Papers by Keyword: Viscoplastic Flow

Abstract: Herschel-Bulkley model is used to describe the constitutive behavior of Magnetorheological (MR) fluids subject to an applied magnetic field. Based on the shear flow equation at the narrow gap, a theoretical analysis of the effect of the applied magnetic field on the viscoplastic flow between two parallel disks is presented. The expression for the velocity in viscoplastic flow is derived. The results indicate that the velocity profile of MR fluid in shear region is deeply dependent on the gradient of the pressure in the flow channel. For the negative pressure gradient value, the velocity peak value point tends to move toward the driven disc wall as absolute value of pressure gradient increases. However, the velocity peak value point tends to move toward the driving disc wall as absolute value of pressure gradient increases for the positive pressure gradient value.

Abstract: The mechanical properties of nickel superalloys are related to the spatial distribution of hardening phases, their size and composition, and on the configurations of dislocations introduced by plastic and viscoplastic straining. Heterogeneous plastic flow in relation with dynamic strain aging is examined and synthesized. Dislocations are usually faced with the alternative of shearing or bypassing the ’ phase occupying up to 60 vol.%. Depending on ’ size, several Orowan bypassing mechanisms are observed, alternatively shearing by dislocation pairs or complex configurations involving S-ISF and S-ESF. Variables such as temperature, strain rate and Schmid factor play a decisive role in determining the dislocation configurations which either percolate through the matrix or shear the ’ structure. Various dislocation strategies and microstructures are analyzed and illustrated; they are reviewed critically and summarized in a strain rate versus 1/T mechanism map.