| Indentation test has been used to assess the mechanical properties of various materials, especially locally embrittled materials. It has a potential to replace a conventional uniaxial tensile test, although the interpretation of experimental results has not been standardized due to complex stress fields beneath the indenter. We intend to analyze the indentation response of a material with an advanced technique, which records the indentation depth continuously as a function of indentation load. The response of materials to indentation can be elastic/plastic deformation and cracking, or their combination. For a spherical indenter, the representative strain of materials can be expressed by the ratio of plastic depth to contact radius, while deformation response can be divided into three stages as load increases; elastic, elastic/plastic and fully plastic stage. At the first stage, material response is reversible. The ratio of mean pressure to flow stress increases at the second stage and third stage is characterized by the constant ratio of mean pressure to flow stress. In each stage, the ratio of mean pressure to flow stress can be taken. Therefore, we can derive the true stress -true strain curve by analyzing the ratio of mean pressure to flow stress through continuous indentation test. |
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