Integrated digital image correlation applied to elastoplastic identification in a biaxial experiment

Adv. Model. and Simul. in Eng. Sci.

Bouterf

Chamoin

et al. 2016

Self Cite

Background: The goal of the present study is to illustrate the full integration of sensor and imaging data into numerical procedures for the purpose of identification of constitutive laws and their validation. The feasibility of such approaches is proven in the context of in situ tests monitored by tomography. The bridging tool consists of spatiotemporal (i.e., 4D) analyses with dedicated (integrated) correlation algorithms. Methods: A tensile test on nodular graphite cast iron sample is performed within a lab tomograph. The reconstructed volumes are registered via integrated digital volume correlation (DVC) that incorporates a finite element modeling of the test, thereby performing a mechanical integration in 4D registration of a series of 3D images. In the present case a non-intrusive procedure is developed in which the 4D sensitivity fields are obtained with a commercial finite element code, allowing for a large versatility in meshing and incorporation of complex constitutive laws. Convergence studies can thus be performed in which the quality of the discretization is controlled both for the simulation and the registration. Results: Incremental DVC analyses are carried out with the scans acquired during the in situ mechanical test. For DVC, the mesh size results from a compromise between measurement uncertainties and its spatial resolution. Conversely, a numerically good mesh may reveal too fine for the considered material microstructure. With the integrated framework proposed herein, 4D registrations can be performed and missing boundary conditions of the reference state as well as mechanical parameters of an elastoplastic constitutive law are determined in fair condition both for DVC and simulation.

Section: Boundary Conditionsmentioning

confidence: 99%

Toward 4D mechanical correlation

Adv. Model. and Simul. in Eng. Sci.

Bouterf

Chamoin

et al. 2016

Self Cite

“…Finite element model updating was performed to calibrate anisotropic plasticity parameters . It was also shown that integrated digital image correlation could be used to tune von Mises plasticity parameters on such type of samples. This technique will be used herein to investigate plastic anisotropy.…”

Section: Introductionmentioning

confidence: 99%

“…In this work, a single experiment on an ultrathin biaxial specimen is performed, and four constitutive laws with increasing complexity are considered to challenge the sought behavior. To enhance the relevance of the model, all data (i.e., displacement fields and reaction forces) are equitably weighted via a Bayesian foundation …”

Section: Introductionmentioning

confidence: 99%

On the identifiability of Hill‐1948 plasticity model with a single biaxial test on very thin sheet

Bertin

Roux

2017

Strain

Self Cite

One biaxial experiment is performed on an ultra-thin specimen made of 17-7 precipitation hardened stainless steel.An anti-wrinkling setup allows for the characterization of the mechanical behavior with Integrated Digital Image Correlation (IDIC). A sensitivity analysis assesses the amount of data available but reveals a discrepancy between observation and model that is interpreted as the occurrence of wrinkling in a confined boundary layer. From this observation, the identification is performed on a refined region of interest where reliable data are accessible. The calibration of parameters of various constitutive equations is performed. In particular, the identifiability of the so-called Hill-1948 model is analyzed.

“…The constrained registration is then limited to the sensitivity fields (ie, variation of the displacement field with respect to unknown parameters of the model) provided by either closed‐form solutions() or FE predictions. ()…”

Section: Introductionmentioning

confidence: 99%

Spatiotemporal regularization for digital image correlation: Application to infrared camera frames

Charbal

Roux

Numerical Meth Engineering

et al. 2018

The spatiotemporal response of a stainless steel plate undergoing cyclic laser shock is recorded with an infrared camera, and Digital Image Correlation (DIC) is used to analyze both displacement and temperature fields. Two very challenging difficulties are addressed: i) large gray level variations (due to temperature changes) and ii) convection effects affecting images. To this aim, a spatiotemporal regularization is designed exploiting a numerical model of the test. The thermomechanical space-time predictions are first processed through Karhunen-Loève decomposition to extract dominant temporal and spatial modes. The temporal modes are then inserted in a spatiotemporal DIC framework to estimate the experimental spatial modes that account for both gray level variations (and hence temperature) and displacement fields. It is shown that with only three modes, the full thermomechanical response of the material is captured. The temporal regularization issued from the model also allows the spurious effect of convection to be filtered out. Because of the drastic decrease in the number of degrees of freedom due to data reduction, the number of analyzed frames can be reduced from 50 down to 6 to capture the thermomechanical response, thereby leading to an enhanced efficiency.