Atomistic modelling of plastic deformation of glassy polymers

Mott, P. H.; Argon, A. S.; Suter, Ulrich W.

doi:10.1080/01418619308213969

Cited by 137 publications

(116 citation statements)

References 21 publications

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“…7,8 However, simulations can be analyzed using alternative conservation laws, for example, summation of the local strains. [19][20][21] Creep/recovery experiments on a polymer melt enable the assumption underlying eq 4 to be assessed directly. The linear creep compliance, D(t), is given by the sum of the recoverable compliance, D rec (t) and the viscous deformation [22][23][24] where t and η are time and viscosity, respectively.…”

Section: Results and Analysismentioning

confidence: 99%

Birefringence of Polymers in the Softening Zone

Mott

Roland

1998

Macromolecules

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Section: Results and Analysismentioning

confidence: 99%

Birefringence of Polymers in the Softening Zone

Mott

Roland

1998

Macromolecules

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“…Furthermore, in glassy fluids below T g , plastic deformations are often induced in the form of large-scale shear bands above a yield stress (corresponding to a few % strain). 13,14 It is of great importance to understand how these nonlinear effects occur depending onγ, T , and N .…”

Section: G(t) = G G (T) + G R (T) (12)mentioning

confidence: 99%

Dynamics and rheology of a supercooled polymer melt in shear flow

Yamamoto

Ōnuki

2002

The Journal of Chemical Physics

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Using molecular dynamics simulations, we study dynamics of a model polymer melt composed of short chains with bead number N = 10 in supercooled states. In quiescent conditions, the stress relaxation function G(t) is calculated, which exhibits a stretched exponential relaxation on the time scale of the α relaxation time τα and ultimately follows the Rouse dynamics characterized by the time τR ∼ N 2 τα. After application of shearγ, transient stress growth σxy(t)/γ first obeys the linear growth t 0 dt ′ G(t ′ ) for strain less than 0.1 but saturates into a non-Newtonian viscosity for larger strain. In steady states, shear-thinning and elongation of chains into ellipsoidal shapes take place for shearγ larger than τ −1 R . In such strong shear, we find that the chains undergo random tumbling motion taking stretched and compact shapes alternatively. We examine the validity of the stressoptical relation between the anisotropic parts of the stress tensor and the dielectric tensor, which are violated in transient states due to the presence of a large glassy component of the stress. We furthermore introduce time-correlation functions in shear to calculate the shear-dependent relaxation times, τα(T,γ) and τR(T,γ), which decrease nonlinearly as functions ofγ in the shear-thinning regime.

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“…The lower limit is well within the range of atomistic simulation. Already in 1993, Mott et al, 21 using simulations with sizes of only a few nm, were able to infer a length scale for inhomogeneous flow of 10 nm, which gives hope to the idea that inhomogeneity on this length scale could be observed.…”

Section: Introductionmentioning

confidence: 99%

Atomistic simulation study of the shear-band deformation mechanism in Mg-Cu metallic glasses

2006

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We have simulated plastic deformation of a model Mg-Cu metallic glass in order to study shear banding. In uniaxial tension, we find a necking instability occurs rather than shear banding. We can force the latter to occur by deforming in plane strain, forbidding the change of length in one of the transverse directions. Furthermore, in most of the simulations a notch is used to initiate shear bands, which lie at a 45°angle to the tensile loading direction. The shear bands are characterized by the Falk and Langer local measure of plastic deformation D min 2 , averaged here over volumes containing many atoms. The D min 2 profile has a peak whose width is around 10 nm;this width is largely independent of the strain rate. Most of the simulations were, at least nominally, at 100 K, about T g / 3 for this system. The development of the shear bands takes a few tens of ps, once plastic flow has started, more or less independent of strain rate. The shear bands can also be characterized using a correlation function defined in terms of D min 2 , which, moreover, can detect incipient shear bands in cases where they do not fully form. By averaging the kinetic energy over small regions, the local temperature can be calculated, and this is seen to be higher in the shear bands by about 50-100 K. Increases in temperature appear to initiate from interactions of the shear bands with the free surfaces and with each other, and are delayed somewhat with respect to the localization of plastic flow itself. We observe a slight decrease in density, up to 1%, within the shear band, which is consistent with notions of increased free volume or disorder within a plastically deforming amorphous material.

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Atomistic modelling of plastic deformation of glassy polymers

Cited by 137 publications

References 21 publications

Birefringence of Polymers in the Softening Zone

Birefringence of Polymers in the Softening Zone

Dynamics and rheology of a supercooled polymer melt in shear flow

Atomistic simulation study of the shear-band deformation mechanism in Mg-Cu metallic glasses

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