The secant modulus is the ratio of
stress to corresponding strain at any selected point on the
stress-strain curve, that is, the slope of the straight line that
joins the origin and a selected point on the actual stress-strain
curve. It shall be expressed in megapascals (pounds per square
inch). The selected point is chosen at a prespecified stress or
strain in accordance with the appropriate material specification
or by customer contract. It is calculated in accordance with Eq
6 by letting m equal the slope of the secant to the loaddeflection
curve. The chosen stress or strain point used for the
determination of the secant shall be reported.