Backscattering of Ultrasonic Waves as the Basis of the Method of Control of Structure and Physicо-Mechanical Properties of Cast Irons

Increasing the reliability of control of cast iron structure and its physical and mechanical characteristics is an important scientific and technical task of the machine-building industry. The paper studies the possibilities of controlling the structure of cast irons using structural noise created by ultrasonic scattering on graphite inclusions of different shapes. The subject of the present studies was such characteristics of structural noise as amplitude-temporal A(t) and as root mean square value of the amplitude of the ultrasonic waves backscattering field AN, compared with the data on ultrasonic velocity and strength or tensile strength of cast iron samples. As a result of the studies, a significant difference between the amplitude parameters of the AN structural noise obtained for samples with different shapes of graphite inclusions at 5 MHz was revealed for the first time. So, for example, for samples of gray cast iron (Russian: СЧ10, СЧ15, СЧ20, СЧ25), having predominantly plate-like form of graphite inclusions, the value of AN on 14–15 dB exceeds that measured in high-strength specimens of the cast iron with the prevailing form of spherical graphite inclusions ВЧ50 (Russian), etc. At the same time growth of longitudinal ultrasonic velocity amounted to 20–25 %. The method of rejection of gray cast iron from high-strength cast iron according to the data of amplitude parameters of structural noise AN at unilateral and local sounding of the object without using an additional reference signal reflected from its oppositional wall is suggested

Возможности использования амплитудно-угловых характеристик поверхностных и подповерхностных волн для контроля материалов с поверхностно упрочнённым неоднородным слоем

Improving the efficiency of ultrasonic control of hardened surface layers of metal products with a heterogeneous structure obtained using different technologies is a pressing problem of industrial production. The purpose of this work was to investigate the possibilities of measuring the depth of the surface inhomogeneous layer of steel objects on the basis of the use of amplitude and amplitude-angle characteristics of surface and subsurface transverse waves.The analysis of ultrasonic methods of control of physical and mechanical properties of metals by using surface and subsurface waves and experimentally investigated amplitude-angular characteristics of surface waves, the maximum angle of which increases by 3° at change of dimensionless layer depth hλ from zero to0.82. For the first time, the ratio of normalized amplitudes of surface waves taken at certain angles on theamplitude-angle characteristic curve obtained in the echo mode was proposed to be used as correlating parameters with the depth of the hardened layer. As a result of this research, the possibility of using a phased array transducers to solve the above problems.The effect of the hardened layer depth varying from zero to five in the working frequency range of 1.8– 10 MHz on the peculiarities of the refraction effect (including interference) and dependence of the subsurface wave amplitude on the acoustic base has been studied, making it possible to establish conditions that provide for the determination of the hardened layer depth.Circuit solutions have been offered in order to increase the efficiency of control of properties of the surface layers of metal articles on the basis of utilization of small-aperture transducers and ultrasonic reflectors making it possible to form fields of surface waves of different directional pattern. Повышение эффективности ультразвукового контроля упрочненных поверхностных слоев металлоизделий с неоднородной структурой, полученных по различным технологиям, является актуальной проблемой опытно-промышленного производства. Целью данной работы являлось исследование возможностей измерения глубины поверхностного неоднородного слоя стальных объектов на основе использования амплитудных и амплитудно-угловых характеристик поверхностных и подповерхностных поперечных волн.Проведён анализ ультразвуковых методов контроля физико-механических свойств металлов с использованием поверхностных и подповерхностных волн и экспериментально исследованы амплитудно-угловые характеристики поверхностных волн, максимальный угол которых увеличивается на 3°при изменении безразмерной глубины слоя hλ от нуля до 0,82. Впервые предложено использовать в качестве коррелирующих параметров с глубиной упрочнённого слоя отношение нормированных амплитуд поверхностных волн, взятых под определёнными углами на кривой амплитудно-угловой характеристики, полученной в эхо-режиме. В результате проведённых исследований была выявлена возможностьиспользования преобразователей с фазированной решёткой для решения вышеуказанных задач.Исследовано влияние глубины упрочнённого слоя, изменяющейся от нуля до пяти в рабочем диапазоне частот 1,8–10 МГц, на особенности эффекта преломления (в том числе интерференции) и импенданса амплитуды подповерхностной волны на акустической базе, что позволило установить условия, обеспечивающие определение глубины упрочнённого слоя.Предложены схемные решения для повышения эффективности контроля свойств поверхностных слоев металлических изделий на основе использования малоапертурных преобразователей и ультразвуковых отражателей, позволяющих формировать поля поверхностных волн различной направленности

