2016
DOI: 10.1002/polb.24110
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Abstract: We performed constant strain rate deformation and stress relaxation on a poly(methyl methacrylate) glass at Tg – 19 K, utilizing three strain rates and initiating the stress relaxation over a large range of strain values. Following previous workers, we interpret the initial rate of decay of the stress during the relaxation experiment as a purely mechanical measure of mobility for the system. In our experiments, the mechanical mobility obtained in this manner changes by less than a factor of 3 prior to yield. D… Show more

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Cited by 19 publications
(24 citation statements)
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References 48 publications
(126 reference statements)
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“…τ (ǫ) decreases rapidly with increasing strain as stress-activated plasticity becomes increasingly important, passes through a minimum at ǫ ≃ ǫ y , increases again for ǫ > ǫ y , and then decreases again for ǫ > ǫ pysm . All trends are consistent with experimental observations [39][40][41] showing that relaxation in real glasses often speeds up by orders of magnitude near yielding, and can then slow down again upon strain softening. Panel (c) shows the dynamical heterogeneity…”
Section: Results For Systems' Mechanics Dynamics and Thermodynamicssupporting
confidence: 90%
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“…τ (ǫ) decreases rapidly with increasing strain as stress-activated plasticity becomes increasingly important, passes through a minimum at ǫ ≃ ǫ y , increases again for ǫ > ǫ y , and then decreases again for ǫ > ǫ pysm . All trends are consistent with experimental observations [39][40][41] showing that relaxation in real glasses often speeds up by orders of magnitude near yielding, and can then slow down again upon strain softening. Panel (c) shows the dynamical heterogeneity…”
Section: Results For Systems' Mechanics Dynamics and Thermodynamicssupporting
confidence: 90%
“…Note that such effects can be finely adjusted within the present model by varying the functional forms of K u and δ(u). [39][40][41] that heterogeneity decreases during yielding and remains relatively low during plastic flow. The different trends shown in panel (c) may arise because currently available SGR theories lack any "facilitation" mechanism.…”
Section: Results For Systems' Mechanics Dynamics and Thermodynmentioning
confidence: 99%
“…And, deformation strain rate makes a main effect, which results in the increase of the maximum stress in this region . This is mainly because molecular segments don't have sufficient time to move at a high strain rate . Hence, the slip and rotation of the molecular segments, that reflect plasticity at break, develop to very little extent before fracture.…”
Section: Resultsmentioning
confidence: 99%
“…Macroscopic deformation is assumed to be the result of a basic processes that is either intermolecular (i.e., chain‐sliding) or intramolecular (i.e., a change in the conformation of the chain) mobility, whose frequency depends on the ease with which a chain segment can surmount a potential energy barrier of height . So, in order to clarify the intrinsic physical mechanism for the strain rate dependency of the PMMA material in the different regions, Eyring's equation is employed, as below σy=ΔUυ+RTυlntrue(2ɛ̇e0true) wherein, σy is the yield stress; T is the test temperature in K ; ΔU is the activation energy of plastic deformation (plastic flow), i.e., the height of potential energy barrier of two adjacent equilibrium positions for element units to jump; υ is the activation volume of the element motion unit; trueɛ̇ is the strain rate; e0 is the pre‐exponential factor, and R is the gas constant.…”
Section: Discussionmentioning
confidence: 99%
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