Cyclic Indentation of Iron: A Comparison of Experimental and Atomistic Simulations

Shayan Deldar,Iyad Alabd Alhafez,Herbert M Urbassek,Marek Smaga,Tilmann Beck

doi:10.3390/met9050541

Shayan Deldar, Iyad Alabd Alhafez + Show 3 more

Open Access

https://doi.org/10.3390/met9050541

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Journal: Metals	Publication Date: May 10, 2019
Citations: 9	License type: CC BY 4.0

Affiliation: University of Kaiserslautern, Daimler (Germany)

Abstract

Cyclic indentation is a technique used to characterize materials by indenting repeatedly on the same location. This technique allows information to be obtained on how the plastic material response changes under repeated loading. We explore the processes underlying this technique using a combined experimental and simulative approach. We focus on the loading–unloading hysteresis and the dependence of the hysteresis width ha,p on the cycle number. In both approaches, we obtain a power-law demonstrating ha,p with respect to the hardening exponent e. A detailed analysis of the atomistic simulation results shows that changes in the dislocation network under repeated indentation are responsible for this behavior.

Highlights

Mechanical characterization of materials by means of micro- and nanoindentation in the form of a hardness test or cyclic indentation with different indenter shapes and measurement parameters is a useful and well-established way to estimate important material parameters such as elastic modulus, or, in some cases, even fatigue limit [1,2,3,4]
Molecular dynamics (MD) simulations provided a valuable understanding of the nanoplasticity and dislocation density generated underneath a nanoindenter [7,8]
The material showed a hysteresis during the loading and unloading of the indenter, which allowed us to use the hysteresis width as a parameter, permitting analysis of the mechanical behavior of the material under cyclic loading

Summary

Introduction

Mechanical characterization of materials by means of micro- and nanoindentation in the form of a hardness test or cyclic indentation with different indenter shapes and measurement parameters is a useful and well-established way to estimate important material parameters such as elastic modulus, or, in some cases, even fatigue limit [1,2,3,4]. While the processes occurring under single indentations are well understood [9], cyclic indentation still poses challenges. In this method, the indenter tip is repeatedly pushed into the surface of a material until a pre-defined value of load is reached. Subsequent indentations probe a material that has been pre-damaged and induce further plastic changes in it [10]

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Conclusion