Evaluation of thermal material properties based on SAW dispersion in the laser-induced dynamic subsurface temperature gradient

In this study non-linear thermal buckling of circular shallow arches made of functionally graded materials subjected to a linear temperature gradient is investigated. For this purpose, a functionally graded circular shallow arch is considered that its strain-displacement relation follows the Donnells nonlinear shallow shell theory. The material properties are varied smoothly through the arch thickness according to the power law distribution of the volume fraction of constituent materials. Also, material properties are considered temperature-dependent. The classical single layer theory assumptions that are reasonable for slender arches are implemented. To investigate the large deformations of such arch, the von-Karman type geometrical nonlinearity is utilized that is suitable for moderately large class of rotations. The virtual displacement principle and calculus of variation are employed to derive the governing equilibrium equations and complete set of boundary conditions of the FGM arch. The adjacent equilibrium criterion is employed for the stability analysis of the FGM arch. An analytical approach is accomplished and a closed-forms solution for thermal bifurcation points of the FGM shallow arches is presented. Also critical bifurcation loads corresponding to the critical temperatures with the presence of non-linear pre-buckling deformations is obtained. Illustrative results examine the effect of various involved parameters such as power law index, opening angle, geometric parameter (or otherwise length to thickness ratio). Obtained numerical results represent that, in most cases, thermal bifurcation for the FGM arches occurs in the high temperatures and the critical buckling temperatures are approximately high even for slender FGM arches. Also effective of ceramic or metal rich area at the bottom surface of the FGM arch is investigated and results are presented for both cases and are compared together. Varieties between this two cases due to contrast between material and structural stretching-bending coupling effect. Results presented illustrative the ceramic rich area at the bottom surface cause the higher critical buckling temperatures for the FGM arches.

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Deformations and Stresses in Symmetrically Loaded Circular Plates of Varying Thickness

Journal of the Royal Aeronautical Society ◽

10.1017/s0001924000121864 ◽

1953 ◽

Vol 57 (511) ◽

pp. 449-454 ◽

Cited By ~ 1

Author(s):

D. C. Boston

Keyword(s):

Temperature Gradient ◽

Gas Turbine ◽

Variable Thickness ◽

Material Properties ◽

Simple Function ◽

Constant Thickness ◽

Circular Plates ◽

Strength Of Materials ◽

Varying Thickness

The problem of symmetrically loaded circular plates of constant thickness is covered adequately in several of the standard textbooks on the strength of materials. Formulae are derived enabling the deflections and stresses to be readily calculated in any portion of the plate. The problem is complicated by the introduction of a variable thickness and by a variation of material properties due to a temperature gradient down the radius of the plate; conditions such as are encountered in gas turbine wheels, bearing support diaphragms and flexible disc couplings. Methods exist whereby the plate can be solved if the thickness is a simple function of the plate radius, but in practice this is not always so, the profile often being complicated by flanges and spigots.

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Laser-Induced Voltages at Room Temperature in YBa2Cu3O7 and PrxY1-xBa2Cu3O7 Thin Films

MRS Proceedings ◽

10.1557/proc-397-229 ◽

1995 ◽

Vol 397 ◽

Author(s):

H.- U. Habermeier ◽

N. Jisrawi ◽

G. Jäger-Waldau ◽

U. Sticher ◽

B. Leibold

Keyword(s):

Thin Films ◽

Temperature Gradient ◽

Single Crystal ◽

Tilt Angle ◽

Material Properties ◽

Defect Structure ◽

Room Temperature ◽

Substrate Surface ◽

Doping Dependence ◽

Photon Fluence

ABSTRACTRecent reports on high transient transverse voltages at room temperature in YBa2Cu3O7 and PrxYl-xBa2Cu3O7 thin films grown on SrTiO3 single crystal substrates, with a tilt angle between the [ 001 ] cubic axis and the substrate surface plane, have been interpreted by thermoelectric fields transverse to a laser-induced temperature gradient which are caused by the non-zero off diagonal elements of the Seebeck tensor. We have studied this effect in epitaxially grown Pr- doped, as well as undoped YBa2Cu3O7, thin films and observed for a 2 mm long YBa2Cu3O7 strip exposed to a UV photon fluence of 100 mJ/cm2 signals as large as 30 V. The unexpected high values for the signals and their doping dependence are discussed within the frame of a model based on a thermopile arrangement, the growth induced defect structure and the doping induced modifications of the material properties.

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Thermal Stresses in Bodies Exhibiting Temperature-Dependent Elastic Properties

Journal of Applied Mechanics ◽

10.1115/1.4010510 ◽

1952 ◽

Vol 19 (3) ◽

pp. 350-354

Author(s):

H. H. Hilton

Keyword(s):

Temperature Gradient ◽

Elastic Properties ◽

Plane Stress ◽

Material Properties ◽

Thermal Stresses ◽

Temperature Gradients ◽

Temperature Dependent ◽

Steady State Temperature ◽

Specific Temperature ◽

Walled Cylinder

Abstract Expressions are derived for thermal stresses and strains due to a steady-state temperature gradient in a thick-walled cylinder and a circular thin plate, made of a material having temperature-dependent elastic properties. Two numerical examples are computed for specific temperature gradients and temperature-dependent elastic properties, which yield results showing that the maximum thermal stresses are appreciably lower and the maximum thermal strains are larger than the corresponding values obtained for temperature-independent properties. The validity of the thermal plane-stress assumptions is investigated and it is shown that such solutions, regardless of whether the material properties are temperature-dependent or constant, are only approximations. The smaller the temperature gradient the more closely are the plane-stress assumptions satisfied.

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Grain boundary segregation in metals

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100130651 ◽

1992 ◽

Vol 50 (2) ◽

pp. 1204-1205

Author(s):

C.L. Briant

Keyword(s):

Fracture Surface ◽

Grain Boundary ◽

Grain Boundaries ◽

Material Properties ◽

Electron Spectroscopy ◽

High Vacuum ◽

Boundary Segregation ◽

Grain Boundary Segregation ◽

Local Concentration ◽

The One

Grain boundary segregation is the process by which solute elements in a material diffuse to the grain boundaries, become trapped there, and increase their local concentration at the boundary over that in the bulk. As a result of this process this local concentration of the segregant at the grain boundary can be many orders of magnitude greater than the bulk concentration of the segregant. The importance of this problem lies in the fact that grain boundary segregation can affect many material properties such as fracture, corrosion, and grain growth.One of the best ways to study grain boundary segregation is with Auger electron spectroscopy. This spectroscopy is an extremely surface sensitive technique. When it is used to study grain boundary segregation the sample must first be fractured intergranularly in the high vacuum spectrometer. This fracture surface is then the one that is analyzed. The development of scanning Auger spectrometers have allowed researchers to first image the fracture surface that is created and then to perform analyses on individual grain boundaries.

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Relationships Between Grain Boundary Structure and Material Properties

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s1431927600001550 ◽

1980 ◽

Vol 38 ◽

pp. 366-369

Author(s):

Brian Ralph ◽

Barlow Claire ◽

Nicola Ecob

Keyword(s):

Grain Boundary ◽

Material Properties ◽

Main Property ◽

Grain Structure ◽

Boundary Structure ◽

Grain Boundary Structure ◽

Property Changes

This brief review seeks to summarize some of the main property changes which may be induced by altering the grain structure of materials. Where appropriate an interpretation is given of these changes in terms of current theories of grain boundary structure, and some examples from current studies are presented at the end of this paper.

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