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Three nondestructive testing techniques, namely, optically- and ultrasonically stimulated infrared thermography, ultrasonic laser vibrometry and laser ultrasonics, have been comparatively investiga...

The problem of workpiece tolerance verification is of high interest in the field of nondestructive testing and evaluation. In this paper, reflection mode immersion 2D laser-ultrasound tomography is proposed for control of dimensions of solid objects with piecewise linear surface profiles. Pulsed laser radiation is used for generation of short ultrasonic probe pulse providing high spatial resolution. Wideband array of piezofilm sensors is used for detection of the waves reflected by the external and internal surfaces of the object. The image reconstruction algorithm accounts for refraction of acoustic waves at the liquid-solid interface. The contrast-enhanced reconstructed image is processed using the virtual model of the inspected part and the least-squares method to measure its actual dimensions. The accuracy obtained in the experiments with PMMA and duralumin samples is better than 100 μm in axial direction and is better than the size of the point-spread function in the material of the inspected part.

Some non-destructive methods for controlling the internal structure of rocks are described and examples of their use are given. Examples of the use of X-ray and neural tomography, scanning electron and acoustic microscopy are also given. It is shown that the method of laser-ultrasound struktroskopii is promising. Two examples of the use of the latter are given: measuring the local porosity of samples of geomaterials and monitoring changes in the internal structure as a result of electromagnetic exposure.

During the operation of engineering structures made of natural stone, for industrial and civil purposes, an important parameter in monitoring their technical condition is the assessment of their reliability and safety under the influence of various external influences. In this case, high-quality monitoring of the stress–strain state of natural stone structures, its physical, mechanical and filtration properties, as well as internal structural features is necessary to study the possibility of replacing individual elements of objects that have lost their original characteristics. To assess the state of geomaterials, this article proposes using a complex of introscopic methods, including infrared radiometry and laser-ultrasound structuroscopy. An important aspect is the calculation based on the Green–Christoffel equation of the velocity of a quasi-longitudinal wave in limestone consisting of densely packed, chaotically oriented calcite grains with a small quartz content. For the first time, using laser-ultrasonic structuroscopy and standard methods for determining open porosity, both total and closed porosity were determined. This allowed us to find the values of specific heat capacities of dry and water-saturated samples. The obtained values are used to find the ratio of changes in the temperature of dry and water-saturated samples at the same stress values. The results obtained demonstrate the need to take into account changes in the intensity of thermal radiation of limestone with different moisture content under conditions of uniaxial compression, when identifying changes in the stress state of elements of stone structures in real conditions.

We report a study of the photoacoustic energy conversion efficiency under femtosecond filamentation in water. We characterized the interaction of ultra-short laser pulse with water under different temperatures and filamentation regimes.

Many acousto-optic paratellurite-based devices use a slow shear bulk wave for interaction with light beams. Strong bulk absorption of this wave leads to a significant inhomogeneous crystal heating, a drift of material constants, and to the consequent change in light diffraction patterns. Current paper is focused on a study of thermal regimes in acousto-optic devices. A method of laser ultrasonic time-of-flight thermography of solid-state devices is proposed. The method is used to experimentally evaluate temperature maps of an acousto-optic dispersive delay line with different acoustic pump frequencies. The comparison of obtained results with thermal imaging is carried out, showing good agreement within measurement error.

The spatial resolution and size of the sensitivity area of tomographic systems are estimated by calculating sensitivity maps and spatial resolution maps in the image plane of complex arrays. The relation between the size of areas of high sensitivity and high spatial resolution for real-time oriented tomographic systems with confocal arrays is studied. It is shown that arrays with toroidal geometry significantly improve the diagnostic capabilities of optoacoustic and laser-ultrasound structural analysis of biological objects, rocks, and composite materials.

We studied the possibility of applying laser ultrasound tomography for profilometry of solids. The proposed approach provides high spatial resolution and efficiency, as well as profilometry of contaminated objects or objects submerged in liquids. The algorithms for the construction of tomograms and recognition of the profiles of studied objects using the parallel programming technology NDIVIA CUDA are proposed. A prototype of the real-time laser ultrasound profilometer was used to obtain the profiles of solid surfaces of revolution. The proposed method allows the real-time determination of the surface position for cylindrical objects with an approximation accuracy of up to 16 μm.

