(a) Schematic of the stress sequence of a two-step creep measurement. (b) Typical strain response for the creep and recovery process.
Instantaneous elastic strain jump as a function of the magnitude of step stress for the creep and recovery process at temperatures of 300 K (solid), 330 K (dashed), 350 K (dotted), and 370 K (dash-dot).
One-step creep curves using variable KWW stretched exponential exponents of (solid), 0.5 (dashed), and 1 (dotted) for a stress of 5 MPa at . Inset: corresponding “delayed elastic deformation” as a function of time for (solid) and 0.5 (dashed).
(a) Nondimensionalized compliance as a function of logarithmic (base 10) time for stresses (top to bottom) of 25, 12.5, 5, 2.5, 0.5, 0.2, and 0.1 MPa and fixed , . The dashed curves are fits of Eq. (26) to the theoretical results. (b) A collapse of these seven compliance curves is obtained by performing a horizontal shift. Inset: logarithmic (base 10) shift factor (solid curve) and normalized alpha relaxation time (dashed curve) as a function of applied stress.
Creep and recovery curves for (a) a fixed stress at three temperatures below the glass transition and (b) three different stresses at 15 K below the glass transition. The stress turnoff time is and .
(a) Creep and recovery curves for variable stress turnoff times at a fixed stress of , , and . (b) (Main panel) Corresponding delayed recovered strain as a function of recovery time for five turn off times. Inset: Elapsed time dependences of the delayed elastic (solid curve) and recovered (dashed curve) strain for .
Two-step creep curves at for (a) (main panel) and three different second stress step values of , 2.5, and 0 MPa, with . Inset: corresponding Maxwell model results ; (b) and four , 7.4, 2.3, and 0 MPa. Inset: corresponding results of Maxwell model results . The solid curves in the main panels are the PMMA experimental data and the dashed and/or short-dashed curves are the theoretical calculations. The statistical segment length is fixed at .
Creep and recovery curves at , 10.06 MPa, and , 14.1 MPa. The solid curves are the PMMA experimental data and the dashed curves are the theoretical results. The KWW stretching parameter and segment length are fixed as and , respectively.
Stress-strain curves at a constant strain rate of for three temperatures (top to bottom): , , and . The solid curves are the PMMA experimental data, the dashed (, ), dash-dot (, ), and dotted (, ) curves are theoretical results.
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