Validation Studies for the Dual Optimization of Indentation Creep and Stress Relaxation of Biological Soft Tissues Using Biphasic Poroviscoelasticity: Potential Method for Brain Tissue

2004 ◽  
Author(s):  
Joseph E. Olberding ◽  
Jun-Kyo Francis Suh
Keyword(s):  
Stress Relaxation ◽  
Brain Tissue ◽  
Material Properties ◽  
Computational Models ◽  
Soft Tissues ◽  
Optimization Technique ◽  
Biomechanical Testing ◽  
Potential Method ◽  
Indentation Creep ◽  
Creep And Stress Relaxation

Traumatic brain injury (TBI) is highly fatal and has profound physical and psychological repercussions for survivors. Knowledge of the precise material properties of brain tissue is crucial in developing holistic computational models to predict and prevent TBI. Despite the recent proliferation of material models of brain tissue, none have utilized porous media theory to explicitly include the significant fluid component of the hydrated soft tissue. Furthermore, the delicate composition of brain tissue limits the number of suitable biomechanical testing methodologies. In order to incorporate these considerations, in situ indentation creep and stress relaxation tests and linear biphasic poroviscoelasticity (BPVE) [1] were proposed to characterize the material properties of cerebral brain tissue. The objective of the present study was to evaluate these experimental and computational protocols in which the data from indentation creep and stress relaxation tests were simultaneously curve-fitted using a dual-optimization technique to determine the material parameters of the linear BPVE model.

Comparison of biphasic material properties of equine articular cartilage estimated from stress relaxation and creep indentation tests

2021 ◽  
Vol 7 (2) ◽  
pp. 363-366
Author(s):  
Thomas Reuter ◽  
Christof Hurschler
Keyword(s):  
Articular Cartilage ◽  
Stress Relaxation ◽  
Material Properties ◽  
Soft Tissues ◽  
Sensitivity Analyses ◽  
Creep Model ◽  
Fe Model ◽  
Relaxation Model ◽  
Marquardt Algorithm ◽  
Indentation Tests

Abstract Mechanical parameters of hard and soft tissues are explicit markers for quantitative tissue characterization. In this study, we present a comparison of biphasic material properties of equine articular cartilage estimated from stress relaxation (ε = 6 %, t = 1000 s) and creep indentation tests (F = 0.1 N, t = 1000 s). A biphasic 3D-FE-based method is used to determine the biomechanical properties of equine articular cartilage. The FE-model computation was optimized by exploiting the axial symmetry and mesh resolution. Parameter identification was executed with the Levenberg- Marquardt-algorithm. Additionally, sensitivity analyses of the calculated biomechanical parameters were performed. Results show that the Young’s modulus E has the largest influence and the Poisson’s ratio of ν ≤ 0.1 is rather insensitive. The R² of the fit results varies between 0.882 and 0.974 (creep model) and between 0.695 and 0.930 (relaxation model). The averaged parameters E and k determined from the creep model yield higher values in comparison to the relaxation model. The differences can be traced back to the experimental settings and to the biphasic material model.

Indentation Creep and Relaxation Measurements of Polymers

2004 ◽  
Vol 841 ◽  
Author(s):  
Mark R. VanLandingham ◽  
Peter L. Drzal ◽  
Christopher C. White
Keyword(s):  
Stress Relaxation ◽  
Mechanical Response ◽  
Creep Compliance ◽  
Relaxation Modulus ◽  
Polymeric Materials ◽  
Indentation Creep ◽  
Dimethyl Siloxane ◽  
Linear Viscoelastic Material ◽  
Linear Viscoelastic ◽  
Creep And Stress Relaxation

ABSTRACTInstrumented indentation was used to characterize the mechanical response of polymeric materials. A model based on contact between a rigid probe and a linear viscoelastic material was used to calculate values for creep compliance and stress relaxation modulus for epoxy, poly(methyl methacrylate) (PMMA), and two poly(dimethyl siloxane) (PDMS) elastomers. Results from bulk rheometry studies were used for comparison to the indentation creep and stress relaxation results. For the two glassy polymers, the use of sharp pyramidal tips produced responses that were considerably more compliant (less stiff) than rheometry values. Additional study of the deformation remaining in epoxy after creep testing revealed that a large portion of the creep displacement measured was due to post-yield flow. Indentation creep measurements of the epoxy using a rounded conical tip also produced nonlinear responses, but the creep compliance values appeared to approach linear viscoelastic values with decreasing creep force. Responses measured for the PDMS were mainly linear elastic, but the filled PDMS exhibited some time-dependence and nonlinearity in both rheometry and indentation measurements.

