Wyniki wyszukiwania - BazTech

1

Refined multi-phase-lags theory and Thomson effect on a micropolar thermoelastic medium with voids

Alharbi Amnah M., Abd-Elaziz Elsayed M., Othman Mohamed I.A.

Archives of Thermodynamics

|

2021

|

Vol. 42, no 3

279--309

EN

The problem considered is that of an isotropic, micropolar thermoelastic medium with voids subjected to the Thomson effect. The solution to the problem is presented in the context of the refined multiphase-lags theory of thermoelasticity. The normal mode analysis was used to obtain the analytical expressions of the considered variables. The nondimensional displacement, temperature, microrotation, the change in the volume fraction field and stress of the material are obtained and illustrated graphically. The variations of these quantities have been depicted graphically in the refined-phase-lag theory, Green and Naghdi theory of type II, Lord and Shulman theory and a coupled theory. The effects of the Thomson parameter and phase lag parameters on a homogeneous, isotropic, micropolar thermoelastic material with voids are revealed and discussed. Some particular cases of interest are deduced from the present investigation.

2

A general study of fundamental solutions in aniotropicthermoelastic media with mass diffusion and voids

Chawla Vijay, Kamboj Deepmala

International Journal of Applied Mechanics and Engineering

|

2020

|

Vol. 25, no. 4

22--41

EN

The present paper deals with the study of a fundamental solution in transversely isotropic thermoelastic media with mass diffusion and voids. For this purpose, a two-dimensional general solution in transversely isotropic thermoelastic media with mass diffusion and voids is derived first. On the basis of the obtained general solution, the fundamental solution for a steady point heat source on the surface of a semi-infinite transversely isotropic thermoelastic material with mass diffusion and voids is derived by nine newly introduced harmonic functions. The components of displacement, stress, temperature distribution, mass concentration and voids are expressed in terms of elementary functions and are convenient to use. From the present investigation, some special cases of interest are also deduced and compared with the previous results obtained, which prove the correctness of the present result.

3

Geometryzacja form zjawisk krasowych na podstawie badań metodą georadarową

Ortyl Łukasz

Przegląd Geologiczny

|

2019

|

Vol. 67, nr 4

252--269

EN

Recognition of subsoil in areas threatened with discontinuous deformation associated with the existence of natural and mining voids can be implemented by various geophysical methods. The purpose of such research, apart from confirming the existence of voids, is to determine their spatial extent. This is not a simple issue, regardless of the geophysical method used. This paper discusses the possibilities of geometrization of karst phenomenon localization using the ground penetrating radar (GPR) method by the example of a karst cave as a natural void. The area of data acquisition is located on limestone formations with numerous karstforms. The study object is the main hall of the karst cave with a height of up to 3 m, located at a depth of 3 to 7 m below the surface. Such location and shape of the subsurface structure made it possible for the author to perform a wide range of research. Their original aspects are presented in this paper. The shape of the hall was obtained using terrestrial laser scanning (TLS). The GPR data were obtained employing the 250 MHz shielded antenna that was directly positioned using a robotized total station with the option of automatic target tracking. Thus, the GPR and geodetic data were immediately achieved in a uniform coordinate system. The accuracy of the data obtained in this way is discussed in this paper. The author’s original algorithm for processing of GPR data into a point cloud is presented. Based on the results obtained, it was possible to compare the GPR signal, which represents the shape of the cave hall, in relation to its image in the form of a point cloud from terrestrial laser scanning. A unique part of this paper is the selection of filtration procedures and their parameters in optimal GPR data processing, which were widely discussed and documented in a way beyond the standard filtration procedures. A significant contribution is the analysis that was carried out on the data obtained in the field and on the model data generated using the finite difference method. Modeling was carried out for two wave sources: exploding reflector and point. The presented methodology and discrimination between the actual shape of the cave, GPR field data and model data made it possible for the author to draw many conclusions related to the possibilities of shape geometrization of the subsurface voids determined by the GPR method.

4

Propagation and reflection of magneto-elastic plane waves at the free surface of a rotating micropolar fibre-reinforced medium with voids

Anya Augustine Igwebuike, Khan Aftab

Journal of Theoretical and Applied Mechanics

|

2019

|

Vol. 57 nr 4

869--881

EN

This work investigates rotational effects on propagation and reflection of waves at the free surface of a micropolar fibre-reinforced medium with voids under magnetic fields. When the P-wave is incident on the free surface, there exist four coupled reflected plane waves traveling in the medium; quasi-longitudinal displacement (qLD) wave, quasi-transverse displacement (qTD) wave, quasi-transverse microrotational (qTM) wave and a wave due to voids. Normal mode analysis is adopted in concomitant with Snell’s laws, and appropriate boundary conditions in determination of the solution. Amplitude ratios which correspond to reflected waves in vertical and horizontal components are presented analytically and graphically.

