Time-Temperature-Stress Equivalence Applied to Accelerated Characterization of Creep Behavior of Viscoelastic Polymer

2007 ◽  
Vol 353-358 ◽  
pp. 1386-1389 ◽  
Author(s):  
Rong Guo Zhao ◽  
Wen Bo Luo ◽  
Chu Hong Wang ◽  
Xin Tang
Keyword(s):  
Temperature Stress ◽  
Stress Level ◽  
Creep Compliance ◽  
Superposition Principle ◽  
Test Duration ◽  
Nonlinear Creep ◽  
Creep Tests ◽  
Test Technique ◽  
Compliance Curve ◽  
Stress Superposition

Temperature induced change, and stress induced change as well, in intrinsic timescale were investigated by nonlinear creep tests on poly(methyl methacrylate). With four different experimental temperatures, from 14 to 26 degrees centigrade, time-dependent axial elongations of the specimen were measured at seven different stress levels, from 14 MPa to 30 MPa, and modeled according to the concept of time-temperature-stress equivalence. The test duration was only 4000 seconds. The corresponding temperature shift factors, stress shift factors and temperature-stress shift factors were obtained according to the time-temperature superposition principle (TTSP), the time-stress superposition principle (TSSP) and the time-temperature-stress superposition principle (TTSSP). The master creep compliance curve up to about two-year at a reference temperature 14 degrees centigrade and a reference stress 14 MPa was constructed by shifting the creep curves horizontally along the logarithmic time axis using shift factors. It is shown that TTSSP provides an effective accelerated test technique in the laboratory, the results obtained from a short-term creep test of PMMA specimen at high temperature and stress level can be used to construct the master creep compliance curve for prediction of the long-term mechanical properties at relatively lower temperature and stress level.

Time-Temperature-Stress Superposition Principle: Brief Description and Application to Polymer Creep Behavior

2012 ◽  
Vol 602-604 ◽  
pp. 681-684
Author(s):  
Yong Hua Li ◽  
Cheng Kai Jiang
Keyword(s):  
Temperature Stress ◽  
Stress Level ◽  
Creep Behavior ◽  
Physical Aging ◽  
Superposition Principle ◽  
Nonlinear Creep ◽  
Stress Superposition ◽  
Lower Temperature ◽  
Term Creep

A new accelerated characterization model for creep performances was briefly introduced first, which considers both the effects of temperature and stress level, named time-temperature- stress superposition principle (TTSSP). TTSSP assumes that the influence of stress level on the intrinsic time is similar to that of temperature for the creep behavior, as well as damage and physical aging. The creep curves at different state can be shifted into a master curve at reference state using TTSSP. Then the long-term creep behavior of viscoelastic materials at lower temperature and/or stress level can be predicted from the short-term ones. Finally, TTSSP was used to investigate the nonlinear creep behavior of high-density polyethylene (HDPE). It was shown that the long-term creep behavior of HDPE can be predicted successfully.

Application of Time-Ageing Time and Time-Temperature-Stress Equivalence to Nonlinear Creep of Polymeric Materials

2008 ◽  
Vol 575-578 ◽  
pp. 1151-1156 ◽  
Author(s):  
Rong Guo Zhao ◽  
Wen Bo Luo ◽  
Qi Fu Li ◽  
Chao Zhong Chen
Keyword(s):  
Creep Rate ◽  
Temperature Stress ◽  
Ageing Time ◽  
Superposition Principle ◽  
Time Shift ◽  
Test Duration ◽  
Nonlinear Creep ◽  
Test Technique ◽  
Term Creep

Based on the observations that high temperature accelerates creep rate of polymer while physical ageing plays a reverse role, and that there is an analogy between the influences of stress and temperature on the intrinsic times of polymers, the time-ageing time superposition principle (TASP) and the time-temperature-stress superposition principle (TTSSP) are used to evaluate the long-term creep behavior of poly(methyl methacrylate) (PMMA). PMMA specimens were aged for 2 to 120 hours at identical temperature, their short-term creep strains with 2-hour test duration were measured under various stress levels ranging from 14 to 30 MPa at room temperature, and modeled by means of time-ageing time equivalence and time-stress equivalence. The results show that the creep rate increases with stress, but decreases with ageing time. The ageing time shift factors vary with the stresses at which the shifts are applied. The ageing shift rate is independent on imposed stress in linear viscoelastic region, while it decreases with increasing stress when the material behaves in a nonlinear viscoelastic manner. The master creep compliance curve up to about 1-month at reference ageing time 120 hours and stress 18 MPa, which is nearly 2.5 decades longer than the test duration, is constructed by shifting the creep curves horizontally along the logarithmic time axis. The result illustrates that TTSSP, combined with TASP, provides an effective accelerated test technique for long-term mechanical behaviors of polymers.

