PSI - Issue 2_B

V. Aleksić et al. / Procedia Structural Integrity 2 (2016) 3313 – 3321

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8

V. Aleksi ć / Structural Integrity Procedia 00 (2016) 000–000

a) Ratio  max and  /2 for strain level  /2=0.35 to 0.80

b) Basic curve of low-cycle fatigue Fig. 11. Construction of BCNCF, BM of NN-70, N f = N f1 (force drop by 25%, ISO 12106:2003(E) (2003))

f) Ratio  max and  /2 for strain level  /2=0.35 to 0.80

g) Basic curve of low-cycle fatigue Fig. 12. Construction of BCNCF, BM of NN-70, N f = N f2 (force drop by 50%, ASTM E606-80 (1985))

In Tab. 6 the transition life of steel NN-70 was calculated on the basis of the parameters determined according to the methods for determination of the stabilized hysteresis from two standards [ISO 12106:2003(E) (2003), ASTM E606-80 (1985)].

Transition life, N fT , for BM of steel NN-70 ranges in an interval from 274 to 292, i.e. transition life determined according to the standard ISO 12106: 2003 (E) (2003) is about 6% lower than the transition life calculated based on the methodology for determination of stabilized hysteresis according to the ASTM E 606-04 standard [ASTM E606-80 (1985), Aleksić (2016)]

Table 6. Transition life of BM of steel NN-70 BM E, MPa

221378

elastic part

plastic part

NN-70

b

 ' f

c

 ' f

N fT

N f

N s

N f-25% = N f1 N f-50% = N f2

N s1 N s2

-0.060 -0.057

1153.8 1132.7

-0.594 -0.620

0.1045 0.1250

N s1 =N f-25% /2 N s2 =N f-50% /2

274 292

b c 1 

  

  

' f   

E

N

Transition life



fT

' f

6. Conclusion The theoretical, experimental and numerical research of the behaviour of low-alloy high-strength steels exposed to loading induced by low-cycle fatigue that are described in this paper are very complex research task. Extensive theoretical studies have required synthesis of knowledge in multiple engineering fields and disciplines, and numerical and experimental studies are an important part of this work. Detailed analysis of the historical review of research in this area and analysis of the latest published