Crack Paths 2009

whereas the ratio between the upper and the lower limits are found to be about equal to

1.3/0.8=1.6 (Fig. 2). The strong variability of the non-dimensional radius R/R0 (notch

root radius to control volume radius ratio, ranging here from about zero to about 500)

makes stringent the check of the approach based on the local SED. The same

scatterband was recently obtained by summarising failure data from 20 different

ceramics, 4 P V Cfoams and some metallic materials [13].

01.6824681

Gomezet al., 2009. Pointed V-notches Mixed mode(I+II) R=0

Ayatollahi and Aliha, 2009 Cr cks, R0=0.1 m m

C W

R/R0

Chen and Ozaki, 2008

Pointed V-notches, mixed mode (I+II)

R0=0.07 m m

P M M A ,-60°C, U-notch, 0

P M M A ,-60°C, U- e V-notch, 0.05

P M M A ,RoomTemp.,V-notch, R≈0, 15°<2α<150°, R0=0.011mm, mode I

0.24

P M M A ,RoomTemp., U-notch, 0.1

0 = 0 . 0 1 1 m m , odeI

0.0

0.0

0.1

1.0

10.0

100.0

1000.0

Figure 2. Static failure data in terms of normalised strain energy density

F R A C T U RINEITIATIOAN N G LFEO RB L U NNT O T C H E S

Dealing with P M M sApecimens weakened by U-notches, the values of the initial crack

angle, ϕ, at the notch tip (see Fig. 3) are recorded in Table 1, together with their mean

value <ϕ>. For the sake of brevity only the data referred to inclined notches are

summarised in the table (see Refs [6, 7] for more details).

crack

R

path

0

R 2

Ω

- θ

θ

ϕ

R

0

ρ=0.05 m m

r θ 0

r

0

P

R 1 (θ)

O’

Ω

(a)

(b)

Figure 3.Control volume under modeIand mixed mode loading. Angle ϕ gives the

fracture direction, evaluated experimentally in the vicinity of the notch edge.

996