Crack Paths 2009

10*5

ll\"

Cgda/dNr(rm/cyacolre)cwakteh,

10*7

i Uncharged

\

(Hydrogencontent:

0.01 ppm)

6 Q6

Constant frequency

10*8

0 : f=2OHz

Frequency switched :

A zf=2Hz

El : f=0.02Hz

Hydrogen-charged

Constant frequency

9 : f=20Hz(0.53—>O.27ppm)

A : f=2Hz(0.58—>0.49ppm)

O : f=0.2Hz (0.58—>0.49ppm)

Frequencyswitched

V : f:2Hz(O.S8—>O.29ppm)

El : f=0.02Hz(0.58—>0.29ppm)

-10 10 10

20

30 40 50 60 708090100

Stress intensity factor range, A K ( M P a ~ / _ m )

Figure 4. Relationship between da/dNand AK. Material: S C M 4 3 5(H.Tanaka, et al[40])

5O

(0.56ppm

(056mm

i

i i

\l \ [ll]

lppm ‘

AK‘=. 17

(d/(1N)h/(da/dzv)air

I

TM'MPaJ'm

H”

l l

.Sppm)

052mm)

50 M P a f m

l

60 M P w / ‘ m

l

0.49ppm)

)

0.1

1

10

100

0.01

Test frequency, f (Hz)

Figure 5. Relationship between acceleration of crack growth rate (da/dN)h/(da/dN) air

and frequency f. Material: S C M 4 3 5(H. Tanaka, et al[40])

Figure 6 shows the crack shapes and slip bands morphologies. The crack of the

hydrogen charged specimen looks thinner than the uncharged specimens. The crack

paths of the hydrogen charged specimens tested under f : 0.2 and 2Hz are relatively

more linear than those of the uncharged specimens and also that of the hydrogen

20