Phenomenological Aspects of Creep Irreversibility

Summary

Creep irreversibility is discussed from a structural point of view. The partial strain recovery following upon unloading of a hyperstatic structure from a state of nonlinear creep deformation is here attributed to two causes: isostatic recovery, being an inherent material property and hyperstatic recovery, being a result of transient stress redistribution between various parts of the structure. The magnitude of hyperstatic recovery strain is studied for a few structural models. It is found to be at most of the order of the elastic strain, and may therefore be disregarded in most cases where isostatic recovery is present. In such cases recovery in various structures may profitably be described by the hereditary theory due to Rabotnov. Some aspects of this theory are finally discussed.