High-rate bulk and shear responses of bovine brain tissue

Nie, Xu; Sanborn, Brett; Weerasooriya, Tusit; Chen, Weinong

doi:10.1016/j.ijimpeng.2012.07.012

Cited by 21 publications

(46 citation statements)

References 22 publications

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“…Figures 11 and 12 illustrate that brain tissue not only stiffens with increasing strain but also with increasing strain rate. Rate-dependence of brain stiffness has consistently been reported in the literature using different testing techniques: shear testing or oscillatory shear testing [44,127,151], uniaxial compression or tension [57,83,85,132,137,140], indentation [20,107,136,163], and magnetic resonance elastography [36,145]. Figure 11 illustrates uniaxial compression, tension, and simple shear experiments performed at strain rates of 0.33 and 0.0067 1/s, respectively.…”

Section: Brain Stiffness Increases With Increasing Strain Ratementioning

confidence: 77%

Fifty Shades of Brain: A Review on the Mechanical Testing and Modeling of Brain Tissue

Budday

Ovaert

Holzapfel

et al. 2019

Arch Computat Methods Eng

253

248

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Brain tissue is not only one of the most important but also the most complex and compliant tissue in the human body. While long underestimated, increasing evidence confirms that mechanics plays a critical role in modulating brain function and dysfunction. Computational simulations-based on the field equations of nonlinear continuum mechanics-can provide important insights into the underlying mechanisms of brain injury and disease that go beyond the possibilities of traditional diagnostic tools. Realistic numerical predictions, however, require mechanical models that are capable of capturing the complex and unique characteristics of this ultrasoft, heterogeneous, and active tissue. In recent years, contradictory experimental results have caused confusion and hindered rapid progress. In this review, we carefully assess the challenges associated with brain tissue testing and modeling, and work out the most important characteristics of brain tissue behavior on different length and time scales. Depending on the application of interest, we propose appropriate mechanical modeling approaches that are as complex as necessary but as simple as possible. This comprehensive review will, on the one hand, stimulate the design of new experiments and, on the other hand, guide the selection of appropriate constitutive models for specific applications. Mechanical models that capture the complex behavior of nervous tissues and are accurately calibrated with reliable and comprehensive experimental data are key to performing reliable predictive simulations. Ultimately, mathematical modeling and computational simulations of the brain are useful for both biomedical and clinical communities, and cover a wide range of applications ranging from predicting disease progression and estimating injury risk to planning surgical procedures.

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Section: Brain Stiffness Increases With Increasing Strain Ratementioning

confidence: 77%

Fifty Shades of Brain: A Review on the Mechanical Testing and Modeling of Brain Tissue

Budday

Ovaert

Holzapfel

et al. 2019

Arch Computat Methods Eng

253

248

View full text Add to dashboard Cite

show abstract

“…The causes of mTBI are currently unknown, and there is no consensus in the literature of injury mechanisms resulting in mTBI as a result of blast, which further emphasizes the need for additional research in the topic. Theories of possible injury mechanisms caused by overpressure exposure include soft-tissue damage from shearing [4][5][6][7], distortion of cellular structures and cell death in the brain [5,[8][9][10][11][12][13][14], and intracranial fluid cavitation [5,[15][16][17][18][19].…”

Section: Introductionmentioning

confidence: 99%

Polymeric Hopkinson Bar-Confinement Chamber Apparatus to Evaluate Fluid Cavitation

2017

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Mild traumatic brain injury associated with blast exposure is an important issue, and cavitation of the cerebrospinal fluid (CSF) has been suggested as a potential injury mechanism; however, physical measurements are required to evaluate cavitation thresholds. Modifications to a Split Hopkinson Pressure Bar (SHPB) apparatus were investigated with the aim to generate localized fluid cavitation and measure the cavitation threshold of fluids. The proposed design incorporated a novel closed cavitation chamber to generate localized cavitation resulting from a reflected compression pulse, which was generated by a spherical steel striker and Polymethyl methacrylate (PMMA) incident bar. A numerical model of the incident bar was developed and validated with 24 independent tests (cross-correlation: 0.970-0.997), and this was extended to a numerical model of the apparatus including the chamber, validated with 27 independent tests (cross-correlation: 0.921) to predict the tensile fluid pressure in the chamber. Tests on distilled water were performed with comparable numerical results for the chamber strain (R 2 : 0.875) and chamber end-wall velocity (R 2 : 0.992). The pressure in the chamber was determined from the model to avoid introducing a nucleation site via a pressure gauge, and was verified with a firstorder approximation showing good agreement (R 2 : 0.892). The 50% probability of cavitation for distilled water was −3.32 MPa ±3%, comparable to values in the literature. This novel apparatus, including a closed confinement chamber integrated with a polymeric SHPB apparatus was able to create localized fluid cavitation with loading comparable to blast exposure. Future studies will include the measurement of CSF cavitation pressure.

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“…Radial accelerations in compression tests may result in stress states that are not uniaxial, that is, radial and Figure 1. Schematic (not to scale) of the experimental setup for the modified torsional Kolsky bar described in [Nie et al 2013]. Only the specimen is included in the simulations.…”

Section: Introductionmentioning

confidence: 99%

“…Recently, a variation of the torsional Kolsky bar test has been developed for studying the strain-rate sensitivity of very soft materials and applied to bovine brain tissue [Nie et al 2013;Sanborn et al 2012]. In this modified torsion test, the transmission bar is replaced with a torque load cell in order to generate a stronger signal than could be obtained from strain gage measurements on a transmission bar; see Figure 1.…”

Section: Introductionmentioning

confidence: 99%

“…The radially averaged shear stress at the specimen-load cell interface is deduced from the torque measured at the load cell. The stress-strain curves in [Nie et al 2013] are obtained by plotting this radially averaged shear stress at the load cell versus the volume averaged shear strain in the specimen. Comparison of stress-strain curves at different strain-rates could (in principle) yield information on the rate-sensitivity of the shear stress.…”

Section: Introductionmentioning

confidence: 99%

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Nonuniform shear strains in torsional Kolsky bar tests on soft specimens

Sokolow

Scheidler

2014

J. Mech. Mater. Struct.

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We investigate inertial effects in torsional Kolsky bar tests on nearly incompressible, soft materials. The results are relevant for materials with instantaneous elastic shear modulus on the order of 1-1000 kPa and density on the order of water. Examples include brain tissue and many other soft tissues and tissue surrogates. We have conducted one-and three-dimensional analyses and simulations to understand the stress and strain states that exist in these materials in a torsional Kolsky bar test. We demonstrate that the short loading pulses typically used for high strain-rate (e.g., 700/s) tests do not allow the softer specimens to "ring-up" to uniform stress and strain states and that consequently the shear stress versus shear strain data reported in the literature are erroneous. We also show that normal stress components, which are present even in quasistatic torsion of nonlinear elastic materials, can be amplified in dynamic torsion tests on soft materials.

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High-rate bulk and shear responses of bovine brain tissue

Cited by 21 publications

References 22 publications

Fifty Shades of Brain: A Review on the Mechanical Testing and Modeling of Brain Tissue

Fifty Shades of Brain: A Review on the Mechanical Testing and Modeling of Brain Tissue

Polymeric Hopkinson Bar-Confinement Chamber Apparatus to Evaluate Fluid Cavitation

Nonuniform shear strains in torsional Kolsky bar tests on soft specimens

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