Studies of thermal destruction of fiberglass plastics under the action of a radiation thermal load

The results of design-theoretical studies of the mechanism of thermochemical destruction of fiberglass plastics are given.     

Nonlinear free and forced vibration behavior of functionally graded plate with piezoelectric layers in thermal environment

In the present study, finite element formulation based on higher order shear deformation plate theory is developed to analyze nonlinear natural frequencies, time and frequency responses of functionally graded plate with surface-bonded piezoelectric layers under thermal, electrical and mechanical loads. The von Karman nonlinear strain–displacement relationship is used to account for the large deflection of the plate. The material properties of functionally graded material (FGM) are assumed temperature-dependent. The temperature field has uniform distribution over the plate surface and varies in the thickness direction. The considered electric field only has non-zero-valued component E_z. Numerical results are presented to study effects of FGM volume fraction exponent, applied voltage in piezoelectric layers, thermal load and vibration amplitude on nonlinear natural frequencies and time response of FGM plate with integrated piezoelectric layers. In addition, nonlinear frequency response diagrams of the plate are presented and effects of different parameters such as FGM volume fraction exponent, temperature gradient, and piezoelectric voltage are investigated.     

Thermomechanical behavior of a viscoelastic finite circular cylinder under harmonic deformations

A coupled thermomechanical behavior of a finite viscoelastic cylinder under harmonic kinematic excitation at its ends is investigated. The method of superposition is utilized to determine the stress-strain state of the cylinder. A refined asymptotic technique is developed to find the stress-strain state at each point of the body including the corner. Stiffness characteristics are examined over a broad range of cylinder-geometry parameters. By use of known stress components the function for the dissipation rate is constructed and the temperature field of vibration heating is calculated by solving the appropriate heat-conduction boundary-value problem. For the case of strong temperature dependence of loss modulus the phenomenon of thermal instability is examined.     

Thermomechanical processes of composite materials under the action of intense energy fluxes

We propose mathematical models for determining the parameters of mechanical action under volumetric absorption of intense energy fluxes acting on targets consisting of heterogeneous materials. We focus on spheroplastics—materials having in their composition multilayer hollow microspheres.     

Thermoelastic stresses in a multilayer plate upon action of laser radiation

The problem of determining thermal stress in a multilayer plate upon action of a laser flux with Gaussian distribution is solved.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 55, No. 5, pp. 816–821, November, 1988.     

Photocatalytic behavior of different titanium dioxide layers

Many recently developed applications are related to the photocatalytic behavior of semiconductive oxides. Among the different oxides, titanium dioxide (TiO₂) is one of the most interesting due to its high photocatalytic efficiency towards a great number of reactions and to its hydrophilic properties. Aim of this work is the evaluation and comparison of the photocatalytic properties of different crystalline titanium dioxide films, directly grown on titanium substrates by surface anodization (eventually followed by thermal annealing) and by Pulsed Laser Deposition (PLD) on titanium and silicon substrates, followed by thermal annealing. The structure and morphology of the layers were characterized by Scanning Electron Microscopy and X-Ray Diffraction and photocatalytic tests on stearic acid mineralization were performed. Results showed that the PLD layers possess a higher photocatalytic efficiency than anodized titanium. This can be attributed to the microstructured/microporous morphology of the related surfaces. Instead, PLD TiO₂ layers with a relatively high content of the rutile phase have a reduced photocatalytic efficiency with respect to mainly anatase containing layers.     

Dynamics of a laminated composite plate with interface layers

Guided Rayleigh-Lamb waves in a laminated composite plate with interlaminar bond layers have been studied in this paper. The predictions for the dynamic response of the plate based on the (mass-less) spring model of the bond layer have been compared with those using the exact multilayer formulation and those of a plate without interface bond layers. It is found that all three model predictions agree well at low frequencies when the bond layer stiffnesses are not too low. As the stiffnesses get smaller, however, the response changes drastically even at low frequencies. These results would be useful in predicting weakening of the bond.     

Edge crack problem in a semi-infinite FGM plate with a bi-directional coefficient of thermal expansion under two-dimensional thermal loading

Summary The temperature distribution in structural elements in practical cases usually changes in two or three directions. Based on such facts, aiming at more effectiveness, a functionally graded material (FGM), whose properties change in two or three directions, is introduced, that investigated here called bi-directional FGM. The current study aims at the formulation, solution and investigation of a semiinfinite edge cracked FGM plate problem with a bi-directional coefficient of thermal expansion under two-dimensional thermal loading. The solution of the boundary value problem that one obtains from the mathematical formulation of the current crack problem under thermal loading reduces to an integral equation with a generalized Cauchy kernel. This integral equation contains many two-dimensional double strongly singular integrals, which can be solved numerically. In order to separate the singular terms and overcome the divergence of the integrals an asymptotic analysis for the singular parts in the obtained integral equation was carried out. Also, the exact solution for many singular integrals is obtained. The obtained numerical results are used in the representation of the thermal stress intensity factor versus the thermal/mechanical nonhomogeneous parameters. The numerical results show that it is possible to reduce and control the thermal stress intensity factor.     

Buckling behavior of a central cracked thin plate under tension

The buckling characteristics of cracked plates subject to uniaxial tensile loads are analysed by the aid of the finite element method. Owing to the fact that crack buckling behavior is affected by the in-plane stress distribution around a crack, to get more accurate results, pre-buckling in-plane stress fields are analysed by the finite element method. For the critical loads calculation, the finite element approach adopted is based on Von Karman's linearize theory for buckling of plates subjected to pre-buckling state of plane stress. Several singular elements based on the Willian series are used in this plate bending approach. In this study, the effect of crack length, the effect of boundary condition, the effect of Poison's ratio and the effect of biaxial force on critical loads are analysed and discussed. Furthermore, the effect of initial imperfection is also discussed. There is a good agreement between other researcher's work and present results.     

Nonlinear stability analysis of a perforated FGM plate under thermal load

The nonlinear thermal stability analysis of a perforated Ni/Al₂O₃ FGM plate with temperature-dependent thermoelastic material properties is carried out through a finite element approach based on the first-order shear deformation theory and the von-Karman's nonlinear kinematics. The thermoelastic material properties of the FGM plate are varied in the thickness direction, and the Mori-Tanaka homogenization scheme is applied to evaluate these properties. After validating the results of the current formulation, parametric studies are conducted to examine the effects of temperature-dependent material properties, material in-homogeneity, cutout shape and size, edge boundary conditions, aspect and slenderness ratios on the thermal buckling and postbuckling response of perforated FGM plate.     

Study of a carbon-ceramic composite material under high-temperature thermal action

The results of testing a carbon-ceramic composite material exposed to multiple high-temperature thermal action are given. The thermophysical characteristics of the material under study are restored based on these results and with the methods of solution of inverse heat-conduction problems. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 79, No. 4, pp. 194–196, July–August, 2006.     

Thermoelastic deformation of a cooled metal plate under the influence of a pulse-periodic radiation flux

A solution to the problem of determining the fields of stress and deformation in a plate under the influence of radiation flux with a Gaussian distribution is obtained.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 53, No. 1, pp. 117–124, July, 1987.     

Thermomechanical behavior of a multicomponent continuous medium interacting with an electromagnetic field

The behavior of a homogeneous mixture of isotropic continua interacting with an electromagnetic field is discussed. It is assumed that the continuum has a simple memory for strains, temperature, polarization, and magnetization. Constitutive functionals are constructed for the continuum and a theorem on free energy is proved.