Explanation

Also known as initial impact. An indicator of the mechanical properties of materials. It represents the ability of materials (or components) to resist impact damage. In the one-time impact test, it is expressed by the energy absorbed by the unit area breaking when the sample is damaged by impact (klm2). The commonly used Charpy test uses ^ B=Eh [B (W-a)] to calculate the impact strength, where Eb is the energy absorbed in the fracture process, and i3 and W are respectively the width, thickness and notch depth of the sample. The impact strength of materials is a structure sensitive property. Influenced by the composition, process, hot working history, organizational structure and directionality of materials, it is more sensitive to the internal defects of materials, so it can be used as an indicator to judge the quality of materials and evaluate the brittle fracture trend of materials. However, due to the correlation between the measured values and the size and shape of the sample, machining accuracy, impact loading speed, and characteristics of the testing machine, the measured values fluctuate greatly and require multiple tests under the same conditions to take the average value. The impact resistance of materials is closely related to the ambient temperature. Below a certain temperature, the cold brittleness of impact strength will decrease significantly. The cold brittleness is more obvious in body core or closely packed hexagonal metal. In addition, since the impact fracture process includes three stages of materials elasticity, plastic deformation and crack propagation, the actual performance of different materials with the same impact strength will be very different, and it is often necessary to measure the impact load deformation curve at the same time for reasonable material selection. According to the actual loading conditions, the commonly used impact test is divided into tensile impact, torsional impact and bending impact. China has also developed a small energy multiple impact test method suitable for working components under dynamic loads

Classification