1,721,026 research outputs found
Femoral biomechanics via CT-based finite element models with nonlinear constitutive response
No full textCharacterization of Femoral Nonlinear Behavior Through Patient-specific CT-based FE Modeling
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Risk assessment of femur failure: a computational model accounting for the influence of metastatic lesion
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Modeling collagen recruitment in hyperelastic bio-material models with statistical distribution of the fiber orientation
No full textVisco-electro-elastic models of fiber-distributed active tissues
No full textWe present a constitutive model for stochastically distributed fiber reinforced visco-active tissues, where the behavior of the reinforcement depends on the relative orientation of the electric field. Following our previous works, for the passive behaviors we adopt a second order approximation of the strain energy density associated to the parameters of the fiber distribution. Consistently, we also assume that the active behavior accounts for the stochastic distribution of the fibers. The ensuing mechanical quantities result to be dependent on two average structure tensors. We introduce an extended Helmholtz free energy density characterized by the inclusion of a directional active potential, dependent on a stochastic anisotropic permittivity tensor. The permittivity tensor is expanded in Taylor series up to the second order, allowing to obtain an approximated active potential with the same structure of the passive Helmholtz free energy density. In particular, the explicit expression of active stress and stiffness are dependent on the two average structure tensors that characterize the passive response. Anisotropy follows from the fiber distribution and inherits its stochastic nature through statistics parameters. The active fiber distributed model is extended here to viscous materials by including the contribution of a dual dissipation potential in the variational formulation of the constitutive updates. Additionally, we present a computational example of application of the electro-viscous-mechanical material model by simulating peristaltic contractions on a portion of human intestine. © 2017 Springer Science+Business Media Dordrech
Modeling the biomechanics of the human cornea accounting for local variations of the collagen fibril architecture
Full text linkWe present a finite element model of the human cornea describing the in-plane organization of the stromal collagen, modified variously to include features of the collagen architecture. We investigate numerically the implication of the local organization of collagen in the stroma on the response of the human cornea to mechanical tests. We compare four different models by simulating three ideal mechanical tests, i. e., the ex-vivo inflation test, the in-vivo probe indentation, and the in-vivo air puff tests. Numerical results show slight differences between the models in terms of global response and stress distribution. Differences in the overall mechanical response are observed in dynamic tests, while quasi-static tests are not able to differentiate between the models. Stress distributions differ markedly when a variation of the shear stiffness across the thickness is considered. We conclude that the actual architecture of the collagen across the thickness of the cornea or at the limbus has a minor relevance from the mechanical point of view with respect to the main anisotropic orthogonal collagen structure that has been considered and acknowledged in the literature. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
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