• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.4
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• pp.623-632
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• 2018

Predicting the behavior of rheological polymers is highly shear rate- and temperature-dependent. The Cross-WLF viscosity model has become a powerful solution that describes the shear rate- and temperature-dependent characteristics. To estimate the behavior of polymers in computational simulations, the coefficients of the Cross-WLF model should be well identified. An identification technique was proposed to determine the Cross-WLF viscosity model coefficient. The assumption is that the Cross-WLF viscosity model well describes the real characteristics of polymers when the calculated viscosity with the parameters is identical to the reference data. In this study, Auto-desk Moldflow data were used as a reference. The numerical examples showed that the proposed method accurately identifies the Cross-WLF viscosity model coefficients.

• Journal of the Korean Chemical Society
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• v.14 no.1
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• pp.45-48
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• 1970

The WLF equation is derived from the theory of rate processes in conjunction with the theory of liquids of significant structures. The empirical parameters in the WLF equation are discussed and compared with the corresponding quantities in the derived equation.

• Korean Journal of Food Science and Technology
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• v.27 no.2
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• pp.193-198
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• 1995

The changes in the rheological properties of soybean curd upon the various storage temperatures ($5{\sim}25^{\circ}C$) were measured by the stress-relaxation test and analysed by time-temperature superposition theory. As the storage temperature was lower, higher initial and equilibrium stress of soybean curd were observed. When the stress-relaxation curves were moved horizontally by using the shift-factor on the basis of reference temperature, the master curve was obtained. By applying master curve and shift-factor to the WLF (Williams-Landel-Ferry) equation, activation energy (30kcal/mol) was calculated and storage time at the specific temperature could be predicted, suggesting the equivalent shelf-life of soybean curd texture.

• Polymer(Korea)
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• v.26 no.1
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• pp.88-97
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• 2002

The effect of aminosiloxane modifier on the chemorheological properties of ortho-cresol novolac epoxy/phenol novelac/triphnylphosphine resin system was investigated aat different isothermal curing temperatures. By adding the aminosiloxane to the resin system, not only conversion rate and conversion were increased but also glass transition temperature was promoted. Critical conversion and gelation time obtained at the crossover point between storage and loss moduli were reduced and thus the viscosity was increased by the aminosiloxane. $C_1$ and $C_2$ in the WLF equation calculated from the glass transition temperature as a function of conversion and measured viscosity were found to vary with the curing temperature. By applying the change of glass transition temperature with conversion, $C_1$ and $C_2$ to WLF equation, it was possible to predict accurately the viscosity change with isothermal curing reaction.

• Elastomers and Composites
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• v.48 no.2
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• pp.156-160
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• 2013

A study on compressive creep behavior of ACM rubber for automotive engine gasket was performed using TMA thermal analysis. From the results of isothermal measurements with constant load of 1 N at several different temperatures of 160, 180, 200, and $220^{\circ}C$, compressive creep data at the given temperatures were obtained, and therefrom, shift factor ($a_T$) and master curve at reference temperature of $160^{\circ}C$ were obtained using time-temperature superposition principle (TTSP). $C_1$ and $C_2$ of WLF (Williams-Landel-Ferry) equation were calculated through the WLF plot as -1.107 and 11.571, respectively. From this, life time of ACM rubber at $120^{\circ}C$ was predicted as about 24,000 hrs.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2002.09a
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• pp.28-31
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• 2002

The water level fluctuation (WLF) method is a conventional method for quantifying groundwater recharge by multiplying the specific yield to the water level rise. A 2-D unconfined flow model with a time series of the recharge rate is developed. It is used for elucidating the errors of the WLF method which is implicitly based on the tank model where the horizontal flow in the saturated zone is ignored. Simulations show that the recharge estimated by the WLF method is underestimated for the observation well near the discharge boundary. This is due to the fact that the hydraulic stress resulting from the recharge is rapidly dissipating by the horizontal flow near the discharge boundary Simulations also reveal that the recharge was significantly underestimated with increase in the hydraulic conductivity and the recharge duration, and decrease in the specific yield.

