PSI - Issue 2_B

Satoshi Igi et al. / Procedia Structural Integrity 2 (2016) 1601–1609 Satoshi Igi / Structural Integrity Procedia 00 (2016) 000–000

7

1607

(a) SM490A and SN490B (b) SA440, SM570Q and HT7 Fig. 8 Correlation of the change in flow stress and temperature shift of the critical CTOD and temperature curve, ΔT PD 4. Effects of compressive pre-strain and cyclic strain 4.1. Effect of compressive pre-strain The comparison of the amount of brittleness caused by tensile pre-strain and compressive pre-strain is shown in Fig. 9. The amount of brittleness was calculated as the temperature shift before and after pre-strain was applied, using the temperature at which the critical CTOD reaches 0.10 mm as an indicator. In this figure, the brittleness of steel subjected to tensile pre-strain is compared with that of steel under compressive pre-strain of the same absolute magnitude as the tensile strain. This figure indicates that steels undergoing tensile pre-strain and compressive pre strain can be treated in the same manner, irrespective of the exact alloy and the amount of pre-strain. Figure 10 shows the relationship between σ f PD and Δ T PD including cases of steel under tensile pre-strain and compressive pre-strain. This figure proves that the method for handling steels subjected to compressive pre-strain which our fracture evaluation flow chart proposes can evaluate the brittle behaviour of steel plates after pre-strain is applied. This approach is based on the assumption that the amount of brittleness due to compressive pre-strain is identical to that caused by tensile pre-strain of the same magnitude.

Fig. 10. Comparison relationship between between Δ σ f

PD and Δ T

Fig. 9. Comparison of change in brittleness.

PD