An invariance principle for dynamical systems on Banach space - Application to the general problem of thermoelastic stability
Invariance principle on Banach space for generalized thermoelastic stability analysis
Infante, E. F.↗
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Variational principles for linear coupled thermoelasticity with microstructure
Variational principles for initial boundary value problem of fully coupled linear thermoelasticity for inhomogeneous anisotropic materials with microstructure
Desilva, C. N.↗
An invariance principle for dynamical systems on Banach space - Application to the general problem of thermoelastic stability
Thermoelastic stability as function of thermodynamic properties of elastic materials, applying invariance principle to dynamical systems on Banach space
Infante, E. F.↗
Thermoelastic analysis of solar cell arrays and their material properties
A thermoelastic stress analysis procedure is reported for predicting the thermally induced stresses and failures in silicon solar cell arrays. A prerequisite for the analysis is the characterization of the temperature-dependent thermal and mechanical properties of the solar cell materials. Extensive material property testing was carried out in the temperature range -200 to +200 C for the filter glass, P- and N-type silicon, interconnector metals, solder, and several candidate silicone rubber adhesives. The analysis procedure is applied to several solar cell array design configurations. Results of the analysis indicate the optimum design configuration, with respect to compatible materials, effect of the solder coating, and effect of the interconnector geometry. Good agreement was found between results of the analysis and the test program.
Salama, M. A.↗
A thermal, thermoelastic, and wear analysis of high-energy disk brakes
A thermomechanical investigation of the sliding contact problem encountered in high-energy disk brakes is described. The analysis includes a modelling, using the finite element method of the thermoelastic instabilities that cause transient changes in contact area to occur on the friction surface. In order to include the effect of wear at the contact surface, a wear criterion is proposed that results in the prediction of wear rates for disk brakes that are quite close to experimentally determined wear rates. The thermal analysis shows that the transient temperature distribution in a disk brake assembly can be determined more accurately by use of this thermomechanical analysis than by a more conventional analysis that assumes constant contact conditions. It also shows that lower, more desirable, temperatures in disk brakes can be attained by increasing the volume, the thermal conductivity, and, especially, the heat capacity of the brake components.
Kennedy, F. E., Jr.↗
A thermal, thermoelastic, and wear simulation of a high-energy sliding contact problem
This paper describes an investigation of the sliding contact problem encountered in high-energy disk brakes. The analysis includes a simulation modeling, using the finite element method, of the thermoelastic instabilities that cause transient changes in contact to occur on the friction surface. In order to include the effect of wear of the concentrated contacts on the friction surface, a wear criterion is proposed that results in prediction of wear rates for disk brakes that are quite close to experimentally determined wear rates. The thermal analysis shows that the transient temperature distribution in a disk brake can be determined more accurately by use of this thermomechanical analysis than by a more conventional analysis that assumes constant contact conditions. It is also shown that lower, more desirable, temperatures in disk brakes can be attained by increasing the volume, the thermal conductivity, and especially, the heat capacity of the brake components.
Kennedy, F. E., Jr.↗
Thermoelastic analysis of solar cell arrays and their material properties
Description of a thermoelastic stress analysis procedure for predicting the thermally induced stresses and failures in silicon solar cell arrays. A prerequisite for the analysis is the characterization of the temperature-dependent thermal and mechanical properties of the solar cell materials. Extensive material property testing was carried out in the temperature range from -200 to +200 C for the filter glass, P- and N-type silicon, interconnector metals, solder, and several candidate silicone rubber adhesives. The analysis procedure is applied to several solar cell array design configurations, which were tested in the Space Molecular Sink. Results of the analysis indicate the optimum design configuration with respect to materials and geometry, effect of the solder coating, and effect of the interconnector geometry.
Salama, M. A.↗
Thermoelastic constitutive equations for chemically hardening materials
Thermoelastic constitutive equations are derived for a material undergoing solidification or hardening as the result of a chemical reaction. The derivation is based upon a two component model whose composition is determined by the degree of hardening, and makes use of strain-energy considerations. Constitutive equations take the form of stress rate-strain rate relations, in which the coefficients are time-dependent functions of the composition. Specific results are developed for the case of a material of constant bulk modulus which undergoes a transition from an initial liquidlike state into an isotropic elastic solid. Potential applications are discussed.
Shaffer, B. W.↗
Thermoelastic analysis of solar window of a vacuum chamber
It has been noted during space simulation test programs that the chamber penetration window becomes the limiting factor as the solar intensity increases. The temperature at the center of the window normally attains a level of 550 C, while the edge temperature remains at about 35 C. The stresses produced by this thermal gradient combined with the atmospheric pressure are studied within the framework of classical theory of elasticity. The solution for the problem is obtained by solving the static uncoupled thermoelastic equations for a circular blank, subjected to nonuniform heat on one face, by introduction of two auxiliary variables. The displacements are expressed in terms of Bessel functions and parameters of interest are computed at various mesh points of the window. The maximum principal stresses thus obtained show that even with steep temperature gradient, the safety factor is acceptable.
Amba-Rao, C. L.↗
Theory of thermoelasticity
The development of the theory of thermoelasticity, which examines the interactions between the deformation of elastic media and the thermal field, is traced and the fundamental problems of the theory are presented. Results of recent studies on the subject are presented. Emphasis is primarily on media with generalized anisotropy, or isotropy media. Thermomechanical problems and mathematical formulations and resolutions are included.
