Slow dynamic elasticity at short times.

Abstract

It has been reported that slow dynamic nonlinear elastic relaxations, widely thought to proceed universally in proportion to the logarithm of time after cessation of mechanical conditioning, actually recover with a smaller slope at early times, with a time of transition that varies with the grain size of the material. This would constitute a heretofore unreported failure of the claimed universality, while suggesting application to nondestructive evaluation and structural health monitoring. Here, we present further observations at short times, in the single bead system, in cement paste, mortar, concrete, sandstone, and granite. Within the limits imposed by finite-duration ring-down such that the effective instant of conditioning cessation is imprecise, and the corresponding ambiguity as to the time at which relaxation begins, we find no reliable sign of such a transition, even in samples of large grain-size mortar and concrete similar to those described elsewhere as having clear and late cutoffs.