ANISOTROPIC DAMAGE MECHANICS BASED ON STRAIN-ENERGY EQUIVALENCE AND EQUIVALENT ELLIPTIC MICROCRACKS

A theory of damage mechanics is introduced based on a principle of str ain energy equivalence. This principle is used to develop the effectiv e continuum elastic properties of a damaged solid in terms of the unda maged elastic properties and a scalar damage field. The damage variabl e is defined as the volume fraction of a damage zone associated with e quivalent elliptical microcracks. This definition provides a means by which a damaged isotropic material can exhibit anisotropic (orthotropi c) properties, and entails determining effective crack orientation and geometry factors from the local deformation. Strain energy dissipatio n associated with crack growth(not nucleation) is used to develop a co nsistent damage evolution equation. This evolution equation is related to the standard power law model of crack growth commonly used in frac ture mechanics, and to the equivalent stress measure commonly used in mechanics of plastic deformation. The combination of representing loca l damage as an effective elliptical crack volume fraction, a consisten t damage evolution equation, and the determination of effective elasti c properties using a strain energy equivalence principle yields a simp le, yet powerful, approach to predicting failure of mechanical compone nts. (C) 1997 Elsevier Science Ltd.