Crack Paths 2012

The influence of stress triaxiality on the stress concentration near a spherical pore was

investigated, using the finite element model shown on figure 2a, representing one eight of a

pore in a cube (5 times as large as the radius of the hole) with symmetry conditions enforced

on the three faces that cut the pore and uniform stresses applied in one, two or three

directions, as illustrated by the colored arrows.

Figure 2: Models used to compute a) the stress concentration near a spherical pore b) KI along the

front of an annular crack initiated from a pore under uniaxial, biaxial or triaxial tension

The stresses along the edges cutting the pore were extracted and the stress concentration deduced

from the values in the first element near the pore. The influence of stress triaxiality on the stress

intensity factor for an annular crack initiated from the pore was investigated, using the mesh shown on

Fig. 2b.

E X P E R I M E N TRAE SLU L TASN DN U M E R I C ANLA L Y S I S

Preliminary computations.

Figure 3 shows the contours of the first principal stress at three moments of a thermal shock

with ΔT=294°C. A weak tension first appears near the edges of the specimen at 45° to the

symmetry axis, then the tension peak is progressively displaced towards the inside and rises.

Finally the maximumtension occurs at mid-height on the symmetry axis.

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Figure 3: contours of the first principal stress at various momentsof a shock

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