Application of TTSP to wood-development of a vertical shift factor

Holzforschung ◽  
2017 ◽  
Vol 71 (1) ◽  
pp. 51-55 ◽  
Author(s):  
Fuli Wang ◽  
Tianlai Huang ◽  
Zhuoping Shao
Keyword(s):  
Stress Relaxation ◽  
Master Curve ◽  
Goodness Of Fit ◽  
Superposition Principle ◽  
Relaxation Curve ◽  
Shift Factor ◽  
Vertical Shift ◽  
Wood Development ◽  
Time Temperature Superposition Principle

Abstract The applicability of the time-temperature superposition principle (TTSP) to wood has been investigated aiming at the prediction of long-term mechanical properties of wood by both horizontally and vertically shifting of short-term stress relaxation data obtained by experiments. The expression of TTSP considering the vertical shift factor (bT) for wood is proposed the first time. The results showed that: (1) TTSP applied to poplar and the master curve that was obtained from 1 h of tests at 283.2, 303.2, 320.2, 343.2, and 363.2 K in a relative humidity (RH) of 60% could predict the stress relaxation behavior for approximately 42 years at 283.2 K and 60% RH. (2) There was a linear correlation between lgaT and T-1, lg aT=6590.40 T-1-23.64 (R2=0.994), which followed the Arrhenius equation well, while the apparent activation energy was 34.6 kcal mole-1. (3) The bT had a linear relationship with temperature, and the relation was lgbT=0.0013T-0.37 (R2=0.999). (4) The long-term relaxation curve of the long-term verification test had high goodness of fit with the master curve. The results can be interpreted that the TTSP expression considering the bT proposed in this paper is rational.

On the Relation between Stress Relaxation and Constant Strain Rate Tensile Behavior for Linear Viscoelastic Materials; An Engineering Approach

2012 ◽  
Vol 729 ◽  
pp. 314-319 ◽  
Author(s):  
Gábor Bódai ◽  
Tibor Goda
Keyword(s):  
Stress Relaxation ◽  
Master Curve ◽  
Superposition Principle ◽  
Constant Strain Rate ◽  
Relaxation Modulus ◽  
Tensile Tests ◽  
Time Frequency ◽  
Construction Methods ◽  
Linear Viscoelastic ◽  
Time Temperature Superposition Principle

The present paper, as a first step summarizes briefly the master curve construction methods applying the stress relaxation and DMTA based approach. Then, authors make recommendation to increase the covered time (frequency) domain of relaxation modulus master curve coming from standard tensile tests-performed at wide temperature range-by utilizing the time-temperature superposition principle. The proposed approach is used for natural rubber, whose tensile tests, for the sake of simplicity, are replaced by calculated engineering stress-strain curves. All in all, the proposed method gives fast and reliable way for engineers to identify the parameters of spring-dashpot models.

Integration of Atomistic Simulation with Experiment Using Time−Temperature Superposition for a Cross-Linked Epoxy Network

2019 ◽  
Author(s):  
Ketan Khare ◽  
Frederick R. Phelan Jr.
Keyword(s):  
Master Curve ◽  
Glassy State ◽  
Superposition Principle ◽  
Quantitative Comparison ◽  
Time Shift ◽  
Data Sets ◽  
Epoxy Network ◽  
Temperature Superposition ◽  
Time Temperature Superposition ◽  
Time Temperature Superposition Principle

<a></a><a>Quantitative comparison of atomistic simulations with experiment for glass-forming materials is made difficult by the vast mismatch between computationally and experimentally accessible timescales. Recently, we presented results for an epoxy network showing that the computation of specific volume vs. temperature as a function of cooling rate in conjunction with the time–temperature superposition principle (TTSP) enables direct quantitative comparison of simulation with experiment. Here, we follow-up and present results for the translational dynamics of the same material over a temperature range from the rubbery to the glassy state. Using TTSP, we obtain results for translational dynamics out to 10<sup>9</sup> s in TTSP reduced time – a macroscopic timescale. Further, we show that the mean squared displacement (MSD) trends of the network atoms can be collapsed onto a master curve at a reference temperature. The computational master curve is compared with the experimental master curve of the creep compliance for the same network using literature data. We find that the temporal features of the two data sets can be quantitatively compared providing an integrated view relating molecular level dynamics to the macroscopic thermophysical measurement. The time-shift factors needed for the superposition also show excellent agreement with experiment further establishing the veracity of the approach</a>.

