The properties of coupling agents in improving ultrasonic transmission

Couvreur, J.F.; Thimus, Jean-François

doi:10.1016/0148-9062(95)00074-7

Cited by 15 publications

(7 citation statements)

References 12 publications

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“…A coupling agent was used to improve the wave transmissibility through the interface between the transducers and the rock sample. A detailed study has determined lead foil as the best choice for the present study (Couvreur and Thimus 1996b).…”

Section: Methodsmentioning

confidence: 99%

Successive cracking steps of a limestone highlighted by ultrasonic wave propagation

Couvreur

Vervoort

King

et al. 2001

Geophysical Prospecting

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A number of laboratory tests (uniaxial, triaxial and hydrostatic) have been conducted on a dry porous limestone. A conceptual model is proposed to correlate deformation and damage fields (including acoustic emission activity) with the variation of ultrasonic velocities, quality factors and energies as measures of attenuation. This correlation is presented in a stress deviator versus confining pressure diagram. In this way, the successive steps occurring in the damage process of this rock are well described. In particular, the quality factor of S‐waves distinguishes clearly the onset of the initially stable cracking, while the velocity of S‐waves and strain measurements are sensitive to dilatancy which appears later in the damage process of the limestone studied.

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Section: Methodsmentioning

confidence: 99%

Successive cracking steps of a limestone highlighted by ultrasonic wave propagation

Couvreur

Vervoort

King

et al. 2001

Geophysical Prospecting

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“…To reduce the transmission losses due to the impedance mismatch at the rock-transducer contact area (seismic impedance of the transducer element is 35.9 MPa-s/m (Cheeke, 2016), and that of Lyons sandstone is 11.4 MPa-s/m), oven-baked honey was used as the coupling medium between the transducer and rock surface. Honey was chosen because of its relatively viscous nature, and because it is widely considered to be the best coupling medium for longitudinal wave propagation (Couvreur & Thimus, 1996;Hedayat, 2013;Modiriasari et al, 2017). The baking process helps in removal of the air pockets present in the honey (Basu & Aydin, 2006;Couvreur & Thimus, 1996;Modiriasari et al, 2015).…”

Section: Journal Of Geophysical Research: Solid Earthmentioning

confidence: 99%

“…Honey was chosen because of its relatively viscous nature, and because it is widely considered to be the best coupling medium for longitudinal wave propagation (Couvreur & Thimus, 1996;Hedayat, 2013;Modiriasari et al, 2017). The baking process helps in removal of the air pockets present in the honey (Basu & Aydin, 2006;Couvreur & Thimus, 1996;Modiriasari et al, 2015). In particular, the honey was dehydrated in an oven at 100°C for 90 min.…”

Section: Journal Of Geophysical Research: Solid Earthmentioning

confidence: 99%

Experimental Relationship Between Compressional Wave Attenuation and Surface Strains in Brittle Rock

2019

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Linear ultrasonic testing (LUT) has been extensively used as a tool for the evaluation of damage processes in various materials ranging from synthetic metals to natural geomaterials, such as rocks. A key limitation of LUT‐based damage studies to date is the lack of explicit evidence used in associating material damage with the changes in measured LUT attributes (e.g., ultrasonic wave amplitude and velocity). In this study, the evolution of the full‐field strains in brittle rock specimens (Lyons sandstone) subjected to failure are analyzed in real time and linked with the changes in the ultrasonic wave amplitude in localized areas illuminated by ultrasonic beams, termed as the ultrasonic image areas. The noncontact optical full‐field displacement measurement method of 2‐D digital image correlation is implemented in combination with the LUT procedure to continuously track changes in the ultrasonic wave amplitude with the evolution of strains across the surface of the uniaxially loaded intact rock specimens. The ultrasonic amplitude showed near‐linear correlation with the intensity of inelastic tensile strain recorded in the rock specimens. The results from the study corroborate that the ultrasonic changes are in fact influenced by the regions of tensile cracking, which is the primary inelastic deformation mechanism in brittle rocks.

