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1

Variable thermal conductivity in micropolar thermoelastic medium without energy dissipation possessing cubic symmetry

Ailawalia Praveen, Priyanka

International Journal of Applied Mechanics and Engineering

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2023

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Vol. 28, no. 1

1--10

EN

This investigation deals with the effect of variable thermal conductivity in a micropolar thermoelastic medium without energy dissipation with cubic symmetry. The normal mode technique is employed for obtaining components of physical quantities such as displacement, stress, temperature distribution and microrotation.

2

Two-dimensional analysis of functionally graded thermoelastic microelongated solid

Sharma Anchal, Ailawalia Praveen

International Journal of Applied Mechanics and Engineering

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2022

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Vol. 27, no. 4

155--169

EN

The present research focuses on two-dimensional deformation in a functionally graded thermoelastic micro-elongated medium. It is supposed that the non-homogeneous properties (thermal and mechanical) of FGM are in the x-direction. The normal mode technique is used to acquire the analytic expression for displacement components, stress, micro-elongation and temperature. The cause and effect relationship of non-homogeneity and physical quantities is shown through graphical results.

3

Elastodynamical disturbances due to laser irradiation in a microstretch thermoelastic medium with microtemperatures

Kumar Arvind, Singh Devinder

Mechanics and Mechanical Engineering

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2019

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Vol. 23, nr 1

103--112

EN

This research is concerned with the study of mechanical disturbances due to presence of ultra-short laser pulse as input heat source in a microstretch thermoelastic medium with microtemperatures. The medium is subjected to normal and tangential forces. The solution of the problems is developed in terms of normal modes. Mathematical expressions have been obtained for normal stress, tangential stress, microstress and temperature change. The numerically computed results are shown graphically. A mathematical model has been developed and various stress quantities have been analyzed. Some particular cases are also derived from the present investigation.

4

Pomiary drgań izolowanych fragmentów konstrukcji płatowcowych z zastosowaniem analizatora modalnego LMS SCADAS Lab

Olejnik A., Rogólski R., Szcześniak M.

Problemy Mechatroniki : uzbrojenie, lotnictwo, inżynieria bezpieczeństwa

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2017

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Vol. 8, Nr 3 (29)

127--144

PL

Przed wydaniem świadectwa typu dla wprowadzanego do eksploatacji samolotu nadzór lotniczy w myśl obowiązujących przepisów określa wymogi dotyczące min. testów wibracyjnych. Na etapie uzyskiwania zgody na próby w locie należy wykazać brak zagrożeń konstrukcji ze strony zjawisk dynamicznych poprzez analizy i symulacje drgań oraz wykonanie naziemnych prób rezonansowych GVT (Ground Vibration Testing). W toku pomiarów typu GVT określa się krytyczne częstotliwości i postacie drgań. W niniejszym artykule opisano proces identyfikacji drgań rezonansowych izolowanego skrzydła zastrzałowego przy użyciu aparatury do pomiarów modalnych z analizatorem widma drgań LMS SCADAS Lab. Wykorzystując wskazaną aparaturę w odniesieniu do rzeczywistej konstrukcji płatowcowej, właściwie przygotowanej pod względem rozkładu masy, sztywności, swobody ruchu sterów i klap oraz warunków mocowania, można wyznaczyć kluczowe charakterystyki drganiowe odpowiadające punktom rezonansowym. Opisano tok procesu pomiarowego obejmującego takie etapy, jak: przygotowanie obiektu, konfiguracja aparatury, przygotowanie modelu symulacyjnego, orientacyjna identyfikacja punktów modalnych w trybie przemiatania zakresowego oraz dostrajanie częstotliwości rezonansowych przy różnych konfiguracjach wzbudzania. Wyniki testów doświadczalnych porównano z częstotliwościami analogicznych postaci własnych wyznaczonych dla modelu dyskretnego MES. Zademonstrowano też sposób wyznaczania postaci lokalnych w toku wymuszania drgań całego płatowca (samolot Flaris).

EN

Prior to the issue of a type-certificate for an airplane put into service, aeronautical surveillance, in accordance with the applicable regulations, the requirements concerning, among other things, vibration tests. At the stage of approval for flight tests, no structural hazards from dynamic phenomena shall be demonstrated by vibration analysis and simulations and ground vibration tests (GVT). In the course of GVT measurements, critical frequencies and vibration mods are defined. This article describes the process of identifying resonant vibrations of an isolated strut-braced wing using modal measurement instruments with LMS SCADAS Lab vibration spectrum analyser. Using the indicated apparatus with respect to the actual fuselage structure, properly prepared in terms of mass distribution, stiffness, freedom of movement of the rudder and flap and mounting conditions, key vibration characteristics corresponding to the resonance points can be determined. The process of measuring process has been described including the preparation of the object, the configuration of the apparatus, the preparation of the simulation model, the indicative identification of the modal points in the sweeping mode and the tuning of the resonant frequencies with different excitation configurations. The results of the experimental tests were compared with the frequencies of analogous self-defined characters for the discrete MES model. Also demonstrated is the way of locating the local characters in the course of enforcing the vibration of the entire airplane (Flaris aircraft).

