A new CDM-based approach to structural deterioration

Structural deterioration often occurs without visible manifestation[ Continuum damage mechanics "CDM# enables one to predict the state of damage in such situations and to estimate residual strength:service life of an existing structure[ The accumulation of damage is modeled as a dissipative process that is governed by the laws of thermodynamics[ The rate of dissipation in a deformable system\ R\ depends on the work done on the system and the evolution of the Helmholtz free energy\C[ Under certain thermodynamical conditionsthe _rst variation of C vanishes\ and partial di}erential equations for damage growth in R prior to damage localization are obtained[ This approach obviates the need of introducing arbitrary dissipation potential functions with undetermined constants in the damage growth equations[ All solutions use only readily available material parameters[ Assuming that damage occurs isotropically under uniaxial loading\ closed! form solutions are obtained for ductile damage as a function of plastic strain\ for creep damage as a function of time and for fatigue damage as function of number of cycles[ The models are validated with published laboratory data[