• 한국공작기계학회:학술대회논문집
• /
• 한국공작기계학회 1998년도 춘계학술대회 논문집
• /
• pp.19-24
• /
• 1998

This paper aims to clarify the effects of grinding conditions on the ground surface and bending strength in surface grinding of various ferrites with diamond wheel. The main conclusions obtained were as follows. The surface roughness becomes better at lower wheel speed in the case of v/V=1$\times$10-3, and the condition of v/V=1$\times$10-4shows the best performance for the finish grinding. When the relative contact temperature becomes lower at a constant value of v/V, the ground surface exhibits lower roughness. The ground surface shows that the fracture process during grinding becomes more brittle at the higher value of v/V. The damage depth which affect the bending strength is below 10$\mu$m in the grinding condition of S=10㎣/mm.s with the diamond tool after dressing & truing, however, the depth increases with increasing removal rate(S). When the strength degradation due to grinding is larger, the removal depth for the recovery of strength requires a larger size.

• 한국세라믹학회지
• /
• 제53권6호
• /
• pp.615-621
• /
• 2016

SiC-polycrystalline fiber (Tyranno SA, Ube Industries, Ltd.) shows very high heat-resistance and excellent mechanical properties up to very high temperatures. However, further increase in the strength is required. Up to now, we have already clarified the relationship between the strength and the defect-size of the SiC-polycrystalline fiber. The defects are formed during the conversion process from the raw material (amorphous Si-Al-C-O fiber) into SiC-polycrystalline fiber. In this conversion process, a degradation of the Si-Al-C-O fiber and a subsequent sintering of the degraded fiber proceed as well, accompanied by a release of CO gas and compositional changes, to obtain the dense SiC-polycrystalline fiber. Since these changes proceed in each filament, the strict control should be needed to minimize residual defects on the surface and in the inside of each filament for achieving the higher strength. In this paper, the controlling factors of the fiber strength and the fine structure will appear.

• 한국건축시공학회:학술대회논문집
• /
• 한국건축시공학회 2014년도 추계 학술논문 발표대회
• /
• pp.141-142
• /
• 2014

Decrease of performance degradation of High Strength Concrete occurs more than that of normal strength concrete at elevated temperature. Therefore, when it comes to evaluating performance of structures, strain of concrete subjected to elevated temperature and loading are important items. In this study, creep strain of High Strength Concrete sunjected to various temperature conditions and 33% loading was evaluated. As a result, creep strain increased with increase of temperature and loading. Creep strain of concrete at high temperature is influenced by loading.

• 한국건축시공학회:학술대회논문집
• /
• 한국건축시공학회 2022년도 봄 학술논문 발표대회
• /
• pp.21-22
• /
• 2022

In order to improve the strength degradation of the cement-based material to which strong alkaline liquid red mud was added, the liquid red mud was neutralized with sulfuric acid and added to the cement paste to examine the mechanical properties according to the amount added. As a result of measuring the compressive strength, the strength was higher when the red mud was neutralized with sulfuric acid and added to the cement paste than the cement paste to which the liquid red mud was added. As a result of hydration heat measurement, when red mud was neutralized with sulfuric acid and added to the cement paste, an initial strength higher than that of liquid red mud was expressed.

• Preventive Nutrition and Food Science
• /
• 제1권2호
• /
• pp.252-255
• /
• 1996

As an index of freeze-injury of yeast, the leakage of intracellular substances from yeast cells after freeze-thawing was investigated. It was found that much more ultraviolet-absorbing substances leaked out from non-freeze tolerant yeast (NETY) than from freeze-tolerant yeast. Furthermore, the rate of leakage of cellular substances form NFTY during incubation exceeded that of FTY, indicating that NFTY is more susceptible to freeze-injury than FTY during frozen-storage. An apparent degradation of phospholipid was observed during incubation of perfermented frozen-cells of NFTY, while little change of phospholipid occurred in FTY, These results suggested that the difference in the sensitivity of yeast might be due to the strength of cell membrane in terms of the degradation of phospholipid by enzymes, phospholipases, attached to cell membranes.

