Revealing the deformation mechanism of amorphous polyethylene subjected to cycle loading<i>via</i>molecular dynamics simulations

Fang, Qihong; Tian, Yuanyuan; Wu, Hong; Li, Jia

doi:10.1039/c8ra05868g

Cited by 13 publications

(9 citation statements)

References 53 publications

(71 reference statements)

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“…For polymers, pioneering MD sliding simulations of PTFE and PE [14][15][16] analyzed in detail the possible wear mechanisms occurring at the molecular level. MD has also been applied to relate material properties to the bulk mechanical response [17,18] in order to investigate interaction of oligomer chains with fillers [19,20] and countersurfaces [21] under shear, or to simulate scratching behavior [22].…”

Section: Introductionmentioning

confidence: 99%

Multiscale Friction Simulation of Dry Polymer Contacts: Reaching Experimental Length Scales by Coupling Molecular Dynamics and Contact Mechanics

et al. 2021

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This work elucidates friction in Poly-Ether-Ether-Ketone (PEEK) sliding contacts through multiscale simulations. At the nanoscale, non-reactive classical molecular dynamics (MD) simulations of dry and water-lubricated amorphous PEEK-PEEK interfaces are performed. During a short running-in phase, we observe structural transformations at the sliding interface that result in flattening of the initial nanotopographies accompanied by strong polymer chain alignment in the shearing direction. The MD simulations also reveal a linear pressure -shear stress dependence and large adhesive friction in dry conditions. This dependence, summarized in a nanoscale friction law, is of central importance for our multiscale approach, since it forms a link between MD and elastoplastic contact mechanics calculations. An integration of the nanoscale friction law over the real area of contact yields a macroscopic friction coefficient that allows for a meaningful comparison with measurements from macroscopic tribometer experiments. Severe normal loading conditions result in significant wear and high experimental friction coefficients µ≈0.5-0.7, which are in good agreement with the calculated values from the multiscale approach in dry conditions. For milder experimental loads, our multiscale model suggests that lower friction states with µ≈0.2 originate in the presence of physisorbed molecules (e.g., water), which significantly reduce interfacial adhesion.

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Section: Introductionmentioning

confidence: 99%

Multiscale Friction Simulation of Dry Polymer Contacts: Reaching Experimental Length Scales by Coupling Molecular Dynamics and Contact Mechanics

et al. 2021

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“…The cause of this effect has not been identified except in amorphous solids, as in polymers and silicate glasses. Theoretical approaches discussed above seem to provide rational explanation [53,[61][62][63][64][65][66][67][68]. For metallic materials, the most plausible mechanism was provided in [13] relying on cyclic dislocation bow-out under imposed ultrasonic vibration.…”

Section: Discussionmentioning

confidence: 99%

“…Additional works on this subject were collected [63], but none dealt with the damping simulation. Other MD works deduced stress-strain relations of PC, PE, and polystyrene and their methods can possibly determine the hysteresis behavior under lower cyclic stressing [64,65]. Fang et al [64] emphasized important roles of shear stresses in driving structural changes in glassy polymers.…”

Section: Materials Groupmentioning

confidence: 99%

“…Other MD works deduced stress-strain relations of PC, PE, and polystyrene and their methods can possibly determine the hysteresis behavior under lower cyclic stressing [64,65]. Fang et al [64] emphasized important roles of shear stresses in driving structural changes in glassy polymers. This appears to contribute to substantially higher transverse attenuation found in all the polymer samples tested in this study.…”

Section: Materials Groupmentioning

confidence: 99%

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Dynamic Viscosity and Transverse Ultrasonic Attenuation of Engineering Materials

