steels. Therefore, an arbitrary definition for the yield strength has been adopted by the aluminum industry: a line parallel to a tangent to the stress-strain curve at its initial point is drawn, passing through the 0.2% strain intercept on the x (strain) axis. The stress where this line intersects the stress-strain curve is defined as the yield stress. The shape of the stress-strain curve for H, O, T1, T2, T3, and T4 tempers has a less pronounced knee at yield when compared to the shape of the curve for the T5, T6, T7, T8, and T9 tempers. (This causes the inelastic buckling strengths of these two groups of tempers to differ, since inelastic buckling strength is a function of the shape of the stress-strain curve after yield.)

Ultimate strength is the maximum stress the material can sustain. All stresses given in aluminum product specifications are engineering stresses; that is, they are calculated by dividing the force by the original cross-sectional area of

TABLE 9.14 Typical Mechanical Properties©©
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