5

Plane waves in thermo-viscoelastic material with voids under different theories of thermoelasticity

Tomar S. K., Goyal N., Szekeres A.

International Journal of Applied Mechanics and Engineering

|

2019

|

Vol. 24, no. 3

691--708

EN

Propagation of time harmonic plane waves in an infinite thermo-viscoelastic material with voids has been investigated within the context of different theories of thermoelasticity. The equations of motion developed by Iesan [1] have been extended to incorporate the Lord-Shulman theory (LST) and Green-Lindsay theory (GLT) of thermoelasticity. It has been shown that there exist three coupled dilatational waves and an uncoupled shear wave propagating with distinct speeds. The presence of thermal, viscosity and voids parameters is responsible for the coupling among dilatational waves. All the existing waves are found to be dispersive and attenuated in nature. The phase speeds and attenuation coefficients of propagating waves are computed numerically for a copper material and compared under different theories of thermo-elasticity. The expressions of energies carried along each wave have also been derived. All the computed numerical results have been depicted through graphs. It is found that the influence of CT and GLT is almost same on wave propagation, while LST influences the wave propagation differently.

6

Rotation, initial stress, gravity and electromagnetic field effect on P wave reflection from stress-free surface elastic half-space with voids under three thermoelastic models

Abo-Dahab S. M., Rida S. Z., Mohamed R. A., Kilany A. A.

Mechanics and Mechanical Engineering

|

2018

|

Vol. 22, nr 1

313--328

EN

The present paper is devoted to investigate the influence of the rotation, thermal field, initial stress, gravity field, electromagnetic and voids on the reflection of P wave under three models of generalized thermoelasticity: Classical and Dynamical coupled model (CD), Lord-Shulman model (LS), Green-Lindsay model (GL), The boundary conditions at stress-free thermally insulated surface are satisfied to obtain Algebraic system of four equations in the reflection coefficients of various reflected waves. It is shown that there exist four plane waves; P1, P2, P3 and P4. In addition, the reflection coefficients from insulated and isothermal stress-free surface for the incident P wave are obtained. Finally, numerical values of the complex modulus of the reflection coefficients are visualized graphically to display the effects of the rotation, initial stress, gravity field magnetic field, thermal relaxation times and voids parameters.

7

Reflection of plane waves from surface of a generalized thermo-viscoelastic porous solid half-space with impedance boundary conditions

Singh B.

Mechanics and Mechanical Engineering

|

2018

|

Vol. 22, nr 4

1483--1496

EN

A phenomenon of reflction of plane waves from a thermally insulated surface of a solid half-space is studied in context of Lord-Shulman theory of generalized thermo-viscoelasticity with voids. The governing equations of generalized thermo-viscoelastic medium with voids are specialized in x-z plane. The plane wave solution of these equations shows the existence of three coupled longitudinal waves and a shear vertical wave in a generalized thermo-viscoelastic medium with voids. For incident plane wave (longitudinal or shear), three coupled longitudinal waves and a shear vertical wave reflect back in the medium. The mechanical boundary conditions at free surface of solid half-space are considered as impedance boundary conditions, in which the shear force tractions are assumed to vary linearly with the tangential displacement components multiplied by the frequency. The impedance corresponds to the constant of proportionality. The appropriate potentials of incident and reflected waves in the half-space will satisfy the required impedance boundary conditions. A non-homogeneous system of four equations in the amplitude ratios of reflected waves is obtained. These amplitude ratios are functions of material parameters, impedance parameter, angle of incidence, thermal relaxation and speeds of plane waves. Using relevant material parameters for medium, the amplitude ratios are computed numerically and plotted against certain ranges of impedance parameter and the angle of incidence.

8

Badania rentgenowskie obiektów elektronicznych

Lipiec K., Araźna A., Stęplewski W., Janeczek K.

