Exponents of the one-term Ogden model: insights from simple shear.

Isotropic one-term Ogden models are widely used to predict the mechanical response of both incompressible elastomers and soft tissue. Even though the exponent might be chosen to yield excellent agreement with some aspects of mechanical response, there is no guarantee that these models will be physically realistic in all situations. We show here that, in particular, the predictions of models with either negative or large positive exponents do not seem physically realistic in simple shear.

The effect of fiber-matrix interaction on the kinking instability arising in the torsion of stretched fibrous biofilaments.

The response of fibrous soft tissues undergoing torsional deformations is a topic of current interest. Such deformations are common in ligaments and tendons and are also of particular interest in cardiac mechanics. The problem of torsion superimposed on extension of incompressible hyperelastic solid circular cylinders is a classic problem of nonlinear elasticity that has been considered by many authors in the context of rubber elasticity particularly for isotropic materials.

Sex- and age-specific mechanical properties of liver tissue under dynamic loading conditions.

The liver is the most commonly injured abdominal organ following either blunt or penetrating impact. Current mechanical properties available in the literature are typically only measured at low strain rates, low strains, or use linear viscoelastic models. There is also a dearth of high-rate, large strain, viscoelastic data available for liver tissue which are required to model the deformation of the liver during high-rate impacts.

Mechanical characterisation of brain tissue up to 35% strain at 1, 10, and 100/s using a custom-built micro-indentation apparatus.

Understanding the behaviour of soft tissues under large strains and high loading rates is crucial in the field of biomechanics in order to investigate tissue behaviour during pathological processes such as traumatic brain injury (TBI). It is, therefore, necessary to characterise the mechanical properties of such tissues under large strain and high strain rates that are similar to those experienced during injury. However, there is a dearth of large strain and high rate mechanical properties for brain tissue.

Author Correction: Region and species dependent mechanical properties of adolescent and young adult brain tissue.

A correction to this article has been published and is linked from the HTML and PDF versions of this paper. The error has been fixed in the paper.

Region and species dependent mechanical properties of adolescent and young adult brain tissue.

Traumatic brain injuries, the leading cause of death and disability in children and young adults, are the result of a rapid acceleration or impact of the head. In recent years, a global effort to better understand the biomechanics of TBI has been undertaken, with many laboratories creating detailed computational models of the head and brain. For these models to produce realistic results they require accurate regional constitutive data for brain tissue.

Fiber orientation effects in simple shearing of fibrous soft tissues.

Fiber-reinforcement is a common feature of many soft biological tissues. Continuum mechanics modeling of the mechanical response of such tissues using transversely isotropic hyperelasticity is now well developed. The fundamental deformation of simple shear within this framework is examined here.

Protection of cortex by overlying meninges tissue during dynamic indentation of the adolescent brain.

Unlabelled: Traumatic brain injury (TBI) has become a recent focus of biomedical research with a growing international effort targeting material characterization of brain tissue and simulations of trauma using computer models of the head and brain to try to elucidate the mechanisms and pathogenesis of TBI. The meninges, a collagenous protective tri-layer, which encloses the entire brain and spinal cord has been largely overlooked in these material characterization studies. This has resulted in a lack of accurate constitutive data for the cranial meninges, particularly under dynamic conditions such as those experienced during head impacts.

A viscoelastic analysis of the P56 mouse brain under large-deformation dynamic indentation.

Unlabelled: The brain is a complex organ made up of many different functional and structural regions consisting of different types of cells such as neurons and glia, as well as complex anatomical geometries. It is hypothesized that the different regions of the brain exhibit significantly different mechanical properties which may be attributed to the diversity of cells within individual brain regions. The regional viscoelastic properties of P56 mouse brain tissue, up to 70μm displacement, are presented and discussed in the context of traumatic brain injury, particularly how the different regions of the brain respond to mechanical loads.

Mechanical characterization of the P56 mouse brain under large-deformation dynamic indentation.

The brain is a complex organ made up of many different functional and structural regions consisting of different types of cells such as neurons and glia, as well as complex anatomical geometries. It is hypothesized that the different regions of the brain exhibit significantly different mechanical properties, which may be attributed to the diversity of cells and anisotropy of neuronal fibers within individual brain regions. The regional dynamic mechanical properties of P56 mouse brain tissue in vitro and in situ at velocities of 0.

Uniform transmural strain in pre-stressed arteries occurs at physiological pressure.

Residual deformation (strain) exists in arterial vessels, and has been previously proposed to induce homogeneous transmural strain distribution. In this work, we present analytical formulations that predict the existence of a finite internal (homeostatic) pressure for which the transmural deformation is homogenous, and the corresponding stress field. We provide evidence on the physical existence of homeostatic pressure when the artery is modeled as an incompressible tube with orthotropic constitutive strain-energy function.

Flutamide administration at 500 mg daily has similar effects on serum testosterone to 750 mg daily.

A prior comparison of 750 mg flutamide daily to 500 mg daily with an LHRH analog or orchiectomy showed no difference in effect on prostate specific antigen (PSA). However, any difference was likely masked by hypogonadism from concomitant LHRH analog or orchiectomy. We sought to evaluate different flutamide dosing schedules without this confounding factor.