University of Minnesota
Aerospace Engineering and Mechanics
Spring 2001 Seminar Series



Mechanics of oxidation induced creep and oxide skin failure


Prof. Tom Pence

Dept. of Materials Science & Mechanics, Michigan State University


Abstract

In certain metal systems, surface stress corrosion can be viewed as a process wherein material progressively transforms from (1) metal to (2) robust oxide to (3) damaged oxide. This gives a zone of robust oxide characterized by simultaneous growth (metal to robust oxide) and loss (robust oxide to damaged oxide). In certain cases, and as a first idealization, this zone can be viewed as bounded by sharp moving interfaces: a leading edge growth interface and a trailing edge loss interface. The growth interface can be viewed as governed by reaction and diffusion processes. The oxide has a natural free volume that differs from that of the original metal whereupon stresses due to elastic constraint naturally arise. These stresses arise both in the oxide zone, and in the as yet unoxidized metal. For ductile metals, these stresses can be relieved by creep. In certain cases, the resulting changes in the oxide zone stress field can then lead to a tensile stresses that damages the oxide. The resulting conversion of robust oxide to damaged oxide then provides a purely mechanical prescription for the loss interface. This talk is meant to introduce these ideas in the context of some very simple examples involving mutliple interface motion.

Friday, April 6, 2001
209 Akerman Hall
2:30-3:30 p.m.


Refreshments served after the seminar in 227 Akerman Hall.
Disability accomodations provided upon request.
Contact Kristal Belisle, Senior Secretary, 625-8000.