On the Yield Behavior of Unplasticized P.V.C. : Analogy with the Yielding of Mild Steel

Abstract

We can recognize that there are two steps in the yield process of unplasticized P.V.C.. The first step of yielding is a process, during which the stress-strain curve reaches its maximum point and drops to the lower yield point ; we may call it the "initial yielding". The original local contraction can be seen in a part of the specimen. When such local contraction proceeded to a limiting value corresponding to the strain ε₁, a new yielding or contraction of the cross section is caused in the neighbour of yielded part ; such yielding or the second step of yield may be called the "progressive yielding". The above two steps of yielding may be considered as analogous to the process of the upper and lower yieldings of the mild steel. Such phenomena of yielding are remarkably affected by the stretching speed v_st. We established a relation between the stretching speed v_st, the yield strain ε₁ and the velocity of propagation of plastic strain wave c, as v_st=c·ε₁.