scholarly journals Effect of Strain Rate on Single Tau, Dimerized Tau and Tau-Microtubule Interface: A Molecular Dynamics Simulation Study

Biomolecules ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 1308
Author(s):  
Md Ishak Khan ◽  
Kathleen Gilpin ◽  
Fuad Hasan ◽  
Khandakar Abu Hasan Al Mahmud ◽  
Ashfaq Adnan
Keyword(s):  
Molecular Dynamics ◽  
Strain Rate ◽  
Tau Protein ◽  
High Strain ◽  
High Rate ◽  
Dynamics Simulation ◽  
Individual Response ◽  
Strain Rates ◽  
Covalent Bonds ◽  
Potential Biomarker

Microtubule-associated protein (MAP) tau is a cross-linking molecule that provides structural stability to axonal microtubules (MT). It is considered a potential biomarker for Alzheimer’s disease (AD), dementia, and other neurological disorders. It is also a signature protein for Traumatic Brain Injury (TBI) assessment. In the case of TBI, extreme dynamic mechanical energies can be felt by the axonal cytoskeletal members. As such, fundamental understandings of the responses of single tau protein, polymerized tau protein, and tau-microtubule interfaces under high-rate mechanical forces are important. This study attempts to determine the high-strain rate mechanical behavior of single tau, dimerized tau, and tau-MT interface using molecular dynamics (MD) simulation. The results show that a single tau protein is a highly stretchable soft polymer. During deformation, first, it significantly unfolds against van der Waals and electrostatic bonds. Then it stretches against strong covalent bonds. We found that tau acts as a viscoelastic material, and its stiffness increases with the strain rate. The unfolding stiffness can be ~50–500 MPa, while pure stretching stiffness can be >2 GPa. The dimerized tau model exhibits similar behavior under similar strain rates, and tau sliding from another tau is not observed until it is stretched to >7 times of original length, depending on the strain rate. The tau-MT interface simulations show that very high strain and strain rates are required to separate tau from MT suggesting Tau-MT bonding is stronger than MT subunit bonding between themselves. The dimerized tau-MT interface simulations suggest that tau-tau bonding is stronger than tau-MT bonding. In summary, this study focuses on the structural response of individual cytoskeletal components, namely microtubule (MT) and tau protein. Furthermore, we consider not only the individual response of a component, but also their interaction with each other (such as tau with tau or tau with MT). This study will eventually pave the way to build a bottom-up multiscale brain model and analyze TBI more comprehensively.

Temperature Rise in Polymeric Materials During High Rate Deformation

2008 ◽  
Vol 75 (1) ◽  
Author(s):  
M. Garg ◽  
A. D. Mulliken ◽  
M. C. Boyce
Keyword(s):  
Strain Rate ◽  
Temperature Rise ◽  
High Strain ◽  
Split Hopkinson Pressure Bar ◽  
Polymeric Materials ◽  
Test System ◽  
High Rate ◽  
Single Element ◽  
Strain Rates ◽  
Work Of Deformation

Many polymeric materials undergo substantial plastic strain prior to failure. Much of this post yield deformation is dissipative and, at high strain rates, will result in a substantial temperature rise in the material. In this paper, an infrared (IR) detector system is constructed to measure the rise in temperature of a polymer during high strain rate compression testing. Temperature measurements were made using a high-speed mercury-cadmium-telluride (HgCdTe) single-element photovoltaic detector sensitive in the mid-infrared spectrum (6–12μm), while mechanical deformation was accomplished in a split Hopkinson pressure bar (SHPB). Two representative polymers, an amorphous thermoplastic (polycarbonate (PC)) and a thermoset epoxy (EPON 862/W), were tested in uniaxial compression at strain rates greater than 1000s−1 while simultaneously measuring the specimen temperature as a function of strain. For comparison purposes, analogous measurements were conducted on these materials tested at a strain rate of 0.5s−1 on another test system. The data are further reduced to energy quantities revealing the dissipative versus storage character of the post yield work of deformation. The fraction of post yield work that is dissipative was found to be a strong function of strain for both polymers. Furthermore, a greater percentage of work is found to be dissipative at high rates of strain (>1000s−1) than at the lower rate of strain (0.5s−1) for both polymers; this is consistent with the need to overcome an additional energy barrier to yield at strain rates greater than 100s−1 in these two polymers. The highly cross-linked thermoset polymer was found to store a greater percentage of the post yield work of deformation than the physically entangled thermoplastic.

