Numerical analysis of micropillar compression behaviour and stress-strain curve estimation verified on glass fused silica


Microcompression testing became an incredibly popular approach to investigating the mechanical response of micro-scale volumes. Among many objectives, the determination of stress-strain relations from experimental force-displacement data is complicated, as compression micropillars are better considered as components a rather than samples, and an experimental force-displacement curve cannot be simply transferred to an accurate stress-strain curve. In this work the microcompression behaviour of fused silica – an amorphous, isotropic material – was investigated to quantitative the extent to which this novel approach can be used to achieve accurate stress-strain relations. Finite element simulations, assuming isotropic hyperelastic behaviour applied for an amorphous material, was essential in assessing the method, while also making comparison to experiments. Symmetric micropillars as well with imperfections were considered, combined with different friction coefficients to provide effects from e.g. slope of contact plane, inclined micropillar height, taper angle, or foot transition. For symmetric micropillars buckling phenomenon additionally occurred due to the predominant elastic deformation. Failure due to fracture was excluded in this approach. Based on the numerical simulations a sufficiently reliable, accurate, and verified approach was achieved providing the determination of stress-strain curves from experimental data and was also experimentally confirmed by a micropillar experiments. It is expected that the approach is also valid for other isotropic amorphous materials.
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