• Journal of Pharmaceutical Investigation
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• 제36권1호
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• pp.31-38
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• 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).

• 한국해양공학회지
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• 제29권3호
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• pp.241-248
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• 2015

A subsea pipeline for oil/gas transportation or gas injection is subjected to extreme variations in internal pressure and temperature, which can involve a strain rate effect on the pipeline material. This paper describes the flow stress characteristics of a pipeline material called API 5L X52N PSL2, using and experimental approach. High-speed tensile tests were carried out for two metal samples taken from the base and weld parts. The target temperature was 100℃, but two other temperature levels of –20℃and 0℃ were taken into account. Three strain rates were also considered for each temperature level: quasi static, 1/s, and 10/s. Flow stress data were proposed for each temperature level according to these strain rates. The dynamic hardening behaviors of the base and weld metals appeared to be nonlinear on the log-scale strain rate axis. A very high material constant value was required for the Cowper-Symonds constitutive equation to support the experimental results.

• 한국재료학회지
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• 제19권12호
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• pp.692-698
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• 2009

Inconel 718 alloy has excellent mechanical properties at room temperature, high temperature and cryogenic conditions. UTS of base metal is about 900MPa at room temperature; this is increased up to 1300MPa after heat treatment & aging-hardening. Mechanical properties of Inconel 718 Alloy were similar to those shown in the the results for tensile test; mechanical properties of Inconel 718 alloy's GTAW were similar to those of base metal's properties at room temperature. Mechanical properties at cryogenic conditions were better than those at room temperature. Heat-treated Inconel 718, non- filler metal GTAW on Inconel 718 and GTAW used filler metal on Inconel 718's UTS was 1400MPa at cryogenic condition. As a result, the excellent mechanical properties of Inconel 718 alloy under cryogenic conditions was proved through tensile tests under cryogenic conditions. In addition, weldability of Inconel 718 alloy under cryogenic conditions was superior to that of its base-metal. In this case, UTS of hybrid joint (IS-G) at -100$^{\circ}C$ was 900MPa. Consequently, UTS of Inconel 718 alloy is estimated to increase from -100$^{\circ}C$ to a specific temperature below -100$^{\circ}C$. Therefore, Inconel 718 alloy is considered a pertinent material for the production of Lox Pipe under cryogenic conditions.

• 한국안전학회지
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• 제31권4호
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• pp.9-14
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• 2016

STS304L of membrane structure has been used for a LNG storage tank and has exposed long time under the cryogenic temperature. The purposes of this study are to evaluate the mechanical properties of base and used materials for STS304L of membrane. The tensile and high cycle fatigue tests were investigated for STS304L of membrane used over 20 years at room temperature and $-162^{\circ}C$. In addition, the test of base STS304L was performed in order to compare with used material properties. The chemical composition and phase change were investigated from EDS and XRD. From results of tensile test, yield and ultimate tensile strengths of used STS304L are smaller than those of base STS304L. S-N curves were obtained from fatigue tests at both temperatures. Also, P-S-N curves were presented with statistical method recommend by JSME-S002. Fractography was conducted for analysis of fracture mechanisms.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집A
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• pp.188-193
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• 2000

A more accurate life prediction for gas turbine blade takes into account the material behavior under the complex thermo-mechanical fatigue(TMF) cycles normally encountered in turbine operation. An experimental program has been carried out to address the thermo-mechanical fatigue life of the IN738LC nickel-base superalloy. In the first phase of the study, out-of-phase and in-phase TMF experiments have been performed on uncoated and coated materials. In the temperature range investigated. the deposition of NiCrAlY air plasma sprayed coating did not affect the fatigue resistance. In the second phase of the study, a physically-base life prediction model that takes into account of the contribution of different damage mechanisms has been applied. This model was able to reflect the temperature and strain rate dependences of isothermal cycling fatigue lives, and the strain-temperature history effect on the thermo-mechanical fatigue lives.

• 대한기계학회논문집A
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• 제31권4호
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• pp.525-531
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• 2007

The operating temperature has been increased to improve the efficiency of gas turbine. The most advanced Gas turbine is operated at above $1,500^{\circ}C$. Improvement in material and cooling method permit hot gas path component to run at increased temperature. But, the repair of blades which are developed with advanced manufacture technique is difficult to use normal welding. Most of gas turbine blades are made of precipitation harden nickel base superalloy, which is very hard to weld. Therefore, the employment of welding filler on blade is solid solution nickel base superalloy(Hastelloy X, Inconel 617). In this study, Tensile test in high temperature was conducted on welded GTD111DS with GTD111 to evaluate effect of variation of pre, post treatment. The result of this study showed that the specimen was treated with optimum pre and post treatment(preweld HT($1200^{\circ}C$), Post treatment($1100^{\circ}C$ HIP, $1200^{\circ}C$ + $1100^{\circ}C$ + $800^{\circ}C$ HT) is mush superior.

