Hardness is the property of a material that enables it to resist plastic deformation, usually by penetration. However, the term hardness may also refer to resistance to bending, scratching, abrasion or cutting. Hardness is a characteristic of a material, not a fundamental physical property. It is defined as the resistance to indentation, and it is determined by measuring the permanent depth of the indentation. More simply put, when using a fixed force (load) and a given indenter, the smaller the indentation, the harder the material. Indentation hardness value is obtained by measuring the depth or the area of the indentation using different test methods. The Rockwell hardness test method, as defined in ASTM E-18, is the most commonly used hardness test method. The Rockwell test is generally easier to perform, and more accurate than other types of hardness testing methods elastic recovery. This major load is then released, returning to the preliminary load. After holding the preliminary test force for a specified dwell time, the final depth of indentation is measured. The Rockwell hardness value is derived from the difference in the baseline and final depth measurements. This distance is converted to a hardness number. The preliminary test force is removed and the indenter is removed from the test specimen. In this method the specimens consists of hot rolled and cold rolled sheets with 2mm thickness and also these rolled sheets with TIG and Gas welding. The Rockwell hardness number is evaluated experimentally for those cases and studied. The Rockwell scale is a hardness scale based on indentation hardness of a material. The Rockwell test determines the hardness by measuring the depth of penetration of an indenter under a large load compared to the penetration made by a preload.
Hardness, sheet metal, Rockwell hardness number
