 21 Dec 2014 04:55:22 124905-2 V. Gusev and N. Chigarev J. Appl. Phys. 107, 124905 ͑2010͒ [This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitation.aip.org/termsconditions. Downloaded to ] IP: 136.165.238.131 On: Sun, 21 Dec 2014 04:55:22 124905-3 V. Gusev and N. Chigarev J. Appl. Phys. 107, 124905 ͑2010͒ [This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitation.aip.org/termsconditions. Downloaded to ] IP: 136.165.238.131 On: Sun, 21 Dec 2014 04:55:22 124905-4 V. Gusev and N. Chigarev J. Appl. Phys. 107, 124905 ͑2010͒ [This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitation.aip.org/termsconditions. Downloaded to ] IP: 136.165.238.131 On: Sun, 21 Dec 2014 04:55:22 124905-5 V. Gusev and N. Chigarev J. Appl. Phys. 107, 124905 ͑2010͒ [This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitation.aip.org/termsconditions. Downloaded to ] IP: 136.165.238.131 On: Sun, 21 Dec 2014 04:55:22 124905-6 V. Gusev and N. Chigarev J. Appl. Phys. 107, 124905 ͑2010͒ [This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitation.aip.org/termsconditions. Downloaded to ] IP: 136.165.238.131 On: Sun, 21 Dec 2014 04:55:22 124905-8 V. Gusev and N. Chigarev J. Appl. Phys. 107, 124905 ͑2010͒ [This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitation.aip.org/termsconditions. Downloaded to ] IP: 136.165.238.131 On: Sun, 21 Dec 2014 04:55:22 124905-9 V. Gusev and N. Chigarev J. Appl. Phys. 107, 124905 ͑2010͒ [This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitation.aip.org/termsconditions. Downloaded to ] IP: 136.165.238.131 On: Sun, 21 Dec 2014 04:55:22 124905-10 V. Gusev and N. Chigarev J. Appl. Phys. 107, 124905 ͑2010͒ [This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitation.aip.org/termsconditions. Downloaded to ] IP: 136.165.238.131 On: Sun, 21 Dec 2014 04:55:22 124905-11 V. Gusev and N. Chigarev J. Appl. Phys. 107, 124905 ͑2010͒ [This article is copyrighted as indicated in the article. Reuse of AIP content is subject to the terms at: http://scitation.aip.org/termsconditions. Downloaded to ] IP: 136.165.238.131 On: Sun, 21 Dec 2014 04:55:22 124905-13 V. Gusev and N. Chigarev

Probing of laser-induced crack modulation by laser-monitored surface waves and surface skimming bulk waves

“…The high contrast achieved in crack imaging by remote optical monitoring of the nonlinear acoustic processes was due to the strong dependence of the optoacoustic conversion efficiency on the state, i.e., open or closed, of the crack. 23 In this letter we report all-optical evaluation of real surface-breaking crack nonlinearity using quasi-continuous laser heating of the crack to induce changes in its elasticity and using laser-generated and laser-detected acoustic pulses, propagating along the material surface, to probe the crack. In comparison with the all-optical frequency-domain technique, 22 based on the harmonically modulated cw lasers and taking an advantage of the acoustical resonances of the crack-containing sample for the detection of nonlinear effects, the time-domain technique presented below is potentially faster for imaging applications.…”

Two dimensional nonlinear frequency-mixing photo-acoustic imaging of a crack and observation of crack phantoms

“…In contrast, non-analytic tapping/clapping nonlinearity excites, because of the non-cascade multi-frequency nature of the initiated nonlinear interactions, 32 the side-lobes of comparable amplitudes just slowly decreasing with increasing order. 27,28,33 It is also worth noting that in the latter case the dependence of the side-lobe amplitudes on their order can be non-monotonous and, depending on the excitation level, the lower order side-lobe can be stronger that the higher-order one or vice versa. 27,28,33 We are aware of several different methods which had been earlier used in order to achieve strongly nonlinear motion of the crack with purposes of its imaging.…”

“…27,28,33 It is also worth noting that in the latter case the dependence of the side-lobe amplitudes on their order can be non-monotonous and, depending on the excitation level, the lower order side-lobe can be stronger that the higher-order one or vice versa. 27,28,33 We are aware of several different methods which had been earlier used in order to achieve strongly nonlinear motion of the crack with purposes of its imaging. In the experiments, 14,15 strongly nonlinear multi-frequency oscillations in the vicinity of the crack/defect had been excited by acting on the complete sample by high power piezoceramic stack oscillators or vibrators.…”

“…Finally, both the initiation of the crack tapping/clapping by the laserinduced thermoelastic stresses and the photo-acoustic generation of the probing acoustic field have been recently combined in the NFMPA technique. 25,26,33 The ultimate spatial resolution of the NFMPA imaging in 3D geometry is only limited by the dimensions of the light absorption region and can be much higher than the one limited by the acoustic and thermal wavelengths. Through the experimental observation of the multiple high-order side lobes, it has been demonstrated 25 that clapping/tapping of the crack can be initiated by the intensity-modulated cw laser radiation of the power ($120 mW), which is importantly lower that in Refs.…”

Application of ultrasonic surface waves in the detection of microcracks using the scanning heating laser source technique

“…Because temporary thermoelastic stresses disappear after turning off the heating laser, this modulation process is fully reversible and does not cause any damage to the samples. Chigarev et al [9,10] first demonstrated nonlinear frequency-mixing detection of cracks using purely optical methods. High-contrast nonlinear photoacoustic imaging can be achieved by exploiting the strong dependence of the conversion efficiency of photoacoustic waves on the mechanical state of cracks, whether open or closed.…”