Crystallization and mechanical behavior of semi-crystalline polyethylene

2021 ◽  
Author(s):  
Z. Yan ◽  
A. Zaoui ◽  
F. Zairi
Keyword(s):  
Mechanical Properties ◽  
Large Strain ◽  
Cavitation Damage ◽  
Structural Composition ◽  
Different Temperatures ◽  
Strain Stress ◽  
Loading Modes ◽  
Dynamics Simulations ◽  
Direction Effect ◽  
Crystalline Polyethylene

Abstract Molecular dynamics simulations are employed to study the crystallinity and mechanical properties of multi-chain polyethylene systems. Results show that structural composition (length and number of chains) and temperature lead to different crystallinity, which are obtained by using two general measurement methods, namely chain orientation and global order. The semi-crystalline polyethylene systems are deformed under various mechanical loading modes and at different temperatures representing different polymer states. The stretching temperature and structural composition have a strong influence on the mechanical properties, including elastic modulus, yield stress and inelastic mechanisms. The orientation crystallization caused by the heat treatment stage induces a significant direction effect on the different parts of the large-strain stress-strain response. Besides, the competition of the two main inelastic deformation mechanisms, namely shear yielding and cavitation damage, are revealed during the course of stretching.

scholarly journals Mechanical Properties of Graphene Nanowiggles

2014 ◽  
Vol 1658 ◽  
Author(s):  
R. A. Bizao ◽  
T. Botari ◽  
D. S. Galvao
Keyword(s):  
Mechanical Properties ◽  
Large Scale ◽  
Graphene Nanoribbons ◽  
Failure Patterns ◽  
Fracture Patterns ◽  
Atomic Chains ◽  
Ultimate Failure ◽  
Strain Stress ◽  
Dynamics Simulations ◽  
Interesting Behavior

ABSTRACTIn this work we have investigated the mechanical properties and fracture patterns of some graphene nanowiggles (GNWs). Graphene nanoribbons are finite graphene segments with a large aspect ratio, while GNWs are nonaligned periodic repetitions of graphene nanoribbons. We have carried out fully atomistic molecular dynamics simulations using a reactive force field (ReaxFF), as implemented in the LAMPPS (Large-scale Atomic/Molecular Massively Parallel Simulator) code. Our results showed that the GNW fracture patterns are strongly dependent on the nanoribbon topology and present an interesting behavior, since some narrow sheets have larger ultimate failure strain values. This can be explained by the fact that narrow nanoribbons have more angular freedom when compared to wider ones, which can create a more efficient way to accumulate and to dissipate strain/stress. We have also observed the formation of linear atomic chains (LACs) and some structural defect reconstructions during the material rupture. The reported graphene failure patterns, where zigzag/armchair edge terminated graphene structures are fractured along armchair/zigzag lines, were not observed in the GNW analyzed cases.

scholarly journals Microstructure of Al-5Cu-1Li-0.6Mg-0.5Ag-0.5Mn Alloys

Metals ◽  
2020 ◽  
Vol 11 (1) ◽  
pp. 37
Author(s):  
Wenzheng Chen ◽  
Wenlong Zhang ◽  
Dongyan Ding ◽  
Daihong Xiao
Keyword(s):  
Mechanical Properties ◽  
Corrosion Current Density ◽  
Corrosion Potential ◽  
Aging Treatment ◽  
Corrosion Current ◽  
Homogenization Temperature ◽  
Tafel Polarization ◽  
Al2cu Phase ◽  
Different Temperatures ◽  
Microstructural Optimization

Microstructural optimization of Al-Li alloys plays a key role in the adjustment of mechanical properties as well as corrosion behavior. In this work, Al-5Cu-1Li-0.6Mg-0.5Ag-0.5Mn alloy was homogenized at different temperatures and holding times, followed by aging treatment. The microstructure and composition of the homogenized alloys and aged alloys were investigated. There were Al7Cu4Li phase, Al3Li phase, and Al2CuLi phases in the homogenized alloys. The Al7Cu4Li phase was dissolved with an increase in homogenization temperature and holding time. Al2Cu phase and Al2CuLi phase coarsened during the homogenization process. The alloy homogenized at 515 °C for 20 h was subjected to a two-stage aging treatment. Peak-age alloy, which had gone through age treatment at 120 °C for 4 h and 180 °C for 6 h, was mainly composed of α-Al, Al20Cu2Mn3, Al2CuLi, Al2Cu, and Al3Li phases. Tafel polarization of the peak-age alloys revealed the corrosion potential and corrosion current density to be −779 mV and 2.979 μA/cm2, respectively. The over-age alloy had a more positive corrosion potential of −658 mV but presented a higher corrosion current of 6.929 μA/cm2.

Dislocation Generation and Crack Propagation in Metals Examined in Molecular Dynamics Simulations

1992 ◽  
Vol 278 ◽  
Author(s):  
J. A. Rifkin ◽  
C. S. Becquart ◽  
D. Kim ◽  
P. C. Clapp
Keyword(s):  
Crack Propagation ◽  
Atomistic Simulations ◽  
Many Body ◽  
Dislocation Generation ◽  
Embedded Atom ◽  
Stress Levels ◽  
Different Temperatures ◽  
The Many ◽  
Dynamics Simulations ◽  
Many Body Interactions

AbstractWe have carried out a series of atomistic simulations on arrays of about 10,000 atoms containing an atomically sharp crack and subjected to increasing stress levels. The ordered stoichiometric alloys B2 NiAl, B2 RuAl and A15 Nb3AI have been studied at different temperatures and stress levels, as well as the elements Al, Ni, Nb and Ru. The many body interactions used in the simulations were derived semi-empirically, using techniques related to the Embedded Atom Method. Trends in dislocation generation rates and crack propagation modes will be discussed and compared to experimental indications where possible, and some of the simulations will be demonstrated in the form of computer movies.

A Zebrafish Embryo Behaves both as a “Cortical Shell – Liquid Core” Structure and a Homogeneous Solid when Experiencing Mechanical Forces

2014 ◽  
Vol 20 (6) ◽  
pp. 1841-1847 ◽  
Author(s):  
Fei Liu ◽  
Dan Wu ◽  
Ken Chen
Keyword(s):  
Mechanical Properties ◽  
Mechanical Behavior ◽  
Zebrafish Embryo ◽  
Large Strain ◽  
Liquid Core ◽  
Small Strain ◽  
Core Structure ◽  
Mechanical Forces ◽  
Cortical Shell ◽  
A Cell

AbstractMechanical properties are vital for living cells, and various models have been developed to study the mechanical behavior of cells. However, there is debate regarding whether a cell behaves more similarly to a “cortical shell – liquid core” structure (membrane-like) or a homogeneous solid (cytoskeleton-like) when experiencing stress by mechanical forces. Unlike most experimental methods, which concern the small-strain deformation of a cell, we focused on the mechanical behavior of a cell undergoing small to large strain by conducting microinjection experiments on zebrafish embryo cells. The power law with order of 1.5 between the injection force and the injection distance indicates that the cell behaves as a homogenous solid at small-strain deformation. The linear relation between the rupture force and the microinjector radius suggests that the embryo behaves as membrane-like when subjected to large-strain deformation. We also discuss the possible reasons causing the debate by analyzing the mechanical properties of F-actin filaments.

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