The paper presents the results of measurements of compressional and shear wave velocities in the near-surface zone in the Zhelezny open pit mine, the Kovdor GOK (Kovdor Mineral Producing and Processing Company). Data on the seismic wave velocities are used to estimate Young's modulus and Poisson's ratio. Poisson's ratios derived from the compressional-to-shear velocity ratios are used to locate fractures that are due to stress redistribution and weathering processes in the stepped walls of the open pit mine.

This article is devoted to solving problems with known theoretical solutions in the Fidesys software package. Within the framework of the work, modeling of a biaxial shear test of the ground and simulating a draft of a flexible foundation was done. The solutions obtained were correlated with the solutions of such problems in the Plaxis software package. According to the results of the study, it can be concluded that the Fidesys software complex allows solving problems in the field of geomechanics. At the same time, it is not inferior to recognized solutions in terms of functionality.

The internal structure of plane-parallel plates of shungite is studied. The broadband ultrasonic pulses are used to measure the velocities of longitudinal and shear elastic ultrasonic waves. The accuracy of measurements is 0.3% in the case of longitudinal wave velocity and 0.5% in the case of shear wave velocity (scanning pitch over the surface of specimens was 0.5 mm). Local elastic moduli of shungite (Young modulus, shear modulus and Poisson's ratio) are uniquely determined from the velocities of elastic waves.

This paper describes the experimental implementation of the laser-ultrasonic method for diagnosing mechanical compression and tensile stresses in steel structures, based on the acoustoelasticity effect. The special laser-ultrasonic transducer that provides the laser excitation and highly sensitive piezoelectric detection of head (longitudinal subsurface) ultrasonic waves is developed. It is shown on the example of R65 rail samples of various quality that, regardless of the structural phase state of the rail, there is one and the same linear relationship between the relative variation of the velocity of head ultrasonic waves and the absolute value of uniaxial compression and tensile stresses acting in the rail.

We describe a universal system for research in combined real-time optoacoustic (OA) and laser-ultrasonic (LU) imaging. The results of its testing on the task of needle insertion into the blood vessel model diagnostics are presented. In OA mode, where laser light is absorbed directly in the sample, the contents of blood vessel model is clearly visible. In LU mode, where the short ultrasonic probe pulse scattered on the sample is detected, the needle is clearly visible. The developed solution combining OA and LU imaging modalities due to the common detection system allowed real-time diagnostics of the position of medical needles (0.63 mm and 0.7 mm in diameter) inside blood vessel models (1.6 mm and 2.4 mm in diameter). Frame rate was 10 Hz. High longitudinal spatial resolution of the system − 0.1 mm − allows distinguishing the two walls of the vessel model and the position of the needle inside.

The paper discusses the use of acoustic emission, stress-memory effect, and X-ray computed microtomography (μST) to detect the onset of destruction of specimens of concrete and basalt which are widely used in construction. It is shown that the most informative parameter is acoustic emission activity based on which the onset of the formation of a main crack can be identified. The geometry of the crack is determined using computed X-ray tomography.

This paper discusses the possibility of studying composite materials by non-destructive laser-ultrasonic testing technique. Concrete samples and carbon-epoxy composites were examined, defects located and elastic wave velocities measured. The internal structure of the samples was visualized in 2D images.

In this paper we report on the first toroidally focused 2D real-time laser-ultrasonic imaging system and a modified filtered back projection algorithm that can be used in the region near the waist of the astigmatic laser-ultrasonic probe beam. The system is capable of visualizing an acupuncture needle 0.2 mm in diameter located at ∼4 cm depth in water. The lateral spatial resolution is better than ∼0.32 mm and axial spatial resolution is ∼30 μm. The achieved frame rate is up to 30 Hz. The depth dependency of the sensitivity region width and lateral resolution are experimentally measured and discussed. The array is intended to be used as a part of combined real-time photoacoustic and laser-ultrasonic imaging system. Keywords: Laser ultrasound, Laser ultrasound imaging, Tomography, Real-time, Back projection, Toroidal array, Focused array

We report on a new experimental technique aimed to investigate femtosecond filamentation process in transparent condensed dielectrics. The proposed method is based on a highly resolved shadow photography and wideband (about 100MHz) photoacoustic imaging. We demonstrate, that combination of these techniques allows conducting comprehensive filament investigation by retrieving the value of the energy deposition into a medium, plasma electron density and the size of the filament formation region. Moreover, applying these techniques we studied the dependence of filament properties on a filamentation regime.