Indentation creep and stress relaxation in amorphous As-S-Se and As-S films

2001 ◽  
Author(s):  
J. Maniks ◽  
Ilze Manika ◽  
Janis Teteris ◽  
R. Pokulis
Keyword(s):  
Stress Relaxation ◽  
Indentation Creep ◽  
Creep And Stress Relaxation

scholarly journals Novel Volumetric Compression Relaxation Testing of Skeletal Muscles

2020 ◽  
Author(s):  
Anurag Vaidya ◽  
Benjamin Wheatley
Keyword(s):  
Skeletal Muscle ◽  
Stress Relaxation ◽  
Human Body ◽  
Material Properties ◽  
Skeletal Muscles ◽  
Computational Models ◽  
Surrounding Tissue ◽  
Unconfined Compression ◽  
Compressive Behavior

Computational models of the human body – such as those that simulate automotive impact – rely onaccurate material properties for bodily tissues. However, the compressive behavior of skeletal muscle is not fullyunderstood, particularly with regards to compression under confinement by surrounding tissue. For example, itis likely that in vivo muscle experiences a variation between confined and unconfined volumetric boundaryconditions, but nearly all previous studies have focused on muscle in unconfined compression (UC) or fullyconfined compression (CC). Thus, we have developed novel instrumentation to investigate the effects ofvolumetric boundary conditions (SC and CC) on stress relaxation of skeletal muscles.

Viscoelastic Properties of Injured and Uninjured Rat Brain Tissue

2007 ◽  
Author(s):  
Mehdi Shafieian ◽  
Kurosh Darvish
Keyword(s):  
Brain Stem ◽  
Rat Brain ◽  
Brain Tissue ◽  
Viscoelastic Material ◽  
Material Properties ◽  
Computational Models ◽  
Diffuse Axonal Injury ◽  
Elastic Response ◽  
Quasilinear Theory ◽  
The Impact

In this study, changes in the viscoelastic material properties of brain tissue due to traumatic diffuse axonal injury (DAI) were investigated. The impact acceleration model was used to generate DAI in rat brain stem. The viscoelastic material properties of brain tissue along the corticospinal (CSpT) tract in the brain stem were characterized using an indentation technique and a quasilinear theory. The results show significant reduction in the elastic response of brain tissue due to injury. In regions with significantly more DAI, larger changes in the elastic shear modulus and relaxation function were observed. These findings can improve the injury predictability of computational models of brain injury.

Changes in Viscoelastic Properties of Brain Tissue Due to Traumatic Injury

2004 ◽  
Author(s):  
Kurosh Darvish ◽  
James Stone
Keyword(s):  
Brain Tissue ◽  
Material Properties ◽  
Computational Models ◽  
Axonal Injury ◽  
Traumatic Injury ◽  
Diffuse Axonal Injury ◽  
Elastic Response ◽  
Tissue Properties ◽  
The Impact ◽  
The Brain

In this study, changes in viscoelastic material properties of brain tissue due to traumatic axonal injury (TAI) were investigated. The impact acceleration model was used to generate diffuse axonal injury in rat brain. TAI in the corticospinal (CSpT) tract in the brain stem was quantified using amyloid precursor protein immunostaining. Material properties along the CSpT were determined using an indentation technique. The results showed that the number of injured axons at the pyramidal decussation (PDx) was approximated 10 times higher than in the ponto-medullary junction (PmJ). The instantaneous elastic response was reduced approximately 70% at PDx compared to 40% at PmJ and the relaxation was uniformly reduced approximately 30%, which were attributed to the effect of injury on tissue properties. Application of a visco-elastic-plastic model that changes due to TAI can significantly alter the results of computational models of brain injury.

Unsteady creep and stress relaxation of AK4-1 alloy in the probability aspect

1975 ◽  
Vol 7 (1) ◽  
pp. 27-31
Author(s):  
S. P. Borisov ◽  
N. I. Borshchev ◽  
M. N. Stepnov ◽  
I. I. Khazanov
Keyword(s):  
Stress Relaxation ◽  
Unsteady Creep ◽  
Creep And Stress Relaxation
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