Vickers hardness test simply explained скачать в хорошем качестве

Vickers hardness test simply explained

The Vickers hardness test was developed to overcome the limitations of the Brinell method, particularly for hard surface layers and thin materials. Unlike the Brinell test, which uses a hard metal ball, the Vickers method employs a four-sided diamond pyramid with an opening angle of 136°. This angle allows Vickers hardness values up to 400 HBW to be comparable with Brinell hardness values. The test force is maintained for 10 to 15 seconds before the indentation is evaluated under a light microscope. The hardness is determined by the ratio of test force to the indentation surface, with the diagonals of the indentation measured and their average calculated. The Vickers method is suitable for all hardness ranges because the pyramid produces geometrically similar indentations regardless of the test force, keeping the hardness value constant even when the test force is doubled. However, at lower forces, the elastic portion of deformation can lead to higher apparent hardness values. Therefore, hardness values should only be compared when measured with the same test force. The method is divided into three test ranges: macro load range (5 to 100 kiloponds), micro load range (0.2 to 3 kiloponds), and nano load range (0.01 to 0.1 kiloponds). The low-load and micro ranges are used for thin sheets, layers, and delicate components, as the indentation depth remains small, and the pyramid shape allows for precise measurement even for small indentations. This higher accuracy is an advantage over the Brinell method, where spherical indentations are more difficult to evaluate. For accurate hardness testing, minimum distances between indentations and from the sample edge must be observed, depending on multiples of the diagonal length. The minimum sample thickness should be at least 1.5 times the diagonal length. Diagrams help estimate the required thickness based on the test force and expected hardness. The Vickers method can precisely test even very thin layers. The standardized representation of hardness includes the hardness value, the test force, and the duration of the applied force. If the standard duration of 10 to 15 seconds is used, it can be omitted. Polished surfaces improve measurement accuracy by providing clear indentations. This makes the method less suitable for automated testing, leading to the development of the Rockwell test, discussed in the next video. 00:00 How is the Vickers hardness test carried out? 01:42 How is Vickers hardness calculated? 02:46 Minimum edge and indentation distance, and sample thickness 03:52 Comparability of hardness values 05:14 Test ranges (macro-, micro and nano-hardness) 06:57 Standard-compliant specification of Vickers hardness