Abstract:Ultrasonic pulse-echo reflectometry provides a convenient method to measure the acoustic impedance of a layer of unknown material bonded to a substrate of another material whose acoustic properties are known. The amplitudes of echoes from the interface are used to calculate the interface reflection coefficient and, from this and a knowledge of the properties of the substrate material, the unknown impedance is obtained. The technique has potential for assessment of adhesive cure and measurement of mechanical mo… Show more
“…In eq 2 Z q is the acoustic impedance of the quartz (i.e., Z q = (μ q ρ q ) 1/2 ), where μ q is the shear modulus of quartz in the plane of the quartz disc used as the oscillator and ρ q is the density of quartz. Quartz has a density of 2.66 g/cm 3 . The shear modulus for the AT cut quartz used in our experiments is 2.95 × 10 10 Pa, giving Z q = 8.84 × 10 6 kg/m 2 s. The complex impedance is defined as the ratio of the interfacial shear stress, σ n *, to the velocity of the shear wave, uṅ *:…”
Section: ■ Introductionmentioning
confidence: 99%
“…22 Equation 10 can be used to determine some general guidelines for the use of quartz crystal resonators as sensors immersed in bulk fluids. For an AT cut quartz crystal operating at a fundamental resonance frequency of 5 MHz exposed on one side to water (η = 10 −3 Pa s and ρ = 1 g/cm 3 ), ΔΓ = −Δf = 713 Hz. As a general rule, we have found that high-quality data can be obtained when Γ is less than ∼20 kHz, corresponding to solution viscosities of less than about 0.5 Pa s (for ρ = 1 g/ cm 3 ).…”
We utilize quartz crystal resonators operating at multiple resonant harmonics to measure the high-frequency rheological properties of materials with a broad range of viscoelastic properties. The technique is demonstrated with poly(t-butyl acrylate) films in the vicinity of the calorimetrically determined glass transition and with rubbery polyisoprene films. The technique is a noncontact technique that can be used to quantify the temperature or time-dependent viscoelastic response in homogeneous films with thicknesses in the micrometer range. This work complements the ability of the resonators to quantify the viscoelastic behavior of viscoelastic polymer solutions and simple Newtonian liquids. For each material we obtain the density-shear modulus product and the viscoelastic phase angle at frequencies of 5 and 15 MHz. A standardized analysis protocol is described that enables this information to be obtained reliably and accurately. The polyisoprene data are found to be in good agreement with measurements obtained by dynamic mechanical analysis using extrapolated temperature shift factors.
“…In eq 2 Z q is the acoustic impedance of the quartz (i.e., Z q = (μ q ρ q ) 1/2 ), where μ q is the shear modulus of quartz in the plane of the quartz disc used as the oscillator and ρ q is the density of quartz. Quartz has a density of 2.66 g/cm 3 . The shear modulus for the AT cut quartz used in our experiments is 2.95 × 10 10 Pa, giving Z q = 8.84 × 10 6 kg/m 2 s. The complex impedance is defined as the ratio of the interfacial shear stress, σ n *, to the velocity of the shear wave, uṅ *:…”
Section: ■ Introductionmentioning
confidence: 99%
“…22 Equation 10 can be used to determine some general guidelines for the use of quartz crystal resonators as sensors immersed in bulk fluids. For an AT cut quartz crystal operating at a fundamental resonance frequency of 5 MHz exposed on one side to water (η = 10 −3 Pa s and ρ = 1 g/cm 3 ), ΔΓ = −Δf = 713 Hz. As a general rule, we have found that high-quality data can be obtained when Γ is less than ∼20 kHz, corresponding to solution viscosities of less than about 0.5 Pa s (for ρ = 1 g/ cm 3 ).…”
We utilize quartz crystal resonators operating at multiple resonant harmonics to measure the high-frequency rheological properties of materials with a broad range of viscoelastic properties. The technique is demonstrated with poly(t-butyl acrylate) films in the vicinity of the calorimetrically determined glass transition and with rubbery polyisoprene films. The technique is a noncontact technique that can be used to quantify the temperature or time-dependent viscoelastic response in homogeneous films with thicknesses in the micrometer range. This work complements the ability of the resonators to quantify the viscoelastic behavior of viscoelastic polymer solutions and simple Newtonian liquids. For each material we obtain the density-shear modulus product and the viscoelastic phase angle at frequencies of 5 and 15 MHz. A standardized analysis protocol is described that enables this information to be obtained reliably and accurately. The polyisoprene data are found to be in good agreement with measurements obtained by dynamic mechanical analysis using extrapolated temperature shift factors.
“…However, it has been shown that the measurements done via the reflection method are less accurate than those done with a transmission configuration [12]. In order to improve the accuracy of the measurements done by reflectometry, one can work with multiple reflections instead of simple one, as it was done by Longin et al [13] on polydimethylsiloxane polymers.…”
“…The values and errors obtained for the reflection coefficient, phase shift and loss modulus as a function of the delay line material are reported in Table 2 [25]. One can notice that according to theory and to viscosity measurements, G 00 should be equal to 81.7 MPa because G 00 = xg.…”
In this work, we propose a study dedicated to the influence of the delay line nature in transverse ultrasonic sensors, dedicated to dynamic high frequency elastic moduli of viscoelastic materials estimation. In literature, these shear ultrasonic rheometers are using delay lines in glass or quartz and normal or oblique incidence of ultrasonic rays. The oblique incidence is used in order to improve the sensitivity of the measurements. We theoretically demonstrate in this work that the use of delay lines in polymers is recommended to improve the sensitivity. Due to modifications, performed on a 10 MHz commercial ultrasonic sensor, we experimentally show on glycerin (which is a Newtonian material) that it is possible to multiply by a factor 10 the sensitivity; compared to delay lines in quartz using a normal incidence of rays. Hence, we overpass the accuracy of the oblique incidence approach with a simpler experimental setup.
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