Numerical Study on the Regression Method to Eliminate the Influence of Surface Morphology on Indentation Hardness of Thin Films

Abstract

The surface morphology of specimens significantly affects the measurement accuracy of indentation hardness. Surface undulation leads to dispersion in measured hardness and makes it very difficult to obtain an accurate hardness. In the past, mechanical polishing and increasing the indentation depth were widely performed to decrease the influence of surface morphology. However, both methods have limitations for the hardness measurement of small-scale structures such as thin films or coatings. Thus, obtaining an accurate hardness measurement from one or two simple indentation tests is of great application value. In this study, we introduced a new regression method to eliminate the influence of surface undulation on hardness measurements. We simulated the indentation tests of thin films with undulating surfaces by finite element simulation and then analyzed the regularity of the measured hardness. The numerical simulations validated that the regression method can effectively eliminate the influence of surface undulation and obtain the accurate hardness of materials. This method breaks through the limitations of conventional methods, simplifies the testing workload, and improves measurement accuracy.