Mechanics Concepts for Life Prediction:  Facts and Foibles

Ken Reifsnider
Alexander Giacco Professor of Engineering Science & Mechanics
Virginia Polytechnic Institute and State University
Blacksburg, Virginia

Sponsored by: UNL Research Council and the Department of Engineering Mechanics

Date:  Thursday, April 17, 1997
Time:  3:30 p.m.
Place:  306 Bancroft Hall

Mechanics has traditionally been concerned with stress and strain, i.e., with the "stress state" in material bodies of finite extent. Although constitutive theory is certainly part of mechanics, and notable developments of philosophy have been fostered in that part of the field (especially in viscoelasticity and rheology), mechanics has traditionally been less concerned with the "state of the material." However, in many composite solids, the constitutive relationships are strongly dependent on time and history, resulting in changes in properties of the order of 30-60 percent over the engineering life of a component. This has introduced a new challenge to the mechanics community. The Materials Response Group at Virginia Tech, with a group of industrial partners, has developed a general framework for the prediction of changes in stress states and material states under long-term applied conditions, especially extreme applied conditions, over the last dozen years. The approach is based on damage accumulation and remaining strength prediction (sometimes called damage tolerance). The present lecture will describe the tenets of that philosophy, provide some examples of its' application, and offer some comments on the utility, advantages, and disadvantages of the approach.