scholarly journals Study of the Nanomechanics of CNTs under Tension by Molecular Dynamics Simulation Using Different Potentials

2014 ◽  
Vol 2014 ◽  
pp. 1-18 ◽  
Author(s):  
S. K. Deb Nath ◽  
Sung-Gaun Kim
Keyword(s):  
Bond Order ◽  
High Strain ◽  
Order Term ◽  
Dynamics Simulation ◽  
Strain Rates ◽  
Plastic Properties ◽  
Elastic Plastic ◽  
Empirical Potentials ◽  
Axial Tension ◽  
Rebo Potential

At four different strain rates, the tensile stress strain relationship of single-walled 12-12 CNT with aspect ratio 9.1 obtained by Rebo potential (Brenner, 1990), Airebo potential (Stuart et al., 2000), and Tersoff potential (Tersoff, 1988) is compared with that of Belytschko et al. (2002) to validate the present model. Five different empirical potentials such as Rebo potential (Brenner, 1990), Rebo potential (Brenner et al., 2002), Inclusion LJ with Rebo potential (Brenner, 1990), Airebo potential (Stuart et al., 2000), and Tersoff potential (Tersoff, 1988) are used to simulate CNT subjected to axial tension differing its geometry at high strain rate. In Rebo potential (Mashreghi and Moshksar, 2010) only bond-order term is used and in Rebo potential (Brenner et al., 2002) torsional term is included with the bond-order term. At high strain rate the obtained stress strain relationships of CNTs subjected to axial tension differing its geometries using five different potentials are compared with the published results and from the comparison of the results, the drawback of the published results and limitations of different potentials are evaluated and the appropriate potential is selected which is the best among all other potentials to study the elastic, elastic-plastic properties of different types of CNTs. The present study will help a new direction to get reliable elastic, elastic-plastic properties of CNTs at different strain rates. Effects of long range Van der Waals interaction and torsion affect the elastic, elastic-plastic properties of CNTs and why these two effects are really needed to consider in bond-order Rebo potential (Brenner, 1990) to get reliable elastic, elastic-plastic properties of CNTs is also discussed. Effects of length-to-diameter ratio, layering of CNTs, and different empirical potentials on the elastic, elastic-plastic properties of CNTs are discussed in graphical and tabular forms with published results as a comparative manner to understand the nanomechanics of CNTs under tension using molecular dynamics simulation.

Anand Viscoplasticity Model for the Effect of Aging on Mechanical Behavior of SAC305 Operating at High Strain Rate and High Temperature

2015 ◽  
Author(s):  
Pradeep Lall ◽  
Di Zhang ◽  
Jeff Suhling ◽  
David Locker
Keyword(s):  
High Temperature ◽  
High Strain ◽  
Operating Temperature ◽  
Uniaxial Stress ◽  
Strain Rates ◽  
High Strain Rates ◽  
Plastic Properties ◽  
Long Term Storage ◽  
Wide Range ◽  
Operational Life

Portable products such as smartphones and tablets stay in the powered on condition for a majority of their operational life during which time the device internals are maintained at higher than ambient temperature. Thus, it would be expected for interconnects in portable products to be at a temperature high than room temperature when subjected to accidental drop or shock. Furthermore, electronics in missile-applications may be subjected to high strain rates after prolonged period of storage often at high temperature. Electronics systems including interconnects may experience high strain rates in the neighborhood of 1–100 per sec during operation at high temperature. However, the material properties of SAC305 leadfree solders at high strain rates and high operating temperatures are scarce after long-term storage. Furthermore, the solder interconnects in simulation of product drop are often modeled using elastic-plastic properties or linear elastic properties, neither of which accommodate the effect of operating temperature on the solder interconnect deformation at high operating temperature. SAC305 solders have been shown to demonstrate the significant degradation of mechanical properties including the tensile strength and the elastic modulus after exposure to high temperature storage for moderate periods of time. Previously, Anand’s viscoplastic constitutive model has been widely used to describe the inelastic deformation behavior of solders in electronic components under thermo-mechanical deformation. Uniaxial stress-strain curves have been plotted over a wide range of strain rates (ε̇ = 10, 35, 50, 75 /sec) and temperatures (T = 25, 50, 75, 100, 125°C). Anand viscoplasticity constants have been calculated by non-linear fitting procedures. In addition, the accuracy of the extracted Anand constants has been evaluated by comparing the model prediction and experimental data.

