Integration of nanoindentation and finite element method for interpretable tensile properties: A cross-scale calculation method of uneven joints

Abstract

Nanoindentation testing and its Reverse Analysis Method (RAM) show great potential in understanding the tensile properties of metallic alloys with various microstructures. Nevertheless, the tensile properties of heterogeneous materials such as nickel-based superalloy welded joints have not been well interpreted by combining the microstructures and nanoindentation results, due to their diverse and complex microscopic zones, which throws shade on the properties of separated zones in the material. Here we demonstrated a new method of implanting nanoindentation results into Finite Element Method (FEM) and applied the method to the welded joints with the zones of various microstructure features. The local properties are calculated by the nanoindentation data using RAM, and used as input of Finite Element (FE) simulation of an identical indentation process, to in turn verify the accuracy and reliability of the reverse model. The simulation results reveal that the global mechanical behaviors, such as Young's modulus, yield strength and strain hardening exponent, are related to the local properties to a great extent. Thus, the global properties can be verified by simulation straight after experiments, taking consideration of local properties and dimension parameters of different zones. It is shown that the maximum error between calculation of RAM and testing is within 5.1% in different zones, and the errors of maximum indentation depth and residual depth obtained by FE simulation are less than 2.4%, which indicates that the method provides a reliable prediction of mechanical properties of superalloy welded joints.