scholarly journals Strain-Rate-Dependent Tensile Response of Ti–5Al–2.5Sn Alloy

Materials ◽  
2019 ◽  
Vol 12 (4) ◽  
pp. 659 ◽  
Author(s):  
Bin Zhang ◽  
Jin Wang ◽  
Yang Wang ◽  
Yu Wang ◽  
Ziran Li
Keyword(s):  
Strain Rate ◽  
Strain Hardening ◽  
Uniaxial Tension ◽  
Temperature Rise ◽  
High Strain ◽  
Adiabatic Temperature ◽  
High Rate ◽  
Strain Rates ◽  
High Strain Rates ◽  
Adiabatic Temperature Rise

This study is an experimental investigation on the tensile responses of Ti–5Al–2.5Sn alloy over a wide range of strain rates. Uniaxial tension tests within the rate range of 10−3–101 s−1 are performed using a hydraulic driven MTS810 machine and a moderate strain-rate testing system. The high-rate uniaxial tension and tension recovery tests are conducted using a split-Hopkinson tension bar to obtain the adiabatic and isothermal stress–strain responses of the alloy under dynamic loading conditions. The experimental results show that the value of the initial yield stress increases with the increasing strain rate, while the strain rate sensitivity is greater at high strain rates. The isothermal strain-hardening behavior changes little with the strain rate, and the adiabatic temperature rise is the main reason for the reduction of the strain-hardening rate during high strain-rate tension. The electron backscatter diffraction (EBSD) analysis of the post-deformed samples indicates that there are deformation twins under quasi-static and high-rate tensile loadings. Scanning electron microscope (SEM) micrographs of the fracture surfaces of the post-deformed samples show dimple-like features. The Zerilli–Armstrong model is modified to incorporate the thermal-softening effect of the adiabatic temperature rise at high strain rates and describe the tension responses of Ti–5Al–2.5Sn alloy over strain rates from quasi-static to 1050 s−1.

AN IMAGE BASED INERTIAL IMPACT TEST TO EXTRACT VISCOELASTIC CONSTITUTIVE PARAMETERS

2021 ◽  
Author(s):  
ANDREW MATEJUNAS ◽  
LLOYD FLETCHER ◽  
LESLIE LAMBERSON
Keyword(s):  
Strain Rate ◽  
Polymer Matrix ◽  
Mechanical Response ◽  
High Strain ◽  
High Rate ◽  
Strain Rates ◽  
High Strain Rates ◽  
Full Field ◽  
Viscoelastic Parameters ◽  
Constitutive Parameters

Polymer matrix composites often exhibit a strong strain rate dependance in their mechanical response. In many of these materials, the viscoelastic behavior of the polymer matrix drives the rate dependence in the composite, however identifying these parameters at high strain rate presents a significant challenge. Common high-rate material characterization techniques such as the Kolsky (split-Hopkinson pressure) bar require a large test matrix across a range of strain rates. Kolsky bars also struggle to identify constitutive parameters prior to the yield due to inertial effects and the finite period of time required to reach force equilibrium. The Image Based Inertial Impact (IBII) test has been successfully used to identify linear elastic constitutive behavior of composites at high strain rates, but, to date, has only been used to extract constitutive properties at a single nominal strain rate in each test. Here, we propose an adaptation of the IBII test to identify viscoelastic parameters at high strain rates using full-field displacement data and the nonlinear virtual fields method (VFM). We validate the technique with finite element simulations of an IBII test on a model viscoelastic material that is characterized with a Prony series formulation of the generalized Maxwell model. The nonlinear VFM is then used to extract the Prony pairs for dynamic moduli and time constants from the full-field deformation data. The nonlinear viscoelastic identification allows for characterization of the evolution of mechanical response across a range of strain rates in a single experiment. The experimentally identified viscoelastic parameters of the matrix can then be used to predict the behavior of the composite at high strain rates. This approach will also be validated experimentally using a single-stage gas-gun to characterize the high-rate viscoelastic response of PMMA.

