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Nonlinear Mechanics of Soft Biological Materials
Published in Heather N. Hayenga, Helim Aranda-Espinoza, Biomaterial Mechanics, 2017
Soft tissues are highly deformable when a mechanical load is applied. In fact, the differences in configuration between the reference (prior to loading) and deformed (as a result of loading) states can be large. Large deformations are best described within the framework of the finite strain theory of continuum mechanics where a clear distinction exists between these two configurations. Examples of soft tissues of the body include tendons, ligaments, skin, muscles, nerves, membranes, and blood vessels. In contrast, hard tissues, such as bone and dentin, contain a highly mineralized ECM that limits deformation. Those hard tissues are well studied within the context of infinitesimal or small strain theory.
Basic Solid Mechanics
Published in Manoj Kumar Buragohain, Composite Structures, 2017
On the other hand, many materials such as elastomers, fluids, etc., which exhibit plastic deformation, undergo large deformations under loads. In such a case, the deformed and undeformed configurations are grossly different. Finite strain theory (also known as large strain theory or large deformation theory) is used in the strain analysis of such materials. Strain–displacement relations are nonlinear and the displacement gradient terms are not small such that squares of these terms are not negligible. Engineering strains are not applicable in this class of deformations and other more complex definitions such as logarithmic strain, Green strain, and Almansi strain are used.
Recent Developments in Computational Modeling of Viscoelastic Properties of Biocomposites
Published in Senthil Muthu Kumar Thiagamani, Md Enamul Hoque, Senthilkumar Krishnasamy, Chandrasekar Muthukumar, Suchart Siengchin, Vibration and Damping Behavior of Biocomposites, 2022
Renuka Sahu, Athul Joseph, Vishwas Mahesh, Vinyas Mahesh, Dineshkumar Harursampath
To investigate the damping behavior of viscoelastic damping structures, a finite element-based optimization method was presented. Using first-order shear deformation theory, the layerwise finite element model was created. Nonstoring genetic algorithm (NSGA-II) was used and implemented in MATLAB®. It was observed that at a higher modal loss factor the modal frequency was lowest. The low elastic modulus of viscoelastic model can be attributed to this finding. To ensure the flexibility of the structure, a viscoelastic damping layer was introduced. The optimal position for introducing the viscoelastic layer was found to be near the middle of the skin plate [59]. Implementing viscoelastic behavior by generalized Maxwell model to pulp fiber, which is in turn idealized as a complex compound bar, a numerical model, was developed. The presence of microfibrils creates anisotropy in the material behavior of the pulp fiber. The large deformations were modeled by considering the finite strain theory. The pulp fiber was simulated in the finite element framework using UMAT subroutine in ABAQUS®. The mesh was developed using linear eight-noded hybrid brick element C3D8RH. The boundary conditions implemented were clamped at one end and tensile stress at the other end. It was observed that with softening due to its viscoelastic nature, the deformation of the fiber increases with time [60]. Yahyaei-Moayyed et al. [61] used the FEM model along with experimental simulation to describe the creep performance of the unidirectional aramid fiber-reinforced polymer sheet (AFRP). Southern yellow pine (SYP) and Douglas-fir (DF) timber beams were strengthened by AFRP to improve their mechanical performance and nonlinear finite element analysis was carried out on these timber beams. Creep was modeled using Norton’s power law. C3D8 brick element in ABAQUS® was used to model the 3D nonlinear viscoelastic behavior of the beam in short- and long-term simulations [61]. The creep behavior depicted by power law is shown in Figure 18.9.
Evaluation of anisotropic elastic and plastic parameters of zircaloy-4 fuel cladding from biaxial stress test data and their application to a fracture mechanics analysis
Published in Journal of Nuclear Science and Technology, 2022
Feng Li, Takeshi Mihara, Yutaka Udagawa
FEM calculations using ABAQUS software [16] were performed to examine the impact of the Zircaloy-4 cladding tube’s modified mechanical properties on their fracture mechanics parameters. A 3D ring model with the same dimensions as a PWR 17 × 17-type cladding on the R-θ cross-section was built. A precrack was created on the model’s outer surface with a depth of 0.04 mm or 0.08 mm, according to the testing conditions of biaxial-EDC tests in the previous study [13]. The model had only one element layer axially, and the elements near the crack tip were refined (Figure 3a). The type of the elements was C3D8R. The typical lengths of elements in the refined zone and in the remote location were ~2 μm and ~10 μm, respectively. The calculations were performed following finite strain theory. Displacement boundary conditions were set under cylindrical coordinate system to simulate the deformation of the cladding tube. Expansion of the tube model in radial direction was achieved by imposing outward displacement on the inner surface, leaving the other two directions free. In the case of εz/εθ = 0, displacement of the top and bottom surfaces were both restricted in axial direction and left free for the other two directions. In the case of εz/εθ = 0.5, displacement of the bottom surface was restricted in axial direction, but an upward displacement was added to the top surface to achieve the strain ratio condition, while both the top and bottom surfaces were left free for the other two directions.