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Strictly speaking, the bulk modulus is a thermodynamic quantity, and in order to specify a bulk modulus it is necessary to specify how the pressure varies during compression: constant- temperature (isothermal ), constant- entropy (isentropic ), and other variations are possible. Such distinctions are especially relevant for gases.
The third-order Birch–Murnaghan isothermal equation of state is given by = [() / /] {+ (′) [() /]}. where P is the pressure, V 0 is the reference volume, V is the deformed volume, B 0 is the bulk modulus, and B 0 ' is the derivative of the bulk modulus with respect to pressure. The bulk modulus and its derivative are usually obtained from ...
These coefficients obtained, and knowing the value of the volume to ambient conditions, then we are in principle able to calculate the volume, density and bulk modulus for any pressure. The data set is mostly a series of volume measurements for different values of applied pressure, obtained mostly by X-ray diffraction.
The bulk modulus is an extension of Young's modulus to three dimensions. Flexural modulus ( E flex ) describes the object's tendency to flex when acted upon by a moment . Two other elastic moduli are Lamé's first parameter , λ, and P-wave modulus , M , as used in table of modulus comparisons given below references.
The Poisson's ratio of a stable, isotropic, linear elastic material must be between −1.0 and +0.5 because of the requirement for Young's modulus, the shear modulus and bulk modulus to have positive values. [3] Most materials have Poisson's ratio values ranging between 0.0 and 0.5.
In the isotropic case, the stiffness tensor may be written: [citation needed] = + (+) where is the Kronecker delta, K is the bulk modulus (or incompressibility), and is the shear modulus (or rigidity), two elastic moduli. If the medium is inhomogeneous, the isotropic model is sensible if either the medium is piecewise-constant or weakly ...
Young's modulus (or Young modulus) is a mechanical property of solid materials that measures the tensile or compressive stiffness when the force is applied lengthwise. It is the modulus of elasticity for tension or axial compression. Young's modulus is defined as the ratio of the stress (force per unit area) applied to the object and the ...
Gassmann's equation. Gassmann's equations are a set of two equations describing the isotropic elastic constants of an ensemble consisting of an isotropic, homogeneous porous medium with a fully connected pore space, saturated by a compressible fluid at pressure equilibrium. First published in German [1] by Fritz Gassmann, the original work was ...