Untaroiu, Costin D.2014-06-122014-06-122013Costin D. Untaroiu, "The Influence of the Specimen Shape and Loading Conditions on the Parameter Identification of a Viscoelastic Brain Model," Computational and Mathematical Methods in Medicine, vol. 2013, Article ID 460413, 7 pages, 2013. doi:10.1155/2013/4604131748-670Xhttp://hdl.handle.net/10919/48911The mechanical properties of brain under various loadings have been reported in the literature over the past 50 years. Step-and-hold tests have often been employed to characterize viscoelastic and nonlinear behavior of brain under high-rate shear deformation; however, the identification of brain material parameters is typically performed by neglecting the initial strain ramp and/or by assuming a uniform strain distribution in the brain samples. Using finite element (FE) simulations of shear tests, this study shows that these simplifications have a significant effect on the identified material properties in the case of cylindrical human brain specimens. Material models optimized using only the stress relaxation curve under predict the shear force during the strain ramp, mainly due to lower values of their instantaneous shear moduli. Similarly, material models optimized using an analytical approach, which assumes a uniform strain distribution, under predict peak shear forces in FE simulations. Reducing the specimen height showed to improve the model prediction, but no improvements were observed for cubic samples with heights similar to cylindrical samples. Models optimized using FE simulations show the closest response to the test data, so a FE-based optimization approach is recommended in future parameter identification studies of brain.application/pdfenCreative Commons Attribution 3.0 Unportedfinite-element modelpedestrian protectionshear deformationtissueinjurycompressionmathematical & computational biologyArticle - RefereedCopyright © 2013 Costin D. Untaroiu. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.http://www.hindawi.com/journals/cmmm/2013/460413/cta/https://doi.org/10.1155/2013/460413