Full-Field Identification Methods: Comparison of FEM Updating and Integrated DIC
Full-field identification methods are increasingly used to adequately identify constitutive parameters to describe the mechanical behavior of materials. This research investigates the more recently introduced, one-step method of Integrated Digital Image C
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Full-Field Identification Methods: Comparison of FEM Updating and Integrated DIC A.P. Ruybalid, J.P.M. Hoefnagels, O. van der Sluis, and M.G.D. Geers Abstract Full-field identification methods are increasingly used to adequately identify constitutive parameters to describe the mechanical behavior of materials. This research investigates the more recently introduced, one-step method of Integrated Digital Image Correlation (IDIC) with respect to the most commonly used, two-step method of Finite Element Model Updating (FEMU), which uses a subset-based digital image correlation algorithm. To make the comparison as objective as possible, both methods are implemented in the most equivalent manner and use the same FE-model. Various virtual test-cases are studied to assess the performance of both methods when subjected to different error sources: (1) systematic errors, (2) poor initial guesses for the constitutive parameters, (3) image noise, (4) constitutive model errors, and (5) experimental errors. Results show that, despite the mathematical similarity of both methods, IDIC produces less erroneous and more reliable results than FEMU, particularly for more challenging test-cases exhibiting small displacements, complex kinematics, misalignment of the specimen, and image noise. Keywords Full-field measurement • Inverse methods • Parameter identification • Finite element model updating • Integrated digital image correlation
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Introduction
Proper identification of constitutive model parameters is essential for trustworthy prediction of mechanical material response. Thanks to increased computing power, large data sets can be processed efficiently, enabling rich, full-field kinematic information to be analyzed for the identification of such parameters through a single experiment, while relaxing the design requirements on the specimen and the loading conditions. The most widely used full-field identification method is that of finite element model updating (FEMU) [1, 4, 8, 14], in which model parameters are optimized by iteratively minimizing the difference between a measured displacement field, acquired through, e.g., Digital Image Correlation (DIC) and a simulated displacement field, acquired through finite element (FE) analysis. More recently, another identification method has been introduced [5, 7, 10–12] that more intimately integrates mechanical descriptions with full-field measurements. The method is termed Integrated DIC, and it integrates the (image) correlation procedure and identification procedure into a one-step approach, making it distinct from other methods (such as FEMU), which are two-step approaches whereby post-processing of experimental data precedes the identification procedure. In the following proceeding, the objective comparison between the performances of the one-step method of IDIC and the two-step method of FEMU is described. To make a fair comparison, both methods are implemented in an equivalent manner and are applied to the same experimental data, and the most important error sources are trigg
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