• 대한기계학회논문집B
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• 제32권10호
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• pp.776-783
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• 2008

The object of this paper is to study on the thermal performance of a micro channel water block for computer CPU cooling. The effects of liquid flow rate, micro channel width and height on the thermal performances of water block are investigated experimentally. The water block was fabricated Al and machined with a micro milling. The water block consisted of rectangular micro channels 0.5 to 0.9 mm width and 1.5 to 4.5 mm height. The experiments were conducted using deionized water, over a liquid flow rate ranging from 0.2 to 2.0 kg/min. The base temperature and thermal resistance decrease with increasing of liquid flow rate. The increase of a channel height is more effective on the thermal resistance than the decrease of a channel width. At the flow rate of 0.7 kg/min, input power of 100 W, the base temperature and thermal resistance of sample 6 is $33^{\circ}C$ and $0.13\;^{\circ}C/W$ respectively.

• 대한화장품학회:학술대회논문집
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• 대한화장품학회 2003년도 IFSCC Conference Proceeding Book II
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• pp.303-306
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• 2003

Indonesia is a tropical country having a temperature range of 25-35$^{\circ}C$ which can affect the skin and causes damages like aging. This aging process is due, at least, to free radical reactions. For this reason, many attempts had been done to find out creams containing natural antioxidant compound which have a potential of free radical scavenger. Kluwek, a fermented form of foot ball fruit or picung (Pangium edule.Reinw), had been proved to contain antioxidant compound in its methanol fraction oil to which antiaging cream was formulated. Stability evaluation was conducted for cream with Kluwek oil compared to base cream, including organoleptic (colour and odour), pH, viscosity, particle size, centrifugation test and flow characteristics either in room temperature (27$^{\circ}C$) or stress condition (4$^{\circ}C$ and 5$0^{\circ}C$) for 8 weeks continuously, and six times cycling test at 4$^{\circ}C$ and 5$0^{\circ}C$ every 24 hours. The results showed that cream with Kluwek oil and base cream were stable at temperature 27 and 4$^{\circ}C$, cycling test and centrifugation test, but not stable at 5$0^{\circ}C$. Free radical evaluation was done by Electron Spin Resonance and the result showed that cream with Kluwek oil had less free radicals compared to base cream.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2012년도 추계학술대회 논문집
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• pp.546-552
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• 2012

This paper is a study on squeal noise simulation under the consideration of temperature and pressure dependent material properties of friction material. For this, data of pressure and temperature dependent material properties of lining is achieved by using lining data base and exponential curve fit. Complex eigenvalue analysis is performed for predicting squeal noise frequency and instability and chassis dynamo test is performed for achieving squeal noise frequency, sound pressure level, occurrence temperature & pressure. Initial multi models are composed for considering complex interface conditions such as pad ear-clip, piston-housing and guide pin-torque member. The simulation result of base models is compared with the test result. Squeal noise simulation under the consideration of temperature and pressure dependent material properties of friction material is performed and analyzed using multi models. And additional condition is disc material property variation. Entire simulation conditions are combined and analyzed. Finally, this paper proposes direction of the warm squeal noise model.

• 한국주조공학회지
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• 제35권6호
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• pp.170-177
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• 2015

Segregation during solidification and homogenization during thermal exposure in GTD 111 were investigated. The microstructures of as-cast, standard heat-treated, and thermally exposed specimens were observed by SEM. A compositional analysis of each specimen was conducted by EDS. The dendrite core was enriched in W and Co, though lower levels of Ti and Ta were observed. An unexpected phase, in this case like the ${\eta}$ phase, was observed due to segregation near the ${\gamma}-{\gamma}^{\prime}$ eutectic in the standard heat-treated specimen. Segregation also induced microstructural evolution near the ${\gamma}-{\gamma}^{\prime}$ eutectic during the standard heat treatment. A quantitative analysis and microstructural observations showed that the thermal exposure at a high temperature enhanced the chemical homogeneity of the alloy.