Dynamic, Regional Mechanical Properties of the Porcine Brain: Indentation in the Coronal Plane

2011 ◽  
Vol 133 (7) ◽  
Author(s):  
Benjamin S. Elkin ◽  
Ashok Ilankova ◽  
Barclay Morrison
Keyword(s):  
Large Strain ◽  
Series Representation ◽  
Relaxation Modulus ◽  
Short Time Scale ◽  
Prony Series ◽  
Porcine Brain ◽  
Linear Viscoelastic ◽  
Viscoelastic Theory ◽  
Linear Viscoelastic Theory ◽  
Anatomic Region

Stress relaxation tests using a custom designed microindentation device were performed on ten anatomic regions of fresh porcine brain (postmortem time <3 h). Using linear viscoelastic theory, a Prony series representation was used to describe the shear relaxation modulus for each anatomic region tested. Prony series parameters fit to load data from indentations performed to ∼10% strain differed significantly by anatomic region. The gray and white matter of the cerebellum along with corpus callosum and brainstem were the softest regions measured. The cortex and hippocampal CA1/CA3 were found to be the stiffest. To examine the large strain behavior of the tissue, multistep indentations were performed in the corona radiata to strains of 10%, 20%, and 30%. Reduced relaxation functions were not significantly different for each step, suggesting that quasi-linear viscoelastic theory may be appropriate for representing the nonlinear behavior of this anatomic region of porcine brain tissue. These data, for the first time, describe the dynamic and short time scale behavior of multiple anatomic regions of the porcine brain which will be useful for understanding porcine brain injury biomechanics at a finer spatial resolution than previously possible.

Characterization of Viscoelastic Behavior of Stereoregular Poly(Isoprenes) by Relaxation Experiments

1974 ◽  
Vol 47 (1) ◽  
pp. 1-18
Author(s):  
L. Szilagyi ◽  
T. Riccò ◽  
F. Danusso
Keyword(s):  
Viscoelastic Behavior ◽  
Supermolecular Structure ◽  
Relaxation Modulus ◽  
Mechanical Relaxation ◽  
Recent Theory ◽  
Mean Values ◽  
Linear Viscoelastic ◽  
Viscoelastic Theory ◽  
Linear Viscoelastic Theory ◽  
Relationship Of

Abstract The mechanical relaxation of twelve samples of unvulcanized cis poly-(isoprene)s, including both natural and synthetic polymers, was studied over a range of temperatures. Master curves of relaxation modulus obtained from these data were used to derive relaxation spectra according to linear viscoelastic theory. A recent theory was used to calculate mean values of quantities related to the supermolecular structure which occurs spontaneously in these materials and is responsible for their viscoelastic properties. This structure is schematized in a model consisting of a system of macromolecules which interact with each other by elastic forces and frictions corresponding to points of entanglement between chains. The analysis leads to the determination, for each sample, of the number of entanglements per molecule, the physical network density, the value of relaxation parameters, and the relationship of each of these quantities to molecular weight.

scholarly journals Viscoelastic Characterization of Peripapillary Sclera: Material Properties by Quadrant in Rabbit and Monkey Eyes

2003 ◽  
Vol 125 (1) ◽  
pp. 124-131 ◽  
Author(s):  
J. Crawford Downs ◽  
J-K. Francis Suh ◽  
Kevin A. Thomas ◽  
Anthony J. Bellezza ◽  
Claude F. Burgoyne ◽  
...  
Keyword(s):  
Optic Nerve ◽  
Viscoelastic Material ◽  
Optic Nerve Head ◽  
Material Properties ◽  
Uniaxial Stress ◽  
Species Group ◽  
Linear Viscoelastic ◽  
Viscoelastic Theory ◽  
Linear Viscoelastic Theory

In this report we characterize the viscoelastic material properties of peripapillary sclera from the four quadrants surrounding the optic nerve head in both rabbit and monkey eyes. Scleral tensile specimens harvested from each quadrant were subjected to uniaxial stress relaxation and tensile ramp to failure tests. Linear viscoelastic theory, coupled with a spectral reduced relaxation function, was employed to characterize the viscoelastic properties of the tissues. We detected no differences in the stress-strain curves of specimens from the four quadrants surrounding the optic nerve head (ONH) below a strain of 4 percent in either the rabbit or monkey. While the peripapillary sclera from monkey eyes is significantly stiffer (both instantaneously and in equilibrium) and relaxes more slowly than that from rabbits, we detected no differences in the viscoelastic material properties (tested at strains of 0–1 percent) of sclera from the four quadrants surrounding the ONH within either species group.