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“…TO improve signal quality, an acoustic couplant can be used to improve Pand S-wave signal amplitude (GCTS, 2001). The acoustic couplant reduces air voids or irregularities between platen and specimen and improve wave transmission (Couvreur and Thimus, 1996). Different materials have been used in previous researches as an acoustic couplant in ultrasonic test: glycerine (Kim et al, 2001), grease (Rao and Ramana, 1993;Li and Nordlund, 1993), honey (Siggins 1993, Guillaume et al, 1994, fibreglass jelly (Leong et al, 2004), water (Kim et al, 2001;Li and Nordlund, 1993).…”

Section: Acoustic Couplingmentioning

confidence: 99%

“…Water could not be used in this research as a couplant in this research since adding of water will change the degree of saturation of unsaturated soil specimen. Moreover, water is not a suitable couplant for Vs measurement in ultrasonic velocity test (Couvreur and Thimus, 1996). Kim et al (2001) found that the amplitude of the first echo measured by using pure glycerine is about three times higher than that using pure water in ultrasonic velocity test.…”

Section: Acoustic Couplingmentioning

confidence: 99%

Use of seismic waves for the characterization of soil properties

Meer.¹

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Seismic waves can be employed in the field and in the laboratory for characterizing soil. Seismic waves propagating through soils induce very low level of strains. Using the framework of linear elasticity, the wave propagation velocity can be linked to the elastic parameters of the soil. This study investigates soil properties using elastic waves in the field as well as in the laboratory. Continuous Surface Wave (CSW) and microtremor surveys were conducted at seven sites in Singapore. Borehole logs were available for all the sites. Pulse transmission tests using ultrasonic velocity test system were conducted in the laboratory. The Spatial Auto-Correlation (SPAC) method was used to analyze the data from microtremor survey to compute the dispersion curve. The dispersion curves obtained from the CSW and microtremor surveys for the same site were not coincidental but the discrepancy did not have any significant effect on the shear wave velocity profile. To obtain the shear wave velocity profile from the dispersion curve, wavelength-depth factor and linear inversion methods were used. The depth of investigation obtained from microtremor surveys was limited by array size. Because of site constraint, the array size of the microtremor is limited to 10 m with the maximum depth of investigation limited to 16 m. A modified wavelength-depth method was developed in this research and the method was verified using data from published literature. The modified wavelength-depth method was found to provide a better estimate of the shear wave velocity profile which can be used as the initial model for more accurate inversion schemes. Ultrasonic velocity tests were conducted on compacted unsaturated soil samples to investigate the effect of degree of saturation and confining pressure on compression wave and shear wave velocities. It was found that degree of saturation did not have significant effect on shear wave velocity but compression wave velocity was found to be dependent on degree of saturation. A relationship between compression wave velocity with shear wave velocity and degree of saturation was developed. The relationship could be used to estimate compression wave velocity of an unsaturated soil/rocklconcrete within 520 % error. vii ATTENTION: The Singapore Copyright Act applies to the use of this document. Nanyang Technological University Library Ultrasonic velocity tests and triaxial compression tests were conducted on undisturbed soil samples to measure the small-strain stiffness and stiffness with strain relationship of soil. The compression wave velocity and shear wave velocity were measured by ultrasonic velocity test. The measured shear wave velocity by ultrasonic velocity test was compared with the shear wave velocity obtained from CSW and microtremor survey methods. The comparison showed good agreement with a discrepancy of h30 %. The small-strain stiffness of soil was measured by triaxial compression test using local strain measurement transducers. The effects of void ratio, confining pressure and plasticity index o...

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The properties of coupling agents in improving ultrasonic transmission

Cited by 15 publications

References 12 publications

Successive cracking steps of a limestone highlighted by ultrasonic wave propagation

Successive cracking steps of a limestone highlighted by ultrasonic wave propagation

Experimental Relationship Between Compressional Wave Attenuation and Surface Strains in Brittle Rock

Use of seismic waves for the characterization of soil properties

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