Skip to main content
U.S. flag

An official website of the United States government

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

Elastic Constants and Thermal Expansion Averages of a Polycrystal



Roland deWit


This paper derives expressions for the overall average elastic constants and thermal expansion coefficients of a polycrystal in terms of its single crystal components. The polycrystal is assumed to be statistically homogeneous, isotropic, and disordered. Upper and lower bounds for the averages are easily found by assuming a uniform strain or stress. The upper bound follows from Voigt s assumption that the total strain is uniform within the polycrystal while the lower bound follows from Reuss s original assumption that the stress is uniform. A self-consistent estimate for the averages can be found if it is assumed that the overall response of the polycrystal is the same as the average response of each crystallite. The derivation method is based on Eshelby s theory of inclusions and inhomogeneities. We define an equivalent inclusion, which gives an expression for the strain disturbance of the inhomogeneity when external fields are applied. The equivalent inclusion is then used to represent the crystallites. For the self-consistent model the average response of the grains has to be the same as the overall response of the material, or the average strain disturbance must vanish. The result is an implicit equation for the average polycrystal elastic constants and an explicit equation for the average thermal expansion coefficients. For the particular case of cubic symmetry the results can be reduced to a cubic equation for the self-consistent shear modulus.
Journal of Mechanics


bulk modulus, compliance, cubic, disordered, effective medium, elastic constants, homogeneous, inclusion, inhomogeneity


deWit, R. (2008), Elastic Constants and Thermal Expansion Averages of a Polycrystal, Journal of Mechanics (Accessed July 15, 2024)


If you have any questions about this publication or are having problems accessing it, please contact

Created October 16, 2008