• International Journal of Highway Engineering
• /
• v.14 no.5
• /
• pp.75-83
• /
• 2012

PURPOSES: Suggestion of asphalt binder constitutive model based on time-temperature superposition principle and overstress concept in order to describe behavior of asphalt binders. METHODS: A series of temperature sweep tests and multiple stress creep and recovery(MSCR) tests are performed to verify the applicability of time-temperature superposition principle(t-Ts) and to develop viscoelastoplastic constitutive equation based on overstress concept. For the tests, temperature sweep tests at various high temperature and various frequency and MSCR test at $58^{\circ}C$, $64^{\circ}C$ $70^{\circ}C$, $76^{\circ}C$, and $82^{\circ}C$ are performed. From the temperature sweep tests, dynamic shear modulus mastercurve and time-temperature shift function are built and the shift function and MSCR at $58^{\circ}C$ are utilized to determine model coefficients of VBO model. RESULTS: It is observed that the time-temperature shift function built at low strain level of 0.1% is applicable not only to 1.0% strain level temperature sweep test but also maximum 500,00% strain level of MSCR test. As well, the modified VBO model shows perfect prediction on MSCR measured strain at the other temperatures. CONCLUSIONS: The Time-temperature superposition principle stands hold from very low strain level to very high strain level and that the modified VBO model can be applicable for various range of strain and temperature region to predict elastic, viscoelastic, and viscoplastic strain of asphalt binders.

• Computers and Concrete
• /
• v.16 no.6
• /
• pp.897-908
• /
• 2015

This article gives analytical dependences for creep of concrete at heating, taking into account conditions of its drying. These dependences are based on the standard nonlinear theory of creep of concrete at a normal temperature and temperature-time analogy. For the description of creep at various stresses and temperatures the principle of superposition are used. All stages of model's creation are confirmed by the existing experimental data. Calculation examples are given.

• Journal of Pharmaceutical Investigation
• /
• v.36 no.1
• /
• pp.31-38
• /
• 2006

Using a Rheometries Dynamic Analyzer (RDA II), the dynamic viscoelastic properties of a semi-solid ointment base (vaseline) in large amplitude oscillatory shear flow fields were measured over a temperature range of $25{\sim}45^{\circ}C$ and the linear viscoelastic behavior in small amplitude oscillatory shear flow fields was investigated over a wide range of angular frequencies. In this article, the nonlinear viscoelastic behavior was reported from the experimentally obtained data and the effect of temperature on this behavior was discussed in detail. In addition, the angular frequency and temperature dependencies of a linear viscoelastic behavior were explained. Finally, the applicability of a time-temperature superposition principle originally developed for polymeric materials was examined using a shift factor. Main results obtained from this study can be summarized as follows : (1) At very small strain amplitude region, vaseline shows a linear viscoelastic behavior independent of the imposed deformation magnitudes. Above a critical strain amplitude $({\gamma}_{0}=0.1{\sim}0.2%)$, however, vaseline exhibits a nonlinear viscoelastic behavior ; indicating that both the storage modulus and dynamic viscosity are sharply decreased with increasing deformation magnitude. (2) In large amplitude oscillatory shear flow fields, an elastic behavior (storage modulus) has a stronger strain amplitude dependence and begins to show a nonlinear behavior at a smaller strain amplitude region than does a viscous behavior (dynamic viscosity). (3) In small amplitude oscillatory shear flow fields, the storage modulus as well as the loss modulus are continuously increased as an increase in angular frequency and an elastic nature is always superior to a viscous behavior over a wide range of angular frequencies. (4) A time-temperature superposition principle can successfully be applicable to vaseline. This finding allows us to estimate the dynamic viscoelastic behavior of vaseline over an extraordinarily extended range (11 decades) of angular frequencies inaccessible from the experimentally measured range (4 decades).

• Food Science and Biotechnology
• /
• v.16 no.4
• /
• pp.610-614
• /
• 2007

Dynamic rheological properties of honeys with invert sugar at different mixing ratios of honey and invert sugar (10/0, 812, and 6/4 ratios) were evaluated at various low temperatures (-15, -10, -5, and $0^{\circ}C$) using a controlled stress rheometer for small-deformation oscillatory measurements. Honey-invert sugar mixtures displayed a liquid-like behavior, with loss modulus (G") predominating over storage modulus (G') (G">>G'), showing the high dependence on frequency (${\omega}$). The magnitudes of G' and G" increased with a decrease in temperature while their predominant increases were noticed at -10 and $-15^{\circ}C$. The greater tan ${\delta}$ values were found at higher temperature and ratio of honey to invert sugar, indicating that the honey samples at subzero temperatures become more viscous with increased ratio of honey to invert sugar and temperature. The time-temperature superposition (TTS) principle was used to bring G" values at various temperatures together into a single master curve. The TTS principle was suitable for the honey samples in the liquid-like state. The progress of viscous property (G") was also described well by the Arrhenius equation with high determination coefficients ($R^2=0.99$). Dynamic rheological properties of honey samples seem to be greatly influenced by the addition of invert sugar.

