Nonlinear ultrasonic imaging method for closed cracks using subtraction of responses at different external loads

Ohara, Yoshikazu; Horinouchi, Satoshi; Hashimoto, Makoto; Shintaku, Yuichi; Yamanaka, Kazushi

doi:10.1016/j.ultras.2010.12.010

Cited by 46 publications

(39 citation statements)

References 23 publications

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“…It is an option of the load difference phased array (LDPA). 19) After confirming the crack opening capability of the global preheating and local cooling (GPLC), 20) we applied STIS to the PA images. As a result, only the crack responses were successfully extracted in the subtracted image, with eliminating the responses of linear scatterers, whereas the conventional subtraction method of subtracting a PA image obtained before a start of LC from that after the start of LC could not eliminate the responses of linear scatterers.…”

Section: Discussionmentioning

confidence: 98%

“…5(e), 6(c), and 7(c), respectively. As a measure of the selectivity, 19) the intensity ratio of cracks to objects other than cracks is defined as…”

Section: Discussionmentioning

confidence: 99%

“…On the other hand, the application of waveform subtraction 19,25,26) is also conceivable. This provides the variance of phase changes as well as of amplitude changes, although it does not provide the increase or decrease in the extent of change.…”

Section: Discussionmentioning

confidence: 99%

“…To solve this problem, we have proposed a load difference phased array (LDPA), 19) which is based on the subtraction between phased array images at different loads. The principle of LDPA was verified in a fundamental experiment using a servohydraulic testing machine for applying external tensile loads to cracks.…”

Section: Introductionmentioning

confidence: 99%

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High-Selectivity Ultrasonic Imaging of Closed Cracks Using Global Preheating and Local Cooling

et al. 2014

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High-selectivity ultrasonic imaging of closed crack is an important subject for avoiding not only underestimation but also misidentification of closed cracks. Thus far, the combination of load difference phased array (LDPA) and the crack opening method (GPLC) that combines global preheating (GP) and local cooling (LC) has been verified. Here the LDPA utilized the subtraction of the phased array (PA) images before and after the application of thermal stress induced by GPLC. However, as the cooling time increased, the change in wave velocity depending on the temperature within specimen is not negligible. This results in ghosts that degrade the selectivity of closed crack in subtracted images. In this study, on the basis of the finding that the change in crack response is faster than that in the wave velocity during GPLC, we propose a short time interval subtraction (STIS) method as an option in LDPA. This is based on the subtraction of a PA image from that obtained before a short time interval. It was experimentally verified in a closed fatigue crack specimen made of aluminum alloy.

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Section: Discussionmentioning

confidence: 98%

“…5(e), 6(c), and 7(c), respectively. As a measure of the selectivity, 19) the intensity ratio of cracks to objects other than cracks is defined as…”

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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High-Selectivity Ultrasonic Imaging of Closed Cracks Using Global Preheating and Local Cooling

et al. 2014

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“…Here the crack depth is the size of a crack in the thickness direction of structures and the crack length is its size in the direction perpendicular to the crack depth. Thus far, measurement of the crack depth by ultrasonic testing (UT) with bulk waves has been widely carried out since ultrasound is scattered at the crack tip in the depth direction, [1][2][3][4][5][6][7][8][9][10][11][12][13] where phased array with bulk waves has been intensively studied recently [14][15][16][17] and most UT has been applied from the side opposite to the crack opening. On the other hand, accurate measurement of the crack length is not easy since the edge part of a crack in the length direction is generally shallow, resulting in the low sensitivity in UT with bulk waves.…”

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confidence: 99%

Ultrasonic phased array with surface acoustic wave for imaging cracks

et al. 2017

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To accurately measure crack lengths, we developed a real-time surface imaging method (SAW PA) combining an ultrasonic phased array (PA) with a surface acoustic wave (SAW). SAW PA using a Rayleigh wave with a high sensitivity to surface defects was implemented for contact testing using a wedge with the third critical angle that allows the Rayleigh wave to be generated. Here, to realize high sensitivity imaging, SAW PA was optimized in terms of the wedge and the imaging area. The improved SAW PA was experimentally demonstrated using a fatigue crack specimen made of an aluminum alloy. For further verification in more realistic specimens, SAW PA was applied to stainless-steel specimens with a fatigue crack and stress corrosion cracks (SCCs). The fatigue crack was visualized with a high signal-to-noise ratio (SNR) and its length was measured with a high accuracy of better than 1 mm. The SCCs generated in the heat-affected zones (HAZs) of a weld were successfully visualized with a satisfactory SNR, although responses at coarse grains appeared throughout the imaging area. The SCC lengths were accurately measured. The imaging results also precisely showed complicated distributions of SCCs, which were in excellent agreement with the optically observed distributions.

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