Impact Test Calculator

Charpy and Izod Impact Tests

Pendulum impact tests measure how much energy a notched specimen absorbs when struck. The hammer rises to an initial height, strikes the sample, and swings to a lower final height. The energy difference is the absorbed impact energy.

Formula

$$E = m g (h_1 - h_2)$$

$m$ is pendulum mass, $h_1$ is initial height, and $h_2$ is height after impact. For normalized results, divide energy by specimen cross-section area (Charpy) or width (Izod).

Practical Notes

Standard Charpy specimens use a 10 mm by 10 mm cross section. Izod results are often reported per unit width. Enter dimensions in millimeters; the calculator converts to meters for area.

Frequently Asked Questions

What is the difference between Charpy and Izod tests?

Both use a pendulum striker, but specimen mounting and notch orientation differ. Normalization also differs: Charpy uses cross-section area; Izod often uses width.

Why measure initial and final heights?

The pendulum loses kinetic energy when it breaks the specimen. The height drop converts directly to absorbed energy via gravitational potential energy.

What pendulum mass should I use?

Use the actual hammer mass from your test machine. Common Charpy machines use roughly 20 to 25 kg pendulum masses.

What if final height exceeds initial height?

That would imply negative absorbed energy, which is not physical for a breaking test. Check height readings and units.

How is energy per area calculated?

Absorbed energy is divided by specimen area. For Charpy, area is width times thickness. For Izod, energy is divided by width only.

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Charpy and Izod Impact Tests

Formula

Practical Notes

Frequently Asked Questions

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