title: On rate-dependent polycrystal deformation: the temperature sensitivity of cold dwell fatigue.
abstract: A temperature and rate-dependent crystal plasticity framework has been used to examine the temperature sensitivity of stress relaxation, creep and load shedding in model Ti-6Al polycrystal behaviour under dwell fatigue conditions. A temperature close to 120°C is found to lead to the strongest stress redistribution and load shedding, resulting from the coupling between crystallographic slip rate and slip system dislocation hardening. For temperatures in excess of about 230°C, grain-level load shedding from soft to hard grains diminishes because of the more rapid stress relaxation, leading ultimately to the diminution of the load shedding and hence, it is argued, the elimination of the dwell debit. Under conditions of cyclic stress dwell, at temperatures between 20°C and 230°C for which load shedding occurs, the rate-dependent accumulation of local slip by ratcheting is shown to lead to the progressive cycle-by-cycle redistribution of stress from soft to hard grains. This phenomenon is termedcyclic load sheddingsince it also depends on the material's creep response, but develops over and above the well-known dwell load shedding, thus providing an additional rationale for the incubation of facet nucleation.
authors.affiliation: Department of Materials , Imperial College London , Royal School of Mines, Exhibition Road, London SW7 2AZ, UK.
authors.forename: Zhen
authors.initials: Z
authors.lastname: Zhang
authors.affiliation: Department of Materials , Imperial College London , Royal School of Mines, Exhibition Road, London SW7 2AZ, UK.
authors.forename: M A
authors.initials: MA
authors.lastname: Cuddihy
authors.affiliation: Department of Materials , Imperial College London , Royal School of Mines, Exhibition Road, London SW7 2AZ, UK.
authors.forename: F P E
authors.initials: FP
authors.lastname: Dunne
keywords: cold dwell; crystal plasticity; facet fatigue; hexagonal close-packed; microtexture; stress relaxation