Abstract:The interdigital transducer–based scanning laser Doppler vibrometer has recently been introduced to efficiently generate the symmetric mode for damage detection of shallow defects in thick plates. To measure shallow defects in a carbon steel plate, the excitation frequency is optimized based on the analysis of wavenumber sensitivity and degree of separation between modes. Even though the interdigital transducer–based scanning laser Doppler vibrometer method using continuous excitation is a promising method for… Show more
“…Based on the author’s previous results, wall thinning up to a depth of at least 3% can be detected using an IDT-based SLDV. 25 To validate our flexible IDT-based SLDV, we prepared specimens with shallower wall thinning of 6% and 4% and obtained the images shown in Figures 17 and 18, respectively.Figure 17.Image of pipe with 6% depth wall thinning.Figure 18.Image of pipe with 4% depth wall thinning.…”
Section: Resultsmentioning
confidence: 99%
“…Based on the author's previous results, wall thinning up to a depth of at least 3% can be detected using an IDTbased SLDV. 25 To validate our flexible IDT-based SLDV, we prepared specimens with shallower wall thinning of 6%…”
Section: Resultsmentioning
confidence: 99%
“…Based on their results, Jeon et al proposed a local wavenumber mapping and 2D-wavelet wavenumber filtering approach for defect detection in composite structures. 21,22 Kang et al 25 developed an interdigital transducer (IDT)-based scanning laser Doppler vibrometer (SLDV) to detect shallow defects in plates 23,24 as well as a dry-coupled IDT-based SLDV that could be applied to a structure without the use of coupling materials. 25 Many of these approaches have shown that the wavenumber estimation method is suitable for representing the damage in plates and pipes.…”
Interdigital transducer (IDT)-based scanning laser Doppler vibrometers (SLDVs) have recently been developed to detect shallow defects in plates. An IDT-based SLDV was augmented with Lamb wave frequency fusion capability to enable the imaging of defects across the entire depth of a plate. Dry-coupled IDTs are a type of field-deployable IDT that do not require the attachment of a couplant to the structure. However, this technique is not applicable to the analysis of shallow wall thinning, because IDTs composed of lead zirconium titanate (PZT) cannot be attached to the curved surface of a structure. To address this issue, we developed a new type of IDT—the flexible IDT—that can be bent along the circumferential direction of a pipe. To set the gap spacing of the flexible IDT, the wavenumber sensitivity and minimum distance from the reference mode (MDRM) was calculated, and the S 0 mode is selected to ensure high-wavenumber sensitivity above the threshold of the MDRM. The proposed flexible IDT-based SLDV was tested by using it to visualize the wall thinning on pipes with 4%, 6%, and 20% thinning. The results of this study will contribute toward the development of systems that improve on existing planar laser scanning schemes and enable shallow defect detection in pipes using laser ultrasonics.
“…Based on the author’s previous results, wall thinning up to a depth of at least 3% can be detected using an IDT-based SLDV. 25 To validate our flexible IDT-based SLDV, we prepared specimens with shallower wall thinning of 6% and 4% and obtained the images shown in Figures 17 and 18, respectively.Figure 17.Image of pipe with 6% depth wall thinning.Figure 18.Image of pipe with 4% depth wall thinning.…”
Section: Resultsmentioning
confidence: 99%
“…Based on the author's previous results, wall thinning up to a depth of at least 3% can be detected using an IDTbased SLDV. 25 To validate our flexible IDT-based SLDV, we prepared specimens with shallower wall thinning of 6%…”
Section: Resultsmentioning
confidence: 99%
“…Based on their results, Jeon et al proposed a local wavenumber mapping and 2D-wavelet wavenumber filtering approach for defect detection in composite structures. 21,22 Kang et al 25 developed an interdigital transducer (IDT)-based scanning laser Doppler vibrometer (SLDV) to detect shallow defects in plates 23,24 as well as a dry-coupled IDT-based SLDV that could be applied to a structure without the use of coupling materials. 25 Many of these approaches have shown that the wavenumber estimation method is suitable for representing the damage in plates and pipes.…”
Interdigital transducer (IDT)-based scanning laser Doppler vibrometers (SLDVs) have recently been developed to detect shallow defects in plates. An IDT-based SLDV was augmented with Lamb wave frequency fusion capability to enable the imaging of defects across the entire depth of a plate. Dry-coupled IDTs are a type of field-deployable IDT that do not require the attachment of a couplant to the structure. However, this technique is not applicable to the analysis of shallow wall thinning, because IDTs composed of lead zirconium titanate (PZT) cannot be attached to the curved surface of a structure. To address this issue, we developed a new type of IDT—the flexible IDT—that can be bent along the circumferential direction of a pipe. To set the gap spacing of the flexible IDT, the wavenumber sensitivity and minimum distance from the reference mode (MDRM) was calculated, and the S 0 mode is selected to ensure high-wavenumber sensitivity above the threshold of the MDRM. The proposed flexible IDT-based SLDV was tested by using it to visualize the wall thinning on pipes with 4%, 6%, and 20% thinning. The results of this study will contribute toward the development of systems that improve on existing planar laser scanning schemes and enable shallow defect detection in pipes using laser ultrasonics.
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