• The Bulletin of The Korean Astronomical Society
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• v.41 no.2
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• pp.67.3-68
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• 2016

An X1.6 flare occurred in AR 12192 on 2014 October 22 around 14:06 UT and was observed by Hinode, IRIS, SDO and RHESSI. We analyze a bright kernel which produces a white light flare (WLF) with continuum enhancement and a hard X-ray (HXR) peak. Taking advantage of the spectroscopic observations of IRIS and EIS, we measure the temporal variation of the plasma properties in the bright kernel in the chromosphere and corona. We found that explosive evaporation was observed when the WLF occurred, even though the intensity enhancement in hotter lines is quite weak. The temporal correlation of the WLF, HXR peak, and evaporation flows indicates that the WLF was produced by accelerated electrons. To understand the white light emission processes, we calculated the deposited energy flux from the non-thermal electrons observed by RHESSI and compared it to the dissipated energy estimated from the chromospheric lines (Mg II triplet) observed by IRIS. The deposited energy flux from the non-thermal electrons is about $3.1{\times}10^{10}erg\;cm^{-2}s^{-1}$ when we assume a cut-off energy of 20 keV. The estimated energy flux from the temperature changes in the chromosphere measured from the Mg II subordinate line is about $4.6-6.7{\times}10^9erg\;cm^{-2}s^{-1}$, 15 - 22 % of the deposited energy. By comparison of these estimated energy fluxes we conclude that the continuum enhancement was directly produced by the non-thermal electrons.

• Journal of the Korean Society of Clothing and Textiles
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• v.2 no.2
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• pp.245-252
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• 1978

In order to obtain some information for solvent dyeing, polyethylene terephthalate (PET) was treated with water, tetrachloroethylene yarn (TCE), and water/TCE emulsion for three hours at the temperatures from $40^{\circ}$ to $140^{\circ}C$. The change of fine structure of substratum by measuring the shrinkage, the degree of crystallinity, the stress relacxation modulus and Young's modulus. The P.E.T. film was also treated in water (at $140^{\circ}C$) for 4 hours to stabilize the substratum. By means of film roll cyliderical method, the Disperse Blue 27 was diffused. Then, calculated the diffusion coefficient and examined the application of WLF equation. However, the temperature dependence of the shrinkage could be explain with WLF equation, the diffusion coefficient couldn't be applied the WLF equation when the substratum was stabilized. From the result, the effects on shrinkage were in the order of water

• Elastomers and Composites
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• v.41 no.1
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• pp.40-48
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• 2006

Mechanical systems with rubber parts have been used widely in industry fields. The evaluation of the physical characteristics of rubber is important in rubber application. Rubber material is useful to machine component for excellent shock absorbing characteristics. The impact characteristics of rubber were examined by experimental and finite element method. The impact test was conducted with a free-drop type impact tester. The ABAQUS/Explicit was used for finite element analysis. In the finite element analysis, elastic modulus of rubber using impact force was used as dynamic modulus, which are measured and predicted with dynamic property test and WLF model. The analysis result was coincided with the experimental results.

• Journal of the Korean Society for Precision Engineering
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• v.23 no.1 s.178
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• pp.159-165
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• 2006

Many rubber products are used in industrial products such as various hoses, rubber belts and oil seals etc. Especially, more then 200 rubber parts are used in the automobile, but design technology of these is largely dependent on Held experiences. These methods brought about too much time and cost in the developing procedures. However, with the help of recent rapid development of non-liner computer analysis, we can develop new sound products at low cost. Therefore in this study, optimizations of design variables such as location and number of gate in order to develop CLIP rubber product made of EPDM were performed by CAE in which Cross-WLF equations are adopted. The validity of proposed variables is evaluated by comparison with real forming results.