We report on a hybrid optoacoustic method aimed to retrieve the three-dimensional spatial distributions of the plasma electron density and the deposited energy density in the region of plasma formation under optical breakdown in condensed medium. The spatial distribution of the plasma electron density obtained by the proposed method with the accuracy of 3 × 1 0 18 c m − 3 gives the qualitative characterization of the laser pulse propagation in the region of plasma formation. The spatial distribution of the deposited energy density retrieved by the proposed method with the accuracy of 14 J / c m 3 provides the quantitative description of the laser impact on the bulk of the medium. The method is based on photoacoustic imaging and shadowgraphy techniques, which have the spatial resolution of 2 μ m and 10 μ m, respectively. The proposed method can be applied both in the area of technological applications, such as micromachining of transparent materials, and in the field of the fundamental science of laser–matter interaction.

Investigation of residual stresses in an infrastructure is important due to the reason of safety. One of the most important problems is non-destructive testing of residual stresses particularly in welded constructions. A quite lot of technologies are used to solve this problem. Ultrasonic testing is based on the dependence of the velocity of ultrasonic waves on the stress value within a material under study. This technology is robust, operative and can be used in field conditions. The main problem is to measure the velocity of ultrasonic waves with high precision at a short trace. The proposed technique of the Contact Laser-Ultrasonic Evaluation (CLUE) is used in our work to overcome this difficulty. The variation of the results of the measurement of the ultrasonic wave velocity using CLUE does not exceed 0.05% and provides the threshold of the detection of the residual stress in steel at the level of 2-3 MPa. Basics of CLUE and some experimental cases of the study of the uniaxial stress in compressed and tensioned rail steel specimens are described. The advantages and disadvantages of CLUE for the stress measurement are discussed.

The paper addresses the use of laser ultrasonic structuroscopy to study how weathering affects the internal structure of rocks used for facing buildings. For 1,250 hours rock samples were subjected to 150 cycles of freezing (at-20°C) and thawing in water (at +20°C) to determine their frost resistance. Also, moistened every 30 minutes, rock samples were exposed to thermal and ultraviolet radiation for 480 hours to determine their weather resistance. The frequency-dependent phase velocity and attenuation coefficient of longitudinal ultrasonic pulses in the samples were measured. It is found that the rock samples are most seriously damaged when exposed to sharp changes in temperature. As a result of freeze-thaw processes, the velocity of elastic waves decreases by 10% on average, and the attenuation coefficient increases by a factor of 1.5 in the range of 300kHz-500kHz and more than 3 times in the range of 1.0MHz-1.5MHz. The coefficient of the relative power of “structural” noise (K parameter) is introduced to characterize the degree of degradation of rock samples. The parameter K is defined as the ratio of the power of noise component in the spectrum of scattered waves to the power of reference signal. It is shown that the parameter K increases almost by a factor of 10 as a result of various weathering processes.

Modern buildings erected on bedrock or is to be equipped directly in an array (in particular hydroelectric power stations, underground storage facilities and soon), are technically complex, often unique objects construction. At the same time, the cost of design and construction of such facilities is very high. In this context, particular relevance is the question of stable and safe operation of facilities. Now, generally recognized that the study of the functioning of large technical systems (such as the base - structure) with a randomly varying characteristics most adequately carried out was done by different types of complex modeling, particularly mathematical, simulation, and in some cases - physical modeling [3]. However, before moving to a system of «building/foundation» is necessary to examine the massif in situ. Modern software systems (such as Plaxis, ZSoil, Comsol, Abaqus, and soon) have are significant opportunities that allow to make calculations with high accuracy. In particular, implemented a specialized model of soils, such as models of Hoek-Brown, Jointed Rock and others [5]. They allow you to get a more objective picture of the state stress of the array according to the degree of fracturing and anisotropy properties. They allow you to get a more objective picture of the state stress of the array according to the degree of fracturing and anisotropy properties. In addition, is possible a reflection of the detailed features of the geological structure in the 3D calculation that gives an idea of the influence of the field to an array of building/foundation. But, it is necessary to understand that the simulation is based on idealization and averaging the physical and mechanical properties of the medium under study. The inevitable errors and inaccuracies in the calculations. As a real rock massif is a complex system, in the work showed of drawing up an analysis of structural models and their implementation using conventional concepts and a more detailed study. The isolation of the structural elements and boundaries in an array of rocky soils should be approached with special attention. This is due, primarily, with the features of the geological structure of the study area: for example, improperly allocate lithological boundaries as in the case of consideration arrays dispersed soils, because rocky soils is a monolithic solid. Select elements should be performed in accordance with the characteristic feature, such as a fracture, blocking and so on. Besides the issue of numerical modeling of rock masses, in the issues of verification data obtained by numerical method. With the increasing complexity of the technical constructions, increasingly there is a need to verify the results of numerical simulations with actual operating voltage value in the array. Since the field of stress research methods is very expensive and labor-intensive, trade-off seems logical to use in the verification of the results of numerical modeling of acoustic emission (AE) [6]. This method may be used in combination of laboratory tests. With this approach, it is possible to achieve significant improvements in the quality of the received information.

