Crack Paths 2012

Figure 10; crackpathes Figure 1]: Zoomon notch

Experiments

Sometests have been performed to validate the hypotheses for L E F Mand to verify the

propagation law (in mode I, Fig. 12). A first fatigue test was carried out with a load

oscillating between 1.8 and 18kN(load ratio 0.1) on a specimen of 3mm-thickness in a

hardened aluminium alloy. It led to a too large stress inducing large scale plasticity. The

crack propagated very fast (16000 cycles, 2 0 m mbefore sudden rupture) and it

encountered a rotation of 45° (Fig. 13), typical of plasticity. This was expected as the

theoretical stress (simulated without plasticity) exceeded 1400 M P ain the notch area.

Figure 12:

Figure 13: Crack surface

Experiment

Further experiments are being carried out at the time this documentwas written.

C O N C L U S I O N S

Thoughthe experiments have not yet been carried out completely, the present workhas

shown that the simulation in particular with X F E Mis a powerful tool to set up an

experiment and verify assumptions. Experiments will then enable to validate more

precisely the assumptions.

R E F E R E N C E S

[1] G. Irwin. Analysis of stresses and strains near the end of a crack traversing a plate.

Journal ofApplied Mechanics, 24:361—364, 1957.

[2] N. Moés, J. Dolbow, T. Belytschko. A finite element method for crack growth

without remeshing,Internat. J. Numer.MethodsEngrg,46, 131-150, 1999.

[3] Morfeo, http://www. cenaero. be.

[4] H M .Westergaard. Bearing pressures and cracks. Journal ofAppliea' Mechanics, 49

53,1939.

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