{"title":"How robust is the virtual fields method with respect to experimental inhomogeneities for bulge inflation testing of hyperelastic materials?","authors":"Paulien Vandemaele , Lauranne Maes , Heleen Fehervary , Stéphane Avril , Nele Famaey","doi":"10.1016/j.jmbbm.2025.106965","DOIUrl":null,"url":null,"abstract":"<div><div>Mechanical characterization of biological soft tissue can be a challenging process due to its inherent inhomogeneities. Constitutive model calibration based on the virtual fields method enables the use of full-field deformation and thickness data in order to obtain region-specific material parameters. However, for practical reasons, assumptions are often made in model calibration frameworks, e.g., by using the average sample thickness and deriving homogenized material parameters.</div><div>This study investigates the effect of these assumptions on the material parameters predicted by the virtual fields method. To this end, synthetic datasets of bulge inflation experiments were created using a finite element model and parameter identification was performed.</div><div>The ground truth parameters could be retrieved for a homogeneous sample with a high accuracy of 0.15%, even when only part of the full-field deformation data was known. For samples with a nonuniform thickness, the parameters could still be obtained with an error of 4% when taking into account the average sample thickness. However by including the region-specific thickness, parameters and stress responses closer to the ground truth were found, within 1% error. When samples showed inhomogeneous material properties spread throughout the sample, the obtained parameters resulted in a more homogenized stress response, eliminating the minimal and maximal stresses of the ground truth response. The ground truth stress response could not be obtained when the sample consisted of regions of different material properties. Further, only an incremental error of <span><math><mrow><mn>0</mn><mo>.</mo><mn>6</mn><mtext>%</mtext><mi>p</mi><mi>t</mi><mo>.</mo></mrow></math></span> was seen when decreasing the resolution in the parameter fitting framework by a factor 2.5 for both homogeneous samples and samples with a nonuniform thickness.</div><div>These results highlight the robustness of the virtual fields method and can be translated to other test types.</div></div>","PeriodicalId":380,"journal":{"name":"Journal of the Mechanical Behavior of Biomedical Materials","volume":"167 ","pages":"Article 106965"},"PeriodicalIF":3.5000,"publicationDate":"2025-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Journal of the Mechanical Behavior of Biomedical Materials","FirstCategoryId":"5","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S1751616125000815","RegionNum":2,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"2025/3/13 0:00:00","PubModel":"Epub","JCR":"Q2","JCRName":"ENGINEERING, BIOMEDICAL","Score":null,"Total":0}
引用次数: 0
Abstract
Mechanical characterization of biological soft tissue can be a challenging process due to its inherent inhomogeneities. Constitutive model calibration based on the virtual fields method enables the use of full-field deformation and thickness data in order to obtain region-specific material parameters. However, for practical reasons, assumptions are often made in model calibration frameworks, e.g., by using the average sample thickness and deriving homogenized material parameters.
This study investigates the effect of these assumptions on the material parameters predicted by the virtual fields method. To this end, synthetic datasets of bulge inflation experiments were created using a finite element model and parameter identification was performed.
The ground truth parameters could be retrieved for a homogeneous sample with a high accuracy of 0.15%, even when only part of the full-field deformation data was known. For samples with a nonuniform thickness, the parameters could still be obtained with an error of 4% when taking into account the average sample thickness. However by including the region-specific thickness, parameters and stress responses closer to the ground truth were found, within 1% error. When samples showed inhomogeneous material properties spread throughout the sample, the obtained parameters resulted in a more homogenized stress response, eliminating the minimal and maximal stresses of the ground truth response. The ground truth stress response could not be obtained when the sample consisted of regions of different material properties. Further, only an incremental error of was seen when decreasing the resolution in the parameter fitting framework by a factor 2.5 for both homogeneous samples and samples with a nonuniform thickness.
These results highlight the robustness of the virtual fields method and can be translated to other test types.
期刊介绍：
The Journal of the Mechanical Behavior of Biomedical Materials is concerned with the mechanical deformation, damage and failure under applied forces, of biological material (at the tissue, cellular and molecular levels) and of biomaterials, i.e. those materials which are designed to mimic or replace biological materials.
The primary focus of the journal is the synthesis of materials science, biology, and medical and dental science. Reports of fundamental scientific investigations are welcome, as are articles concerned with the practical application of materials in medical devices. Both experimental and theoretical work is of interest; theoretical papers will normally include comparison of predictions with experimental data, though we recognize that this may not always be appropriate. The journal also publishes technical notes concerned with emerging experimental or theoretical techniques, letters to the editor and, by invitation, review articles and papers describing existing techniques for the benefit of an interdisciplinary readership.
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