Shape features and finite element model updating from full-field strain data

Abstract

a b s t r a c tFinite element model updating is an inverse problem based on measured structural outputs, in this case maximum principal strain measured using digital image correlation. Full-field responses in the form of strain maps contain valuable information for model updating but within large volumes of highly-redundant data. In this paper, shape descriptors based on Zernike polynomials having the properties of orthogonality and rotational invariance are shown to be powerful decomposition kernels for defining the shape or map of the strain distribution. A square plate with a circular hole subject to a uniaxial tensile load is considered and effective shape features are constructed using a set of modified Zernike polynomials. The modification includes the application of a decaying weighting function to the Zernike polynomials so that high strain magnitudes around the hole are well-represented. The Gram-Schmidt process is then used to ensure orthogonality for the obtained decomposition kernels over the domain of the specimen, i.e. excluding the hole. Results show that only a very small number of Zernike moment descriptors are necessary and sufficient to represent the full-field data. The onset of yielding may be quantified using the descriptors. Furthermore, model updating of nonlinear elasto-plastic material properties is carried out using the Zernike moment descriptors derived from full-field strain measurements.

Sub-Millimeter Measurement of Finite Strains at Cutting Tool Tip Vicinity

“…This approach, though uncommon in strain derivation applications, has proved its worth in various noise related problems [12,45,27].…”

A Review of Surface Deformation and Strain Measurement Using Two-Dimensional Digital Image Correlation

“…In their report, the modulus of elasticity of a steel specimen determined by the DIC technique was equal to 201 GPa, whereas its benchmark value was 206 GPa. Several researchers further employed the concept and studied mechanical properties of materials with the finite element-based integrated DIC technique [96][97][98][99][100][101]. According to Leclerc et al [102], the DIC technique was applied to update material properties in simulation of finite elements, so that the difference between the real and simulated displacements was minimized.…”

Application of the virtual fields method to the identification of the homogeneous anisotropic hardening parameters for advanced high strength steels

“…It basically determines the material parameters by minimizing the discrepancy between FE simulation results and the experimental measurements. This has been applied over the years to a wide range of constitutive models, among which elasticity and elasto-plasticity (Broggiato et al, 2008;Güner et al, 2012;Lecompte et al, 2007;Wang et al, 2011;Zang et al, 2014;Zhang et al, 2014). Nevertheless, FEMU is computationally demanding since a FE model has to be updated iteratively, even for the simplest case of elasticity.…”