A Noncontact Method for the Detection and Diagnosis of Surface Damage in Immersed Structures

<div>(Colour online) Phase (a1) and group (b1) velocities of the symmetrical Lamb wave <svg height="11.9661pt" id="M142" style="vertical-align:-3.16057pt" version="1.1" viewbox="-0.0498162 -8.80553 11.2181 11.9661" width="11.2181pt" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink"><g transform="matrix(.013,0,0,-0.013,0,0)"><path d="M463 633C453 636 427 644 417 648C388 660 349 667 316 667C183 667 100 592 100 483C100 398 176 335 223 305L259 282C321 242 358 203 358 149C358 66 301 22 234 22C110 22 70 131 57 208L24 205L28 48C51 23 128 -17 215 -17C342 -17 446 60 446 174C446 262 394 310 317 361L284 383C229 420 183 455 183 515C183 569 222 628 298 628C384 628 418 563 428 481L461 487C459 527 458 593 463 633Z" id="g50-84"></path><glyph.data ascent="3443" descent="-2856" horiz-adv-x="487" vert-adv-y="487"></glyph.data></g><g transform="matrix(.0091,0,0,-0.0091,6.149,3.001)"><path d="M245 635C92 635 37 457 37 312C37 149 91 -12 244 -12C395 -12 449 166 449 312C449 469 395 635 245 635ZM243 598C332 598 358 454 358 312C358 173 334 26 245 26C158 26 128 174 128 313S152 598 243 598Z" id="g50-49"></path><glyph.data ascent="3443" descent="-2856" horiz-adv-x="487" vert-adv-y="487"></glyph.data></g></svg>, phase (a2), and group (b2) velocities of the antisymmetric Lamb wave <svg height="8.85534pt" id="M143" style="vertical-align:-0.04981041pt" version="1.1" viewbox="-0.0498162 -8.80553 9.37728 8.85534" width="9.37728pt" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink"><g transform="matrix(.013,0,0,-0.013,0,0)"><path d="M722 32C646 41 636 48 622 116L544 496L509 667L472 658L153 123C106 45 93 42 27 32L18 0H259L268 32C178 40 172 48 204 107L272 233H509C523 180 533 137 540 96C548 50 546 39 466 32L457 0H714L722 32ZM502 283H299L448 547H450L502 283Z" id="g50-66"></path><glyph.data ascent="3443" descent="-2856" horiz-adv-x="740" vert-adv-y="740"></glyph.data></g></svg>.</div>

Advances in Acoustics and Vibration

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Figure 4

Figure 4: A Noncontact Method for the Detection and Diagnosis of Surface Damage in Immersed Structures 