Issue 33

T. Itoh et alii, Frattura ed Integrità Strutturale, 33 (2015) 289-301; DOI: 10.3221/IGF-ESIS.33.33

   3 



Case 0

Case 1

Case 3

Case 4

Case 2

Case 9

Case 8

Case 5

Case 6

Case 7

Case 10

Case 11

Case 13

Case 14

Case 12

Figure 8 : 15 strain paths employed in the non-proportional LCF test.

SUS304, T=923K

SUS304, T=923K

SUS304, T=923K

3000

Case0 Case1 Case2 Case3 Case4 Case5 Case6 Case7 Case8 Case9 Case10 Case11 Case12 Case13 Case14

800

Case0 Case1 Case2 Case3 Case4 Case5 Case6 Case7 Case8 Case9 Case10 Case11 Case12 Case13 Case14

Case0 Case1 Case2 Case3 Case4 Case5 Case6 Case7 Case8 Case9 Case10 Case11 Case12 Case13 Case14

2

0.4 Strain range   ASME , % 1

1000 Stress range   I e , MPa 2000

600

400 Stress range   I , MPa

0.2

0

200

10 2

10 3

10 4

10 5

10 2

10 3

10 4

10 5

10 2

10 3

10 4

10 5

Number of cycles to failure N f

, cycles

Number of cycles to failure N f

, cycles

Number of cycles to failure N f

, cycles

(a) (b) (c)

Figure 9 : Correlation of non-proportional LCF lives with   ASME

,   I e and   I

: (a)   ASME

 N f

, (b)   I e  N f

, (c)   I

 N f

.

Fig. 10 correlates the non-proportional LCF lives with   NP correlates the non-proportional fatigue lives with a small scatter.  employed was determined from the degree of additional hardening. This result suggests that a suitable strain parameter for multiaxial LCF life evaluation must take account of intensity of non-proportionality of loading and additional hardening due to non-proportional loading. The former is the non proportional factor, f NP or f  NP , and the latter is the material constant,  , in   NP . , where material constant,  , is set to 0.4.   NP

SUS304, T=923K

Case0 Case1 Case2 Case3 Case4 Case5 Case6 Case7 Case8 Case9 Case10 Case11 Case12 Case13 Case14

2

0.4 Strain range   NP , % 1

 = 0.4

0.2

10 2

10 3

10 4

10 5

Number of cycles to failure N f

, cycles

Figure 10 : Correlation of non-proportional LCF lives with   NP .

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