Analysis on the Creep Mechanism of 12Cr-Mo-W-0.25V Steel Based on Long-Term Stress Relaxation Test Data

2016 ◽  
Vol 853 ◽  
pp. 158-162
Author(s):  
Jie Zhao ◽  
Tie Shan Cao ◽  
Cong Qian Cheng ◽  
Hui Fang Li
Keyword(s):  
Stress Relaxation ◽  
Test Data ◽  
Activation Volume ◽  
High Stress ◽  
Relaxation Curve ◽  
Relaxation Test ◽  
Dislocation Slip ◽  
Stress Relaxation Test ◽  
Steel Base

The current paper investigates on the creep behavior of 12Cr-Mo-W-0.25V heat resistant steel base on the long-term stress relaxation test data. It is shows that the stress relaxation curve can be divided into 2 stages: the high stress stage has higher apparent activation volume of 79~350 b3 and the low stress stage is 35~78 b3. Besides, the Helmholtz free energy at the high stress stage is 827~1034 kJ/mol which is higher than 210~252 kJ/mol of the low stress stage. Taking both apparent activation volume and activation energy into account, it is assumed that the high stress stage is mainly controlled by dislocation slip and the low stress stage is more related to diffusion.

scholarly journals Rubber aging life prediction based on interpolation and improved time-temperature superposition principle

2021 ◽  
Author(s):  
Kunheng Li ◽  
Zhiyong Chen ◽  
Wenku Shi
Keyword(s):  
Life Prediction ◽  
Room Temperature ◽  
Superposition Principle ◽  
Accelerated Aging ◽  
Shift Factor ◽  
Performance Degradation ◽  
Polymer Materials ◽  
Temperature Superposition ◽  
Time Temperature Superposition ◽  
Time Temperature Superposition Principle

Abstract With focus on quickly and accurately predicting and evaluating the aging performance degradation of rubber at room temperature, the pseudo-failure life at each different acceleration temperature is proposed to be calculated by interpolation method based on indoor high temperature accelerated aging data, and on the basis of the obtained pseudo-failure life.By introducing the time–temperature equivalence principle, a shift factor obeying to an Arrhenius law is derived, and master curves are built as well for the compression set as for the ultimate mechanical properties.The concept of the sum of squares of dispersion coefficient errors is proposed to evaluate the prediction accuracy.Meanwhile a quantitative calculation method that considers the effect of temperature on the performance degradation curve and the shift factor is innovatively proposes.The results show that the proposed optimization method based on the traditional time-temperature superposition principle can quickly process the aging life at room temperature, and the prediction results are distributed within the 3-fold dispersion line, which can well meet the engineering requirements. The reduction of the DSC value from 1.4164 to 1.0828 further demonstrates the effectiveness of the proposed method above. This method can provide some reference for other related polymer materials accelerated aging data processing and life prediction.

Prediction of fiber-directional flexural strength of carbon fiber-reinforced polypropylene based on time–temperature superposition principle

2017 ◽  
Vol 52 (6) ◽  
pp. 793-805 ◽  
Author(s):  
Tsuyoshi Matsuo ◽  
Masayuki Nakada ◽  
Kazuro Kageyama
Keyword(s):  
Carbon Fiber ◽  
Flexural Strength ◽  
Master Curve ◽  
Superposition Principle ◽  
Bending Test ◽  
Thermoplastic Composites ◽  
Fiber Reinforced ◽  
Temperature Superposition ◽  
Time Temperature Superposition ◽  
Time Temperature Superposition Principle

This study verified that the time–temperature superposition principle for fiber-directional flexural strength can be applied to thermoplastic composites undergoing instantaneous fast phenomena such as impact failure and long-term phenomena such as creep failure, by constructing the time- and temperature-dependent master curve of relaxation modulus of thermoplastic resin. The master curve could be transformed to another master curve that predicts fiber-directional flexural strength of carbon fiber-reinforced thermoplastic composites based on the micro-buckling failure theory expressed mainly by the resin’s elastic modulus. The experimental results obtained from high-speed bending test, static bending test at various temperatures, and creep bending test demonstrated that kink band failure occurred on the compressive surface of the specimen at every test condition. This validation and verification related to thermoplastic composites made it possible to predict static and dynamic flexural strengths at arbitrary temperature and creep flexural strength.

The Stress-Relaxation Behavior of Rice as a Function of Time, Moisture and Temperature

2017 ◽  
Vol 13 (2) ◽  
Author(s):  
Pan Wang ◽  
Li-jun Wang ◽  
Dong Li ◽  
Zhi-gang Huang ◽  
Benu Adhikari ◽  
...  
Keyword(s):  
Stress Relaxation ◽  
Moisture Content ◽  
Master Curve ◽  
Superposition Principle ◽  
Relaxation Modulus ◽  
Maxwell Model ◽  
Relaxation Behavior ◽  
Stress Relaxation Behavior ◽  
Linear Viscoelastic ◽  
Single Rice

Abstract: Stress-relaxation behavior of single rice kernel was studied using a dynamic mechanical analyzer (DMA) in compression mode. The relaxation modulus was measured in a moisture content range of 12–30 % on dry basis (d.b.) and a temperature range of 25–80°C. A constant stain value of 1 % (within the linear viscoelastic range) was selected during the stress-relaxation tests. The relaxation modulus was found to decrease as the temperature and moisture increased. A master curve of relaxation modulus as a function of temperature and moisture content was generated using the time–moisture–temperature superposition principle. Results showed that the generalized Maxwell model satisfactorily fitted the experimental data of the stress-relaxation behavior and the master curve of relaxation modulus (R2> 0.997). By shifting the temperature curves horizontally, the activation energy of the stress relaxation was obtained which significantly decreased with increase in the moisture content.

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