Find useful definitions of many terms related to materials testing below. Have questions about a term or a suggestion for one that isn’t on the list? Feel free to contact us!

Ductility

Ductility

Governed by ASTM E8, ductility is the ability of a material to deform before fracture. For a more in-depth definition, explore our ductility page.

Elongation at Break

Elongation at Break

One measure of ductility governed by ASTM E8, elongation at break is obtained by pulling a specimen in tension until fracture. Read our elongation at break page to learn more about the process and how elongation is calculated.

Engineering Stress / True Stress

Engineering Stress / True Stress

Before rupture or break, ductile materials undergo plastic deformation. Engineering Stress and True Stress can tell us a lot about the forces before and after necking. Engineering Stress (ES) is the applied uniaxial tensile or compressive force at time i divided by the original cross-sectional area of the specimen. In contrast, True Stress (TS) is equivalent to the applied uniaxial tensile or compressive force at time i divided by the cross-sectional area of the specimen at time i.

Take a look at our engineering stress / true stress page to learn more about these measures and how they are calculated.

Gauge Length

Gauge length

The Gauge Length is the original length of the portion of the specimen over which strain, elongation, or the change of length is determined. Testing standards often specify a gauge length selection based on the material being tested. For further information on the effect of different gauge lengths on test results, click here.

Offset Yield