This paper covers design diagrams and algorithms for determining the strain state of soil mass in case of its underworking. When tunnels are constructed in restrained urban conditions peculiar to megapolises, there is an acute problem related to the assessment of their influence on the existing above-and underground facilities. The strains of buildings and structures that occur as a result of underground construction work may have an impact on the operation reliability of these facilities. Russian regulatory documents in the area of underground urban construction strictly govern the basic parameters of the subsidence trough, such as maximum vertical subsidence, curvature, inclination, etc., for most of the existing underworked structures. Such facilities include both buildings and structures of various purposes above ground and different types of utilities (roads and railways, pipelines, cable lines, etc.). The method described in the paper offers the use of an integral quantity of "volume loss" when tunneling is performed by tunnel-boring machines. The "volume loss" term shall be understood to mean the distance between tunnel lining and soil mass, which initially occurs due to the difference between rotor diameter and lining outside diameter. There are also a number of other technology factors affecting the increase of this parameter, and their quantitative assessment is given in this paper. The method proposed in this paper makes it possible to promptly assess the impact of tunneling operations on the existing underworked structures with account of basic influencing factors.

We present a novel approach to the characterization of ultrafast laser–matter interaction processes in solids and liquids under extreme conditions of microplasma generation. Through the combination of three-dimensional propagation imaging, absorption measurements, shadowgraphy and photoacoustic imaging we can restore plasma electron density distribution, laser pulse fluence profile and the value of deposited energy density inside the bulk of the material and characterize the regime of the laser pulse propagation. The developped concept is important for understanding the physics of ultrafast laser–matter interactions with strong implications for precision control of laser micromachining, bioprocessing and biotreatment.

In this paper a real-time experimental system and algorithms for immersion two-dimensional laser ultrasonic imaging of solids with complex geometry of surface are presented. Wideband probe ultrasonic pulse is generated photoacoustically in an opaque plate, which absorbs pulsed laser radiation. The back-scattered acoustic field is recorded by a multi-element piezoelectric array. The signals are used to reconstruct refraction-corrected ultrasonic images, which are post-processed to determine positions of the external and internal boundaries of the object. The numerical simulations are carried out to verify the developed algorithms. The proposed approach allowed measuring the positions of the boundaries of the polymethyl methacrylate (PMMA) sample with accuracy of ∼0.1 mm in the direction of the probe beam propagation, and ~0.2-0.3 mm in the perpendicular direction.

We report a first-of-its-kind optoacoustic tomography of femtoseconds filament in water. Using wide-band (about 100 MHz) piezoelectric detector and back-projection reconstruction technique a filament profile was retrieved. Obtained pressure distribution induced by the femtosecond filament determines the filament location and its radial size with spatial resolution better than 10μm

The paper describes a novel laser ultrasonic profilometry method which uses pulsed laser radiation for imaging of the surface profile of solid objects in optically opaque liquids by scattering of ultrasonic waves. Algorithms for the construction of laser ultrasonic images and for profile segmentation are presented. An experimental setup for profile measurements is described. It allows reconstructing of laser ultrasonic images with a frame rate of 10 Hz and performing an automated 3D scanning of samples. The results of the experimental testing of laser ultrasonic profilometry on duralumin samples are presented. The approximation error of duralumin cylinder surface profile measurements in water is 15 μm. The results are compared to those obtained by x-ray tomography.

The composition, structure, and properties of different genetic types of serpentinites developed after ultrabasic rocks are studied. The rocks were sampled from massifs located along the Main Uralian Fault, in a Paleozoic subduction zone. We consider specific features of serpentinites developed after chromite-bearing ultrabasic rocks, in metamorphic zones of carbonate rocks, and within the zone of weathering of ultrabasic rocks. A comparative study of the microstructure and chemical and phase compositions of serpentinites is carried out by IR spectroscopy, scanning electron microscopy, and thermal, X-ray diffraction, and microprobe analyses. The petrophysical properties and acoustic emission of the rocks are examined. Several genetic and structural groups of serpentinites developed after different protoliths (mantle and crustal) in different geologic conditions are recognized. © 2014, V.S. Sobolev IGM, Siberian Branch of the RAS. Published by Elsevier B.V. All rights reserved.

