Crack Paths 2012

KHexp vC 0C

(1)

where C0 is the initial volume fraction of cavities and is the fracture strain. Following

Lee and Huang [25], whobased their analysis on the Stowell et al. relationship [26], one

can express the cavity growth exponent K as follows [26]:

2 32

§ mm

m

ª

º

¸ ¸ ¹ ¸ ·

¨

«

»

(2)

K

23 1 sinh

¨ ¨ ©

«

»

« ¬

» ¼

where m is the strain rate sensitivity of flow stress.

Fig.7 compares the experimental values of cavitation (Cs%) with calculated values

(Cv%). Although this calculation is based on very rough assumptions, the model of

cavity growth controlled by plastic strain describes very well the observed cavitation

trend. It can be thus reasonably concluded that, in the investigated range of

experimental conditions, the cavity growth is mainly driven by plastic straining.

10

10

Cv250°C

Cs23500°C

Cv300°C

Cv400°C

Cs400°C

%

1

1

%

C

C

0,1

0,1

-5

-3

-4

log strain rate

Figure 7: experimental values of cavitation (Cs%) and calculated one (Cv%) Vs log

strain rate showing that both curves have similar trend at fixed T

This conclusion is supported by Fig. 8 which shows the fracture-mechanism map as

obtained by Ashby and co-workers [14] for 99%Al. The map also presents the

experimental conditions used in the present study. The analysis of Fig. 8 suggests that

the material investigated in the present study behaves like 99%Al. According to the

map, almost all the experimental conditions used in the present study fall in the region

of ductile and transgranular dimple fracture.

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