Ductility is a mechanical property of materials that refers to the degree of plastic deformation a material can sustain prior to fracture. If little or no plastic deformation can occur, the material is brittle. You can express ductility in terms of either a percent elongation or a percent reduction in an area. However, the values for percent elongation and percent reduction in area are not necessarily the same for the same material.

## Calculating Percent Elongation

## Measure Gauge Length

Measure the original gauge length (Lo) of the material around the point of intended fracture. This value is commonly 2 inches or 50 millimeters.

## Apply Tensile Force

Apply a tensile force to the material slowly until fracture occurs.

## Measure Fracture Length

Fit the broken parts back together and measure the fracture length (Lf), using the same endpoints on the material as the initially measured gauge length.

## Work out Elongation

Calculate the percent elongation using the equation 100 x (Lf-Lo) ÷ Lo.

## Calculating Percent Reduction in an Area

## Measure Diameter

Measure the diameter of the solid cylindrical material to be tested (d).

## Find Area

Calculate the original cross-sectional area (Ao) of the rod by inserting the diameter into the equation pi x (d ÷ 2)^2.

## Apply Tensile Force

Apply a tensile force to the material slowly until fracture occurs.

## Find Area at Point of Fracture

Measure the diameter of the cylinder at the point of fracture (df) then calculate the cross-sectional area at the point of fracture (Af), using the same equation.

## Apply Equation

Calculate the percent reduction in area using the equation 100 x (Ao-Af) ÷ Ao.

#### TL;DR (Too Long; Didn't Read)

The magnitude of percent elongation depends on specimen gauge length and therefore it is customary to specify the initial gauge length when reporting the percent elongation.

#### Warning

Metals tend to become more brittle in lower temperatures and more ductile in higher temperatures.