Element-specific probe of quantum criticality in CeCoIn5\mathrm{CeCoIn_{5}}

Employing the elemental sensitivity of x-ray absorption spectroscopy (XAS) and x-ray magnetic circular dichroism (XMCD), we study the valence and magnetic order in the heavy fermion superconductor CeCoIn$_5$. We probe spin population of the f-electrons in Ce and d-electrons in Co as a function of temperature (down to 0.1 K) and magnetic field (up to 6 T). From the XAS we find a pronounced contribution of Ce$^{4+}$ component at low temperature and a clear temperature dependence of the Ce valence below 5 K, suggesting enhanced valence fluctuations, an indication for the presence of a nearby quantum critical point (QCP). We observe no significant corresponding change with magnetic field. The XMCD displays a weak signal for Ce becoming clear only at 6 T. This splitting of the Kramers doublet ground state of Ce$^{3+}$ is significantly smaller than expected for independent but screened ions, indicating strong antiferromagnetic pair interactions. The unconventional character of superconductivity in CeCoIn$_5$ is evident in the extremely large specific heat step at the superconducting transition.Comment: 5 pages, 5 figures. Supplementary information (4 pages, 5 figures

Влияние геометрии и граничных условий в области сцепления материалов на рассеяние ультразвуковых волн. Ч. 1. Теоретическое моделирование

The improvement of efficiency, reliability and productivity of ultrasonic testing of objects with cohesion between materials connected by welding, soldering, gluing, etc. is 'an important problem of the modern production technologies. The purpose of the paper is to determine in 3D space the conditions for increasing the sensitivity and reliability of the flaw detection in the cohesion zone between materials when the form of defect interface can be different.In the first part of the theoretical study the features of the formation of the acoustic fields of ultrasonic waves scattered from solid's interface when spot of an acoustic beam crosses the boundary of the defective region in the shape of an ellipse or a long strip have been investigated. In this case, the boundary conditions in the defect area change discretely or linearly.It was suggested to use a phase shift between reflected waves from the defect and defect-free interfaces as the more informative parameter depending on the cohesion between materials. There is shown that there are conditions to achieve sufficiently high sensitivity detection of interface defects when the scattered waves receiving are to be at angles outside the main directivity lobe of the scattering field pattern. The evolution features of the scattering field structure which are needed for the development of the method of evaluation the cohesion of materials has been got.Повышение эффективности, надёжности и производительности ультразвукового контроля соединения материалов сваркой, пайкой, склеиванием и др. является важной народнохозяйственной задачей. Цель работы состояла в установлении условий повышения чувствительности и достоверности обнаружения дефектов сцепления материалов на основе моделирования полей ультразвуковых мод, рассеянных дефектами разной геометрии.Впервые в максимальном приближении выполнен расчёт и анализ полей рассеяния ультразвуковых волн при перемещении пятна акустического луча в виде эллипса или длинной полосы относительно дефектной области с дискретными и плавно изменяющимися в ней граничными условиями. Для характеристики последних с точки зрения взаимодействия упругой волны с границей сред предложено использовать преимущественно фазовый сдвиг θ между волнами, рассеянными от дефектной и бездефектной границы, существенно сказывающийся на изменении параметров результирующего поля рассеяния в его периферийной зоне. Т. е., θ является важным параметром, характеризующим степень сцепления материалов и оказывающим превалирующее влияние на чувствительность предлагаемого метода обнаружения слабо выявляемых дефектов.Установлены особенности эволюции структуры полей рассеяния, являющиеся первичными для разработки методик контроля сцепления материалов предложенным методом. При достаточно малых значениях угла приёма ультразвуковых колебаний в меридиональной плоскости максимум чувствительности измерений достигается в динамическом режиме и приёме рассеянных волн под азимутальными углами, соответствующими 1-му экстремуму диаграммы направленности поля рассеяния опорного акустического луча

