Crack Paths 2009

The elastic-plastic

finite element analysis was performed by using the

incrementaltheory of plasticity with a von Mises flow rule and multilineal isotropic

hardening. The following Ramberg-Osgood material constants were introduced in a

0 σ =385 MPa, E=72 GPa, ν=0.33 and α =0.86. To analyze the effect

material model:

of hardening, two strain hardening exponents n=10 and 3 were considered.

As a result of calculations, the load-total displacement and load-crack opening

displacement curves were created. To determine the load versus plastic displacement

plv record (Fig. 2), the elastic displacement was subtracted from the total

displacementv, i.e. C− ⋅P. Thve compliance C was calculated from the elastic part of

the load versus total displacement curves.

500

400

300

L o a d , k H

200

100

0

0.1

0.2

0.3

0.4

0.5

Plastic displacement, m m

Figure 2. Load versus plastic displacement curves of the tension plate with an inclined

centre crack for n=10

Moreover, the load–plastic C O Dcurves (not shown) have been also obtained to analyze the plastic CTODplη factors for inclined cracks. In the original blunting crack, the

points of intersections 1 and 2 of two 45o lines, drawn back from the crack tip with the

deformed profile, are defined as the original measured points of the COD,as shown in

Fig. 3a. After mixed loading, the blunting profile is changed to a blunting-sharpening

model [6] and the C O Dis the line segment shown in Fig. 3b.

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