Iesan, D.↗
Thermoelastic limit cycling of zippered cross section spacecraft booms
The phenomenon of thermal flutter of open cross section storable tubular extendible member (STEM) spacecraft booms was first observed in OGO IV and subsequently on a number of other satellites. Theoretical work ultimately ascribed the anomalous, undamped oscillations to the low torsional rigidity of the open section booms. This was confirmed when 'zippered' cross section booms, with substantially higher torsional rigidity, were later flown without exhibiting thermal flutter. However, zippered STEM booms generally have sizeable torsional backlash zones. It is shown here that small amplitude thermoelastic limit cycling within this backlash zone is theoretically possible and is the likely explanation for undamped oscillations recorded on Voyager 1 and 2 in the early stages of the Voyager mission.
Laskin, R. A.↗
A Transversely Isotropic Thermoelastic Theory
A continuum theory is presented for representing the thermoelastic behavior of composites that can be idealized as transversely isotropic. This theory is consistent with anisotropic viscoplastic theories being developed presently at NASA Lewis Research Center. A multiaxial statement of the theory is presented, as well as plane stress and plane strain reductions. Experimental determination of the required material parameters and their theoretical constraints are discussed. Simple homogeneously stressed elements are examined to illustrate the effect of fiber orientation on the resulting strain distribution. Finally, the multiaxial stress-strain relations are expressed in matrix form to simplify and accelerate implementation of the theory into structural analysis codes.
Arnold, S. M.↗
Special purpose hybrid transfinite elements and unified computational methodology for accurately predicting thermoelastic stress waves
This paper represents an attempt to apply extensions of a hybrid transfinite element computational approach for accurately predicting thermoelastic stress waves. The applicability of the present formulations for capturing the thermal stress waves induced by boundary heating for the well known Danilovskaya problems is demonstrated. A unique feature of the proposed formulations for applicability to the Danilovskaya problem of thermal stress waves in elastic solids lies in the hybrid nature of the unified formulations and the development of special purpose transfinite elements in conjunction with the classical Galerkin techniques and transformation concepts. Numerical test cases validate the applicability and superior capability to capture the thermal stress waves induced due to boundary heating.
Tamma, Kumar K.↗
A new boundary element formulation for two- and three-dimensional thermoelasticity using particular integrals
New two- and three-dimensional BEM formulations are developed for steady-state and transient uncoupled thermoelasticity. These new procedures differ from previous work in that additional surface of volume integration is not required to incorporate thermal loads in the analysis. Instead, thermal body forces are introduced in the BEM system via particular integrals. The present formulation is implemented in a general-purpose multiregion system, and examples are presented to demonstrate the accuracy and versatility of the method.
Henry, Donald P., Jr.↗
Thermoelastic micromechanical stresses associated with a large alpha-silicon carbide grain in a polycrystalline beta-silicon carbide matrix
The thermoelastic micromechanical stresses associated with a single large hexagonal alpha-SiC grain within a fine-grain-size cubic (3C) beta-SiC matrix were calculated. The naturally occurring residual stresses which are created during cooling from the processing temperatures and the effects of superimposed applied external stresses are both considered. A significant effect of the shape or geometry of the alpha-SiC grain is revealed, with the largest residual stresses associated with the naturally occurring tabular or platelet structure. The stresses are compared with the published strength results for these materials, which suggests that the residual stresses assume a significant role in the strength reduction that is observed.
Li, Zhuang↗
A thermoelastic transversely isotropic thick walled cylinder/disk application: An analytical solution and study
A continuum theory is utilized to represent the thermoelastic behavior of a thick walled composite cylinder that can be idealized as transversely isotropic. A multiaxial statement of the constitutive theory employed is presented, as well as the out of the plane of isotropy, plane stress, and plane strain reductions. The derived analytical solution presented is valid for a cylindrical tube or thin disk with a concentric hole, subjected to internal and/or external pressure and a general radial temperature distribution. A specific problem examined is that of a thick walled cylinder subjected to an internal and external pressure loading and a linear radial temperature distribution. The results are expressed in nondimensional form and the effects on the response behavior are examined for various material properties, fiber orientation and types of loadings.
Arnold, S. M.↗
Approximation in LQG control of a thermoelastic rod
Control and estimator gains are computed for linear-quadratic-Gaussian (LQG) optimal control of the axial vibrations of a thermoelastic rod. The computations are based on a modal approximation of the partial differential equations representing the rod, and convergence of the approximations to control and estimator gains is the main issue.
Gibson, J. S.↗
Bounds on the thermoelastic properties of suspensions of spheres
Results are presented on computations of three-point upper and lower bounds on the effective thermal expansion coefficient, the effective constant-pressure specific heat, and the effective constant-volume specific heat of statistically isotropic suspensions of mutually impenetrable spheres. The effect of polydispersivity in sphere size on the thermoelastic properties is investigated by considering the cases of both equisized and multisized spheres. For reasons of mathematical analogy, the results obtained for the effective thermal expansion coefficient translate immediately into equivalent results for the hygroscopic expansion coefficient.
Torquato, S.↗