Wave Ultrasonic Velocity Research Articles

Time and Temperature Dependent Creep in Tournemire Shale

AbstractWe conducted a series of triaxial creep experiments on shale specimens coming from Tournemire, France, using the stress‐stepping method up to failure, at a confining pressure of 80 MPa, on two orientations (parallel and perpendicular to bedding), and at temperatures of 26 and 75 °C. In these week‐long experiments, stress, strains, and P wave ultrasonic velocities were recorded (quasi‐) continuously. The strength at creep failure of Tournemire shale was ~70% higher than the peak strength measured during constant strain rate (~10−7/s) experiments, and failure was reached at larger strains. An overall transition from P wave velocity increase at moderate differential stress to P wave velocity decrease closer to brittle failure was also observed. At a smaller timescale, P wave velocities initially decreased and then increased gradually during each step of creep deformation. The magnitude of these variations showed important (i) stress, (ii) orientation, and (iii) temperature dependences: larger increase was observed for P wave propagating along the main compressive stress orientation, larger decrease for P wave propagating perpendicular to it, and a changing behavior enhanced at a higher temperature. Scanning electron microscopy performed postmortem revealed evidence of time‐dependent pressure solution, localized compaction, crack growth, and sealing/healing. Our data reveal that shale deformation is highly stress sensitive only in a narrow stress domain where stress corrosion cracking‐induced brittle dilatant creep deformation is dominant. At stresses below, pressure solution compaction creep dominates the deformation and shales compact, consolidate, and heal. This has important implications for the mechanics of shallow fault zones and accretionary prisms.

Young's modulus of BF wood material by longitudinal vibration

All engineered structures are designed and built with consideration of resisting the same fundamental forces of tension, compression, shear, bending and torsion. Structural design is a balance of these internal and external forces. So, it is interesting to calculate the Young's moduli of Borassus Flabellifier BF wood are quite important from the application point of view. The ultrasonic waves are closely related with the elastic and inelastic properties of the materials. In the present study, we measured longitudinal wave ultrasonic velocities in BF wood material by longitudinal vibration method. After measuring ultrasonic velocity in BF wood material, we calculated Young's modulus of Borassus Flabellifier BF wood material. We used ultrasonic interferometer for measuring longitudinal wave ultrasonic velocity in BF wood material made by Mittal Enterprises, New Delhi, India in our laboratory. Borassus Flabellifier BF wood material was collected from Dhar district of Madhya Pradesh, India.

Characterisation of sintered metal products by using ultrasonics

This study describes briefly the production of sintered metal components and their characterisation with respect to the physical and mechanical properties by using ultrasonics. Pellet samples of sintered metal powder compacts have been prepared with different fabrication parameters to obtain different densities and thus different elastic properties. Longitudinal and transverse wave ultrasonic velocities have been measured to determine the elastic moduli of the samples and then correlated with densities The results of the ultrasonic measurements have shown that ultrasonic velocity may be used to determine precisely the basic production parameters and therefore as a quality control tool of the sintered metal products.

The use of ultrasonic properties of cr-39 track detectors in neutron dosimetry

The longitudinal and shear wave ultrasonic velocities have been measured before and after exposing 5-mm thick CR-39 solid state nuclear track detectors to both a mixed field of γ-rays and fast neutrons from an Am-Be source in the ranges from 0 to 104 mSv. The change in the intermolecular structure as caused by the fast neutron exposure was studied by the ultrasonic pulse echo method at a frequency of 2 MHz and at room temperature. The elastic coefficients, Poisson's ratio, microhardness, ultrasonic absorption coefficient and internal friction have been determined. The study shows that the γ-ray irradiation had no effect on the ultrasonic properties of CR-39 at least at the used doses. However, all the ultrasonic properties are influenced by the fast neutrons at doses up to 104 mSv. Our experimental results confirmed that the ultrasonic technique is useful for fast neutron detection, by exploiting the differences in mechanical properties of CR-39.

Relationships between cortical bone properties and head wave ultrasonic velocity at 1 MHz: An in vitro investigation

The axial transmission technique provides a measurement of the velocity (SOS) of elastic waves propagating along the surface of cortical bone. Currently, SOS is derived from the time of flight of the first arriving signal. Our goal was to investigate the relationship between SOS and several bone properties that independently contribute to bone strength. One-MHz SOS measurements were performed with a proprietary probe on 41 excised human radius with soft tissue removed. Small pieces of cortical bone were removed from the site of ultrasonic testing to be investigated using synchrotron radiation microtomography (resolution 10 μm). Cortical thickness, cortical porosity, and tissue mineralization were derived from the 3-D data set. Mean SOS values were 3940 (3796–4120) m<th>s−1. The reproducibility of the SOS measurements expressed as a variation coefficient (CV) was 0.5%. The relationships between SOS and bone properties were assessed using linear regression and displayed significant correlations : R2=0.20 (p<10−5) for cortical thickness, R2=0.30 (p<10−3) for cortical porosity, R2=0.37 (p<10−4) for tissue mineralization. A multiple regression analysis showed that cortical porosity and tissue mineralization in the periosteal region were the most predictive variables and explained 60% of the total variance of the SOS. These results are in agreement with predictions obtained using 3-D numerical computations based on a finite-difference method.