• Food Science and Biotechnology
• /
• v.17 no.1
• /
• pp.90-94
• /
• 2008

Dynamic rheological properties of honey samples with 3 different moisture contents (17.2, 19.0, and 21.0%) were evaluated at various low temperatures (-15, -10, -5, and $0^{\circ}C$) using a controlled stress rheometer. The honey samples displayed a liquid-like behavior, with loss modulus (G") predominating over storage modulus (G') (G">>G'), showing the high dependence on frequency ($\omega$). The magnitudes of G' and G" decreased with an increase in temperature and water content while a predominant increase of G' was noticed at $-15^{\circ}C$. The time-temperature superposition (TTS) principle was applied to bring G" values for honeys at various temperatures together into a master curve. The G" over the temperature range of -15 to $0^{\circ}C$ obeyed the Arrhenius relationship with a high determination coefficient ($R^2=0.98-0.99$). Activation energy value (Ea=112.4 kJ/mol) of honey with a moisture content of 17.2% was higher than those (Ea=98.8-101.1 kJ/mol) of other honey samples with higher moisture contents.

• Proceedings of the KSME Conference
• /
• 2000.04a
• /
• pp.751-754
• /
• 2000

Stress relaxation experiments were performed to obtain the material properties to be used in the linear viscoelastic study. Master curve of the modulus of polystyrene were obtained by using the time-temperature superposition principle. Because Shyu and Tobolsky's tensile relaxation modulus master curve or Polystyrene material showed very large difference, in-house data were required to calculate the residual stresses in injection-molded products more accurately. Our own experimental data showed that the master curve Shyu's data should be shifted about two orders in material time coordinate.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.23 no.1
• /
• pp.46-51
• /
• 2019

Intermittent CSR testing was used to investigate the degradation of a NBR O-ring, and also the prediction of its life-time. An intermittent CSR jig was designed taking into consideration the O-ring's environment under use. Degradation of O-rings by thermal aging was observed between $40^{\circ}C$ and $120^{\circ}C$. O-rings showed non-linear degradation behavior under $80^{\circ}C$. At 20% of failure condition, predicted life-times were 32.5 years by Arrhenius plot and 22.6 years by WLF plot.

• Journal of the Korean Geotechnical Society
• /
• v.19 no.5
• /
• pp.291-299
• /
• 2003

The effect of temperature and soil confining stress on geosyntheic creep behaviour was studied by performing the temperature dependent confined creep tests for HDPE geogrid and geomembrane specimen. The visco-elastic creep coefficients of the geosynthetics were evaluated by the test results and it was proposed that the simple expressions for the instantaneous and limit creep strain of geosynthetics was considered as a function of temperature and confining stress on geosynthetics. Based on the time-temperature superposition principle, a master curve has been drawn for extrapolating tensile creep strains to longer time intervals(1$\times$10 $^7$min.∼1$\times$10$^{10}$min.). By using this master curves, the shift factors which can be used in establishing master curve considering confining stress on geosynthetics were carried out. Each tests was performed during 8,000∼12,000 min., with temperature ranging between 5$^{\circ}C$ and 4$0^{\circ}C$ and with confining stress ranging between 0 t/$m^2$ and 9 t/$m^2$.

• Bulletin of the Korean Chemical Society
• /
• v.23 no.3
• /
• pp.413-416
• /
• 2002

The dielectric responses of 10 and 40 wt% siloxane-epoxy copolymers were investigated in temperature range near the glass transition of polydimethylsiloxane at which the dielectric transitions were also observed. On the other hand, the pure epoxy did not show any dielectric transition in measurement temperature range -90 to 150 $^{\circ}C.$ The experimental data showed that for the copolymer investigated, the temperature-frequency super-position principle could be applied to the dielectric response. From the Cole-Cole equation, the dielectric relaxation of the 10 wt% siloxane near the glass transition temperature resulted in a broad distribution with ${\beta}=$ 0.19 and the relaxation time at -70 $^{\circ}C$ was 5.3 ${\times}$ $10^{-2}$s. The glass transition temperature, 188 K, was estimated by using WLF relation, which was consistent with the data presented in experiment.

• Elastomers and Composites
• /
• v.45 no.4
• /
• pp.263-271
• /
• 2010

Intermittent CSR testing was used to investigate the degradation of an FKM O-ring, also the prediction of its life-time. An intermittent CSR jig was designed taking into consideration the O-ring's environment under use. The testing allowed observation of the effects of friction, heat loss, and stress relaxation by the Mullins effect. Degradation of O-rings by thermal aging was observed between 60 and $160^{\circ}C$. In the high temperature of range ($100-160^{\circ}C$) O-rings showed linear degradation behavior and satisfied the Arrhenius relationship. The activation energy was about 60.2 kJ/mol. From Arrhenius plots, predicted life-times were 43.3 years and 69.9 years for 50% and 40% failure conditions, respectively. Based on TTS (time-temperature superposition) principle, degradation was observed at $60^{\circ}C$, and could save testing time. Between 60 and $100^{\circ}C$ the activation energy decreased to 48.3 kJ/mol. WLF(William-Landel-Ferry) plot confirmed that O-rings show non-linear degradation behavior under $80^{\circ}C$. The life-time of O-rings predicted by TTS principle was 19.1 years and 25.2 years for each failure condition. The life-time predicted by TTS principle is more conservative than that from the Arrhenius relationship.