# How to Calculate Ductility

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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.

1. ## Measure Gauge Length

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

3. ## Apply Tensile Force

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

5. ## Measure Fracture Length

6. 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.

7. ## Work out Elongation

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

1. ## Measure Diameter

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

3. ## Find Area

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

5. ## Apply Tensile Force

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

7. ## Find Area at Point of Fracture

8. 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.

9. ## Apply Equation

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

#### Tips

• 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.

#### Warnings

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