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, Psi. Under certain thermodynamical conditions, the first variation of Psi vanishes, and partial differential 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. (C) 1998 Elsevier Science Ltd. All rights reserved.