Impact Test
Calculate energy absorbed by a material during Izod or Charpy pendulum impact tests. Get absorbed energy, impact velocity, and height results with charts.
About This Calculator
The Impact Test Calculator determines the energy absorbed by a notched material specimen during a pendulum-based impact test, such as the Izod test or Charpy test. These tests evaluate the fracture toughness and impact resistance of materials including metals, plastics, composites, ceramics, and concrete under dynamic loading conditions. Engineers and materials scientists use impact tests to predict how materials will behave under sudden loads like vehicle crashes, bird strikes, falling objects, and shock loads in military and aerospace applications.
The calculator uses the pendulum energy method. When the striker is released from an initial angle β (angle of fall), it swings down and strikes the notched specimen, then rises to a final angle α (angle of rise). The energy absorbed by the specimen is calculated as E = mgS(cos α − cos β) − El, where m is the mass of the anvil, g is the gravitational acceleration (9.80665 m/s²), S is the distance from the center of rotation to the striker, and El accounts for energy losses due to bearing friction, windage, and machine vibration. The calculator also computes the impact velocity V = √(2gh) and the initial and final heights of the striker.
Regional Notes
India: Impact testing follows IS 1598 (Izod) and IS 1757 (Charpy) standards, widely used in quality control labs for steel, polymers, and automotive components. The National Accreditation Board for Testing and Calibration Laboratories (NABL) accredits impact testing facilities.
United States: ASTM standards govern impact testing — ASTM D256 for plastics (Izod), ASTM D6110 for plastics (Charpy), and ASTM E23 for metallic materials. Impact test results are critical for structural steel certification per ASTM A370 and for aerospace materials per ASTM E2298.
United Kingdom: BS EN ISO 180 (Izod) and BS EN ISO 179 (Charpy) are the primary standards for plastics impact testing. For metals, BS EN ISO 148-1 specifies the Charpy pendulum impact test method used across European and UK manufacturing quality assurance.
Frequently Asked Questions
What is an impact test?
An impact test measures the energy absorbed by a material specimen when struck by a pendulum hammer. The most common types are the Izod test and Charpy test, which evaluate fracture toughness and impact resistance of metals, plastics, ceramics, and composites under dynamic loading conditions.
How is the energy absorbed calculated in an impact test?
The energy absorbed is calculated using the formula E = mgS(cos α − cos β) − El, where m is the mass of the anvil, g is gravitational acceleration (9.80665 m/s²), S is the distance from center of rotation to striker, β is the angle of fall, α is the angle of rise, and El is the energy loss due to friction, windage, and bearing losses.
What is the difference between Izod and Charpy tests?
In the Izod test, the specimen is held vertically as a cantilever beam with the notch facing the striker, while in the Charpy test, the specimen is supported horizontally at both ends and struck at the center behind the notch. Both tests use a pendulum hammer and measure energy absorbed, but the specimen orientation and support differ per ASTM D256 (Izod) and ASTM D6110 (Charpy).
What types of specimens can be tested?
Impact tests can be performed on metals, plastics, composites, ceramics, and concrete. Specimens are typically notched to create a stress concentration, which promotes brittle fracture. Common standards include ASTM D256 for plastics, ASTM E23 for metallic materials, and ASTM D6110 for plastics (Charpy).
What is the impact velocity of the striker?
The impact velocity is calculated as V = √(2gh), where g is gravitational acceleration and h is the initial height of the striker. For a typical Izod or Charpy tester with a fall angle of 60° and arm length of 1 m, the striker velocity is approximately 3.13 m/s.
How do energy losses affect impact test results?
Energy losses (El) occur due to friction in the pendulum bearing and indicating mechanism, windage or air drag on the pendulum arm, vibration in the machine frame, and rubbing of the striker over the face of bent specimens. To estimate losses, perform a test with no target specimen and measure the pendulum's swing on both sides.
What failure modes can occur during an impact test?
Per ASTM D256, four failure scenarios are possible: Complete Break (C) where the specimen separates into two or more pieces, Hinge Break (H) where one part cannot support itself above horizontal, Partial Break (P) where the fracture extends at least 90% of the distance from notch vertex to opposite side, and Non-Break (NB) where the fracture extends less than 90%.
Why are impact tests important in materials science?
Impact tests are critical for understanding how materials behave under sudden, dynamic loads — such as vehicle crashes, bird strikes on aircraft, falling objects, and shock loading in military and space applications. The test results help engineers select materials with adequate fracture toughness and predict failure modes in safety-critical structures.