Impact testing has developed rapidly since its invention around 1905, becoming an indispensable part of material performance testing. Initially, various testing methods existed, but with advancements, Charpy lock-notch impact testing, Charpy V-notch impact testing, and Charpy-McClover impact testing gained prominence. Before 1968, the United States primarily used the Charpy lock-notch impact test. However, this method had a drawback: due to the blunt notch, the brittle transition temperature was determined to be lower than the brittle fracture temperature of the structure. Therefore, after 1968, ASTM standards adopted the standard Charpy V-notch specimen. Thus, the use of V-notch and McClover impact specimens is more common. Generally, Europe and America predominantly use the Charpy V-notch, while Russia uses the Charpy-McClover specimen.
Impact testing in my country was virtually nonexistent before the founding of the People's Republic of China. After the liberation, China fully adopted the Soviet model, and the first impact testing standard, GB229-1963, was not published until 1963. The latest standard we use is GB/T229-2020, "Metallic Materials - Charpy Pendulum Test Method," which is also applicable to American and European standards. The principle of impact testing machines is based on the law of conservation of energy, calculating the impact energy based on the amount lost after the pendulum breaks the impact specimen. However, this testing method inherently has a drawback: unlike tensile testing machines, it cannot directly display the force-displacement curve. This is because the measured result is only impact energy, a unit of energy measured in joules. The formula for energy is: W = FS, i.e., Impact Energy = Force * Displacement. Therefore, any change in either of these variables will cause a change in impact energy, especially displacement. Thus, the impact energy value cannot directly indicate the toughness of a material or describe the changes in the material during impact; it can only serve as a reference. To solve this problem, instrumented impact testing methods were invented.
