Issue 13

A. Finelli et alii, Frattura ed Integrità Strutturale, 13 (2010) 24-30; DOI: 10.3221/IGF-ESIS.13.03 28 Both specimens “B” and “C” did not allow to use conventional extensometers; strain measurements were performed by means of resistive strain gages: these strain gages were able to detect strains up to 5% max. (Fig. 8) . All the tests were carried out in compliance with the ASTM A 370 standards according to the methods reported in ASTM E 8 and E 9 [1, 2]. At least, three tests were performed for all the investigated conditions. E XPERIMENTAL RESULTS onsidering standard specimens (S), the following parameters were considered: ‐ Yield strength at 0.2% (σ s(0.2%) ). ‐ Ultimate Tensile Strength (σ u ). ‐ Elongation measured on a base of 25 mm (A% 25 mm). Mean values are shown in Tab. 3. σ s(0.2%) [MPa] σ m [MPa] A (25) [%] A1SL 477 764 49 A1LSL 1046 1110 19 5SL 339 683 59 4LSL 833 925 19 Table 3 : Tensile test average results of standard specimen (S) The same parameters were also considered with the "short gage length" (B) specimens, with a difference in the elongation measurement (a base of 12.5 mm instead of 25 mm) Results are summarized in Tab. 4. σ s(0.2%) [MPa] σ m [MPa] A (12.5) [%] A1BL 491 771 27 A1BT 507 772 25 A1LBL 971 1063 16 A1LBT 908 1111 13 5BL 308 669 36 5BT 337 696 34 4LBL 830 915 16 4LBT 749 916 16 Table 4 : Tensile test average results of short gage length specimen (B). Considering compression specimens (C), it was only possible to measure the yield strength value at 0.2%, since both the specimen geometry and the material ductility prevent the other parameters from being detected. Mean values are shown in Tab. 5. σ s(0.2%) [MPa] A1LCL 860 A1LCT 1081 A1LCR 1065 4LCL 714 4LCT 938 4LCR 866 Table 5 : Compression test average results (C). Tab. 6 s ummarizes all the experimental results for all the investigated steels and all the considered specimens. C