In materials science, the Charpy impact test (also known as the Charpy V-notch test) is a standardized high-strain-rate test used to determine the energy absorbed by a material during fracture. The absorbed energy is a measure of the material’s notch toughness.
The test determines the toughness of a material by measuring the energy absorbed when the material is subjected to a sudden impact, particularly for evaluating the brittle behavior of materials at low temperatures.
The Charpy impact test was invented by Georges Augustin Albert Charpy (1865–1945) in 1900 and is considered one of the common tests for quickly and economically assessing the relative toughness of materials.
Test Principle
The test involves clamping a machined specimen (of specified dimensions, typically 55 mm × 10 mm × 10 mm) at both ends, with a precisely machined notch of specific dimensions, as a simple beam. A pendulum strikes the specimen, and the starting and ending heights of the pendulum are measured. The difference in height equals the energy absorbed by the specimen before fracture. This absorbed energy is usually measured in joules using a scale attached to the machine.
Specimen
Standard specimens with a notch (typically V-shaped or U-shaped) are used.
The notch simulates stress concentration in the material, providing a more realistic reflection of the material’s impact resistance.
| Standard | Standard Specimen Dimensions (mm) | Sub-sized Specimen Dimensions (mm) |
| ASTM A370 | 10 × 10 × 55 | 10 × 7.5 × 55, 10 × 6.7 × 55, 10 × 5 × 55, 10 × 3.3 × 55, 10 × 2.5 × 55 |
| EN 10045-1 | 10 × 10 × 55 | 10 × 7.5 × 55, 10 × 5 × 55 |
| ISO 148 | 10 × 10 × 55 | 10 × 7.5 × 55, 10 × 5 × 55, 10 × 2.5 × 55 |
| MPIF Standard 40 | 10 (±0.125) × 10 (±0.125) × 55 (±2.5) | Unnotched specimens |
Test Equipment
A pendulum-type impact testing machine is used.
The pendulum is released from a certain height to strike and fracture the specimen.
Measurement Parameters
The energy difference before and after the pendulum fractures the specimen is recorded as the absorbed energy (impact energy).
Higher impact energy indicates better material toughness.
With technological advancements, measurements can now be obtained with computer assistance.
Test Procedure
- Prepare a standard specimen and machine a notch on it.
- Fix the specimen on the support base of the testing machine.
- Release the pendulum to strike the specimen.
- Record the energy absorbed during the fracture of the specimen.
Result Representation
Results are typically expressed in impact energy (joules or ft-lbs).
Fracture surface morphology can also be analyzed to determine the fracture mode (ductile or brittle fracture).
Applications
Material Selection:
Used to evaluate the toughness of metals, plastics, composites, etc.
Quality Control:
Detects whether the material’s impact performance meets standards during manufacturing.
Low-Temperature Performance Evaluation:
Particularly suitable for assessing the brittle behavior of materials in low-temperature environments (e.g., liquefied natural gas equipment, polar facilities).
Advantages of the Charpy Impact Test
Simple, fast, and cost-effective.
Effectively evaluates material toughness and impact resistance.
Relevant Standards
ASTM E23: Standard Test Methods for Notched Bar Impact Testing of Metallic Materials.
ISO 148: Metallic Materials—Charpy Pendulum Impact Test.
Summary
The Charpy impact test is an important material testing method for evaluating the toughness of materials under impact loading, especially for assessing material performance in low-temperature environments. Through this test, it is possible to determine whether a material is suitable for use under specific conditions.
For more information about Charpy Impact Test, please contact SSM. We provide product and technical service support.
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