5

Effect of thermal loading due to laser pulse on 3-d problem of micropolar thermoelastic solid with energy dissipation

Othman M. I. A., Atwa S. Y., Elwan A. W.

Mechanics and Mechanical Engineering

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2017

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Vol. 21, nr 3

679--701

EN

The aim of this paper is to introduce the Green-Naghdi (G-N) theory of type III (with energy dissipation) to study the effect of thermal loading due to laser pulse on generalized micropolar thermoelastic homogeneous isotropic medium in three dimensions. The normal mode analysis technique is used to solve the resulting non-dimensional equations of the problem. Numerical results for the displacement, thermal stress, strain, temperature, couple stresses and micro-rotation distributions are represented graphically to display the effect of the laser pulse on the resulting quantities. Comparisons are made within the theory in the presence and absence of the laser pulse.

6

Effect of rotation in an orthotropic elastic slab

Santra S., Lahiri A., Das N. C.

International Journal of Applied Mechanics and Engineering

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2017

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Vol. 22, no. 1

163--174

EN

The fundamental equations of the two dimensional generalized thermoelasticity (L-S model) with one relaxation time parameter in orthotropic elastic slab has been considered under effect of rotation. The normal mode analysis is used to the basic equations of motion and heat conduction equation. Finally, the resulting equations are written in the form of a vector-matrix differential equation which is then solved by the eigenvalue approach. The field variables in the space time domain are obtained numerically. The results corresponding to the cases of conventional thermoelasticity CTE), extended thermoelasticity (ETE) and temperature rate dependent thermoelasticity (TRDTE) are compared by means of graphs.

7

Effect of rotation on a semiconducting medium with two-temperatures under L-S theory

Othman M. I. A., Tantawi R. S., Eraki E. E. M.

Archives of Thermodynamics

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2017

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Vol. 38, no. 2

101--122

EN

The model of the equations of generalized thermoelasticity in a semi-conducting medium with two-temperature is established. The entire elastic medium is rotated with a uniform angular velocity. The formulation is applied under Lord-Schulman theory with one relaxation time. The normal mode analysis is used to obtain the expressions for the considered variables. Also some particular cases are discussed in the context of the problem. Numerical results for the considered variables are obtained and illustrated graphically. Comparisons are also made with the results predicted in the absence and presence of rotation as well as two-temperature parameter.

8

Plane strain deformation in a thermoelastic microelongated solid with internal heat source

Ailawalia P., Sachdeva S. K., Pathania D. S.

International Journal of Applied Mechanics and Engineering

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2015

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Vol. 20, no. 4

717--731

EN

The purpose of this paper is to study the two dimensional deformation due to an internal heat source in a thermoelastic microelongated solid. A mechanical force is applied along an overlaying elastic layer of thickness h. The normal mode analysis has been applied to obtain the exact expressions for the displacement component, force stress, temperature distribution and microelongation. The effect of the internal heat source on the displacement component, force stress, temperature distribution and microelongation has been depicted graphically for Green-Lindsay (GL) theory of thermoelasticity.

9

The effect of thermal relaxation times on wave propagation of a micropolar thermoelastic medium with voids due to various sources

Othman M. I. A., Lotfy K.

International Journal of Applied Mechanics and Engineering

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2011

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Vol. 16, no 3

791-807

EN

A model of the equations of a two-dimensional problem with the deformation of a micropolar generalized thermoelastic medium with voids under the influence of various sources is formulated in the context of the Lord-Shulman, Green-Lindsay theories, as well as the classical dynamical coupled theory. The normal mode analysis is used to obtain the exact expressions of the displacement components, force stress, coupled stress, change in volume fraction field and temperature distribution. Numerical results are given and illustrated graphically when the volume source is applied. Comparisons are made with the results predicted by the three theories in the presence and absence of material constants due to voids.

10

The effect of rotation and thermal shock on a perfect conducting elastic half-space in generalized magneto-thermoelasticity with two relaxation times

Othman M. I. A.

Mechanics and Mechanical Engineering

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2010

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Vol. 14, nr 1

31-55

EN

The propagation of electromagneto-thermoelastic disturbances produced by a thermal shock in a perfectly conducting elastic half-space when the entire elastic medium is rotating with a uniform angular velocity is investigated. The problem is in the context of the Green and Lindsay's generalized thermoelasticity with two relaxation times. There acts an initial magnetic field parallel to the plane boundary of the half-space. The medium deformed because of thermal shock, and due to the application of the magnetic field. The normal mode analysis is used to obtain the exact expressions for the considered variables. The distributions of the considered variables are represented graphically. From the distributions, it can be found the wave type heat propagation in the medium. This indicates that the generalized heat conduction mechanism is completely different from the classic Fourier's in essence. In generalized thermoelasticity theory heat propagates as a wave with finite velocity instead of infinite velocity in medium. Comparisons are made wit h the results predicted by the coupled theory in present and absent rotation.

