Indentation Characteristic Strain Determined Based on Metallic Material Damage

Characteristic strain is a key parameter connecting the hardness and flow stress for indentation experiments. However, there are significant difference between the characteristic strains obtained from previous models. In this work, the indentation characteristic strain is determined based on continuum damage mechanics for Al 5052. Combined indentation tests with the repeated loading-unloading tensile experiments, the indentation characteristic strain is deduced from the reduced Young’s modulus. The relationship between indentation characteristic strain and indent depth is established, and the limitation of indentation characteristic strain is determined as 0.12703. From the simulation study, average equivalent plastic strain (PEEQ) is calculated, which also is a function of indent depth. The limitation of average PEEQ is 0.11168, which well agrees with Tekkaya’s result (0.112). Furthermore, the relationship between indentation characteristic strain and average PEEQ is deduced.