34 Uniaxial tension testing

Uniaxial tension tests can be performed on either waisted cylinder or dogbone specimens. The specimens should be machined to the shape specified in ASTM E8-96a, to avoid failure of the specimen in the neck region or at the grips. The minimum dimension of the specimen (the diameter of the cylinder or the thickness of the dogbone) should be at least seven times the cell size to avoid specimen/cell size effects. Gripping is achieved by using conventional grips with sandpaper to increase friction, or, better, by adhesive bonding.

Displacement is best measured using an extensometer attached to the waisted region of the specimen. A typical tensile stress-strain curve for an aluminum foam is shown in Figure 3.4. Young's modulus is measured from the unloading portion of the stress-strain curve, as in uniaxial compression testing. The tensile strength is taken as the maximum stress. Tensile failure strains are low for aluminum foams (in the range of 0.2-2%). The standard deviation in the tensile strengths of aluminum foams, like that of the compressive strength, is between 5% and 15% of the mean. Typical data for the tensile strength of metallic foams are given in Chapter 4.

Strain

Figure 3.4 Stress-strain curve from a uniaxial tension test on a dogbone specimen of a closed-cell aluminum foam (8% dense Alporas) (from Andrews et al., 1999a)

Strain

Figure 3.4 Stress-strain curve from a uniaxial tension test on a dogbone specimen of a closed-cell aluminum foam (8% dense Alporas) (from Andrews et al., 1999a)

0 0

Post a comment