Elektronika : konstrukcje, technologie, zastosowania

|

2018

|

Vol. 59, nr 12

21--24

PL

Obecnie szerokim zainteresowaniem naszych klientów cieszą się badania rentgenowskie, ze względu na szybką wykrywalność różnego rodzaju wad w badanych wyrobach elektronicznych, bez konieczności trwałego niszczenia zmontowanych płytek lub innych trudno demontowanych podzespołów. Aby wyjść naprzeciw oczekiwaniom naszych klientów w Instytucie Tele i Radiotechnicznym staramy się nadal unowocześniać park maszynowy podnosząc jednocześnie naszą wiedzę w tego rodzaju badaniach.

EN

Currently, our customers are widely interested in X-Ray inspection, due to the fast detection of various types of defects in the tested electronic products, without permanently destroying the assembled board or other hard-to-demount components. In order to meet the expectations of our clients at the Tele and Radio Research Institute, we still try to modernize the machine park, while raising our knowledge in this type of research.

9

Reflection of Plane Waves from Surface of a Generalized Thermo-viscoelastic Porous Solid Half-space with Impedance Boundary Conditions

Singh B.

Computational Methods in Science and Technology

|

2018

|

Vol. 24, No. 4

273--283

EN

A phenomenon of reflection of plane waves from a thermally insulated surface of a solid half-space is studied in the context of Lord-Shulman theory of generalized thermo-viscoelasticity with voids. The governing equations of generalized thermo-viscoelastic medium with voids are specialized in x-z plane. The plane wave solution of these equations shows the existence of three coupled longitudinal waves and a shear vertical wave in a generalized thermo-viscoelastic medium with voids. For incident plane wave (longitudinal or shear), three coupled longitudinal waves and a shear vertical wave reflect back in the medium. The mechanical boundary conditions on the free surface of solid half-space are considered as impedance boundary conditions, in which the shear force tractions are assumed to vary linearly with the tangential displacement components multiplied by the frequency. The impedance corresponds to the constant of proportionality. The appropriate potentials of incident and reflected waves in the half-space will satisfy the required impedance boundary conditions. A non-homogeneous system of four equations in the amplitude ratios of reflected waves is obtained. These amplitude ratios are functions of material parameters, impedance parameter, angle of incidence, thermal relaxation and speeds of plane waves. Using relevant material parameters for medium, the amplitude ratios are computed numerically and plotted against certain ranges of the impedance parameter and the angle of incidence.

10

The effect of initial stress on generalized thermoviscoelastic medium with voids and temperature-dependent properties under Green-Neghdi theory

Othman M. I. A., Fekry M.

Mechanics and Mechanical Engineering

|

2017

|

Vol. 21, nr 2

291--308

EN

The present paper aims to study the effect of initial stress on the 2-D problem of a homogeneous, isotropic, generalized thermo-viscoelastic material with voids in the context of Green-Naghdi theory. The modulus of elasticity is taken as a linear function of reference temperature. The analytical expressions for the physical quantities are obtained in the physical domain by using the normal mode analysis. These expressions are calculated numerically for a specific material and explained graphically. Comparisons are made with the results predicted by (G-N II) and (G-N III) theory in the presence and absence of the initial stress and temperature-dependent properties.

11

Propagation of plane waves in a rotating transversely isotropic two temperature generalized thermoelastic solid half-space with voids

Bijarnia R., Singh B.

International Journal of Applied Mechanics and Engineering

|

2016

|

Vol. 21, no. 2

285--301

EN

The paper is concerned with the propagation of plane waves in a transversely isotropic two temperature generalized thermoelastic solid half-space with voids and rotation. The governing equations are modified in the context of Lord and Shulman theory of generalized thermoelasticity and solved to show the existence of four plane waves in the x – z plane. Reflection of these plane waves from thermally insulated stress free surface is also studied to obtain a system of four non-homogeneous equations. For numerical computations of speed and reflection coefficients, a particular material is modelled as transversely isotropic generalized thermoelastic solid half-space. The speeds of plane waves are computed against the angle of propagation to observe the effects of two temperature and rotation. Reflection coefficients of various reflected waves are also computed against the angle of incidence to observe the effects of various parameters.

12

Microstructural failure criteria for S235JR steel subjected to spatial stress states

Kossakowski P. G.

Archives of Civil and Mechanical Engineering

|

2015

|

Vol. 15, no. 1

195--205

EN

The study deals with failure criteria for S235JR steel subjected to spatial stress states. The predictions were made using the modified Gurson–Tvergaard–Needleman (GTN) material model, which takes into account the effect of microstructural damage. The relationship between the material strength parameters and the microstructural changes caused by plastic deformation was established by analyzing the void volume fraction. The microstructural failure criteria determined for S235JR steel refer to the moment of decrease in strength and rupture.

