Issue 40

E. D. Pasiou et alii, Frattura ed Integrità Strutturale, 40 (2017) 41-51; DOI: 10.3221/IGF-ESIS.40.04 44 Figure 2 : Typical stress-axial strain curves for (a) marble, (b) mortar and (c) glass specimens. (d) The three aforementioned curves together for comparison reasons. Material Specimen Modulus of elasticity [GPa] Fracture stress [MPa] Peak axial strain [-] Dionysos marble M1 68.8 98.7 1.7·10 -3 M2 71.2 92.5 1.9·10 -3 M3 70.7 94.7 2.2·10 -3 Mean value ± standard deviation 70.2 ± 0.2 95.3 ± 0.5 1.9·10 -3 ± 0.3 Cement mortar C1 19.8 50.1 3.5·10 -3 C2 18.1 46.4 2.4·10 -3 C3 23.3 51.7 3.1·10 -3 Mean value ± standard deviation 20.4 ± 0.8 49.4 ± 0.5 3.0·10 -3 ± 0.5 Soda glass G1 68.7 18.8 2.7·10 -4 G2 70.5 20.5 3.3·10 -4 G3 70.0 19.4 3.1·10 -4 Mean value ± standard deviation 69.7 ± 0.2 19.6 3.0·10 -4 ± 0.3 Table 2 : The mechanical characteristics of all specimens. Electric signals The electric signal produced during a typical compressive test of a marble specimen and the axial strain obtained (normalized over its maximum value) versus the normalized stress are presented in Fig.3. A weak current (from 0.5 pA in- creases slightly to 2 pA) is initially observed until point A 1 in Fig.3(a1) where the stress level equals ~75% of the maximum stress and strain is ~55% of the fracture strain. This point almost corresponds to point A where the stress-strain curve y = 70653x - 15.2 0 25 50 75 100 0.0E+0 8.0E-4 1.6E-3 2.4E-3 Stress [MPa] Axial strain 0 25 50 75 100 0E+00 8E-04 2E-03 2E-03 3E-03 4E-03 Stress [MPa] Axial strain Marble Mortar Glass y = 70458x - 1.6 0 6 12 18 24 0E+0 1E-4 2E-4 3E-4 4E-4 Stress [MPa] Axial strain y = 19790x - 9 0 14 28 42 56 0E+0 1E-3 2E-3 3E-3 4E-3 Stress [MPa] Axial strain A B C (a) (b) (c) (d)