*2.5. Stress-Strain Responses and Overall Stresses at Plastic Yielding*

Figure 2c,d show the stress–strain responses of the compression tests for Ni and *α*-Brass, respectively. As designed, most of the deformation was in the elastic state, and only the last small part corresponded to plasticity. However, the yield point occurred at about 8.5% strain for Ni and 6.3% for *α*-Brass from the originally experimental measurement. These strains are of course too large for characterizing the yield point of such metals. This error came from the drift of the tip during the compression test. Hence, the displacement measurement was not accurate, but the force measurement was accurate. Therefore, CPFEM simulations of the compression tests with the same configuration were performed for both Ni and *α*-Brass samples. Then, the experimentally measured stress–strain curves were corrected by using CPFEM simulations such that both elastic parts match together. After the correction, the yield point occurred at the stain about 0.33% for Ni and 0.24% for *α*-Brass, which are reasonable values for such metals. Thus, the effective average loading strain rate was about 7.7 × <sup>10</sup>−5s−<sup>1</sup> for Ni and 5.0 × <sup>10</sup>−5s−<sup>1</sup> for *<sup>α</sup>*-Brass. The applied stress at the end of the compression test was about 289.4 MPa for Ni and 127.4 MPa for *α*-Brass. These values will be used in Section 4.
