Rich Geoffroy Polymer Services Group
POLYSERV@cox.net
Actually, permanent set can occur well before the yield strain. Viscoelastic flow occurs as soon as the elastic limit is exceeded, i.e., anywhere after the linear portion of the stress-strain curve. Most of that viscoelastic flow that occurs prior to yield is generally recoverable with time --- but not all of it. That which is not recoverable is permanent set.