Molecular Dynamics Simulation and Analysis on the Stress Induced Crystallization Behavior of Metallic Glass Cu

2007 ◽  
Vol 121-123 ◽  
pp. 1011-1016 ◽  
Author(s):  
H.L. Wang ◽  
Xiu Xi Wang ◽  
H.Y. Liang
Keyword(s):  
Molecular Dynamics ◽  
Metallic Glass ◽  
Strain Rate ◽  
Plastic Material ◽  
Young Modulus ◽  
Amorphous Structure ◽  
Dynamics Simulation ◽  
Stress Effect ◽  
Strain Rates ◽  
Dynamics Simulations

The compressive deformation of metallic glass Cu was studied under uniformly distributed strains with different rates at 1 K temperature using molecular dynamics simulations. The interaction between atoms in the system adopts the embedded atom method (EAM) reported by Mishin. We found that MG Cu is an elastic/perfect plastic material and the Young modulus is about 50 Gpa with strain rates from 0.1ns-1 to 10 ns-1. At low strain rates the sample deforms inhomogeneously and the amorphous phase transforms continuously to a crystalline phase. It was observed that the nucleation, growth and mergence processes of crystalline are induced by stress. At high strain rates the system passes through plastic deformations homogeneously and keeps the amorphous structure. The higher flow stress occurs at higher strain with the strain rate increasing. The stress effect is an important factor that induces MG crystallization just like temperature effect. The relationship between characteristic nucleation rate and strain rate determines the different deformation mechanism of MG.

scholarly journals The Effect of Temperature and Strain Rate on the Interfacial Behavior of Glass Fiber Reinforced Polypropylene Composites: A Molecular Dynamics Study

Polymers ◽  
2019 ◽  
Vol 11 (11) ◽  
pp. 1766 ◽  
Author(s):  
Muhan Zhang ◽  
Bingyan Jiang ◽  
Chao Chen ◽  
Dietmar Drummer ◽  
Zhanyu Zhai
Keyword(s):  
Molecular Dynamics ◽  
Strain Rate ◽  
Glass Fiber ◽  
Tensile Deformation ◽  
Interfacial Strength ◽  
Dynamics Simulation ◽  
Strain Rates ◽  
Fiber Reinforced ◽  
Interfacial Behavior ◽  
Glass Fiber Reinforced

To make better use of fiber reinforced polymer composites in automotive applications, a clearer knowledge of its interfacial properties under dynamic and thermal loadings is necessary. In the present study, the interfacial behavior of glass fiber reinforced polypropylene (PP) composites under different loading temperatures and strain rates were investigated via molecular dynamics simulation. The simulation results reveal that PP molecules move easily to fit tensile deformation at higher temperatures, resulting in a lower interfacial strength of glass fiber–PP interface. The interfacial strength is enhanced with increasing strain rate because the atoms do not have enough time to relax at higher strain rates. In addition, the non-bonded interaction energy plays a crucial role during the tensile deformation of composites. The damage evolution of glass fiber–PP interface follows Weibull’s distribution. At elevated temperatures, tensile loading is more likely to cause cohesive failure because the mechanical property of PP is lower than that of the glass fiber–PP interface. However, at higher strain rates, the primary failure mode is interfacial failure because the strain rate dependency of PP is more pronounced than that of the glass fiber–PP interface. The relationship between the failure modes and loading conditions obtained by molecular dynamics simulation is consistent with the author’s previous experimental studies.

A Molecular Dynamics Simulation of High Strain-rate Deformation in Nanocrystalline Silicon Carbide

2007 ◽  
Vol 1021 ◽  
Author(s):  
Yifei Mo ◽  
Izabela Szlufarska
Keyword(s):  
Molecular Dynamics ◽  
High Strain Rate ◽  
Strain Rate ◽  
Grain Boundaries ◽  
High Strain ◽  
Nanocrystalline Silicon ◽  
Dynamics Simulation ◽  
Atomic Diffusion ◽  
Effect Of Temperature ◽  
Nanocrystalline Silicon Carbide

AbstractMulti-million atom molecular dynamics simulations of tensile testing have been performed on nc-SiC. Reduction of grain size promotes simultaneous enhancement of ductility, toughness, and strength. Simulations show that the nc-SiC fails by intergranular fracture preceded by atomic level necking. Atomic diffusion can prevent premature cavitation and failure, and therefore it sets an upper limit on high strain-rate deformations of ceramics. We report a non-diffusional mechanism for suppressing premature cavitation, which is based on unconstrained plastic flow at grain boundaries. In addition, based on the composite's rule of mixture, we estimate Young's modulus of random high-angle grain boundaries in nc-SiC to be about 130 GPa. The effect of temperature and strain rate on mechanical properties is studied.

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