Crack Paths 2009

140

250

Experimental

120

Homogenou(sparent

100

200

material strength) Heterogneous(localwelds ength)

.5 )

a*m0

0

K e ff ( M P

24680

Experimental Homogenou(sparent material strength), [10] Heterogeneous(local w ld str ngth)

105 0

50

0 10 20 30 40 50 60 70

Δa (mm) 6

Δa

(mm)

0

2

4

8 10 12

eff

Fig. 5: comparison FEM-experiment, M(T) Fig. 6: comparison FEM-experiment,

specimen, 2W=160mm.

M(T)specimen, 2W=750mm.

PLASTIDC E F O R M A T IA ONNDC R A CPKA T H

The experiments [7, 8] recorded generally an instability of the crack path of the kind

shown in Fig. 7. After a few millimeters of propagation the crack jumps suddenly in the

TMAZ,characterized by a lower strength and fracture toughness [7].

Fig. 7: experimental crack path, [7].

From the optical strain measurements done with the A R A M I sSystem [7] the instant

of fracture instability corresponds to point 5 in Fig. 8, where te plastic zone has spread

910