Failure Analysis and Microcrack Dependent Discontinuum Mechanics

摘要

The failure of many materials involves creating dense sets of microcracks. Each microcrack created results in a discontinuity in the deformation between atoms in the material and a change in the thermodynamic energy content of the material. Continuum mechanics does not provide a physical description of the discontinuities nor assign correct internal energy contributions for various thermodynamic processes during microcrack kinetics. In order to represent discontinuities in the deformation and various internal energy contributions during microcrack kinetics, a microcrack dependent discontinuum mechanics has been formulated. This discontinuum mechanics describes a microcrack density function in terms of physical attributes and statistical concepts; represents deformation as a functional to explicitly include interatomic discontinuities from the density of microcrack defects; and models both equilibrium and nonequilibrium thermodynamic processes of microcrack creation, microcrack growth, and microcrack surface energy changes. This contrasts to the empirical methodology of continuum mechanics that seeks a phenomenological description. An illustrative example of the microcrack dependent discontinuum approach is presented for the uniaxial tensile test. This analysis provides realistic representations for microcrack density evolution, local (true) stress response, and loading history for an input of total strain rate. 13 refs., 6 figs. (ERA citation 11:025009)