Crack Paths 2012

In Figures 5(b), the F E Aresults of the variation of SIFs around the crack contour for

angular misalignments are shown. The distribution of SIFs depends on the direction of

angular misalignment. The maximumSIF is observed at the degree of zero (θ=0), and

the minimum SIF is observed at the degree, π (θ=π). The angular misalignments

increases, asymmetric crack growth is also accelerated so that the time to reach the

critical SIF decreases, and, for example, the normalized time to failure with 0.4° of the

angular misalignment decreases by almost 31% by comparing with that without any

misalignment as shown in Figure 6(b). However, this level of the angular misalignment

is very possible practically, so, it can cause a large scatter of test results and prevent

quantitative analysis of fatigue crack growth behavior of C N Bspecimens. As shown in

Figure 7, it can be confirmed that the crack propagation contours obtained from F E A

and the experimental result are similar each other.

01.46802468

01.46802468

N/Nf0=0.136236 N f0 489

Degree(T) N/Nf0=0.685016 C0.020_A0.0

0

3S/4

5S/4 3S/2 7S/4 2S

S/4 S/2 N/Nf0=0.136236

S N/Nf0=0.6591 C0.000_A0.4

N/N f0 =0.489

0.02

0.02

0

3S/4

5S/4 3S/2 7S/4 2S

S/4 S/2

S

Degree(T)

(a) Concetric misalignment (e/R=0.02)

(b) Angular misalignment (eθ =0.4)

Figure 5. The example of the variation of normalized SIFs at the crack contour for

concentric and angular misalignment

1.00

1.00

0.95

0.95

0.90

0.90

0.85

0.85

0.80

0.80

0.75

0.75

0.70

0.70

0.65

0.65

0.000

0.005

0.010

0.015

0.020

0.0

0.1

0.2

0.3

0.4

Angularmisalignment

Normalizedconcentricmisalignment,e/R

(a) Concentric misalignment

(b) Angular misalignment

Figure 6. Variation of the normalized time to failure for various concentric and angular

misalignments

260