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1
Content available Magnetothermoelastic vibrations on a viscoelastic microbeam subjected to a laser heat source
Abouelregal A. E., Zenkour A. M.
Archives of Mechanics
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2021
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Vol. 73, nr 1
3--26
EN
The linear theory of viscoelasticity remains an important field of research like most solids and polymer materials when exposed to a vicious dynamic loading effect. This article introduces a new model for describing the behavior of thermoviscoelastic microbeams considering the effects of temperature change and the longitudinal magnetic field. The governing equations in this model are derived based on the Euler–Bernoulli beam theory, Kelvin–Voigt model of viscosity, the generalized thermoelasticity, and the classical Maxwell equations. The two ends of the microbeam are clamped and subjected to the influence of a laser pulse with a temporal intensity profile. The analytical solutions to the physical fields are evaluated using the Laplace transform and its inversion transforms are performed numerically. The thermo-viscoelastic responses of the microbeam are calculated numerically and investigated graphically. The effect of different parameters such as viscosity, laser intensity, and the magnitude of the magnetic field are studied in detail.
2
Content available remote 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
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2017
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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.
3
Content available remote Wear characterization of polymeric roller bearings during normal operation conditions and overloading
Katunin A., Szrejber Z.
Scientific Problems of Machines Operation and Maintenance
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2012
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Vol. 47, nr 1
39--49
EN
The paper presents the results of experimental studies of the thermomechanical behaviour of the polymer roller bearings under the different operation conditions. The analysis of various combinations of materials usually used in commercial solutions was performed in order to evaluate specific states characteristic for these tribological pairs. The influence of a temperature growth during workloads was investigated, including the nature of the heating sources. The surfaces subjected to the rolling friction of elements of polymeric bearings were examined using a microscope, and typical damages resulting from the frictional heating were evaluated and discussed.
PL
Artykuł przedstawia wyniki badań eksperymentalnych dotyczących termomechanicznego zachowania polimerowych łożysk tocznych w różnych warunkach eksploatacji. Przeprowadzono analizę różnych kombinacji materiałów stosowanych zazwyczaj w rozwiązaniach komercyjnych w celu określenia charakterystycznych stanów tych par tribologicznych. Zbadano wpływ obciążeń na przyrost temperatury, uwzględniając naturę źródeł ciepła. Powierzchnie elementów łożysk polimerowych narażone na tarcie toczne zostały zbadane przy użyciu mikroskopu. Ocenie i dyskusji poddano typowe uszkodzenia wynikające z tarciowego rozgrzania.
4
Content available remote The Thermal Relaxation Effect on 2-D Problems of the Generalized Linear Thermo-Viscoelasticity
Othman M. I. A.
Mechanics and Mechanical Engineering
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2009
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Vol. 13, nr 1
45-62
EN
In this paper we introduced the normal mode analysis for two-dimensional problems of the generalized linear thermo-viscoelasticity with one relaxation time. The exact expressions for the temperature distribution, the displacement components and the stress are obtained. The resulting formulation is applied to three different concrete problems. The first deals with a thick plate subjected to a time-dependent heat source on each face. The second concerns to the case of a heated punch moving across the surface of a semi-infinite thermo-viscoelastic half-space subjected to appropriate boundary conditions and the third problem deals with a plate with thermo-isolated surfaces subjected to a time-dependent compression. Numerical results are given and illustrated graphically for each problem. Comparisons are made with the results predicted by the coupled theory.
5
Content available remote 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.
6
Content available remote Phase transitions in thermoelastic and thermoviscoelastic shells
Eremeyev V. A., Pietraszkiewicz W.
Archives of Mechanics
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2009
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Vol. 61, nr 1
41-67
EN
Applaying the general non-linear theory of shells undergoing phase transitions, we derive the balance equations along the singular surface curve modelling the phase interface in the shell. From the integral forms of balance laws of linear momentum, angular momentum, and energy as well as the entropy inequality, we obtain the local static balance equations along the curvilinear phase interface. We discuss general forms of the constitutive equations for thermoelastic and thennoviscoelastic shells, as well as propose their simple cases for the linear isotropic shell behaviour. We also derive the thermodynarnic condition allowing one to determine the interface position on the deformed shell miclsurface. The theoretical model is illustrated by the example of thin circular cylindrical shell made of a two-phase elastic material subjected to tensile forces at the shell boundary. The solution reveals the existence of the hysteresis loop whose size depends upon values of several loading parameters. Key words: non-linear shell, phase transition, kinetic equation, quasi-static loading, thermoviscoelasticity, extended cylinder.
7
Content available remote Optimal control for a class of mechanical thermoviscoelastic frictional contact problems
Denkowski Z., Migórski S., Ochal A.
Control and Cybernetics
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2007
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Vol. 36, no 3
611-632
EN
We study optimal control of systems governed by a coupled system of hemivariational inequalities, modeling a dynamic thermoviscoelastic problem, which describes frictional contact between a body and a foundation. We employ the Kelvin-Voigt vis-coelastic law, include the thermal effects and consider the general nonmonotone and multivalued subdifferential boundary conditions. We consider optimal control problem for boundary and distributed parameter control systems, time optimal control problem and maximum stay control problem. We deliver conditions that guarantee the existence of optimal solutions.
8
Content available remote Forced vibrations due to mechanical loads in thermoviscoelastic halfspaces
Sharma J. N., Chand R., Chand D.
International Journal of Applied Mechanics and Engineering
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2006
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Vol. 11, no 1
105-121
EN
In the present article the Kelvin-Voigt model of linear viscoelasticity which describes the viscoelastic nature of a material is used to investigate the forced vibrations due to mechanical loads acting on the boundary of a thermoviscoelastic continuum. The Laplace and Hankel transform technique has been employed to solve the boundary value problem in the transform domain, in the context of various theories of generalized thermoelasticity. The inverse transform integrals are evaluated by using Romberg integration in order to obtain the results in the physical domain. The temperature and stresses so obtained in the physical domain are computed numerically and presented graphically in different situations for a copper material. The comparison of results for different theories of generalized thermoviscoelasticity is also presented at appropriate stages of this work.
9
Content available remote The uniqueness and reciprocity theorems for generalized thermo-viscoelasticity with thermal relaxation times
Othman M. I. A.
Mechanics and Mechanical Engineering
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2004
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Vol. 7, nr 2
77-87
EN
The equations of generalized thermo-viscoelasticity based on Lord-Shulman (L-S), Green and Lindsay (G-L) and Classical dynamical coupled (CD) theories are given. Using Laplace transforms, a uniqueness theorem for these equations is proved. Also, a reciprocity theorem is obtained.
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