Charpy Impact Test: Definition, History, Importance, How To Calculate, and Procedures
What Is Charpy Impact Test?
The Charpy Impact Test is a form of testing used to determine the fracture toughness of metals. The test is performed by striking a metal sample with an impacting tool, such as a hammer or pendulum, and measuring the amount of energy required to fracture the material. The test is often used to evaluate the tensile strength and ductility of metals, as well as the resistance to brittle fracture.
In this test, a notched sample of metal is subjected to an impact force by a swinging pendulum. The pendulum is released from a certain height, and its impact energy is measured when it breaks the sample. The energy required to break the material is the Charpy Impact Energy and is usually expressed in joules (J). The higher the impact energy, the more ductile and tough the material is.
History of Charpy Impact Test
The Charpy Impact Test was developed in the early 1900s by Frenchman Georges Charpy. Charpy was studying the fracture toughness of steel and iron and realized that the impact test could be used to measure the energy required to fracture the material. He developed the first standardized Charpy Impact Test in 1911.
Since then, the Charpy Impact Test has become one of the most widely used tests for evaluating the fracture toughness of materials. It is used in various industries, including automotive, aerospace, and construction, for quality control and failure analysis.
Importance of Charpy Impact Test
The Charpy Impact Test is an important tool for evaluating the ability of a material to withstand brittle fracture. It is particularly useful for testing metals susceptible to brittle fracture, such as low-carbon steels and cast irons. By measuring the energy required to fracture the material, engineers can determine if the material has sufficient ductility and toughness to withstand dynamic loads and vibrations.
The Charpy Impact Test is also useful for determining the notch sensitivity of a material. It allows engineers to determine how much of an effect the presence of a notch will have on the material’s fracture toughness. This can be useful for design purposes, as it can help engineers develop materials that are less susceptible to brittle fracture.
How To Calculate Charpy Impact Test Results
The Charpy Impact Test results are calculated by measuring the impact energy of the pendulum when it fractures the test sample. The impact energy is usually expressed in joules (J). Generally speaking, the higher the impact energy, the more ductile and tough the material is.
In addition to the impact energy, the Charpy Impact Test results will also include the percentage of elongation and the percentage of reduction in area. These values provide further information about the material’s ductility and toughness.
Charpy Impact Test Procedures
The Charpy Impact Test procedure is relatively simple and straightforward. The following steps outline the general procedure for conducting the test:
- Select a sample of material and cut it to the desired size.
- Notch the sample according to the standard test procedure.
- Mount the sample in the testing apparatus.
- Adjust the pendulum to the desired height.
- Release the pendulum and measure the impact energy when it breaks the sample.
- Calculate the elongation and reduction in the area of the sample.
- Compare the results to the expected values for the material.
The Charpy Impact Test is a simple and effective way to evaluate the fracture toughness of materials. By measuring the impact energy required to break the sample, engineers can determine the material’s flexibility, toughness, and susceptibility to brittle fracture.