Issue 38

T. Morishita et alii, Frattura ed Integrità Strutturale, 38 (2016) 281-288; DOI: 10.3221/IGF-ESIS.38.38

2.0

PP-FF PP-SS PP-SS* PP-TH-3 PP-TH-10 PP-CH-3 PP-CH-10 CI-FF CI-SS CI-SS* CI-TH-3 CI-TH-10

1.0 Strain range  ' NP , % 0.4

Factor of 2

0.2

10 2

10 3

10 4

Failure life N f

, cycles

Figure 7 : Correlation of N f by modified non-proportional strain range. Fig. 8 shows a correlation of failure life by the modified non-proportional strain range. In the figure, all of the date can be plotted within the factor of 2 band. It suggests that   NP becomes a suitable parameter for evaluation of the creep-fatigue failure life under non-proportional loading. Further creep-fatigue tests using other materials will be obtained for the discussion of this modified non-proportional strain range considering the strain rate.

2.0

PP-FF PP-SS PP-SS* PP-TH-3 PP-TH-10 PP-CH-3 PP-CH-10 CI-FF CI-SS CI-SS* CI-TH-3 CI-TH-10

1.0 Strain range  * NP , % 0.4

Factor of 2

0.2

10 2

10 3

10 4

Failure life N f

, cycles

Figure 8 : Correlation of N f

by modified non-proportional strain range.

C ONCLUSIONS

(1) In the push-pull loading test (proportional loading test), failure life is decreased with decreasing in the strain rate resulting in creep damage.

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