PSI - Issue 16

Andrzej Kurek et al. / Procedia Structural Integrity 16 (2019) 19–26 25 Andrzej Kurek, Justyna Koziarska, Tadeusz Łagoda, Karolina Łago da / Structural Integrity Procedia 00 (2019) 000 – 000 7

(X-tra) and it amounts to 21.37%. Whereas, when analysing fatigue limit exponents for small deformations and finite deformations, it may be observed that the average increase amounts to 14.33% and it is the highest for the same steel, and it amounts to 25.71%. By analogy, when analysing the relative change of the fatigue plastic deformation coefficient for small deformations and finite deformations, it may be observed that in this case there is a drop on average of 11.91% and it is the highest for aluminium 1100Al (42.66%). Also the relative change of the fatigue plastic deformation exponent for small deformations and finite deformations, which on average decreases by 273% is the highest for aluminium alloy. When analysing the relative change of the deformation cyclic strengthening coefficients for small deformations and for finite deformations, it may be observed that it always grows. The average growth value is 21.51% and it is the highest for aluminium alloy 1100Al (36.94%). Whereas, the relative change of the cyclic strengthening exponents for small deformations and for finite deformations grows on average by 20.19%. The highest growth may be observed with aluminium alloy and it amounts to 52.73%. Figs. 3 and 4 present the exemplary fatigue characteristics for the analysed materials determined with the assumptions of small and finite deformations theories.

N-A-Xtra 70 (X-tra)

N-A-Xtra 70 (X-tra)

1600

100

Engineering tension

Logarithm tension

1400

1200

10

1000

Engineering tension

800

1

 a , %

 a , MPa

600

Logarithm tension

400

0,1

200

0,01

0

10 0

10 1

10 2

10 3

10 4

10 5

10 6

0

20

40

60

80

100

a , %



N f , cykle

Fig. 3. Cyclic deformation curves (Ramberg-Osgood) and Manson-Coffin-Basquin according to small and finite deformations theories for N-A-Xtra 70.

1100Al

1100Al

250

100

Logarithm tension

Engineering tension

200

10

150

Engineering tension

1

 a , %

 a , MPa

Logarithm tension

100

0,1

50

0

0,01

10 0

10 2

10 4

10 6

0

20

40

60

80

100

a , %



N f , cykle

Fig. 4. Cyclic deformation curves (Ramberg-Osgood) and Manson-Coffin-Basquin according to small and finite deformations theories for aluminium alloy 1100Al.