• Geomechanics and Engineering
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• v.18 no.2
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• pp.133-140
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• 2019

Strain-rate and temperature have significant effects on the one-dimensional (1D) compression behavior of soils. This paper focuses on the bonding degradation effect of soil structure on the time and temperature dependent behavior of soft structured clay. The strain-rate and temperature dependency of preconsolidation pressure are investigated in double logarithm plane and a thermal viscoplastic model considering the combined effect of strain-rate and temperature is developed to describe the mechanical behavior of unstructured clay. By incorporating the bonding degradation, the model is extended that can be suitable for structured clay. The extended model is used to simulate CRS (Constant Rate of Strain) tests conducted on structural Berthierville clay with different strain-rates and temperatures. The comparisons between predicted and experimental results show that the extended model can reasonably describe the effect of bonding degradation on the stain-rate and temperature dependent behavior of soft structural clay under 1D condition. Although the model is proposed for 1D analysis, it can be a good base for developing a more general 3D model.

• Nuclear Engineering and Technology
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• v.54 no.7
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• pp.2408-2417
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• 2022

The nanoindentation behavior of P92 steel with thermomechanical treatment under 3.5 MeV Fe¹³⁺ ion irradiation at room temperature, 400 and 700 ℃ was investigated. Pop-in behavior is observed for all the samples with and without irradiation at room temperature, while the temperature dependence of pop-in behavior is only observed in irradiated samples. The average load and penetration depth at the onset of pop-in increase as the irradiation temperature increases, in line with the results of the maximum shear stress. Irradiation induced hardening is exhibited for all irradiated samples, but there is a significant reduction in the hardness of sample irradiated at 700 ℃ in comparison to the samples irradiated at room temperature and 400 ℃. The ratio of hardness to elastic modulus for all samples decreases with increasing penetration depth except for samples at 700 ℃. With the increasing of irradiation temperature, the ratio of the irreversible work to the total work gradually decreases. In contrast, it increases for samples without irradiation.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.05b
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• pp.25-28
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• 2005

The experimental results on the mechanical behavior of high-strength concretes subjected to high temperature were presented. Main variables were heating temperature, heating continuance time, and cooling condition. The compressive strength properties of high strength concrete(HSC) varied differently with temperature than those of normal strength concrete(NSC). HSC had higher rates of strength loss than NSC in the temperature range of between $20^{circ}C$ and $400^{circ}C$. Especially, HSC exploded in $400^{circ}C$ of high temperature.

• Journal of Power System Engineering
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• v.1 no.1
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• pp.70-79
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• 1997

Ni-base self-fluxing alloy powder particles were flame sprayed onto the SS400 mild steel substrate surface. The effects of both substrate temperature and spraying distance on the splat behavior of sprayed particles were examined. The results obtained are summarized as follows: 1) In the splat behavior of Ni-base self-fulxing alloy particles sprayed onto the SS400 mild steel substrate, splashing was observed under the room temperature condition. On the contrary, it showed circular plate pattern in the substrate temperature range over 373K. 2) It was cleared that there was close relationship between mechanical properties of coating layer and splat behavior of sprayed particles. 3) From the experimental results, optimum spraying conditions showed excellent mechanical properties in the case of Ni-base self fluxing alloy sprayed onto the SS400 mild substrate were 473K of substrate temperature and 250mm of spraying distance.

• Journal of Pharmaceutical Investigation
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• v.25 no.3
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• pp.213-221
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• 1995

The steady shear flow properties of six kinds of commercial toothpastes were measured using a concentric cylinder type rheometer. In this paper, the shear rate and temperature dependencies of their flow behavior were investigated and the validity of the Casson and Herschel-Bulkley models was examined. Further, the flow properties over a wide temperature range were quantitatively evaluated by calculating the various material parameters. Main results obtained from this study can be summarized as follows: (1) Toothpastes are plastic fluids with a yield stress and their flow behavior shows shear-thinning characteristics. (2) With increasing temperature, the degree of shear-thinning becomes weaker and the Newtonian flow behavior occurs at a lower shear rate range. (3) The Herschel-Bulkley model is more effective than the Casson model in predicting their flow behavior. (4) As the temperature increases, the yield stress, plastic viscosity and consistency index become smaller, on the contrary, the flow behavior index becomes larger.

