Metal Foams: A Design Guide

instead to:
�
Pε 3
D
Pε0 2
s
Ł
0
� n
9.4 Creep data for metallic foams
Design for creep with metal foams 107
⊲9.5⊳
The limited creep data for metallic foams are consistent with equation (9.3).
Figure 9.3 shows log(steady-state creep rate) plotted against log(stress) and
against 1/T for a Duocel 6101-T6 aluminum foam, allowing the power, n, and
activation energy, Q, to be determined. The measured creep exponent n D 4.5
Strain rate, (1/s)
Strain rate, (1/s)
10 −6
10 −7
10 −8
10 −4
10 −5
10 −6
10 −7
Compression
Tension
b
3
n = 4.8
4
n = 4.1
Stress (MPa)
T = 275°C
Compression, Q = 157 kJ/mole
Tension, Q = 174 kJ/mole
10−8 10−9 Regression
fits
σ = 42 MPa
0.0017 0.0018
1/ T (1/ °K)
0.0019 0.0020
5
Figure 9.3 Secondary creep strain rate plotted against (a) stress
(T D 275 °C) and (b) 1/ Temperature ( D 0.42 MPa) for an open-cell
aluminum foam (Duocel Al 6101 T6 foam, Ł / s D 0.09; Andrews et al.,
1999)
6
7
8
a
10