Tension/Compression
Tension: The rod is stretched a length ΔL when a force is applied parallel to its length. (b) Compression: The same rod is compressed by forces with the same magnitude in the opposite direction. For very small deformations and uniform materials, ΔL is approximately the same for the same magnitude of tension or compression. For larger deformations, the cross-sectional area changes as the rod is compressed or stretched.
Source
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"OpenStax College, Elasticity: Stress and Strain. January 16, 2015."
http://cnx.org/content/m42081/latest/
OpenStax CNX
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