A Phenomenological Theory of Aging Effects of Metals

A constitutive law is developed for metals which have aging properties. The development of this law is based on the assumption that the mechanical properties of simple aging materials can be mathematically represented by a functional of the strain history, and that this functional depends upon the age of the material. A perturbation technique allows the separation of the nonaging response from the aging effects, and leads to convenient representations for viscoelasticity and plasticity. The mechanical behavior of aging metals is studied by applying the arc length parameterization of the strain history. The final rate independent results are transformed to the time domain for efficient use in engineering applications and in solving boundary value problems.