Tensile Properties - ASTM D638

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Tensile testing is performed by elongating a specimen and measuring the load carried by the specimen. From a knowledge of the specimen dimensions, the load and deflection data can be translated into a stress-strain curve. A variety of tensile properties can be extracted from the stress-strain curve.

Tensile Test

Property	Definition
Tensile Elongation at Break	Tensile elongation corresponding to the point of rupture.
Tensile Elongation at Yield	Tensile elongation corresponding to the yield (an increase in strain does not result in an increase in stress).
Tensile Strength at Break	Tensile stress corresponding to the point of rupture.
Tensile Strength at Yield	Tensile stress corresponding to the yield point (an increase in strain does not result in an increase in stress).
Tensile Strength	Tensile stress at a specified elongation.
Tensile Strength, Ultimate	The highest tensile stress a material can support before failing.
Tensile Modulus	The ratio of tensile stress to tensile strain of a material in the elastic region of a stress-strain curve. A "Tangent" tensile modulus value is the slope of the elastic region of the stress-strain curve and is also known as Young's Modulus, or the Modulus of Elasticity. A "Secant" tensile modulus value is the slope of a line connecting the point of zero strain to a point on the stress-strain curve at a specified strain. This is used for materials that exhibit little or no linear behavior.

Illustration of Tangent and Secant Tensile Moduli

Test Specimen Summary

Specimen	Rigidity Case	Note	Thickness
Type I	Rigid	Preferred specimen.	<7 mm (0.28 in)
Type II	Rigid	Use when Type I specimen does not break in the narrow section.	<7 mm (0.28 in)
Type III	Rigid/Nonrigid		>7 mm (0.28 in) <14 mm (0.55 in)
Type IV	Rigid/Nonrigid	Should be used for comparison between materials in different rigidity cases. Essentially the same as Die C specimen from ASTM D412.	<4 mm (0.16 in)
Type V	Rigid	Used when limited material is available or laboratory space is a concern (for environmental testing)	<4 mm (0.16 in)

Type I, II, III, and V Specimen

Type IV Specimen

Similar Standards

• ISO 527-1,-2