Impact Test Calculator - Charpy and Izod

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Charpy uses a simply-supported horizontal specimen; Izod clamps the specimen vertically. The energy formula is identical but specimen dimensions and standards differ.
Choose heights if your machine reads initial and final heights directly, or angles if you know the arm length and the release and rebound angles.
Height of the pendulum striker above the specimen plane before release.
m
Height reached by the striker after breaking the specimen.
m
Mass of the pendulum hammer and striker combined.
kg
Maximum rated energy of the testing machine (e.g. 150 J, 300 J). Used to compute capacity utilization.
J
Parasitic energy lost to friction and air resistance. Often given in the machine certificate. Enter 0 if unknown.
J
Width of the specimen at the notch plane (standard Charpy/Izod: 10 mm).
mm
Thickness of the specimen (standard: 10 mm). Not used if notch depth is entered.
mm
Depth of the notch. Net cross-section area = width x (thickness - notch depth). Standard V-notch: 2 mm.
mm
Energy absorbed (E)Valid range (20-80% capacity)
97.09

Energy transferred to the specimen during fracture, after subtracting friction losses.

Energy unitJ
Impact strength (aK)1,213.57
Impact strength unitkJ/m²
Capacity utilization32.4%
Impact velocity (V)3.96
Velocity unitm/s
Initial height (h1)0.8
Final height (h2)0.35
Net cross-section area0.8
32.4% %
Low (< 20%)<20%Valid range (20-80%)20%-80%High (> 80%)80%+

Charpy impact energy: 97.09 J

  • The specimen absorbed 97.09 J of energy during the Charpy test.
  • Impact strength at the notch is 1213.57 kJ/m², which characterises the material's toughness per unit area.
  • Capacity utilization is 32.4%, well within the recommended 20-80% window for reliable results.
  • Absorbed energy is moderate, typical of structural steels that meet the 27 J minimum Charpy toughness requirement.

Next stepCompare the result against the material specification or run tests at multiple temperatures to map the ductile-to-brittle transition curve.

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