On the Measurement of two Independent Viscoelastic Functions with Instrumented Indentation Tests

Abstract

In the present paper, a methodology for complete characterization of linear isotropic viscoelastic material with spherical instrumented indentation test is proposed. The developed method allows for measuring two independent viscoelastic functions, shear relaxation modulus and time-dependent Poisson's ratio, from the indentation test data obtained at non-decreasing loading, but otherwise arbitrary. Finite element modelling (FEM) is relied upon for validating the proposed methodology and for quantifying the influence of experimental variables on the measurements accuracy. Spherical indentation experiments are performed on several viscoelastic materials: polyoxymethylene, bitumen and bitumen-filler mastics. The viscoelastic material functions obtained with the indentation tests are compared with the corresponding results from the standard mechanical tests. Numerical and experimental results presented indicate that the methodology proposed allows mitigating the machine compliance and loading rate effects on the accuracy of the viscoelastic indentation tests.

Measurement of the viscoelastic properties of asphalt mortar and its components with indentation tests

“…First, in order to identify homogenised viscoelastic properties of asphalts mortar, straincontrolled periodic boundary conditions (PBC) are specified for a material's RVE, the PBC is utilised to reduce the size of the model. Secondly, a model of instrumented indentation test on asphalt mortar is set up and the analysis procedure proposed in (Fadil et al, 2018) is used to obtain the apparent material properties from the analysis results.…”

“…Viscoelastic matrix in mortar and sub-mortar models is assumed to be incompressible with constant Poisson's ratio of 0.499. The matrix at the sub-mortar model is assumed to be comprised of bitumen-filler mastics, with its G(t) obtained as a power law fit, as shown in Equation (2), of the measured shear relaxation modulus of bitumen mixed with 20% by weight of hydrated lime filler at T = 0 • C reported in (Fadil et al, 2018). The power-law fit was found to be suitable for the time range with R 2 = 0.9988.…”

“…In a recent study by (Fadil, Jelagin, & Larsson, 2018) a new methodology for viscoelastic characterisation of bituminous material with spherical indentation test has been proposed, which allows extracting the linear viscoelastic properties of materials at arbitrary non-decreasing loading. The method developed in (Fadil et al, 2018) has been applied to measure viscoelastic properties of bitumen and bitumen-filler mastics. The intention of the present study is to extend the methodology developed in (Fadil et al, 2018) to the multi-scale characterisation of bituminous materials.…”

“…The method developed in (Fadil et al, 2018) has been applied to measure viscoelastic properties of bitumen and bitumen-filler mastics. The intention of the present study is to extend the methodology developed in (Fadil et al, 2018) to the multi-scale characterisation of bituminous materials.…”

“…In order to further evaluate the feasibility of indentation testing for multiscale characterisation of asphalt mortar a brief experimental study is performed. Indentation testing technique proposed in (Fadil et al, 2018) is used to measure shear relaxation modulus of bitumen-filler mastics as well as of asphalt mortar at two different indenter-specimen contact area sizes. In order to establish baseline for comparison, relaxation modulus of bitumen and of bitumen-filler mastics is also measured with the DSR.…”