Влияние геометрии и граничных условий в области сцепления материалов на рассеяние ультразвуковых волн. Ч. 2. Особенности экспериментального моделирования

Improving the efficiency of diagnostics of objects with layered structure as applied to detection of poorly detectable material bonding defects is an important production task. The aim of the work was to experimentally simulate ultrasonic scattering by samples of proposed defect simulator designs with discretely and smoothly varying boundary conditions correlating with the phase response of longitudinal waves during their interaction with the defect boundary of contacting materials. A brief analysis of some methods and means for experimental simulation of the volume and surface wave scattering at the interfaces of contacting materials as applied to improvement of method of detection of poorly detectable adhesion defects of materials proposed earlier was carried out. For this purpose an immersion installation working in the shadow mode and allowing for simulation the spatial fields of scattered longitudinal waves at inhomogeneous or defective adhesion boundaries was developed and constructed. It is assumed that the waves interacting with such a boundary acquire a discrete or smoothly varying phase shift which significantly affects the formation of the scattering field in its peripheral zone. The greater this shift, the stronger these changes are, which can significantly increase the sensitivity of detection of poorly detected defects. In order to increase the efficiency of such inspection and to develop its methodology a new principle of simulation of such defects has been proposed. Experimental study of longitudinal waves scattering using the developed installation and defect simulators, simulating discretely and smoothly changing boundary conditions which are consistent with a change in the phase shift of the scattered waves is carried out. The amplitude dependences of the scattering field vs. the receiving angle received mainly in the range from - 20º to + 20º and the displacement of the simulated defect relative to the axis of the probing acoustic beam were obtained. As it has been established, there is a quality conformity between the calculated and experimental data. The present study is of interest for solving a number of tasks of increasing efficiency of ultrasonic testing of modern objects with layered structure and will contribute to practical application

The morphofunctional and biochemical characteristics of opisthorchiasis-associated cholangiocarcinoma in a Syrian hamster model

The validity of experimental models of pathologies is one of the key challenges in translational medicine. Cholangiocarcinoma, or bile duct cancer, ranks second among oncological diseases of the liver. There is a strong association between bile duct cancer and parasitic infestation of the liver caused by trematodes in the family Opisthorchiidae. We have recently demonstrated that cholangiocarcinoma can develop in Syrian hamsters (Mesocricetus auratus) infected by Opisthorchis felineus and administered with dimethylnitrosamine. However, there is still no description of how this experimental model can possibly be used in translational research. The aim of this work was to study the morphological, functional and biochemical characteristics during cholangiocarcinoma development in Syrian hamsters infected by O. felineus and administered with dimethylnitrosamine. The experi­ment lasted 30 weeks with combined exposure to dimethylnitrosamine in drinking water at a dose of 12.5 ppm and a single injection of 50 metacercariae O. felineus. It was shown that the development of cholangiocarcinoma (18 weeks) increased the total number of basophils, eosinophils and monocytes, the relative number of granulocytes, the amount of total and direct bilirubin, and cholesterol and ALT levels, but reduced the relative number of lymphocytes. Based on pathological, morphometric and biochemical analyses, our model has characteristics similar to those in patients with opisthorchiasisassociated cholangiocarcinoma. Thus, this model can be used to test anticancer drugs, to study the mechanisms of cholangiocarcinogenesis and to search for molecular markers for early diagnosis of bile duct cancer