Showing papers in "Journal of Applied Mechanics in 1978"

Theory of Thermoelasticity With Applications

Abstract: 1 Introduction.- 2 Mathematical groundwork.- 2.1 Tensor calculus.- 2.2 List of useful formulas.- 3 Fundamentals of thermodynamics.- 3.1 System. State. State parameters and functions.- 3.2 The laws of thermodynamics.- 3.3 Nonuniform systems.- 4 Thermodynamics of elastic deformations.- 5 Modes of heat transfer.- 5.1 Radiation.- 5.2 Convection.- 5.3 Conduction.- 6 Theory of heat conduction.- 6.1 Classical differential equation of heat conduction.- 6.2 Initial and boundary conditions.- 7 An hyperbolic equation of heat conduction.- 8 The linear thermoelastic solid.- 8.1 Anisotropy of materials.- 8.2 Certain types of thermoelastic coupling.- 9 The temperature field.- 9.1 Integral transforms.- 9.1a The Laplace transform.- 9.1b Fourier transforms.- 9.1c Hankel transforms.- 9.2 Separation of variables.- 9.3 Green's, or influence, functions.- 9.3a Steady states.- 9.3b Time-dependent states.- 9.4 Duhamel's superposition theorems.- 9.5 Solidification and melting.- 10 Stress and deformation fields.- 10.1 Goodier's thermoelastic potential.- 10.2 Method of biharmonic representations.- 10.3 Betti-Maysel reciprocal method.- 10.4 Thermoelastic-elastic correspondence principle.- 10.5 Method of Green's function.- 10.6 Method of a complex variable.- 10.6a General concepts and theorems.- 10.6b Series expansions.- 10.6c Conformai mapping.- 10.6d Applications to elasticity.- 10.6e Uniqueness of solution. Connectivity of regions.- 10.6f Cauchy integrals.- 10.7 The extended Boussinesq-Papkovich-Neuber solution.- 11 Uniqueness of solution. Stress-free thermoelastic fields.- 11.1 Uniqueness of solution.- 11.2 Stress-free thermoelastic fields.- 11.2a Three-dimensional regions.- 11.2b Two-dimensional regions.- 12 Anisotropic bodies.- 12.1 Correspondence principle for anisotropic bodies.- 12.2 Thermal stresses in an orthotropic hollow cylinder.- 12.3 Thermal stresses in a transversely isotropic half-space.- 13 Stresses due to solidification.- 14 Thermoelastic stresses in plates.- 14.1 General equations.- 14.2 Boundary conditions.- 14.3 Correspondence principle for isotropic plates.- 14.4 Two characteristic cases.- 14.5 Laminated composite plates.- 15 Thermoelastic stresses in shells.- 15.1 Deformation of shells of revolution under axisymmetric mechanical and thermal load.- 15.2 State of stress in shells of revolution deformed axisymmetrically.- 15.3 General theory of shells.- 15.4 Shells of revolution deformed arbitrarily.- 15.5 Donnell's theory of cylindrical shells.- 15.6 Boundary conditions.- 15.7 Equation of heat conduction for shells.- 16 Thermoelastic stresses in bars.- 16.1 Bars of solid cross-section.- 16.2 Bars of thin-walled open cross-section.- 16.3 Bars of thin-walled closed cross-section.- 16.4 Torsion of bars of thin-walled open cross-section.- 17 Thermoelastic stresses around cracks.- 18 Thermoelastic stability of bars and plates.- 18.1 Bars of solid and thin-walled closed cross-section.- 18.2 Bars of thin-walled open cross-section.- 18.3 Plates.- 18.4 Post-buckling behavior of plates.- 19 Moving and periodic fields.- 19.1 General remarks.- 19.2 Illustrative examples.- 20 Thermoelastic vibrations and waves.- 20.1 General concepts and equations.- 20.2 Thermoelastic harmonic waves in infinite media.- 20.3 Thermoelastic Rayleigh waves.- 20.4 Thermoelastic vibrations of a spinning disk.- 20.5 Wave discontinuities.- 21 Coupled thermoelasticity.- 22 Thermoelasticity of porous materials.- 23 Electromagnetic thermoelasticity.- 23.1 Basic concepts of electromagnetism.- 23.2 Maxwell's equations.- 23.3 Lorentz force. Maxwell stresses.- 23.4 Moving bodies.- 23.5 Electromagnetic energy.- 23.6 Electromagnetic thermoelastic equations.- 23.6a Thermoelasticity of dielectrics.- 23.6b Thermoelasticity of ferromagnetic bodies.- 23.6c Applications.- 24 Piezothermoelasticity.- 25 Random thermoelastic processes.- 25.1 General concepts and equations.- 25.1a Random variables.- 25.1b Random processes.- 25.2 Spectral density.- 26 Variational methods in thermoelasticity.- 26.1 General remarks.- 26.2 Virtual work.- 26.3 Principles of stationary energy of Hemp.- 26.4 Principle of Washizu.- 26.5 Principle of Biot.- Literature.- Author index.

Study of the Random Vibration of Nonlinear Systems by the Gaussian Closure Technique

Abstract: A technique is developed to study random vibration of nonlinear systems. The method is based on the assumption that the joint probability density function of the response variables and input variables is Gaussian. It is shown that this method is more general than the statistical linearization technique in that it can handle non-Gaussian excitations and amplitude-limited responses. As an example a bilinear hysteretic system under white noise excitation is analyzed. The prediction of various response statistics by this technique is in good agreement with other available results.

Uniqueness of Damping and Stiffness Distributions in the Identification of Soil and Structural Systems

Abstract: As the interest in the seismic design of structures has increased considerably over the past few years, accurate predictions of the dynamic responses of soil and structural systems has become necessary. Such predictions require a knowledge of the dynamic properties of the systems under consideration. This paper is concerned with the uniqueness of the results in the identification of such properties. More specifically, the damping and stiffness distributions, which are of importance in the linear range of response, have been investigated. An N-storied structure or an N-layered soil medium is modeled as a coupled, N-degree-of-freedom, lumped system consisting of masses, springs, and dampers. Then, assuming the mass distribution to be known, the problem of identification consists of determining the stiffness and damping distributions from the knowledge of the base excitation and the resulting response at any one mass level. It is shown that if the response of the mass immediately above the base is known, the stiffness and damping distributions can be uniquely determined. Following this, some nonuniqueness problems have been discussed in relation to the commonly used ideas of system reduction in the study of layered soil media. A numerical example is provided to verify some of these concepts and the nature of nonuniqueness of identification is indicated by showing how two very different (yet physically reasonable) systems could yield identical excitation-response pairs. Errors in the calculation of the dynamic forces, due to erroneous identification have also been illustrated thus making the results of the present study useful from the practical standpoint of the safe design of structures to ground shaking.

On the Uniqueness and Stability of Endochronic Theories of Material Behavior

Abstract: : Endochronic models represent the difference between the loading and unloading behavior of materials without employing the classical plasticity concept of a yield condition In this report such models are shown to violate Drucker's stability postulate in the small for a cycle, and the implications of this violation are discussed In particular, some simple problems involving endochronic models are analyzed, illustrating the difficulties which can arise when such models are used, and leading to the conclusion that they are unsuitable for the numerical solution of mechanical problems (Author)