11

Generalized electro-magneto-thermoelasticity in case of thermal shock plane waves for a finite conducting half-space with two relaxation times

Othman M. I. A.

Mechanics and Mechanical Engineering

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2010

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Vol. 14, nr 1

5-30

EN

The propagation of electromagneto-thermoelastic disturbances produced by a thermal shock in a finitely conducting elastic half-space is investigated. The formulation is applied to two-dimensional equations of generalized thermoelasticity Green and Lindsay's theory with two relaxation times. There acts an initial magnetic field parallel to the plane boundary of the half-space. The medium deformed because of thermal shock and due to the application of the magnetic field, there result an induced magnetic and an induced electric field in the medium. The Maxwell's equations are formulated and the electromagneto-thermoelastic coupled governing equations are established. The normal mode analysis is used to obtain the exact expressions for the considered variables. The distributions of the considered variables are represented graphically for different values of times. From the distributions, it can be found the wave type heat propagation in the medium. This indicates that the generalized heat conduction mechanism is completely different from the classic Fourier's in essence. In generalized thermoelasticity theory heat propagates as a wave with finite velocity instead of infinite velocity in medium.

12

Effect of Rotation in Case of 2-D Problem of the Generalized Thermo-viscoelasticity with Two Relaxation Times

Othman M. I. A.

Mechanics and Mechanical Engineering

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2009

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Vol. 13, nr 2

105-127

EN

In this paper, a two-dimensional problem of thermoviscoelasticity with two relaxation times when the entire medium rotates with a uniform angular velocity is studied. The normal mode analysis is used to obtain the exact expressions for the temperature, displacement and thermal stress components. The resulting formulation is applied to the case of a thick plate subjected to a time-dependent heat source on each face. Numerical results are given and illustrated graphically. Comparisons are made with the results predicted by the coupled theory and with the theory of generalized thermoelasticity with two relaxation times in the absence of rotation and for different values of time.

13

Thermal instability of compressible electrically conducting couple-stress fluid in the presence of a uniform magnetic field

Singh M., Kumar P.

International Journal of Applied Mechanics and Engineering

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2009

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Vol. 14, no 3

879-889

EN

The problem of thermal instability of compressible, electrically conducting couple-stress fluid in the presence of a uniform magnetic field is considered. Following the linearized stability theory and normal mode analysis, the dispersion relation is obtained. For stationary convection, the compressibility, couple-stress and magnetic field postpone the onset of convection. Graphs have been plotted by giving numerical values to the parameters to depict the stability characteristics. The principle of exchange of stabilities is found to be satisfied. The magnetic field introduces oscillatory modes in the system that were non-existent in its absence. The case of overstability is also studied wherein a sufficient condition for the non-existence of overstability is obtained.

14

Efect of Reference Temperature on the Modulus of Elasticity in Case of 2-D Generalized Thermal Shock Problem for a Half-Space

Othman M. I. A.

Mechanics and Mechanical Engineering

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2007

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Vol. 11, nr 1

49-63

EN

The model of the equations of two-dimensional coupled problem in thermo-elasticity for a thermally half-space solid whose surface is subjected to a thermal shock is established. The problem is in the context of the Green and Lindsay's generalized thermoelasticity theory with two relaxation times in an isotropic medium with the modulus of elasticity being dependent on the reference temperature. The normal mode analysis is used to obtain the exact expressions for the temperature, the displacement and thermal stress components. The resulting formulation is applied to two kinds of boundary conditions. Numerical results are illustrated graphically for each case considered. Comparison is carried out with the results predicted by the coupled theory and with the case where the modulus of elasticity is independent of temperature.

15

Relaxation effects on thermal shock problems in an elastic half-space of generalized magneto-thermoelastic waves

Othman M. I. A.

Mechanics and Mechanical Engineering

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2004

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Vol. 7, nr 2

165-178

EN

The propagation of electromagneto-thermo-elastic disturbances produced by thermal shock based on Lord-Shulman (L-S), Green-Lindsay (G-L) and classical dynamical coupled (CD) theories in a perfectly conducting half-space are studied. There acts an initial magnetic field parallel to the plane boundary of the half-space. The normal mode analysis is used to obtain the exact expressions for the considered variables. The distributions of the considered variables are represented graphically for each case. A comparison is made with the results predicted by the coupled theory. It is found that the magnetic field has decreasing effect.