• Earthquakes and Structures
• /
• 제1권1호
• /
• pp.69-91
• /
• 2010

Current seismic design codes do not contemplate explicitly some variables that are relevant for the design of structures subjected to ground motions exhibiting large energy content. Particularly, the lack of explicit consideration of the cumulative plastic demands and of the degradation of the hysteretic cycle may result in a significant underestimation of the lateral strength of reinforced concrete structures built on soft soils. This paper introduces and illustrates the use of a numerical performance-based methodology for the predesign of standard-occupation reinforced concrete ductile structures. The methodology takes into account two limit states, the performance of the non-structural system, and in the case of the life safety limit state, the effect of cumulative plastic demands and of the degradation of the hysteretic cycle on the assessment of structural performance.

• Journal of Electrical Engineering and Technology
• /
• 제12권2호
• /
• pp.840-845
• /
• 2017

In this paper, in order to investigate the lifetime of oil-paper insulation, specimens were artificially aged with thermal and electrical multiple stresses. Accelerated ageing factors and equivalent operating years for each aging temperatures were derived from results of tensile strengths for the aged paper specimens. Also, the evaluation for the multi-stress aged specimens were carried out through the measurement of impulse breakdown voltage at high temperature of $85^{\circ}C$. The lifetimes of the oil-paper insulations were calculated with the value of 66.7 for 1.0 mm thickness specimens and 69.7 for 1.25 mm thickness specimens throughout the analysis of impulse BD voltages using equivalent operating years, which means that dielectric strengths would not be severely decreased until the mechanical lifetime limit. Therefore, for the lifetime evaluation of the oil-paper insulation, thermal aging would be considered as a dominant factor whereas electrical degradation would be less effective.

• Nuclear Engineering and Technology
• /
• 제49권7호
• /
• pp.1472-1482
• /
• 2017

Zirconium alloy cladding tube specimens were irradiated at $380^{\circ}C$ up to a fast neutron fluence of $7.5{\times}10^{24}n/m^2$ in a research reactor to investigate the effect of neutron irradiation on hydride reorientation and mechanical property degradation. Cool-down tests from $400^{\circ}C$ to $200^{\circ}C$ under 150 MPa tensile hoop stress were performed. These tests indicate that the irradiated specimens generated a smaller radial hydride fraction than did the unirradiated specimens and that higher hydrogen content generated a smaller radial hydride fraction. The irradiated specimens of 500 ppm-H showed smaller ultimate tensile strength and plastic strain than those characteristics of the 250 ppm-H specimens. This mechanical property degradation caused by neutron irradiation can be explained by tensile hoop stress-induced microcrack formation on the hydrides in the irradiation-damaged matrix and subsequent microcrack propagation along the hydrides and/or through the matrix.

• International Journal of Human Ecology
• /
• 제8권1호
• /
• pp.1-8
• /
• 2007

Degradation of cellulose during prolonged exposure in atmospheric conditions has been recognized as one of main problems in preserving cellulose-made products. The purpose of this research was therefore to study effects of borohydride reduction in improving both the color and strength retention of cotton fabrics artificially aged at temperatures ranging from $100^{\circ}C$ to $150^{\circ}C$. Results indicated that the fabrics treated with either sodium or tetramethylammonium borohydrides (TMA) were degraded at rates about one-half that of water-washed cotton. These results were consistent over the temperature range. Calculation of the activation energy (Ea) by different methods showed $Ea\;=\;25.5{\pm}\;1.5\;Kcal$, in keeping with measurements made by others at lower temperatures. The TMA-treatment was effective in minimizing discoloration of the fabrics with pre-baking, but not of the un-prebaked fabrics.

• 한국세라믹학회지
• /
• 제49권1호
• /
• pp.1-10
• /
• 2012

Super-plastic deformation that originates from transformation plasticity has favorable aspects for steels with improved strength and ductility. However, it also causes undesirable deformation of products or specimens, leading to their degradation. This article reviews recent investigations of transformation plasticity. A combination of newly suggested models, numerical analyses, and novel experiments has attempted to reveal the mechanism. Since the nature of the transformation plasticity is still unclear, there are significant challenges still to be solved. Fundamental understanding of transformation plasticity will be essential for the development of advanced steels.