tension engineering stress vs true stress

When a ductile material is loaded beyond its Ultimate Tensile Strength, necking occurs and the cross sectional area and applied force both decrease. 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.Ī i = Cross Sectional Area of Specimen at time, iĭuctile materials undergo plastic deformation prior to rupture or break. If any portion of the fracture occurs on or outside a gauge mark, Elongation may not be representative of the material.ĪSTM E8 governs the determination of Elongation for Metals.Įngineering Stress (ES) is equivalent to the applied uniaxial tensile or compressive force at time, i divided by the original cross sectional area of the specimen.Ī o = Original Cross Sectional Area of Specimen

In reporting Elongation, both the original gauge length and percentage increase are to be reported.

The change in gauge length, ΔL, is determined by carefully fitting the ends of the fractured specimen together and measuring the distance between the gauge marks. ΔL is the change in length of the original gauge length measured after the specimen fractures and the specimen is fitted togetherĪ punch is often used to apply the gauge marks to each specimen. Elongation is expressed as a percentage of the original gauge length and is given by: Elongation is defined as the increase in the gauge length, L o, of a test piece subjected to tensile forces divided by the original gauge length. The conventional means by which we obtain Elongation is by pulling a specimen in tension until fracture. Elongation at Break or Elongation is one measure of ductility.

Tension engineering stress vs true stress