Fig. 4. Stress-strain curves. (A) Representative curves from strain-mode-specific (S-M-S) tests. The arrows indicate the yield points, which were defined using the 0.002 strain offset criterion (see B). Note that in B the tension curve has been offset toward the right so that it can be viewed clearly. (B) Illustration showing the 0.002 strain offset criterion, which is modified from Turner (Turner, 1989). This criterion is used because it helps to avoid the nonlinear `toe' region of the stress-strain curve, which ends at about 15% of the yield stress in linearly elastic materials. E indicates the portion of the curve where elastic modulus was determined.