SYMPOSIA PAPER Published: 01 January 1982
STP28878S

Time-Independent and Time-Dependent Deformation of Metals

Source

In most contemporary theories the deformation of metals is treated as a time-dependent or viscous process. A quasi time-independent character is sometimes introduced by means of an athermal back “stress” from long-range obstacles, but only at T = 0 K or in other limited temperature ranges is the deformation predicted to show time-independent behavior. Several experimental results, mainly on pure face-centered-cubic metals, are in disagreement with this theoretical approach. The most important results are that (1) time-independent strain (loading strain) has been measured on sudden increase of stress during creep deformation, even for very small stress increments; and (2) the strain rate ratio measured in a load relaxation experiment, R = ˙εr/˙ε, is consistently less than unity and increases toward unity as the stress approaches saturation. These results are reviewed and new data from load relaxation on lead and the superplastic Pb-Sn eutectic are presented. It is the author's conclusion from these data that time-independent deformation may be more important than is normally acknowledged. Thus, in future efforts at modeling plasticity, the possibility of a dual time-dependent, time-independent nature ought to be considered.

Author Information

Alden, TH
University of British Columbia, Vancouver, British Columbia, Canada
Price: $25.00
Contact Sales
Related
Reprints and Permissions
Reprints and copyright permissions can be requested through the
Copyright Clearance Center
Details
Developed by Committee: E28
Pages: 29–47
DOI: 10.1520/STP28878S
ISBN-EB: 978-0-8031-4830-7
ISBN-13: 978-0-8031-0737-3