Issue 50

Ch. Apostolopoulos et alii, Frattura ed Integrità Strutturale, 50 (2019) 548-559; DOI: 10.3221/IGF-ESIS.50.46 552 exposure to the corrosive environment. On the contrary, for the same exposure period, elongation of B450c steel was diminished about 77.12% against 69.87% of B400c category. However, it is remarkable, that plastic deformation recorded for both steel categories, after the completion of the first 45 days, was lower than the value that Eurocode 2 requires, which is equal to 7.5%. The corresponding results of LCF tests are presented in Figs.3 and 4. Steel Grade TCorr (Days) Mass Loss (%) Rp (MPa) Rm (MPa) Agt (%) B400c 0 0 437 549 15.6 B400c 0 0 435 548 16.0 B400c 0 0 433 550 15.3 AVERAGE 0 435 549 15.6 B400c 45 5.9 435 518 6.3 B400c 45 5.5 431 520 5.7 B400c 45 4.8 429 520 6.3 AVERAGE 5.4 432 519 6.1 B400c 90 8.5 400 497 5.2 B400c 90 9.7 414 494 4.1 B400c 90 9.6 408 488 4.7 AVERAGE 9.3 407 493 4.7 Table 3 : Mass Loss Results and Mechanical Characteristics of B400c steel bar samples, of 16mm nominal diameter before and after their exposure to corrosive conditions Steel Grade TCorr (Days) Mass Loss (%) Rp (MPa) Rm (MPa) Agt(%) B450c 0 0 541 651 11.4 B450c 0 0 532 644 12.3 B450c 0 0 536 649 11.7 AVERAGE 0 536.4 648 11.8 B450c 45 6.0 528 614 4.6 B450c 45 6.2 534 613 4.1 B450c 45 6.1 533 617 4.3 AVERAGE 6.1 532 615 4.3 B450c 90 11.2 512 566 2.4 B450c 90 11.3 509 581 2.7 B450c 90 10.1 496 575 3.0 AVERAGE 9.3 506 574 2.7 Table 4 : Mass Loss Results and Mechanical Characteristics of B450c steel bar samples, of 16mm nominal diameter, before and after their exposure to corrosive conditions. Examining the performance of both steel categories, in ±2.5% deformation (where buckling effects are relatively mild), refer- ence B450c steel achieves 22.4% higher life cycle (67cycles) than the reference B400c steel (52 cycles). However, after 45 and 90 days of exposure to the corrosive conditions, life cycles of both steel categories are approximately equal. According to the results presented in Figs.3 and 4, it seems that although corrosion factor is responsible for similar mass loss percentages in both steel categories, however they demonstrate different performance under the cyclic testing. This fact is owed to the different thickness of the martensite layer of the two steel grades [18]. Precisely, B400c steel bar category recorded a great drop, of more than 60%, on the number of cycles up to failure until the first 45 days of exposure to the