Brazilian disk test and digital image correlation: a methodology for the mechanical characterization of brittle materials
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In this paper, an optimized and reliable approach for the evaluation of the mechanical properties of brittle materials is proposed and applied to the characterization of geopolymer mortars. In particular, the Young’s modulus, the Poisson’s ratio and the tensile strength are obtained by means of a Brazilian disk test combined with the digital image correlation (DIC) technique. The mechanical elastic properties are evaluated by a special routine, based on an over-deterministic method and the least square regression, that allows to fit the displacement fields experienced by the samples during the experiment. Error sources, like center of the disk location and rigid-body motion components, were analyzed and estimated automatically with the proposed procedure in order to perform an accurate evaluation of the elastic constants. The strain field measured by DIC and the computed elastic properties were then used to perform a local stresses analysis. This latter was exploited to investigate the failure mechanisms and to evaluate the tensile strength of the investigated material and the obtained data were compared with those predicted by the ASTM and ISMR standards. Three different loading platens (flat, rod and curved) were adopted for the Brazilian test in order to evaluate their effect on the elastic properties calculation, on the failure mechanisms and tensile strength evaluation. Results reveal that the curve platens are the most suitable for the tensile strength calculation, whereas the elastic properties did not show any influence from the loading configuration. Furthermore, the proposed procedure, of easy implementation, allows to accurately calculate Young’s modulus, Poisson’s ratio and the tensile strength of brittle materials in a single experiment.
KeywordsBrazilian disk test Digital image correlation Young’s modulus Poisson’s ratio Tensile strength Inverse problem Geopolymer
The authors wish to thank “MaTeRiA Laboratory” (University of Calabria), funded with “Pon Ricerca e Competitività 2007/2013”, for providing equipment to perform the experiments.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
This chapter does not contain any studies with human participants or animals performed by any of the authors.
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