Application of Time-Temperature-Stress Superposition Principle to Nonlinear Creep of Poly(methyl methacrylate)

2007 ◽  
Vol 340-341 ◽  
pp. 1091-1096 ◽  
Author(s):  
Wen Bo Luo ◽  
Chu Hong Wang ◽  
Rong Guo Zhao
Keyword(s):  
Methyl Methacrylate ◽  
Temperature Stress ◽  
Superposition Principle ◽  
Temperature Shift ◽  
Tensile Creep ◽  
Uniaxial Tensile ◽  
Test Duration ◽  
Nonlinear Creep ◽  
Poly Methyl Methacrylate ◽  
Stress Superposition

The uniaxial tensile creep of a commercial grade Poly(methyl methacrylate) was measured for 4000 seconds under various temperatures and stress levels ranging from 14 oC to 26 oC and 6 MPa to 32 MPa. The resultant creep compliance curves depart from each other for stresses beyond a critical value which varies with temperature, indicating nonlinear viscoelastic behavior. The time-temperature-stress superposition principle (TTSSP) was used to construct a smooth master compliance curve with a much longer time-scale interval from the short-term tests at higher stresses and temperatures. It is shown that the master curve covers a period of over 290 days, which is nearly 3.9 decades longer than the test duration. Moreover, it is verified that the time-temperature shift factors are dependent on stresses at which the shifts are applied, and that the time-stress shift factors are dependent on reference temperatures.

Effect of Stress-Induced Damage Evolution on Long-Term Creep Behavior of Nonlinear Viscoelastic Polymer

2006 ◽  
Vol 324-325 ◽  
pp. 731-734 ◽  
Author(s):  
Rong Guo Zhao ◽  
Wen Bo Luo ◽  
Chu Hong Wang ◽  
Xin Tang
Keyword(s):  
Methyl Methacrylate ◽  
Temperature Stress ◽  
Creep Behavior ◽  
Damage Evolution ◽  
Creep Compliance ◽  
Superposition Principle ◽  
Nonlinear Viscoelastic ◽  
Compliance Curve ◽  
Term Creep

The mechanical behaviors were investigated by nonlinear creep tests of poly(methyl methacrylate) under different temperatures. The test duration was 4000 seconds. The corresponding temperature shift factors, stress shift factors and temperature-stress shift factors were obtained according to time-temperature superposition principle, the time-stress superposition principle and the time-temperature-stress superposition principle (TTSSP). The master creep compliance curve up to about 1-month at a reference temperature 22 degrees centigrade and a reference stress 14 MPa was constructed, and the effect of stress-induced damage evolution on the long-term creep behavior of polymeric material was accounted. It was shown that TTSSP provides an effective accelerated test technique in the laboratory, the results obtained from a short-term creep test of poly(methyl methacrylate) specimen at high temperature and stress level can be used to construct the master creep compliance curve for prediction of the long-term mechanical properties at relatively lower temperature and stress level, and the master creep compliance curve with damage considered can be applied to accurately characterize the long-term creep behavior of nonlinear viscoelastic polymer.

Physical Aging and Creep Behavior of Poly(Methyl Methacrylate)

2007 ◽  
Vol 561-565 ◽  
pp. 2041-2044 ◽  
Author(s):  
Wen Bo Luo ◽  
Xin Tang ◽  
Rong Guo Zhao ◽  
Jiang Hua Tan ◽  
Yoshihiro Tomita
Keyword(s):  
Methyl Methacrylate ◽  
Aging Time ◽  
Stress Level ◽  
Creep Behavior ◽  
Physical Aging ◽  
Superposition Principle ◽  
Test Time ◽  
Nonlinear Creep ◽  
Poly Methyl Methacrylate ◽  
Compliance Curve

