22
0
5 0
1 00
150
2 00
250
3 00
10
15
20
25
30
35
40
f (%)
X (%)
Temperature
0
C
f (%)
30
40
50
60
70
80
X (%)
e
e
Fig. 4.9 Variation of ε f and
area reduction (X %) with
temperature
D avg
model
=
-
´
=
å
1
100
1
N i
N
i
i
i
s
s
s
exp
exp
(4.4)
R
i
i
i
N
i
i
N
i
=
=
=
-
(
) -
(
)
å
-
(
)
å
-
s
s
s
s
s
s
s
s
exp
exp
mod
mod
exp
exp
mod
mo
1
2
1
d d
(
)
å
=
2
1
i
N
(4.5)
where s mod
i
and s exp
i
are the flow stress obtained from experiment and model, respectively. s exp and s mod are the mean
experimental and model values, respectively.
The absolute error and correlation coefficient between experimental and model value is calculated from Eqs. (4.4) and
(4.5), reported in Table 4.5. Good correlation was found between model and experimental data. A good agreement between
JC fit and experimentally obtained plastic flow stress at strain rates 10-4 s-1 and 10-1 s-1can be observed in Fig. 4.10.
Table 4.4 Johnson-Cook parameter of AA7475-T7351
A (MPa)
B (MPa)
n (MPa)
C
m
473.441
381.079
0.593
0.06614
1.0735
Table 4.5 Average absolute error and correlation coefficient data
Strain rate (s
−1
)
Average absolute error (Δ avg )
Correlation coefficient (R
%)
10
−4
1.337477
96.9163
10
−3
1.491383
96.8764
10
−2
1.717395
94.9178
10
−1
1.420802
96.7273
P. Chakraborty et al.