• Nuclear Engineering and Technology
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• v.48 no.6
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• pp.1376-1386
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• 2016

This study investigated the loading rate effect on the fracture resistance under cyclic loading conditions to understand clearly the fracture behavior of piping materials under seismic conditions. J-R fracture toughness tests were conducted under monotonic and cyclic loading conditions at various displacement rates at room temperature and the operating temperature of nuclear power plants (i.e., $316^{\circ}C$). SA508 Gr.1a low-alloy steel and SA312 TP316 stainless steel piping materials were used for the tests. The fracture resistance under a reversible cyclic load was considerably lower than that under monotonic load regardless of test temperature, material, and loading rate. Under both cyclic and monotonic loading conditions, the fracture behavior of SA312 TP316 stainless steel was independent of the loading rate at both room temperature and $316^{\circ}C$. For SA508 Gr.1a lowalloy steel, the loading rate effect on the fracture behavior was appreciable at $316^{\circ}C$ under cyclic and monotonic loading conditions. However, the loading rate effect diminished when the cyclic load ratio of the load (R) was -1. Thus, it was recognized that the fracture behavior of piping materials, including seismic loading characteristics, can be evaluated when tested under a cyclic load of R = -1 at a quasistatic loading rate.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.05a
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• pp.711-714
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• 2002

Although recent research of metallic materials in high temperature fatigue have been much accomplished, many studies about brittle material as a die steel in high temperature fatigue does not have been reported. Especially, the study on the fatigue behavior over the transformation temperature is not studied sufficiently because of its difficult analysis and experiment. Therefore, reliable results of brittle material in high temperature fatigue behavior are needed. In this paper, stress-strain curves and stress-life curves in die STD61 steel at 700 and 900 are carefully examined, as the basic experimental data are used to predict from fatigue life over 700.

• 한국연소학회:학술대회논문집
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• 2012.11a
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• pp.329-332
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• 2012

The droplet behavior of 83.9 wt.% HAN water solution was investigated experimentally with various ambient temperature and nitrogen environment. At the initial stage of evaporation under thermal decomposition temperature of HAN, gradual decreasing of droplet diameter was observed. After that, the droplet started to expand due to the internal pressure build up by water nucleation inside the droplet. The micro explosion was observed at higher temperature than the decomposition temperature of HAN and the remaining droplet showed similar behavior of single composition droplet. The decreasing rate was augmented as the ambient temperature increasing.

• Geomechanics and Engineering
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• v.24 no.2
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• pp.157-166
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• 2021

This paper aims at the temperature and slenderness ratio effects on physical and mechanical properties of Beishan granite. A series of uniaxial compression tests with various slenderness ratios and temperatures were carried out, and the acoustic emission signal was also collected. As the temperature increases, the fracture aperture of intercrystalline cracks gradually increases, and obvious transcrystalline cracks occurs when T > 600℃. The failure patterns change from tensile failure mode to ductile failure mode with the increasing temperature. The elastic modulus decreases with the temperature and increases with slenderness ratio, then tends to be a constant value when T = 1000℃. However, the peak strain has the opposite evolution as the elastic modulus under the effects of temperature and slenderness ratio. The uniaxial compression strength (UCS) changes a little for the low-temperature specimens of T < 400℃, but a significant decrease happens when T = 400℃ and 800℃ due to phase transitions of mineral. The evolution denotes that the critical brittle-ductile transition temperature increases with slenderness ratio, and the critical slenderness ratio corresponding to the characteristic mechanical behavior tends to be smaller with the increasing temperature. Additionally, the AE quantity also increases with temperature in an exponential function.

• Journal of the Korean housing association
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• v.16 no.4
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• pp.65-71
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• 2005

The present study performed subjective evaluation experiments using slides and scale down models in order to propose guidelines for lighting environment desirable for each behavior in the house. The evaluation measure was composed of 20 mood items and 15 behavior items. As for experiment methods, the slide experiment used SD method, and the scale down model experiment used Scheffe's paired comparison. The results of this study are as follows. 1) Desirable lighting environment for working and talking is active atmosphere. 2) Lighting environment desirable far relaxation is to heighten lighting contrast using candescent lamps and local lights. In other words, active atmosphere, which is desirable for working and talking, is not desirable for relaxation. 3) Lighting for working requires bright illuminance and high color temperature(6000k). 4) Lighting for relaxation requires somewhat low brightness regardless of color temperature. If the light is bright it is better to use lamps of low color temperature. 5) for conversation, bright illuminance is more desirable than dark one, and the most adequate color temperature is 4000K.