PSI - Issue 2_B

Joern Berg et al. / Procedia Structural Integrity 2 (2016) 3554–3561 Joern Berg, Natalie Stranghoener, Andreas Kern, Marion Hoevel / Structural Integrity Procedia 00 (2016) 000–000

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were determined and the damage sum was evaluated for each specimen of the VAL fatigue tests, see Eq. (8).



 1/ m 



   

m   i 

n

N N

i

  

exp

eq   



D

(7)

(8)



n

i

calc

4. Experimental results and discussion As expected, all as welded test specimens failed due to crack initiation from the weld toes to the base material. Due to HFHP treatment the crack initiation changes and most of specimens failed due to crack initiation from notches in the base material. Only 3 of 9 HFHP treated specimens which were loaded with the highest stress ranges failed by crack initiation from the treated weld toes. Consequently, especially at lower stress ranges the fatigue life

CAL-AW VAL-AW CAL, AW VAL, AW

CAL-HFH VAL-HFH CAL, HFH VAL , HFH

CAL-AW VAL-AW CAL-AW

CAL-HFH VAL-HFH CAL-HFH

1280

1280

 (  max = f y )

 (  max = f y )

640

640

80 Stress range  nom,eq [N/mm²] 5  1 3 160 320 5,E+03

342

80 Stress range  nom [N/mm²] 5  1 3 160 320 5,E+03

342

125

125

  nom = k m    mem

  nom = k m    mem

5,E+04 5  1 4

5,E+05 5  1 5

5,E+06 5  1 6

5,E+04 5  1 4

5,E+05 5  1 5

5,E+06 5  10 6

Load cycles N f [-]

Load cycles N f [-]

CAL-AW VAL-AW CAL, AW VAL , AW

CAL-HFH VAL-HFH CAL, HFH VAL , HFH

CAL-AW VAL-AW CAL, AW

CAL-HFH VAL-HFH CAL, HFH

1280

1280

 (  max = f y )

 (  max = f y )

640

640

80 Stress range  mem [N/mm²] 5  1 3 160 320 5,E+03

80 Stress range  mem,eq [N/mm²] 5  1 3 160 320 5,E+03

262

262

99

99

5,E+04 5  1 4

5,E+05 5  1 5

5,E+06 5  1 6

5,E+04 5  1 4

5,E+05 5  1 5

5,E+06 5  1 6

Load cycles N f [-]

Load cycles N f [-]

a) VAL test results evaluated with  max

b) VAL test results evaluated with  eq

Fig. 5. nominal stress range with (a)  max and (b)  eq for VAL test results