In this work, the physical aging and its effect on nonlinear creep behavior of poly(methyl methacrylate) are presented. After annealing above Tg to release the previous thermal and stress history, the samples were quenched to 60oC, aged for various times, and were then tested at three different stress levels (22MPa, 26MPa and 30MPa) at room temperature of 27oC. At each stress level, the creep strain was converted to compliance and measured as a function of test time and aging time. The test results show that higher stress accelerates creep rate of the material while physical aging plays a reverse role. The time-aging time superposition is applicable to build a master creep compliance curve at each stress level, and it is demonstrated that the shift rate deceases with increasing stress. Moreover, based on the time-stress superposition principle, a unified master curve was constructed by further shifting the sub-master curves at 30MPa and 26 MPa to a reference stress level of 22MPa.

Drained creep of undisturbed cohesive marine sediments

1994 ◽  
Vol 31 (6) ◽  
pp. 841-855 ◽  
Author(s):  
W.-M. Tian ◽  
A.J. Silva ◽  
G.E. Veyera ◽  
M.H. Sadd
Keyword(s):  
Stress Level ◽  
Simple Shear ◽  
Test Duration ◽  
Time Behavior ◽  
Creep Tests ◽  
Shear Creep ◽  
Central Pacific ◽  
Stress Strain ◽  
The North ◽  
Triaxial Creep

Long-term, drained triaxial creep and direct simple shear creep tests were conducted on undisturbed marine specimens from the Gulf of Mexico and the north-central Pacific. Results indicated that time-dependent deformations can be represented by a power law equation, and the creep strain rate can be represented by an equation similar to that suggested earlier by other researchers. However, it was found that the m parameter suggested by these scientists was not a constant but dependent on stress level and sediment plasticity. Ageing effects were evidenced in triaxial specimens by the increase of shear strength with both test duration and stress level. The results provided a guide for the development of mathematical stress–strain–time relationships that will be developed in a separate paper. Key words : drained triaxial creep, simple shear creep, stress–strain–time behavior.

Prediction of Bending Creep Behavior of Rice Hull Flour/Polypropylene Composite

2012 ◽  
Vol 200 ◽  
pp. 203-206
Author(s):  
Zhao Yang Xu ◽  
Da Gang Li ◽  
Yan Wu
Keyword(s):  
Stress Level ◽  
Creep Behavior ◽  
Equivalence Principle ◽  
Master Curve ◽  
Creep Compliance ◽  
Bending Test ◽  
Rice Hull ◽  
Polypropylene Composite ◽  
Stress Levels ◽  
Compliance Curve

The creep behaviors of rice hull flour/PP composite under different stress levels were studied through bending test. The results show that the bending creep behaviors of rice hull flour/PP composite have obviously correlation to the stress levels. Based on the time-temperature-stress equivalence principle and 15% stress level as a reference, the creep compliance master curve of 15% stress level was constructed by horizontally shift the creep compliance curve of other stress levels, which can predict the creep behavior of rice hull flour/PP composite at the 15% stress level.

Modeling and Prediction of Creep Behavior of Polypropylene Packaging Belt

2011 ◽  
Vol 117-119 ◽  
pp. 1168-1171
Author(s):  
Zhao Yang Xu
Keyword(s):  
Stress Level ◽  
Creep Behavior ◽  
Creep Compliance ◽  
Element Model ◽  
Tensile Creep ◽  
Elastic Coefficient ◽  
Horizontal Shift ◽  
Stress Levels ◽  
Compliance Curve ◽  
Short Time

The short term tensile creep behaviors of polypropylene (PP) packaging belt under different stresses levels were studied through tensile creep test. The four-element model was applied to simulate the creep behaviors of the PP packaging belt. The results show that four-element model can be used to simulate the short time creep of PP packaging belt. The tensile creep behaviors of PP packaging belt have obviously correlation to the stress levels. The instantaneous elastic coefficient, delayed elastic coefficient and glutinous coefficient in Maxell model show a decreasing tendency with the increase of stress level. Based on the time-temperature-stress equivalence principle and take 15% stress level as a reference, the creep compliance master curve of 15% stress level was constructed by horizontal shift of the creep compliance curve of other stress levels, which can predict the creep behavior of PP packaging belt at the 15% stress level.

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