13

The effects of severe temperature changes and high humidity on porous CFRP

Dinnebier H., Ehrlich I.

Journal of Achievements in Materials and Manufacturing Engineering

|

2014

|

Vol. 67, nr 1

14--20

EN

Purpose: A route to manufacture porous carbon fiber reinforced plastic (CFRP) for study purposes is described. Design/methodology/approach: The porous CFRP is characterized using standard techniques such as matrix digestion as well as the more sophisticated method of high resolution Microfocus X-Ray Tomography (μCT). A comparison of the results of those methods is presented. The mass gains of specimens with a wide range of porosity have been measured both in constant humidity and in alternating environments. Findings: It could be shown that severe temperature changes can temporarily increase the moisture content of porous CFRP. However, after the return to a constant environment, the moisture content returns back to saturation levels. Furthermore, it could be shown by X-Ray Tomography that even under severe climatic conditions no permanent liquid water condensates inside the pores. Research limitations/implications: Using Microfocus Computed Tomography it could be shown that even after nearly a year under hot-wet conditions and more than 150 severe temperature cycles there is no liquid water detectable inside the pores. Originality/value: In this paper the effects of severe temperature changes and high humidity on porous CFRP.

14

Analysis of stresses in Al-5%Si alloy under loading conditions

Borowiecka-Jamrozek J., Lachowski J.

Journal of Achievements in Materials and Manufacturing Engineering

|

2014

|

Vol. 65, nr 1

26--31

EN

Purpose: This paper analyses the structure and tensile strength of AlSi5Cu2 silumin produced in accordance with PN-EN 1706:2001, categorized as C355 in the US. The study was supplemented with a numerical failure analysis conducted with Abaqus 6.12. Design/methodology/approach: The alloy selected for this study was an Al base alloy containing 5% Si and 2% Cu. Tensile tests on notched round bars with three sizes of the notch radius were performed. Findings: A micromechanical model for the ductility of plastically deforming material was applied to the alloy using the finite-element program ABAQUS. The model is validated by comparing the predictions to experimental results. Research limitations/implications: Average stress triaxiality and ductility for the three types of tensile test specimens were obtained. Originality/value: This paper presented computer simulation of the stress state in notched specimens.

15

Response due to concentrated force in micropolar elastic solid with voids

Singh R., Singh K.

International Journal of Applied Mechanics and Engineering

|

2014

|

Vol. 19, no. 4

755--769

EN

The eigen value approach, following Laplace and Fourier transforms has been employed to find the general solution of the field equation in a micropolar elastic solid with voids for the plane strain problem. An application of an infinite space with impulsive force has been taken to illustrate the utility of the approach. The integral transformations have been inverted by using a numerical inversion technique to get result in physical domain. The result in the form of normal displacement, volume fraction, normal force stress, tangential force stress and tangential couple stress components has been obtained numerically and illustrated graphically to depict the effect of micropolarity and voids.

16

Analiza ilościowa pustek w próbkach stalowych z zastosowaniem technik przetwarzania obrazu

Gumuła A., Dębiński T., Głowacki M., Jędrzejczyk D.

Hutnik, Wiadomości Hutnicze

|

2014

|

Vol. 81, nr 4

186--191

PL

W artykule przedstawiono wyniki ilościowej analizy pustek powstałych podczas odkształcania próbek stalowych z półciekłym rdzeniem na urządzeniu Gleeblee 3800. Przedstawiono oraz scharakteryzowano wskaźniki, opisujące kształt pustek oraz ich wzajemne położenie, jako kwalifikatory jakości próbek. Przestawiono także korelację pomiędzy wartościami wskaźników opisowych pustek, a możliwymi defektami w materiale. Praca zawiera wyniki oraz omówienie przeprowadzonej analizy.

EN

In this paper the digital image analysis of voids formed during the deformation of steel samples in the Gleeble 3800 physical simulator device with the semi-solid core are presented. The presented and characterized indicators describe the shape of voids, and their relative position as qualifiers of quality indicators as well as the correlation between the indicators and possible defects in the material. This paper contains results and discussion of presented analysis.

17

Badania rentgenowskie zespołów elektronicznych

Lipiec K., Kozioł G., Futera K.

Elektronika : konstrukcje, technologie, zastosowania

|

2014

|

Vol. 55, nr 7

33-34

PL

W Instytucie Tele- i Radiotechnicznym od wielu lat prowadzone są prace badawcze, pozwalające ocenić jakość uzyskanych połączeń lutowanych po montażu elektronicznym. Obecnie szerokim zainteresowaniem naszych klientów cieszą się badania rentgenowskie, ze względu na szybką wykrywalność różnego rodzaju wad w badanych połączeniach, bez konieczności trwałego niszczenia zmontowanych płytek.