The components of electric field of the third harmonic beam, generated in isotropic medium with cubic nonlinearity by a monochromatic light beam carrying polarization singularity of an arbitrary type, are found analytically. The relation between C-points characteristics in the fundamental and signal beams are determined, as well as the impact of the phase mismatch on the shape of the C-lines.

This article addresses theoretical and numerical investigation of image formation in photoacoustic (PA) imaging with complex-shaped concave sensor arrays. The spatial resolution and the size of sensitivity region of PA and laser ultrasonic (LU) imaging systems are assessed using sensitivity maps and spatial resolution maps in the image plane. This paper also discusses the relationship between the size of high-sensitivity regions and the spatial resolution of real-time imaging systems utilizing toroidal arrays. It is shown that the use of arrays with toroidal geometry significantly improves the diagnostic capabilities of PA and LU imaging to investigate biological objects, rocks, and composite materials.

The problem of internal temperature gradients is topical in design of high-performance acousto-optic devices. Current study is focused on the application of laser ultrasound method for evaluation of temperature fields in the paratellurite acousto-optic cell. An automatized laser ultrasonic structuroscope UDL-2M is used to scan the cell surface and to evaluate the temperature distribution from the time-of-fight measurements. The experimental results are presented and precision is discussed. The proposed method has the accuracy of 2–3 degrees Celsius.The problem of internal temperature gradients is topical in design of high-performance acousto-optic devices. Current study is focused on the application of laser ultrasound method for evaluation of temperature fields in the paratellurite acousto-optic cell. An automatized laser ultrasonic structuroscope UDL-2M is used to scan the cell surface and to evaluate the temperature distribution from the time-of-fight measurements. The experimental results are presented and precision is discussed. The proposed method has the accuracy of 2–3 degrees Celsius.

The development of a laser ultrasonic imaging technique for diagnostics of heterogeneous materials involves solving the inverse problem of ultrasound scattering. The paper describes the back-projection algorithm for the reconstruction of laser-ultrasonic images of inhomogeneous media. To demonstrate the capabilities of laser ultrasonic imaging, an experiment was carried out to reconstruct the image of an orifice 1 mm in diameter in a duralumin half-cylinder with a radius of 65 mm.

Porosity is one of the most important composite structure failure, influenced on the properties of the construction and the residual service to fatigue. The non-destructive technologies able to detect the intimate structure transformation are well-come to the market. The comparative analysis of advantages and disadvantages of several technologies, such as X-ray tomography, conventional ultrasonic testing, thermal wave testing, remote laser-ultrasonic testing and contact laser-ultrasonic evaluation is presented. Contact laser-ultrasonic material evaluation seems to be the very technology for CFRF construction test. The advantages of contact laser-ultrasonic evaluation (CLUE) are described in detail. The possibility to evaluate the residual life-time of the objects of critical structure composite construction with CLUE is discussed.

Broadband ultrasonic spectroscopy used to measure residual stresses in samples of high-temperature alloys. It is shown that the acoustoelasticity method and laser ultrasonic spectroscopy can be used to determine the depth distribution of residual stresses. Measurements were carried out on test samples of heat-resistant nickel-base and titanium-base alloys with specified distribution of residual stresses after vacuum heat treatment, vibratory stress relief or shot peening. The results were compared with the residual stresses determined from changes in the deformation upon the removal of layers from the sample by electrochemical etching.

As material for structural components, isotropic pyrolytic graphite (IPG) is widely used in such objects of critical infrastructure as nuclear fission reactors. There is the possibility of using IPG as a facing material for experimental thermonuclear facilities; this is currently being explored. Also, IPG is used as a sealing and anti-friction material in the aerospace industry. It is shown that X-ray tomography is not very suitable for studying the internal structure of IPG produced by chemical vapor deposition because its density is much the same as that of heterogeneities encountered in IPG, such as carbon black inclusions and anisotropic pyrographite crystallites. Broadband ultrasonic spectroscopy has been used to detect pores and carbon deposited layers in IPG samples, 2D images of the internal structure produced.

