Metal Foams: A Design Guide

Time to failure (hours)
10 2
10 1
1
Tension
Compression
10−2 10−8 10−7 10−6 10−5 10−4 10−1 Monkman-Grant parameters
m = 0.96 log C = −2.21 (Tension)
m = 0.83 log C = −1.16 (Compression)
Creep strain rate (1/s)
Design for creep with metal foams 109
Figure 9.5 Time to failure in tension and compression plotted against
secondary creep strain rate for an open-cell aluminum foam for a range of
stresses and temperatures (Duocel aluminum 6101-T6 foam, Ł / s D 0.09;
Andrews et al., 1999)
9.5 Creep under multi-axial stresses
The secondary creep rate under multiaxial stresses is found using the constitutive
equation for metallic foams (equation (7.12)):
O 2 D
1
1 C ⊲˛/3⊳ 2 [ 2 e C ˛2 2 and
m ] ⊲9.6⊳
∂ O
Pεij D f⊲ O ⊳ ⊲9.7⊳
∂ ij
In uniaxial tension, we have that e D 11 and m D 11/3, giving O D 11.
For uniaxial stress we have that ∂ O /∂ 11 D 1 and we know that
� �n 11
Pε11 DPε0
0
giving
�
O
f⊲ O ⊳ DPε0
0
� n
9.6 Creep of sandwich beams with metallic foam cores
⊲9.8⊳
⊲9.9⊳
A sandwich beam of span ℓ and width b, loaded in three-point bending with
a concentrated load, P, is shown in Figure 9.6. The thicknesses of the face