A method for developing stress-strain relationships using Nanoindentations

Abstract: This thesis is a material science research collaboration between the Division ofProduction and Materials Engineering at Lund Faculty of Engineering and theComputer-Aided Engineerings group at BorgWarner, Landskrona. The objectiveof the thesis is to explore the convertion of nanoindentation load-depth curves intotensile stress-strain curves, and to provide BorgWarner Landskrona with nanoin-dentation data on materials used in their standard production. The materials usedin the thesis includes unhardened and hardened steels as well as aluminium.The conversion of experimental deformation data from nanoindentation in thematerials into stress-strain parameters is made analytically based on well establishedcommon practice indentation theory. The direct results of extracting yield strengthand strain hardening exponent of the materials were deemed to be inconclusivedue to experimental effects, while a comparison between hardened and unhardenedregions and different materials was possible.Tensile tests of a C45 steel provided by the Division of Production and MaterialsEngineering where executed and used as reference material to confirm the validity ofthe analytical method. Scanning Electron Microscopy (SEM) was used to confirmthe radius of the chosen indenter, a spherical indenter with a radius of 25μm.Nanoindentation tests were performed with Nanotest Vantage from MicroMaterialsfor all nanoindentations. Simulations of nanoindentations were made in ANSYSWorkbench 2020 R1 and used to compare both simulation with experimental load-depth curves as well as stress-strain conversion results.Further recommendations are made to BorgWarner to execute in order to makeuse of the potential application of nanoindentation to extract stress-strain data fromunknown materials.