Laser ultrasonic sensing of the melting and solidification of cadmium telluride

A noninvasive laser ultrasonic method has been used to investigate the melting and solidification of a (Cd,Zn)Te alloy during vertical Bridgman growth. A single zone vertical Bridgman furnace was integrated with a laser ultrasonic system and used to monitor the time-of-flight of ultrasonic pulses that propagate across an ampoule during the melting and solidification of Cd 0.96Zn 0.04Te. The measurement approach is based upon the difference in the elastic stiffness of the solid and liquid phases of Cd 0.96Zn 0.04Te (Queheillalt et al., J. Appl. Phys. 83 (1998) 4124) and its significant dependence upon temperature. This results in a reduction of the longitudinal wave ultrasonic velocity as the temperature was increased (from ambient temperature) followed by a ∼ 45% decrease upon melting. The laser ultrasonic sensor provided a robust in-situ method for monitoring the melting and solidification of Cd 0.96Zn 0.04Te. The data indicated that the melting was slow and that solidification was accompanied by a 10–15°C undercooling.

Correlation between Surface Area Reduction and Ultrasonic Velocity in Sintered Zinc Oxide Powders

Specific surface area and longitudinal wave ultrasonic velocity were measured in zinc oxide (ZnO) powder compacts partially sintered to different pore fractions (P). A linear correlation was observed between the reduction in surface area and the increase in ultrasonic velocity at all P up to the onset of pore closure. During the initial stage of sintering, the ultrasonic velocity increased by as much as 300%, with negligible reduction in P, whereas during the intermediate stage, the surface area reduction was accompanied by increasing ultrasonic velocity and decreasing P. During the final stage of sintering, the pores closed and became isolated. The linear relation between the reduction in surface area and the increase in longitudinal wave velocity encompassed the entire range of porosity from completely unsintered to the onset of pore closure, thus spanning the transition from initial‐ to intermediate‐stage sintering. Ultrasonically inferred surface areas were used to evaluate the kinetics of the initial stage of sintering, and the results compared favorably with previously published values.

Analysis of ultrasonic velocity measurements on sintering zinc oxide

Abstract A technique is presented for accurate measurement of the longitudinal wave velocity up to 1050 °C in sintering powder compacts. The technique uses laser generation and contact detection of the ultrasonic signal. Representative results are presented for heating cycles performed upon sintering ZnO powder compacts, and upon a pre-sintered dense ZnO sample. The data demonstrate the capability for performing in-situ longitudinal wave velocity measurements at high temperatures, and in attenuative materials such as sintering ceramic powder compacts. In addition, the data demonstrate the sensitivity of ultrasonic velocity measurements to changes within the sintering compact which are not detectable by dimension measurement alone. A novel application of ultrasonic velocity measurements performed in-situ on sintering ZnO is presented. This application is based upon interpretation of longitudinal wave velocity measurements in the context of existing models treating surface area reduction during sintering. A previously observed correlation between the longitudinal wave ultrasonic velocity and the specific surface area facilitates this interpretation. The analysis yields an activation energy for surface area reduction in sintering ZnO which compares well with values reported in the literature.

Non destructive methods for investigation of some mechanical properties of natural stones in the protection of monuments

The investigation of the physical and mechanical properties of stones in monuments needs non-destructive methods and small quantity of testing material. The non-destructive methods can be divided into laboratory andin situ techniques. P P S wave ultrasonic velocities and Schmidt hammer can be used for bothin situ and laboratory measurements, in contrast to the mechanical resonance frequency and abrasion resistance that can be used only for investigation in the laboratory. In the present paper the above methods were used for the study of properties such as mechanical anisotropy, weathering degree, mechanical strength and deformation ability of stones, using data from Italy, France, Malta and Pacific Ocean.

Determination of the moduli of elasticity of rocks. Comparison of the ultrasonic velocity and mechanical resonance frequency methods with direct static methods

In the present investigation, dynamic methods for the determination of moduli of elasticity were compared with direct static methods. The dynamic moduli of rocks, such as Young's modulus (E) and Poisson's ratio (v) were determined, using both mechanical resonance frequency and classic P and S wave ultrasonic velocity techniques. For this purpose rock samples from different areas of France, covering a wide range of velocity values, were used. The mechanical resonance frequencies were investigated using a Grindo-Sonic machine while the P and S wave ultrasonic velocities were measured using a Pundit ultrasonic machine, connected to an oscilloscope. The static moduli were determined using deformation gauges. Statistical interpretation of the test results indicated significant correlation between these dynamic and static methods. Accordingly, the above non-destructive dynamic methods are suitable for the determination of static moduli of elasticity.

A note on the composition dependence of elastic properties of Se-P glasses

Longitudinal and shear wave ultrasonic velocities are reported in Se-P glasses over the composition range 0–50 at % P. The glass transition temperaturesT g show maxima at 30 and 50 at % of P, in consonance with earlier data. The bulk modulus shows minima at these compositions, contrary to the expectation of maxima. These are discussed in relation to the formation of compounds at specific compositions and the nature of the covalent bonding in the glasses.

Estimation Of Damage At The Surface Of StonesUsing Non Destructive Techniques

The investigation of the physical and mechanical properties of stones in monuments needs non destructive methods and small quantity of testing material. In this framework, P & S wave ultrasonic velocities can be used for both in situ and laboratory measurements. In the present paper the above methods was used for the study of properties like the mechanical anisotropy, weathering degree, mechanical strength and deformation ability of stones, using data from different countries, like France, Italy and Greece. The P-waves were also used, in indirect mode, for the estimation of the depth of weathering at the stone surfaces of three representative monuments in Greece.