Towards a Quantitative Ultrasonic NDE of Thick Composites

Sachse, Wolfgang

doi:10.1007/978-1-4615-3742-7_57

Cited by 7 publications

(3 citation statements)

References 13 publications

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“…Centroid locations for each micro-pore were tracked as a function of applied strain in the sequential tomographic scans thereby allowing to estimate the local strain distribution in the cell materials. As such, high density mapping with a micrometer level resolution has been realized by the procedure as has been demonstrated by the present authors [4][5][6][7]. Local strain distribution in the cell wall is represented in Fig.…”

Section: Resultssupporting

confidence: 61%

In Situ Observation of Fracture of Aluminium Foam Using Synchrotron X-Ray Microtomography

Toda

Ohgaki

Uesugi

et al. 2005

KEM

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Synchrotron X-ray microtomography has been utilized for the 3D characterisation of microstructure in the cell materials of aluminium foams. Tomographs, consisting of about 109 isotropic voxels with a maximum of 1.0µm edge, were collected at the SPring-8 in Japan. A combination of high-resolution phase contrast imaging technique and several state-of–the-art application techniques has enabled the quantitative image analyses of micro-pore, intermetallic particles and grain boundary as well as the assessment of their effects on compressive deformation and fracture behaviours in two kinds of aluminium foams.

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Section: Resultssupporting

confidence: 61%

In Situ Observation of Fracture of Aluminium Foam Using Synchrotron X-Ray Microtomography

Toda

Ohgaki

Uesugi

et al. 2005

KEM

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“…The energy or group velocity vector V is, in general, different from the phase velocity in anisotropic materials. It can be determined from 22 an; an V= -an;ac • B. Laser-generated acoustic imaging (5) It was already shown how the arrival times of the quasilongitudinal and quasitransverse wave modes can be determined from the time signals comprising the scan images. From such arrival-time data, where each set typically consists of more than a hundred data points, the elastic constants of the specimen material can be recovered using an inversion procedure that has been described in earlier publications.…”

Section: A Membrane Waves In Thin Specimensmentioning

confidence: 99%

“…Although PS/PR waveform data is generally more complex than that obtained using conventional, plane-wave ultrasonic measurements, many of the measurement problems and limitations of the latter are minimized or avoided. For example, when generating signals in thick and absorptive materials, 5 such as fiber-reinforced thermoset composites, a broadband excitation that is rich in low frequencies is often desired and for this application, a step-type source function may be used. To obtain such an excitation, the point source may be a normal force which can be generated by the fracture of a capillary or a focused, pulsed laser that is operating in its ablative regime.…”

Section: Introductionmentioning

confidence: 99%

Ultrasonic point-source/point-receiver measurements in thin specimensa)

Veidt

Sachse

1994

The Journal of the Acoustical Society of America

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This paper reports on the application of the ultrasonic point-source/point-receiver technique (PS/PR) to thin, anisotropic specimens. By using a scanned source and viewing a large number of signals measured at adjacent source/receiver configurations, one obtains a so-called scan image which represents the detailed spatial and temporal characteristics of the elastic wave field in a specimen. The measurement system uses either a focused, pulsed laser beam operating as a dipole source or a small aperture, piezoceramic shear transducer serving as a monopolar source. Detection of the signals is with a sensitive piezoceramic sensor that responds to the lateral or shear motions of the specimen surface. Scan images were obtained in a Silicon wafer whose thickness was 625 µ,m and in one-or two-ply, unidirectional, graphite/epoxy laminates whose thicknesses were approximately 145 and 275 µ,m, respectively. The experimental data are analyzed using a simple plane-wave, plane-stress model that describes the propagation of quasilongitudinal and quasitransverse membrane waves in the plane of the plate. Good agreement is obtained between the experimental and theoretical group velocity curves of the membrane waves in the laminates. It is shown that the measured group velocity data of different wave modes can be inverted to recover the elastic constants of a material with excellent reliability and accuracy. The measurement system was also used to map out the group velocities in branches comprising the cuspidal region of the quasi-transverse group velocity curve.

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