Evaluation of the Viscoelastic Properties of the Intact Medial Collateral Ligament in a Goat Model

1999 ◽  
Author(s):  
Theodore D. Clineff ◽  
Richard E. Debski ◽  
Sven U. Scheffler ◽  
John D. Withrow ◽  
Savio L.-Y. Woo
Keyword(s):  
Medial Collateral Ligament ◽  
Viscoelastic Properties ◽  
Analytical Approach ◽  
Cruciate Ligament ◽  
Collateral Ligament ◽  
Future Studies ◽  
Linear Viscoelastic ◽  
Viscoelastic Theory ◽  
Anterior Cruciate ◽  
Linear Viscoelastic Theory

Abstract The time and history dependent viscoelastic properties have been determined for the normal medial collateral ligament (MCL) of canine (Woo, 1981), porcine anterior cruciate ligament (Kwan, 1993), and human patellar tendon in a cadaver model (Johnson, 1994). The objective of this study was to use a combined experimental and analytical approach to quantify the viscoelastic properties of the intact MCL in a goat model. A thorough understanding of the viscoelastic properties at low strain levels is necessary to future studies of the healing MCL. The quasi-linear viscoelastic theory (QLV) (Fung, 1972) was used to characterize the properties of the MCL during stress relaxation.

The Time and History-Dependent Viscoelastic Properties of the Canine Medial Collateral Ligament

1981 ◽  
Vol 103 (4) ◽  
pp. 293-298 ◽  
Author(s):  
S. L.-Y. Woo ◽  
M. A. Gomez ◽  
W. H. Akeson
Keyword(s):  
Medial Collateral Ligament ◽  
Viscoelastic Properties ◽  
Cyclic Stress ◽  
Elastic Response ◽  
Collateral Ligament ◽  
Stress Strain ◽  
Linear Viscoelastic ◽  
Viscoelastic Theory ◽  
Linear Viscoelastic Theory

The viscoelastic properties of the canine medial collateral ligament (MCL) were investigated. Stress-strain relationships at different strain rates, long-term stress relaxation and cyclic stress-strain curves of the MCL were obtained experimentally using a bone-MCL-bone preparation. The experimental data were used in conjunction with the quasi-linear viscoelastic theory as proposed by Fung [15] to characterize the reduced relaxation function, G(t) and elastic response σe (ε) of this tissue. It was found that the quasi-linear viscoelastic theory can adequately describe the time and history-dependent rheological properties of the canine medial collateral ligament.

Use of linear viscoelastic theory to predict resilient behavior of unbound granular materials

2015 ◽  
Vol 20 (5) ◽  
pp. 1806-1812
Author(s):  
Sung-Hee Kim ◽  
Kevin McFall ◽  
Jayhyun Kwon ◽  
Jidong Yang ◽  
Jin-Hoon Jeong
Keyword(s):  
Granular Materials ◽  
Unbound Granular Materials ◽  
Linear Viscoelastic ◽  
Viscoelastic Theory ◽  
Linear Viscoelastic Theory ◽  
Resilient Behavior

Interconversions between linear viscoelastic functions with a time-dependent bulk modulus

2017 ◽  
Vol 23 (6) ◽  
pp. 879-895 ◽  
Author(s):  
Dao-Long Chen ◽  
Tz-Cheng Chiu ◽  
Tei-Chen Chen ◽  
Ping-Feng Yang ◽  
Sheng-Rui Jian
Keyword(s):  
Bulk Modulus ◽  
Relaxation Modulus ◽  
Time Dependent ◽  
Reasonable Assumption ◽  
Prony Series ◽  
Relaxation Rates ◽  
Unknown Parameters ◽  
Linear Viscoelastic ◽  
Shear Relaxation ◽  
Increasing Function

The interconversion relations for viscoelastic functions are derived with the consideration of the time-dependent bulk modulus, K( t), for both traditional and fractional Prony series representations of viscoelasticity. The application of these relations is to replace the fitting parameters of Young’s relaxation modulus, E( t), by the unknown parameters of K( t) and the known parameters of the shear relaxation modulus, G( t), and to fit the E( t) to the experimental data for obtaining the parameters of K( t). The fitting results show that only two experiments for measuring the viscoelastic functions of an isotropic material are not enough to determine the other viscoelastic functions. However, if we consider the relaxation rates of K( t) and G( t), we may conclude that the constant bulk modulus is a more reasonable assumption, and the corresponding Poisson’s ratio, ν( t), is a monotonic-increasing function.

Analysis of Stress Singularity Induced in Viscoelastic Thin Layer Subjected to Shear Loading

2003 ◽  
Vol 17 (08n09) ◽  
pp. 1248-1253
Author(s):  
Myung Kyu Park ◽  
Sang Soon Lee ◽  
Chang Min Suh
Keyword(s):  
Thin Layer ◽  
Edge Crack ◽  
Viscoelastic Model ◽  
Stress Singularity ◽  
Adhesive Layer ◽  
Rigid Bodies ◽  
Shear Loading ◽  
Linear Viscoelastic ◽  
Viscoelastic Theory ◽  
Linear Viscoelastic Theory

This paper deals with the stress singularity developed in a viscoelastic thin layer bonded between two rigid bodies and subjected to a shear loading. A boundary element method is employed to investigate the behavior of interface stresses. Within the context of a linear viscoelastic theory, a stress singularity exists at the point where the interface between one of the rigid adherends and the adhesive layer intersects the free surface. Numerical results are presented for a given viscoelastic model, indicating that such stress singularity might lead to edge crack or delamination.

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