Fatigue Crack Paths 2003

60

60

50

50

P

σ =

40

40

wt

C T 1

400000 600000 N (cycles) C T S TSC S

800000

30

30

20

20

10

10

0

0

0

200000

0

200000 400000 600000

N (cicles)

Figure 4. Applied load history (in kN) for standard C(T) and modified CT1(VA).

Figure 5 shows the predicted and measured crack paths for the three modified speci

mens (in mm)under C A or V Aloading, presenting a very good match. This suggests

that the curved crack paths predicted under C A loading give good estimates of the

measured paths under V Aloading. Therefore, assuming that the Linear Elastic Fracture

Mechanics (LEFM)conditions apply, the discussed two-step methodology can be gen

eralized to the V Aloading case.

CT2(CA) 2mm203.02.5.0103i.0y18n.0 x in m m xmm23.i01n013 .020.025.0 T1( A) y i m m y2m3.018.0132.0x0.0nn25.m0mx C V

CT1(CA)

CT2(CA)

25.0

20.0

13.0

18.0

23.0 (mm)

13.0

18.0

23.0 (mm)

25.0

CT1(VA)

20.0

13.0

18.0

23.0 (mm)

Figure 5. Predicted and measured crack paths for the modified C(T) specimens (mm).

The SIF values calculated under C A loading along the crack path using the Que

bra2D program were exported to the

ViDa software to predict fatigue life, considering

load interaction effects. Figure 6 shows predicted and measured crack sizes for the

modified C(T) specimens under C Aloading.