Fatigue Crack Paths 2003

102.0

CrackPathon Front Side

68.0

-0248642.0

y = 0.8306x- 2 0 . 3 0 7

]

m

[ m

c o o r d i n a t e

Z

y = -0.8423x+ 2 0 . 8 8 3

ncroatckhat 0-4d0edge.g. + 4 0deg. Linear(crack at + 4 0deg. )

Linear(crack at -40 deg.) C r a c k P t h o n B a c k S i d e

-120.0

16.0 18.0 20.0 22.0 24.0 26.0 28.0 30.0 32.0 34.0 36.0

X c o o r d i n a t[em m ]

102.0

68.0

-024642.0

y = 0.8031x - 20.293

m m ]

c o o r d i n a t e [

Z

y = -0.8476x + 21.408

ncroatckh at 0 deg.

crack at -40 deg. +39 deg. Linear (crack at +39 deg.)

-1-208.0

Linear (crack at -40 deg.)

16.0 18.0 20.0 22.0 24.0 26.0 28.0 30.0 32.0 34.0 36.0

X coordinate [ m m ]

Figure 2. Crack Path on the front and backside of the CT-specimen tested in nitrogen

at 83 Hz (load decreasing test).

Fig. 3 right. Following the solution for a forked crack with b/a = 0.1 from Kitagawa et

al. [9] the local mode I stress intensity factor k1 for an angle α of 38° is approximately

65%of KI. The local modeII stress intensity factor k2 is approximately 28%of KI. If the

b/a-ratio is bigger than 0.5 the local stress intensities can be calculated from a kinked

crack with an inclined angle β = 90° - α:

() s i n β

kKI1

=

(1)

2