Ultrasonic Sounding Research Articles

POWER SPECTRUM OF AN INTERFEROMETER SIGNAL IN EXPERIMENTS ON SOUNDING OF A TURBULENT WATER STREAM WITH PULSATING VELOCITY

The paper is related to studies of a turbulent medium by the sounding method with the interferometric reception. We performed a theoretical analysis of a multiplicative interferometer response to noise quasi-monochromatic emission, disturbed by a turbulent water stream. The effect of turbulent pulsations of the stream velocity on output interferometer signal was considered. Spectral analysis of the output interferometer signal allowed to perform the diagnostics of the propagation media. Particularly, it was shown, that the interferometer power spectrum carries information on the spatial spectrum of fluctuations of cavity bubbles concentration and on the average stream velocity. The theoretical evidence has been compared with the results of interferometric experiments on ultrasonic sounding of the water stream inside a pipe.

Fabric symmetry of low anisotropic rocks inferred from ultrasonic sounding: Implications for the geomechanical models

The geomechanical models were established based on the absence or presence of certain rock fabric elements — texture (crystallographic preferred orientation), microstructure (shape preferred orientation) and microcracks (flat voids). The proposed models include both (i) the ideal material showing random texture and structure but no microcracks, i.e. the material which is hardly to be found in nature, and (ii) the materials possessing various combinations of fabric elements that show different spatial arrangements. The mutual relationship between those parameters and seismic and geomechanical properties are discussed. Selected models were experimentally verified during laboratory experiments. These consist of measurement of P-wave velocities in 132 independent directions under several confining pressures in the range 0.1–400 MPa. From measured data 3D P-wave patterns can be constructed and the influence of microcracks and of texture and structure on the rock seismic anisotropy can be determined. The seismic anisotropy established at different levels of confining pressure can be used for the interpretation of rock fabric symmetry of rocks showing low anisotropy in macroscale and for the selection of directions in which the geomechanical test can be performed. The measured P-wave velocities were then mathematically processed by using a fitting function V P = V 0 + k v · P − v dif · 10 ( − P P O ) which reflects contribution of P-wave velocity in the mineral skeleton of an ideal sample without microcracks extrapolated to the atmospheric pressure level from high confining pressure interval (ca. 200–400 MPa) ( v 0), linear compressibility of the samples ( k v ), and confining pressure during which most of the cracks are closed ( P 0). These parameters improve the understanding of the response of various rock fabric elements on increasing confinement and corresponding changes in elasticity. The observed seismic and geomechanical anisotropies reflect intensity of the fabric of rock-forming minerals and microcracks. The magnitude of seismic anisotropy measured at atmospheric pressure corresponds to the anisotropy of static elastic modulus and is governed by the spatial arrangement of microcracks. The magnitude of strength anisotropy (uniaxial compressive strength) correlates more likely to the seismic anisotropy determined at high confining pressure and is connected to the preferred orientations (either CPO or SPO or both) of rock-forming minerals.

A first arrival identification system of acoustic emission (AE) signals by means of a high-order statistics approach

One of the fundamental problems in non-destructive testing and geophysics is the precise determination of the first arrival of acoustic emission (AE) signals (or seismic signals) recorded by multi-channel systems. The knowledge of this time is very important, mainly in the case of automatic localization of individual AE events. Several approaches are routinely used in practice such as crossing of the threshold level, analysis of the LTA/STA (long-time average/short-time average), etc. In our paper, an approach based on high-order statistics (HOS) that is able to carry out precise arrival time determination without human intervention is presented. The approach was tested on real AE data recorded by an eight-channel recording system. This simple, accurate and quite fast method is predetermined to be used in automatic processing of transient waveform data from acoustic emission, seismic signals, ultrasonic sounding, etc.

Ultrasonic echo sounding by thermal optical sources of longitudal waves

Experimental device for ultrasonic laser echo sounding of geomaterials is described. The examples of its application to estimate acoustic characteristics, inhomogeneities, and damaged state intrinsic to structure sample of various-age volcanics are considered.

Pulsed Sounding of Cracks with the Use of the Modulation of Ultrasound by Vibrations

The possibility of using the effect of the modulation of ultrasound by vibrations due to the presence of cracks for the nonlinear acoustic detection of cracks is demonstrated. The method is based on a pulsed ultrasonic sounding with gating the received signal and simultaneously exciting low-frequency vibrations in the sample. The presence of a crack is characterized by the modulation of the ultrasonic wave reflected from the crack. The visualization of the crack position in a model object (a metal rod) is performed. The possibility of selecting a crack on the background of an intense signal reflected from a cavity is experimentally demonstrated. The manifestation of the nonlinear properties of a crack is studied as a function of the polarization of the flexural vibrations of the rod.

Investigation of rock samples by neutron diffraction and ultrasonic sounding

The interpretation of large-scale geophysical anisotropies largely depends upon the knowledge of rock anisotropies of any kind (compositions, foliations, grain shape, physical properties). Almost all physical rock properties (e.g. elastic, thermal, magnetic properties) are related to the textures of the rock constituents since they are anisotropic for the single crystal. Although anisotropy determinations are numerous, systematic investigations are scarce. Therefore, several rock samples with different microfabrics were selected for texture analysis and to determine its P-wave distributions at various confining pressures.