A laser optoacoustic method for analyzing the effect of porosity on the local isotropic Young’s modulus of composite materials was proposed and experimentally implemented. Using as an example samples of a metal matrix composite based on silumin with reinforcing microparticles of silicon carbide, SiC, in various concentrations, it is shown that to provide an effective increase in Young’s modulus with increasing concentration of SiC, the porosity of the final sample should not exceed 2%.

Laboratory studies of the stress-strain behavior of rocks specimens were conducted by using acoustic emission and laser-ultrasonic diagnostics. The sensitivity of the techniques allowed changes in the internal structure of the specimens under uniaxial compressive load to be examined at micro- and macro scales. It was shown that microcracks appear in geologic materials when the stress level reaches about 50% of breaking strength. Also, the characteristic stress of the main crack formation was registered in the process of single-stage compression of rocks. On the base of laser-ultrasonic echoscopy, 2D visualization of the internal structure of rocky soil specimens was realized, and the microcracks arising during uniaxial compression were registered., {"references":["Brantut, N., Heap, M. J., Meredith, P. G., & Baud, P. (2013). Time-dependent cracking and brittle creep in crustal rocks: A review. Journal of Structural Geology, 52, 17-43","Duncan C. Wyllie. Rock Fall Engineering. CRC Press, 2014, p. 270","Fusao O., Akira M., Ryosuke U., Sayuri K. Computer Methods and Recent Advances in Geomechanics. CRC Press, 2014, p. 472","The Japanese Society for Non-Destructive Inspection. Practical Acoustic Emission Testing. Springer, 2016, p. 130","Xue, L., Qin, S., Sun, Q., Wang, Y., Min Lee, L., Li, W., 2014. A study on crack damage stress thresholds of different rock types based on uniaxial compression tests. Rock Mech. Rock. Eng. 47, 1183–1195.","Aker, E., Kühn, D., Vavryèuk, V., Soldal, M., Oye, V., Experimental investigation of acoustic emissions and their moment tensors in rock during failure. International Journal of Rock Mechanics & Mining Sciences, 70 (2014) 286-295.","A.A. Karabutov, E.B. Cherepetskaya, Y.G. Sokolovskaya, D.V. Morozov, Study of Effects of Weathering Factors on Internal Structure of Rocks by Laser Ultrasonic Spectroscopy. Applied Mechanics and Materials, vol.843(2016), P.51-58.","A. A. Karabutov, N. B. Podymova, E. B. Cherepetskaya Measuring the Dependence of the local Young's Modulus of isotropic Composite Materials by a pulsed acoustic Method using a Laser Source of Ultrasound, Journal of Applied Mechanics and Technical Physics, Vol. 54, No.3, pp. 500–507, 2013","Ariskin A.A. and Barmina G.S. Modeling Phase Equilibriums at Crystallization of Basalt Magmas, Moscow, Nauka, MAIK Nauka/Interpreriodika, 2000 (in Russian)\n[10]\tBortnikova S.B., Sharapov V.N., and Bessonova E.P. Geochemical Composition of Thermal Springs in the Donnoye Fumarole Field near the Mutnovsky Volcano, South Kamchatka, and Problems of Relating them to Above-Critical Magmatic Fluids, Dokl. Akad. Nauk, 2007, Vol. 413, No. 4, pp. 530-534\n[11]\tMartynov Yu.A. Perepelov A.B., and Chashchin A.A. Geochemical Typification of the Basaltoids of the Mutnovsky Volcanic Field, South Kamchatka, Tikhookean. Geol., 1995, vol. 14, No.5, pp. 72--83\n[12]\tMartynov Yu.A. and Chashchin A.A. Rock-Forming Minerals of Basic Volcanic Rocks of the Mutnovsky Geothermal Area, in New Data on Petrology of Magmatic and Metamorphic Rocks of Kamchatka, Vladivostok, DVO Akad. Nauk, 1989, pp. 112--128\n[13]\tSelyangin O.B. New Data on the Mutnovsky Volcano: Structure, Evolution, and Prediction, Vulkanol. Seismol., 1993, No.1, pp. 17--35"]}

We report a first-of-its-kind optoacoustic tomography of a femtosecond filament in water. Using a broadband (~100 MHz) piezoelectric transducer and a back-projection reconstruction technique, a single filament profile was retrieved. Obtained pressure distribution induced by the femtosecond filament allowed us to identify the size of the core and the energy reservoir with spatial resolution better than 10 µm. The photoacoustic imaging provides direct measurements of the energy deposition into the medium under filamentation of ultrashort laser pulses that cannot be obtained by existing techniques. In combination with a relative simplicity and high accuracy, photoacoustic imaging can be considered as a breakthrough instrument for filamentation investigation.

