scholarly journals Study on Mechanical Relaxations of 7075 (Al–Zn–Mg) and 2024 (Al–Cu–Mg) Alloys by Application of the Time-Temperature Superposition Principle

2017 ◽  
Vol 2017 ◽  
pp. 1-12 ◽  
Author(s):  
Jose I. Rojas ◽  
Jorge Nicolás ◽  
Daniel Crespo
Keyword(s):  
Temperature Region ◽  
Master Curve ◽  
Amorphous Materials ◽  
Superposition Principle ◽  
Mg Alloys ◽  
Loading Frequency ◽  
Master Curves ◽  
Storage And Loss Moduli ◽  
Temperature Superposition ◽  
Time Temperature Superposition

The viscoelastic response of commercial Al–Zn–Mg and Al–Cu–Mg alloys was measured with a dynamic-mechanical analyzer (DMA) as a function of the temperature (from 30 to 425°C) and the loading frequency (from 0.01 to 150 Hz). The time-temperature superposition (TTS) principle has proven to be useful in studying mechanical relaxations and obtaining master curves for amorphous materials. In this work, the TTS principle is applied to the measured viscoelastic data (i.e., the storage and loss moduli) to obtain the corresponding master curves and to analyze the mechanical relaxations responsible for the viscoelastic behavior of the studied alloys. For the storage modulus it was possible to identify a master curve for a low-temperature region (from room temperature to 150°C) and, for the storage and loss moduli, another master curve for a high-temperature region (from 320 to 375°C). These temperature regions are coincidental with the stable intervals where no phase transformations occur. The different temperature dependencies of the shift factors for the identified master curves, manifested by different values of the activation energy in the Arrhenius expressions for the shift factor, are due to the occurrence of microstructural changes and variations in the relaxation mechanisms between the mentioned temperature regions.

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>.

Applicability of time temperature superposition principle to an immiscible blend of polyphenyleneoxide and polyamide

2011 ◽  
Vol 31 (2-3) ◽  
Author(s):  
Narendra A. Hardikar ◽  
Somasekhar Bobba ◽  
Roshan Jha
Keyword(s):  
Storage Modulus ◽  
Master Curve ◽  
Loss Modulus ◽  
Superposition Principle ◽  
Strict Sense ◽  
Cole Plot ◽  
Temperature Superposition ◽  
Immiscible Blend ◽  
Thermorheological Behavior ◽  
Time Temperature Superposition

Abstract The immiscible blend of polyphenyleneoxide (PPO) and polyamide (PA) is used in several applications exposed to high temperature. The complexity of numerical modeling of such materials is dependent on their thermorheological behavior with significant simplification possibilities, if the material is found to follow the time temperature superposition (TTS) principle and show thermorheological simplicity (TRS). Hence as a precursor to selecting accurate constitutive modeling approach, the paper investigates the applicability of the TTS principle and the nature of thermorheological behavior to the blend. Dynamic mechanical analysis (DMA)frequency scans were performed in the range of 0.1–100 rad/s from 0°C to 210°C at 10°C intervals. Temperature dependency was observed on the Cole-Cole plot pointing to the thermorheological complexity and the need for vertical shift factors. 2-D minimization algorithm was used to shift the isotherms horizontally and vertically to obtain master curves. Except, in the vicinity of glass transition temperature T g , the isotherms overlap to form a master curve, but further analysis considering various conditions indicate that in a strict sense TTS is not applicable to the blend when both storage G′ and loss modulus G″ are considered. However, a continuous master curve of storage modulus spanning 31 decades of time is obtained using horizontal shifting alone when loss modulus is neglected. Further testing is required to ascertain if relaxation modulus can be approximated with storage modulus alone before taking recourse to characterization methods developed for thermorheologically complex (TRC) materials.

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.

scholarly journals 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>.

Note. Modelling the Rheological Properties of the Solution of Konjac Glucomannan and Milk Powder

2006 ◽  
Vol 12 (2) ◽  
pp. 127-132 ◽  
Author(s):  
X. H. Yang ◽  
W. L. Zhu
Keyword(s):  
Superposition Principle ◽  
Milk Powder ◽  
Maxwell Model ◽  
Angular Frequency ◽  
Konjac Glucomannan ◽  
Temperature Ramp ◽  
Storage And Loss Moduli ◽  
Temperature Superposition ◽  
Time Temperature Superposition ◽  
Time Temperature Superposition Principle

Shear storage and loss moduli (G″ and G ′) of a solution of konjac glucomannan (KGM) and milk powder were measured while varying angular frequency and temperature. Results showed that both G′ and G″ increased with the angular frequency sweeping from 0.1 rad/s to 100 rad/s, in a variety of temperatures and KGM concentrations. However, they decrease with temperature sweeping from 10°C to 50°C. These recorded curves were satisfactorily fitted to a multi-element Maxwell model. The angular sweep and temperature ramp data sitting along a sole line on the G″ –G′ diagram demonstrates the solution of KGM and milk powder obeys the time–temperature superposition principle. Furthermore, the fitted magnitude of G1 of the first multi-element Maxwell model is proportional to the concentration of the solution. These results are valuable for the optimising production of the functional KGM-milk food.

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