PSI - Issue 35

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Domen Šeruga et al. / Procedia Structural Integrity 35 (2022) 150–158 Sˇ eruga et al. / Structural Integrity Procedia 00 (2021) 000–000

153

Fig. 2. The load history of the pipe bend consists of variable temperature, internal pressure and mechanical load on the free end. Every load step lasts 10 s .

Table 1. Elastic modulus E , Ramberg–Osgood parameters K and n , tensile strength R m and proportional limit stress σ p for ferritic stainless steel EN 1.4512. T [ ◦ C] E [MPa] K [MPa] n [-] R m [MPa] σ p [MPa] 20 200000 603.42 0.1211 407 140 300 180000 508.16 0.1103 360 120

Table 2. Manson–Co ffi n parameters σ f , f , b and c for ferritic stainless steel EN 1.4512. T [ ◦ C] σ f [MPa] f [ − ]

b [ − ] -0.09 -0.09

c

20

672.97 521.62

0.45 0.45

-0.59 -0.59

300

Fig. 3. Temperature dependent a) stress-strain curves and b) durability curves for ferritic stainless steel EN 1.4512. Material properties at 20 ◦ C and 300 ◦ C are represented by thick and thin lines, respectively.

the proportional limit stress of the material at both temperatures, 20 ◦ C and 300 ◦ C, so elastoplastic response of the pipe bend is expected. The highest stresses occur at the inner side of the arch in steps 3, 5 and 7 when the pipe bend is mechanically loaded upwards (Figs. 4c, 4e and 4g). The inner pressure induces equivalent stresses up to 50 MPa in step 1 (Fig. 4a) which however counteract the stresses due to the mechanical load downwards in steps 2, 4, 6 and