EN

In Tele and Radio Research Institute research works have been conducted for many years which allows to assess the quality of formed solder joints after electronic assembly. Currently, our customers are widely interested in X-ray inspection, due to the fast detection of various types of defects in the tested connections, without permanently destroying the assembled board.

18

Eigen value approach in micropolar elastic medium with voids

Singh R., Singh K.

International Journal of Applied Mechanics and Engineering

|

2013

|

Vol. 18, no. 2

521--536

EN

The eigen value approach, following the Laplace and Hankel transformation has been employed to find a general solution of the field equations in a micropolar elastic medium with voids for an axisymmetric problem. An infinite space with the mechanical source has been applied to illustrate the utility of the approach. The integral transformations has been inverted by using a numerical inversion technique to get the result in physical domain. The results in the form of normal displacement, volume fraction, normal force stress, tangential force stress and tangential couple stress components have been obtained numerically and illustrated graphically.

19

Thermally induced damage in hexanitrohexaazaisowurtzitane

Tian Q., Yan G., Sun G., Huang C., Xie L., Chen B., Huang M., Li H., Liu X., Wang J.

Central European Journal of Energetic Materials

|

2013

|

Vol. 10, no. 3

359--369

EN

The evolution of the microstructure of hexanitrohexaazaisowurtzitane (CL-20) after a thermal stimulus plays a key role in the performance of CL-20. In the current work, microstructural variations of CL-20 caused by thermal treatment were investigated by X-ray diffraction, in situ variable-temperature optical microscopy, atom force microscopy, and small-angle X-ray scattering. A wave-like process, an abrupt volume expansion, movement, and fragmentation of CL-20 particles during phase transition were observed. After the phase transition (160 °C) the CL-20 sample acquired a very rough surface with numerous dimple depressions, and during the thermal decomposition stage (200 °C) a large number of voids were produced in both the bulk and the surface of the CL-20.

20

Modelowanie efektu grawitacyjnego generowanego przez pustki poeksploatacyjne o zmiennych parametrach

Kortas Ł.

Przegląd Górniczy

|

2012

|

T. 68, nr 6

9--20

PL

Metoda grawimetryczna jest jednym z najefektywniejszych sposobów nieinwazyjnej identyfikacji występowania pustek pogórniczych. Istotą tej metody jest pomiar rozkładu natężenia siły ciężkości, którego anomalie wskazują miejsca występowania pustek. W tej pracy podjęto próbę wyznaczenia w trybie badań modelowych prostych związków funkcyjnych, pomiędzy parametrami fizycznymi i geometrycznymi pustki a spodziewanym efektem grawitacyjnym identyfikowanym przez pomiary grawimetryczne, w formie anomalii. Wyniki modelowań stanowiły podstawę do sporządzenia odpowiednich wykresów w formie funkcji dyskretnych, które następnie aproksymowano w celu znalezienia relacji pomiędzy badaną zmienną a efektem grawitacyjnym. Formuły te aproksymują tylko ścisłe funkcje i dotyczą pustek o niewielkich wymiarach i znajdujących się na małych głębokościach (nie przekraczających znacząco 50 m). Otrzymane rozwiązanie stanowić może podstawę weryfikacji tradycyjnie przeprowadzonej interpretacji wyników pomiarów grawimetrycznych, a następnie wykonania badania rozkładu obiektów zaburzających na drodze analizy odwrotnej.

EN

The gravimetric method is one of the most efficient methods of non-invasive identification of post-mining voids occurrence. The essence of this method is the measurement of distribution of the force of gravity intensity, the anomalies of which indicate the sites of voids occurrence. In the present work an attempt was undertaken to determine in the course of model investigations the simple functional connections between the physical and geometrical parameters of the void and the expected gravitational effect identified by gravimetric measurements in the form of anomalies. The modelling results constituted the basis to draw up suitable graphs in the form of discrete functions, which were next approximated in order to find relations between the investigated variable and the gravitational effect. These formulas approximate only strict functions and concern voids with small dimensions and occurring at low depths (not exceeding 50 m). The obtained solution can constitute the basis for the verification of traditionally performed interpretation of results of gravimetric measurements and next carrying out of investigation of the distribution of disturbing objects by means of the reverse analysis.