Title:Towards Simpler Modelling Expressions for the Mechanical
Characterization of Soft Materials
Volume: 16
Issue: 3
Author(s): Stylianos-Vasileios Kontomaris*, Anna Malamou, Andreas Stylianou*Georgios Chliveros
Affiliation:
- Faculty of Engineering and Architecture, Metropolitan College, Athens, Greece
- BioNanoTec LTD, Nicosia, Cyprus
- Department of Mechanical Engineering, Faculty of Engineering, School of Sciences,
European University Cyprus, 2404 Nicosia, Cyprus
Keywords:
Indentation, mechanical properties, young's modulus, hertzian theory, spherical indentation, atomic force microscopy.
Abstract:
Aims: The aim of this paper is to develop a new, simple equation for deep spherical indentations.
Background: The Hertzian theory is the most widely applied mathematical tool when testing soft
materials because it provides an elementary equation that can be used to fit force-indentation data
and determine the mechanical properties of the sample (i.e., its Young’s modulus). However, the
Hertz equation is only valid for parabolic or spherical indenters at low indentation depths. For large
indentation depths, Sneddon’s extension of the Hertzian theory offers accurate force-indentation
equations, while alternative approaches have also been developed. Despite ongoing mathematical
efforts to derive new accurate equations for deep spherical indentations, the Hertz equation is still
commonly used in most cases due to its simplicity in data processing.
Objective: The main objective of this paper is to simplify the data processing for deep spherical indentations,
primarily by providing an accurate equation that can be easily fitted to force-indentation
data, similar to the Hertzian equation.
Methods: A simple power-law equation is derived by considering the equal work done by the indenter
using the actual equation.
Results: The mentioned power-law equation was tested on simulated force-indentation data created
using both spherical and sphero-conical indenters. Furthermore, it was applied to experimental
force-indentation data obtained from agarose gels, demonstrating remarkable accuracy.
Conclusion: A new elementary power-law equation for accurately determining Young’s modulus in
deep spherical indentation has been derived.