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Glossary
M10-94400-1
Depending on the type of loading represented by the
stress-strain diagram, modulus of elasticity may be re-
ported as: compressive modulus of elasticity (or modu-
lus of elasticity in compression); flexural modulus of
elasticity (or modulus of elasticity in flexure); shear
modulus of elasticity (or modulus of elasticity in shear);
tensile modulus of elasticity (or modulus of elasticity in
tension); or torsional modulus of elasticity (or modulus
of elasticity in torsion). Modulus of elasticity may be de-
termined by dynamic testing, where it can be derived
from complex modulus.
Modulus used alone generally refers to tensile modulus
of elasticity. Shear modulus is almost always equal to
torsional modulus and both are called modulus of rigid-
ity. Moduli of elasticity in tension and compression are
approximately equal and are known as Young's modu-
lus. Modulus of rigidity is related to Young's modulus
by the equation:
E = 2G(1+r)
where E is Young's modulus (psi), G is modulus of rigid-
ity (psi) and r is Poisson's ratio. Modulus of elasticity
also is called elastic modulus and coefficient of elasticity.
Modulus of Rigidity.
Rate of change of strain as a function of stress in a speci-
men subjected to shear or torsion loading. It is the modu-
lus of elasticity determined in a torsion test. Alternate
terms are modulus of elasticity in torsion and modulus
of elasticity in shear.
Apparent modulus of rigidity is a measure of the stiff-
ness of plastics measured in a torsion test (ASTM D-
B-20
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