摘要:

When the temperature and/or moisture at the surfaces of a composite change suddenly, stresses will arise in the composite owing to the nonuniform diffusion of heat and moisture. Recent investigations have shown that under certain conditions the classical uncoupled theory of diffusion can significantly underestimate the coefficient of diffusion. The coupling between heat and moisture is an inherent part of the diffusion process that cannot be neglected on intuitive grounds. This investigation is an inquiry into the influence of antisymmetric boundary conditions on the magnitude of the hygrothermal stresses in a plate made of T300/5208 epoxy material, commonly used in graphite fiber-reinforced composites. Both moisture and temperature boundary conditions are considered. Because of the nonlinear character of the coupled equations, a finite-difference scheme is adopted. Numerical results involving time-dependent moisture, temperature, and stress distributions in the plate are displayed graphically; they show that the stresses derived from the coupled theory differ appreciably from the uncoupled results, both qualitatively and quantitatively. The hygrothermal stresses with coupling taken into account acquire an oscillatory character when the temperature on the plate is raised suddenly; this factor could contribute to material damage. In addition, antisymmetric boundary conditions can either raise or lower the stress levels, depending on time and the transient nature of the applied temperature.

ISSN:0149-5739    

DOI:10.1080/01495738008926972

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

The stresses due to “thermal trapping” of internally absorbed radiation in solid materials are analyzed for a flat plate symmetrically heated by radiation and cooled by convection for finite values of the heat transfer coefficient. The thermal-stress state consists of an initial transient followed by a steady-state stress at t -> ∞ and involves a reversal in the sign of the stresses. The maximum value of the transient stress increases with optical thickness, whereas the maximum value of the steady-state stress occurs at an optical thickness μa = 1·3 with zero stresses at μa. = 0 and ∞.

ISSN:0149-5739    

DOI:10.1080/01495738008926973

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

This paper is a treatment of the three-dimensional nonaxisymmetric thermal-stress problem in a finite polygonal cylinder with a cylindrical circular hole under a steady-state temperature field. The problem is formulated in terms of the thermoelastic displacement potential and Boussinesq's, Dougall's, and Neuber's stress functions in cylindrical coordinates, which seem particularly convenient and have the advantage of being applicable to nonaxisymmetric problems. The problem is among the most difficult to solve by the usual analytical approach; therefore, the unknown coefficients involved in these functions are approximated by the boundary-point least-squares method.

ISSN:0149-5739    

DOI:10.1080/01495738008926974

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

Thermal deformations and stress resultants in rectangular, antisymmetric cross-ply and angle-ply laminates are investigated. Exact solutions are obtained for the response of simply supported plates to general three-dimensional temperature variations. To illustrate the thermoelastic behavior, deflections are computed for fiber-reinforced laminates undergoing constant and linearly varying temperature fields. Thermal membrane-bending coupling is found to be significant when the total number of layers is small, but it rapidly becomes unimportant as the number of layers within a plate of a given thickness increases.

ISSN:0149-5739    

DOI:10.1080/01495738008926975

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

This paper describes, by means of coupled thermoelastic theory, the transient stresses induced in a half-space by sudden energy input. The influence of energy-flux penetration length on stress-wave evolution is studied, and the effects of volume energy addition and surface energy deposition are compared. Qualitative and numerical results are presented. The effects of thermo-mechanical coupling and heat conduction are discussed.

ISSN:0149-5739    

DOI:10.1080/01495738008926976

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

A domain-of-influence theorem for an initial-boundary-value problem of thermoelasticity with one relaxation time, proposed by Lord and Schulman, is established. The theorem asserts that for a finite time t > 0 a pair (<φ, ), in which φ and are the thermoelastic potential and temperature, respectively, generates no thermoelastic disturbances outside a bounded domain Dt.

ISSN:0149-5739    

DOI:10.1080/01495738008926977

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

The existence of generalized solutions of a nonlinear problem concerning thermally induced vibrations in a nonhomogeneous plate is considered. The boundary conditions are for convenience, assumed to be homogeneous. This corresponds to the physical situation of a clamped plate. The initial conditions are imposed on one function only. The method of dealing with the problem is analogous to that for a homogeneous plate without the influence of temperature. Some lemmas and a theorem are formulated; the theorem asserts that under certain conditions on the temperature there exists at least one generalized solution to the problem.

ISSN:0149-5739    

DOI:10.1080/01495738008926978

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

Quasistatic extension of a penny-shaped crack, which occurs prior to its spontaneous propagation, is studied by means of nonlinear fracture mechanics analogous to the methods used to describe plastic deformation in metals. Wnuk's model of final stretch is employed to describe the displacement and stress fields in the vicinity of the crack border. Three kinds of thermal loadings are considered: (a)prescribed heat flux across the surface of the crack, (b) prescribed temperature difference, and (c) given heat extraction rate resulting from the steady-state flow of a cooling fluid circulating in and out of the crack. The latter case is directly applicable to power-generating geothermal systems. All three problems, if treated by linear elastic fracture mechanics methods, lead to singular thermal stresses around the circumference of the crack. Although the first two problems are of a positiveK-gradient nature, i.e., inherently unstable, the third one results in a negativeK-gradient. Through the approach used in this work the existence of a preliminary phase of stable crack growth, which precedes the catastrophic (cases a and b) or the spontaneous (case c) crack extension, has been demonstrated. The critical parameters involving the thermal load and the terminal dimension of the crack, at which the transition from stable to unstable propagation takes place, are predicted.

ISSN:0149-5739    

DOI:10.1080/01495738008926979

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

A recent study of steady-state thermoelastic contact between two solids has shown that the conventional boundary conditions lead to a lack of uniqueness for heat flowing in one of the two possible directions. Owing to the complexity of the fields satisfying the full equations of thermoelasticity, the resulting solutions are not well suited for investigating the stability of the different states. A model using a much simplified response of a material to stresses and temperature changes is proposed in this article for an eventual study of history dependence and stability in thermoelastic contact.

ISSN:0149-5739    

DOI:10.1080/01495738008926980

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor

摘要:

A constitutive theory for hygrothermoelasticity in anisotropic media is developed. The first and second laws of thermodynamics are extended to include moisture diffusion. The resulting equations are capable of fully coupling the deformation field with hygroscopic phenomena and temperature distributions. It is shown that, upon decoupling, the present theory reduces to the well-known equations of diffusion, heat conduction, and elasticity. With appropriate numerical schemes, the coupled equations can be applied to matrix-fiber composite structures subject to hygrothermal environments. As a step toward major numerical applications to aerospace and other structures, the present paper demonstrates one-dimensional finite element solutions. The results predicted by the theory appear to be quite satisfactory.

ISSN:0149-5739    

DOI:10.1080/01495738008926981

出版商:Taylor & Francis Group    

年代:1980

数据来源: Taylor