In this paper, a technique for reflection mode immersion 2D laser-ultrasound tomography of solid objects with piecewise linear 2D surface profiles is presented. Pulsed laser radiation was used for generation of short ultrasonic probe pulses, providing high spatial resolution. A piezofilm sensor array was used for detection of the waves reflected by the surface and internal inhomogeneities of the object. The original ultrasonic image reconstruction algorithm accounting for refraction of acoustic waves at the liquid-solid interface provided longitudinal resolution better than 100 μm in the polymethyl methacrylate sample object.

Surface control is an important problem for production inspection in industry. Traditionally it is solved using mechanical and optical profilometry, providing high spatial resolution. However, such methods are inappropriate for bodies immersed in opaque liquids and require preliminary preparation of samples. Current work focuses on an application of a method of laser ultrasound tomography to mapping of solid surfaces. The suggested approach combines high acoustical resolution, high performance and allows profilometry of contaminated and immersed samples. An automated prototype for real-time surface profile measurements is constructed and tested on several bodies of revolution. Linear approximation of a cylinder profile obtained by the prototype shows maximum approximation inconsistency of 15 μm. The results are verified by those obtained by the conventional x-ray method.

The laser-ultrasonic method is realized for quantifying the influence of porosity on the local Young's modulus of isotropic composite materials. The method is based on a laser thermooptical method of ultrasound generation combined with measurement of the phase velocity of longitudinal and shear acoustic waves in samples. The main advantage of this method compared with traditional ultrasonic research methods is the efficient generation of short and powerful probing acoustic pulses required for reliable testing of ultrasound absorbing and scattering heterogeneous materials. Using as an example samples of a metal matrix composite with reinforcing microparticles of silicon carbide in various concentrations, it is shown that to provide an effective increase in Young's modulus with increasing concentration of microparticles, the porosity of the final sample should not exceed 2%., {"references":["Springer handbook of nanotechnology / Ed. B. Bhushan. Springer-\nVerlag, Berlin (2007), 1916 p.","A.D. Romig, jr, M.T. Dugger, PJ. McWhorter.ActaMater. 51, 5837\n(2003).","Yu Golovin.Introduction to nanotech.Machinery, M. (2007).496 pp.","P.D. Tall, S. Ndiaye, A.C. Beye, Z. Zong, W.O. Soboyejo,H.-J. Lee,\nA.G. Ramirez, K. Rajan, Mater. Manuf. Processes22 (2007) 175-179.","E. Wibowo, C.Y. Kwok, J. Micromech. Microeng. 16 (2006)101-108.","A.K. Nanda Kumar, C.K. Sasidharan Nair, M.D. Kannan,S. Jayakumar,\nMater. Chem. Phys. 97 (2006), 308-314.","M. Callisti, F.D. Tichelaar, B.G. Mellor, T. Polcar, Surf.Coat. Technol.\n237 (2013) 261-268.","V. V. Polyakov and A. V. Golovin, \"Elastic Characteristics of Porous\nMaterials,\" Prikl. Mekh. Tekh. Fiz. 34 (5), 32-35 (1993) (J. Appl. Mech.\nTech. Phys. 34 (5), 625-628 (1993)).","V. E. Gusev and A. A. Karabutov, Laser Optoacoustics (Nauka,\nMoscow, 1991) (in Russian)\n[10] S. Yu. Davydov, \"Effect of Pressure on the Elastic Properties of Silicon\nCarbide,\" Fiz. Tverd. Tela 46 (7), 1169–1173 (2004)."]}