Molecular Dynamics Simulation to Study the Effect of Empirical Potential Functions on Modeling of Diamond-Like Carbon

2013 ◽  
Author(s):  
Longqiu Li ◽  
Ming Xu ◽  
Wenping Song ◽  
Guangyu Zhang ◽  
Andrey Ovcharenko
Keyword(s):  
Molecular Dynamics ◽  
Amorphous Carbon ◽  
Md Simulations ◽  
Distribution Functions ◽  
Dynamics Simulation ◽  
Empirical Potential ◽  
Mechanical And Tribological Properties ◽  
Empirical Potentials ◽  
Rebo Potential ◽  
Quenching Method

Molecular dynamics (MD) simulations is an effective method to investigate the mechanical and tribological properties of amorphous carbon since the coordinates of all atoms can be calculated as a function of time. Several empirical potentials can be used to model the interatomic interactions of carbon atoms, including the Tersoff potential, the Reactive Bond Order (REBO) potential and its revised versions, and the Reactive Force Field (ReaxFF) potential. The choice of empirical potential is one of the fundamental and important assumptions in the MD approach since it can affect the properties of amorphous carbon during the MD simulations. In this study, liquid quenching method is used to model amorphous carbon for computational efficiency. We will study the influence of the three types of potentials, specifically the Tersoff potential, the 2nd REBO potential and the ReaxFF potential on DLC parameters. These parameters include the sp3 content as a function of density, the arrangement of the amorphous carbon atoms, hybridization and the radial distribution functions G(r).

Anand Parameters for SAC305 Alloys After Prolonged Storage up to 1-Year

2017 ◽  
Author(s):  
Pradeep Lall ◽  
Di Zhang ◽  
Jeff Suhling ◽  
David Locker
Keyword(s):  
High Temperature ◽  
High Strain ◽  
Operating Temperature ◽  
Uniaxial Stress ◽  
Prolonged Storage ◽  
Strain Rates ◽  
High Strain Rates ◽  
Plastic Properties ◽  
Wide Range ◽  
Operational Life

Electronics in automotive underhood environments may be subjected to high temperatures in the neighborhood of 175°C while subjected to high strain rate mechanical loads of vibration. Portable products such as smartphones and tablets stay in the powered on condition for a majority of their operational life during which time the device internals are maintained at higher than ambient temperature. Thus, it would be expected for interconnects in portable products to be at a temperature high than room temperature when subjected to accidental drop or shock. Furthermore, electronics in missile-applications may be subjected to high strain rates after prolonged period of storage often at high temperature. Electronics systems including interconnects may experience high strain rates in the neighborhood of 1–100 per sec during operation at high temperature. However, the material properties of SAC305 leadfree solders at high strain rates and high operating temperatures are scarce after long-term storage. Furthermore, the solder interconnects in simulation of product drop are often modeled using elastic-plastic properties or linear elastic properties, neither of which accommodate the effect of operating temperature on the solder interconnect deformation at high operating temperature. SAC305 solders have been shown to demonstrate the significant degradation of mechanical properties including the tensile strength and the elastic modulus after exposure to high temperature storage for moderate periods of time. Previously, Anand’s viscoplastic constitutive model has been widely used to describe the inelastic deformation behavior of solders in electronic components under thermo-mechanical deformation. Uniaxial stress-strain curves have been plotted over a wide range of strain rates (ε. = 10, 35, 50, 75 /sec) and temperatures (T = 25, 50, 75, 100, 125, 150, 175, 200°C). Anand viscoplasticity constants have been calculated by non-linear fitting procedures. In addition, the accuracy of the extracted Anand constants has been evaluated by comparing the model prediction and experimental data.

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.

Solid Solution Effects and Deformation Micros trueture of Shock-Loaded Iron Manganese Alloys

1970 ◽  
Vol 28 ◽  
pp. 420-421
Author(s):  
A. Christou ◽  
J. V. Foltz ◽  
N. Brown
Keyword(s):  
Solid Solution ◽  
Shock Loading ◽  
High Strain ◽  
Local Stress ◽  
Strain Rates ◽  
Local Stress Concentration ◽  
Bcc Metals ◽  
Manganese Alloys ◽  
Iron Manganese ◽  
Transmission Microscope

In general, all BCC transition metals have been observed to twin under appropriate conditions. At the present time various experimental reports of solid solution effects on BCC metals have been made. Indications are that solid solution effects are important in the formation of twins. The formation of twins in metals and alloys may be explained in terms of dislocation mechanisms. It has been suggested that twins are nucleated by the achievement of local stress-concentration of the order of 15 to 45 times the applied stress. Prietner and Leslie have found that twins in BCC metals are nucleated at intersections of (110) and (112) or (112) and (112) type of planes.In this paper, observations are reported of a transmission microscope study of the iron manganese series under conditions in which twins both were and were not formed. High strain rates produced by shock loading provided the appropriate deformation conditions. The workhardening mechanisms of one alloy (Fe - 7.37 wt% Mn) were studied in detail.

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