A Continuum Model for the Effect of Dynamic Recrystallization on the Stress⁻Strain Response.

Austenitic Stainless Steels and High-Strength Low-Alloy (HSLA) steels show significant dynamic recovery and dynamic recrystallization (DRX) during hot forming. In order to design optimal and safe hot-formed products, a good understanding and constitutive description of the material behavior is vital. A new continuum model is presented and validated on a wide range of deformation conditions including high strain rate deformation. The model is presented in rate form to allow for the prediction of material behavior in transient process conditions. The proposed model is capable of accurately describing the stress⁻strain behavior of AISI 316LN in hot forming conditions, also the high strain rate DRX-induced softening observed during hot torsion of HSLA is accurately predicted. It is shown that the increase in recrystallization rate at high strain rates observed in experiments can be captured by including the elastic energy due to the dynamic stress in the driving pressure for recrystallization. Furthermore, the predicted resulting grain sizes follow the power-law dependence with steady state stress that is often reported in literature and the evolution during hot deformation shows the expected trend.

Regaining the preventive medicine edge: training for 2000 and beyond.

We review the state of preventive medicine in the context of four factors that have eroded the influence and effectiveness of the specialty: (1) historical; (2) cultural; (3) political-economic; and (4) changing epidemiological and demographic factors. We address the implications for public and medical peer recognition of preventive medicine, for funding of residency programs, and for recruitment of medical students. We outline five objectives for preventive medicine training as steps to improve the response of the specialty to the above factors and to regain its edge. Also, we propose two specific innovative training programs to partially meet these objectives: a cross-cultural public health exchange and a preventive medicine fellowship in policy and public administration. We discuss the pertinence of these programs in terms of reversing preventive medicine's growing obsolescence.