Nonlinear evolution of broadband ultrasonic pulses passed through the rock specimens is studied using the apparatus "GEOSCAN-02M". Ultrasonic pulses are excited by the pulses of Qswitched Nd:YAG laser with the time duration of 10 ns and with the energy of 260 mJ. This energy can be reduced to 20 mJ by some light filters. The laser beam radius did not exceed 5 mm. As a result of the absorption of the laser pulse in the special material – the optoacoustic generator–the pulses of longitudinal ultrasonic waves are excited with the time duration of 100 ns and with the maximum pressure amplitude of 10 MPa. The immersion technique is used to measure the parameters of these ultrasonic pulses passed through a specimen, the immersion liquid is distilled water. The reference pulse passed through the cell with water has the compression and the rarefaction phases. The amplitude of the rarefaction phase is five times lower than that of the compression phase. The spectral range of the reference pulse reaches 10 MHz. The cubic-shaped specimens of the Karelian gabbro are studied with the rib length 3 cm. The ultimate strength of the specimens by the uniaxial compression is (300±10) MPa. As the reference pulse passes through the area of the specimen without cracks the compression phase decreases and the rarefaction one increases due to diffraction and scattering of ultrasound, so the ratio of these phases becomes 2.3:1. After preloading some horizontal cracks appear in the specimens. Their location is found by one-sided scanning of the specimen using the backward mode detection of the ultrasonic pulses reflected from the structure defects. Using the computer processing of these signals the images are obtained of the cross-sections of the specimens with cracks. By the increase of the reference pulse amplitude from 0.1 MPa to 5 MPa the nonlinear transformation of the ultrasonic pulse passed through the specimen with horizontal cracks results in the decrease by 2.5 times of the amplitude of the rarefaction phase and in the increase of its duration by 2.1 times. By the increase of the reference pulse amplitude from 5 MPa to 10 MPa the time splitting of the phases is observed for the bipolar pulse passed through the specimen. The compression and rarefaction phases propagate with different velocities. These features of the powerful broadband ultrasonic pulses passed through the rock specimens can be described by the hysteresis model of Preisach- Mayergoyz and can be used for the location of cracks in the optically opaque materials., {"references":["Landau, L., and Lifshitz, E. (1986). Theory of Elasticity (Pergamon,\nOxford), pp. 1–187.","Breazeale, M., and Thompson, D. (1963). \"Finite amplitude ultrasonic\nwaves in aluminum,\" Appl. Phys. Lett. 3, 77.","Cantrell, J., and Yost, W. (2001). \"Nonlinear ultrasonic characterization\nof fatigue microstructures,\" Int. J. Fatigue 23, 487–490.","Guyer, R. A., and Johnson, P. A. (2009). Nonlinear Mesoscopic\nElasticity: The Complex Behaviour of Rocks, Soil, Concrete (Wiley-\nVCH, Weinheim), pp. 1–410.","Finkel, P., Zhou, A. G., Basu, S., Yeheskel, O., and Barsoum, M. W.\n(2009). \"Direct observation of nonlinear acoustoelastic hysteresis in\nkinking nonlinear elastic solids,\" Appl. Phys. Lett. 94, 241904","Ostrovsky, L. A., and Johnson, P. A. (2001). \"Dynamic nonlinear\nelasticity in geomaterials,\" Riv. Nuovo Cimento 24, 1–46.","Zaitsev, V., Nazarov, V., Gusev, V., and Castagnede, B. (2006). \"Novel\nnonlinear-modulation acoustic technique for crack detection,\" NDT & E\nInt. 39, 184–194.","Zaitsev, V. Y., and Matveev, L. (2006). \"Microinhomogeneous medium,\nelastic nonlinearity, linear dissipation, amplitude dependent dissipation,\"\nRuss. Geol. Geophys. 47, 694–709.","Zaitsev, V. Y., Matveev, L., Matveev, A., and Arnold, W. (2008).\n\"Cascade cross modulation due to the nonlinear interaction of elastic\nwaves in samples with cracks,\" Acoust. Phys. 54, 398–406.\n[10] Zaitsev, V. Y., Matveev, L., and Matveyev, A. (2009). \"On the ultimate\nsensitivity of nonlinear-modulation method of crack detection,\" NDT &\nE Int. 42, 622–629.\n[11] Ostrovsky, L. A., and Johnson, P. A. (2001). \"Dynamic nonlinear\nelasticity in geomaterials,\" Riv. Nuovo Cimento 24, 1–46.\n[12] Zaitsev, V., Nazarov, V., Gusev, V., and Castagnede, B. \"Novel\nnonlinear-modulation acoustic technique for crack detection,\" NDT & E\nInt. 39, 184–194, 2006.\n[13] Zaitsev, V. Y., Matveev, L., and Matveyev, A. \"Elastic-wave\nmodulation approach to crack detection: Comparison of conventional\nmodulation and higher-order interactions,\" NDT & E Int. 44, 21–31,\n2011.\n[14] V.E. Gusev, A.A. Karabutov, Laser Optoacoustics, New York: AIP\nPress, 1993."]}