The influence of crack forms on indentation hardness test results for ceramic materials

In this work, the influence of crack forms [radial crack (RC) and half-penny crack (HPC)] on indentation hardness test results of ceramic materials (We/Wt = 0.3–0.7) was studied by finite element analysis and verified by experiments. Excluding the influence of size effect, the values of HPC and RC indentation hardness from instrumented indentation tests on five ceramic materials (Si3N4, ZrO2, ZTA, Al2O3, and silica) were compared with that of “Non-Crack” indentation hardness. The results show that the influence of RC or HPC on indentation hardness test results of isotropic and homogeneous ceramic materials is verified to be negligible, both analytically and experimentally. But the “Pop-in phenomenon” is found to have a great impact on indentation hardness test results for ceramic materials. Therefore, in the absence of “Pop-in phenomenon,” the test results of indentation hardness of ceramic materials were practically reliable. This work provides a theoretical foundation for further study on instrumented indentation for determining the elastic–plastic properties and fracture toughness of ceramic materials.