PSI - Issue 2_B

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

3318

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

Fig. 8. Comparison of cyclic and monotonous stress-strain curve of BM of NN-70 steel, N f = N f2 (force drop by 50% [ASTM E 606-04e (2004)])

Table 3. Exponents n’ and coefficients K’ of cyclic stress-strain curves BM n'

K', MPa

log K'

NN-70

N f

N s

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

N s1 N s2

0.047 0.045

946.2 937.6

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

2.976 2.972





p

' n log

'

log

logK





Linearized step function

2

2

n ' 1



' 2K      2

  

Cyclic stress-strain curve

 

E

In Fig. 9a (for N s1 ) and Fig. 10a (for N s2 ) the linearized elastic components of the total-strain amplitude and in Fig. 9b (for N s1 ) and Fig. 10b (for N s2 ) linearized plastic components of the total-strain amplitude determined on the basis of experimental data are shown, in order to determine the exponents and coefficients required for construction of BCLCF. [Aleksić (2016)]

a) Exponent b = -0.060 and coefficient log  f ’ /E = -2.283 of basic curve of low-cycle fatigue

b) Exponent c = -0.594 and coefficient log  f ’ = -0.981 of basic curve of low-cycle fatigue

Fig. 9. Linearized components of total-strain amplitude, BM of NN-70, N f = N f1 (force drop by 25%, ISO 12106:2003(E) (2003))