On the Dynamics of Knowledge-Based Economic Growth

A geometric approach to characterize the solutions of higher-dimensional dynamic optimization problems is applied to a model of knowledge-based economic growth. The characterization reveals a variety of growth patterns, ranging from sustained growth to stagnation. Growth processes exhibit a turnpike property, reaching as rapidly as possible the path along which human and physical capital are equally productive at the margin and evolving along it thereafter. Some growth processes display overshooting behavior and some are sensitive to threshold capital stocks. This work has been supported by the Paul Ivanier Center of Robotics and Production Management, Ben Gurion University of the Negev, Beer Sheva, Israel.     

A practical two-surface plasticity model and its application to spring-back prediction

A practical two-surface plasticity model based on classical Dafalias/Popov and Krieg concepts was derived and implemented to incorporate yield anisotropy and three hardening effects for non-monotonous deformation paths: the Bauschinger effect, transient hardening and permanent softening. A simple-but-effective stress-update scheme avoiding overshooting was proposed and implemented. Constitutive parameters were fit to 5754-O aluminum alloy using uniaxial tension/compression data. Spring-back predictions using the resulting material model were compared with experiments and with single-surface material models which do not account for permanent softening. The two-surface model improved such predictions significantly as compared with single-surface models, while the differences between two-surface simulations and experiments were insignificant.