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From page 12...
... 12 Theoretical Models for Mechanical Wave Technology: Impact Echo, Impulse Response, and Ultrasonic Surface Waves The numerical simulations presented in this chapter were carried out by Infrasense with support from Dr. Kim Belli of Northeastern University in Boston, Professor Dennis Hiltunen of the University of Florida, and Professor Rajib Mallick of Worcester Polytechnic Institute.
From page 13...
... 13 for the base, and one 100-mm layer for the subgrade, for a total depth of 0.5 m. • Nonreflecting boundaries were used to absorb energy.
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... 14 Source: Munoz 2009.
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... 15 Source: Munoz 2009.
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... 16 Impulse Response The impulse response methodology was investigated by using a standard one-impact source and one-receiver configuration. The significant findings were as follows: • Degree of defect: totally and partially debonded defects could be differentiated from the intact response (Figure 3.7)
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... 17 Figure 3.8. Defect depth: (a)
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... 18 • HMA thickness: totally debonded defect responses were similar for thicknesses of 150 and 200 mm; the response was smaller for 100 mm (Figure 3.12)
From page 19...
... 19 Figure 3.13. Degree of defect: (a)
From page 20...
... 20 Source: Munoz 2009.
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... 21 Source: Munoz 2009.
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... 22 Source: Munoz 2009.
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... 23 Source: Munoz 2009.
From page 24...
... 24 Source: Munoz 2009.
From page 25...
... 25 Numerical Modeling As reviewed in the previous sections, Munoz (2009) has demonstrated the significant capability of mechanical wave methods to characterize pavements with delaminations.
From page 26...
... 26 • Absorbing boundaries were applied along the bottom and right edges to simulate the continuity of the materials, thus eliminating reflecting waves bouncing back from the boundaries. Parametric Study The parametric study was conducted by using a control model as described above and having material properties as indicated in Table 3.1.
From page 27...
... 27 are a form of 3-D power spectrum in which the surface wave phase velocity versus frequency (dispersion) of the propagating waves is displayed on the horizontal axes, and the energy present at each velocity-frequency pair is displayed via a color coding, with the cold colors corresponding to low energy, and the hot colors corresponding to high energy.
From page 28...
... 28 image (a) and image (b)
From page 30...
... 30 some extent related to the depth of the delamination. For the cases of delamination at 15 cm (Figure 3.26)
From page 31...
... 31 Figure 3.29. Dispersion image of total delamination at a depth of 5 cm with HMA Vs 5 400 m/s.
From page 32...
... 32 response and a slight drop in phase velocity at high frequencies. It is known that the low-frequency discontinuity is the feature of an intact pavement profile.
From page 33...
... 33 ends at 1.3 m, it is constrained from both ends. Therefore, a Lamb wave approximation is not appropriate in this case.
From page 34...
... 34 Figure 3.40. Deformed mesh of total delamination with full interface extension.
From page 35...
... 35 Figure 3.41. Deformed mesh of partial delamination with full array coverage (Case 1)
From page 36...
... 36 Figure 3.42. Deformed mesh of partial delamination with partial array coverage (Case 2)
From page 37...
... 37 of dispersion images significantly depends both on the size of the delamination and the array configuration. Conclusions A surface wave technique has been applied to detect pavements with delamination.

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