Characterization of Material Properties Based on Inverse Finite Element Modelling

Jamal Jamal,Morgan Morgan

doi:10.3390/inventions4030040

Abstract

This paper describes a new approach that can be used to determine the mechanical properties of unknown materials and complex material systems. The approach uses inverse finite element modelling (FEM) accompanied with a designed algorithm to obtain the modulus of elasticity, yield stress and strain hardening material constants of an isotropic hardening material model, as well as the material constants of the Drucker–Prager material model (modulus of elasticity, cap yield stress and angle of friction). The algorithm automatically feeds the input material properties data to finite element software and automatically runs simulations to establish a convergence between the numerical loading–unloading curve and the target data obtained from continuous indentation tests using common indenter geometries. A further module was developed to optimise convergence using an inverse FEM analysis interfaced with a non-linear MATLAB algorithm. A sensitivity analysis determined that the dual spherical and Berkovich (S&B) approach delivered better results than other dual indentation methods such as Berkovich and Vickers (B&V) and Vickers and spherical (V&S). It was found that better convergence values can be achieved despite a large variation in the starting parameter values and/or material constitutive model and such behaviour reflects the uniqueness of the dual S&B indentation in predicting complex material systems. The study has shown that a robust optimization method based on a non-linear least-squares curve fitting function (LSQNONLIN) within MATLAB and ABAQUS can be used to accurately predict a unique set of elastic plastic material properties and Drucker–Prager material properties. This is of benefit to the scientific investigation of properties of new materials or obtaining the material properties at different locations of a part which may be not be similar because of manufacturing processes (e.g., different heating and cooling rates at different locations).

Highlights

In this paper, outcomes of a research study concerned with the application of indentation processes with different indenter geometries are reported
It was found that better convergence values can be achieved despite a large variation in the starting parameter values and/or material constitutive model and such behaviour reflects the uniqueness of the dual spherical and Berkovich (S&B) indentation in predicting complex material systems
A special code was written in MATLAB, including the optimisation function and commands to read input files, write output files and execute the ABAQUS solver

Summary

Introduction

Outcomes of a research study concerned with the application of indentation processes with different indenter geometries are reported. Finite element modelling (FEM)-based algorithms using single and multiple indenters have been proposed by other researchers to determine the mechanical properties of different engineering material systems. This approach has been used on some complex or non-standard materials or surfaces, such as in vivo tension and brittle indentation [4,5,6]. The first approach predicts material properties based on the single indentation test, examined separately, with all indenters sharing the same initial start value The application of such an approach, which has been investigated by many researchers, has failed to achieve high accuracy as the range of tested material properties produced non-identical load displacement curves. In some cases the accuracy of this approach could be improved depending on the previous knowledge about the material [7,8,9]

Objectives

Results

Conclusion