Ono

2020

Applied Sciences

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In this paper, ultrasonic attenuation of the transverse waves of engineering materials is evaluated, covering metals, ceramics, polymers, fiber-reinforced plastics, and rocks. After verifying experimental methods, 273 measurements are conducted and their results are tabulated. Fifty of the tests are for the longitudinal mode. Attenuation behavior is determined over broadband spectra. The attenuation spectra are characterized in four patterns, with 2/3 of the tests showing linear frequency dependence and another ¼ linear spectrum plus Rayleigh scattering (Mason-McSkimin relation). The longitudinal and transverse damping factors varied from 0.004 to 0.065, which are 1/3 to 5 times those of polymethyl methacrylate, suggesting that almost all the engineering materials tested may be viscoelastic. The present test results make the term dynamic viscosity more appropriate for exploring the underlying processes. The observed results were compared between the longitudinal and transverse modes and among similar material types. In more than a half of the tests, the transverse attenuation coefficients were higher than the corresponding longitudinal attenuation coefficients by 1.5× or more. Some material groups had similar attenuation coefficients for the two modes. Since the physical basis for viscous damping is hardly understood, especially in hard solids, further studies from new angles are keenly desired. This collection of new attenuation data will be of value for such works. Practically, this will assist in materials selection and in designing structural health monitoring and non-destructive inspection protocols.

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“…For polymers, pioneering MD sliding simulations of PTFE and PE [12,13,14] analyzed in detail the possible wear mechanisms occurring at the molecular level. MD has also been applied to relate material properties to the bulk mechanical response [15,16] in order to investigate interaction of oligomer chains with fillers [17,18] and counter surfaces [19] under shear, or to simulate scratching behavior [20].…”

Section: Introductionmentioning

confidence: 99%

Multiscale Friction Simulation of Dry Polymer Contacts: Reaching Experimental Length Scales by Coupling Molecular Dynamics and Contact Mechanics

Savio

Hamann

Romero

et al. 2021

Preprint

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This work elucidates friction in Poly-Ether-Ether-Ketone (PEEK) sliding contacts through multiscale simulations. At the nanoscale, non-reactive classical molecular dynamics (MD) simulations of dry and water-lubricated amorphous PEEK-PEEK interfaces are performed. During a short running-in phase, we observe structural transformations at the sliding interface that result in flattening of the initial nanotopographies accompanied by strong polymer chain alignment in the shearing direction. Our MD simulations reveal a linear pressure-dependence of the shear stress τMD (P,σH2o) [MPa]=0.18P + 50.5 - 1.25σH2o, where σH2o [nm-2] is the surface number density of adsorbed water molecules. This constitutive law is of central importance for our multiscale approach, since it forms a link between MD and elastoplastic contact mechanics calculations. An integration of τMD (P,σH2o) over the real area of contact yields a macroscopic friction coefficient μmacro (σH2o) that allows for a meaningful comparison with friction coefficients μexp≈0.5-0.7 which are in good agreement with the calculated dry friction coefficients μmacro(σH2o=0).For milder experimental loads, our multiscale model suggests that the lower friction states with μexp≈0.2 originate in the presence of physisorbed molecules (e.g. water), which significantly reduce interfacial adhesion.

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Revealing the deformation mechanism of amorphous polyethylene subjected to cycle loadingviamolecular dynamics simulations

Abstract: Despite tremendous efforts being devoted to the study of the deformation behavior of polyethylene, the deformation mechanism of an amorphous polyethylene polymer under cycle shear-loading remains largely unknown.

Cited by 13 publications

References 53 publications

Multiscale Friction Simulation of Dry Polymer Contacts: Reaching Experimental Length Scales by Coupling Molecular Dynamics and Contact Mechanics

Multiscale Friction Simulation of Dry Polymer Contacts: Reaching Experimental Length Scales by Coupling Molecular Dynamics and Contact Mechanics

Dynamic Viscosity and Transverse Ultrasonic Attenuation of Engineering Materials

Multiscale Friction Simulation of Dry Polymer Contacts: Reaching Experimental Length Scales by Coupling Molecular Dynamics and Contact Mechanics

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