Time Effects of Failure of Rock Samples Subjected to Uniaxial Compression

Using ultrasonic sounding, the degree of discontinuity of a rock sample subjected to uniaxial compression is determined. It is shown that attenuation in an acoustic signal is due to the developing crack which screens the transmission of the signal from the source to a receiver. A correlation between the longitudinal strain and signal attenuation is established.

A Method for the Investigation of High-Temperature Hydrogen-Assisted Fracture of Bimetallic Structural Elements

We propose a theoretical and experimental method for the investigation of high-temperature hydrogen-assisted fracture of bimetallic structural elements operating in hydrogen-containing media. It is shown that fracture occurs as a result of the coalescence of pores followed by the formation of a crack and its subsequent growth promoted by the high pressure of the gas accumulated in the crack. The time dependences of the processes of nucleation of the crack and growth of its area on the boundary of fusion of 15Kh2MFA-A steel with austenitic coating are plotted according to the data of theoretical investigations. The correctness of the theoretical foundations of the proposed method is corroborated experimentally. For this purpose, we use the method of acoustic emission, ultrasonic sounding, and metallographic analysis.

Experience in determining the water stability of rocks by the ultrasonic method

A method of obtaining a number of indices evaluating the water stabiliby of soil was developed on the basis of ultrasonic sounding.

Gravel-bed deposition and erosion by bedform migration observed ultrasonically during storm flow, North Fork Toutle River, Washington

Ultrasonic depth sounding provides useful and unexpected information about peak discharge and sediment transport when applied during storm flow in channels with erodible beds. Streambed elevation was measured with dual ultrasonic depth sounders during the rise, crest, and recession of a storm flow in the North Fork Toutle River, Washington, on 3 December 1987. The sounder transducers were held in the flow on a rigid pipe which was suspended from a boom over the channel thalweg. The 12 h episode of depth sounding detected the superposition of fine-gravel dunes on large bed waves, the depth-limited growth of mean dune heights from 13 to 25 cm, and bedform-related deposition and erosion in the channel thalweg. The streambed elevation rose 0.3 m in 2 h with increasing stream discharge. Dune heights diminished for about an hour before the peak river stage was attained. Scour of the streambed continued through the peak stage and recession, with 0.7 m of scour over 10 h. Rapid scour of the streambed produced a falling stage while discharge was still rising. Dune heights grew as flow depth increased after peak stage. Streambed elevation was lowered as large bed waves of fine gravel migrated along the thalweg with successively lower troughs leading each bed wave. Bed elevation records from the dual depth sounders were used to calculate dune celerities of 3–6 cm s −1 and bedform wavelengths of 2–11 m. The large bed waves were subtle, dune-like gravel bedforms with wavelengths of 25–30 m. The celerities and bedform dimensions yielded bedform transport weight rates between 3 and 20 kg s −1 m −1 and grain shear stresses between 40 and 100 N m −2 for the depth-sounding episode.

Friction welding of couplings with Du+100?150 mm made of steels 20 and 15Kh5M

Production Combine Bugul'maneftemash investigated and developed friction welding technology and nondestructive control of couplings by studying the dependence of strength indices of the welded joint on the welding regime parameters. The quality of the welded joints was checked by studying the macro- and microstructures and also by x-ray examination and ultrasonic sounding. The plasticized layer formed on the separation layer, favorable for obtaining a strong weld, was studied. The mean values of mechanical properties of welded specimens are given. Ultrasonic control confirmed the high quality of the welded joints produced by the friction welding. The inner and outer fins formed during friction welding, one of the deficiencies of the method, are also studied for their effect.

Ultrasonic echo sounding in obstetrical and gynecological diagnosis

Echo sounding within the abdomen, using low energy high frequency ultrasound, reveals the location of boundaries between different tissues and structures such as between fetal surfaces and surrounding liquor amnii, particularly the fetal head whose biparietal diameter can thus be measured. The echoes in early pregnancy are readily distinguished from those of hydatidiform mole. By using the patient's full bladder as a transmitting medium, a “view” can be obtained of the uterus which has not enlarged sufficiently to be palpable above the symphysis pubis. The usefulness of this technique in the diagnosis of early pregnancy or ectopic gestation is discussed.In gynecology, different types of pelvic tumors provide different echo patterns in accordance with macroscopic features, and the appearances of malignant ascites are characteristic.

Demonstration of tissue interfaces within the body by ultrasonic echo sounding.

Ultrasonic echo sounding has been established for several years in industrial practice for the detection of flaws in metals. We have applied the principle of this technique to reveal the boundaries between the different tissue structures within the body. Ultrasonic energy is mechanical, vibrational energy whose frequency is beyond the range of hearing and, at the high frequencies which we are employing, namely 2·5 and 1·5 Mc/s, it can be focussed into a narrow, almost parallel beam which, apart from its greater ability to penetrate tissue, is transmitted and reflected in much the same way as a beam of light. The physical nature, however, of this ultrasonic energy is totally different from that of electromagnetic radiation but this difference in itself may provide scope for enlarging the field of diagnostic radiology. The sound is transmitted into the patient in exceedingly short pulses or “wave packets”. Such a pulse is in some ways similar to a single quantum of X-ray energy except, of course, that it is...