• 열처리공학회지
• /
• 제12권1호
• /
• pp.21-30
• /
• 1999

The present study were investigated changes of precipitation behaviour of laves phase in ferrite single phase and ferrite-martensite dual phase and precipitation of laves phase under stress. Hardness changes in ferrite phase appeared two hardness peaks by precipitation of initial fine precipitator and laves phase in 3Mo-0.3Si and 3Mo-0.3Si-C specimens, respectively. Hardness changes in martensite phase of 3Mo-0.3Si-C specimen was lower in the initial stage of aging by carbide precipitation and after this, increased by re-hardening due to precipitation of laves phase. In the ferrite phase, laves phase was mainly precipitated, whereas in the martensite phase, carbide was preferentially formed during the initial stage of aging and with increasing aging time, laves phase and carbide were simultaneously precipitated by precipitation of laves phase at around carbide. In the ferrite-martensite interface, laves phase was mainly precipitated and carbide was mainly formed at boundary of lath martensite than grain boundary. Adding the stress in aging, fine precipitator of inital precipitation of laves phase precipitated in (100) of perpendicular to tensile direction and has grown to only followed<010>direction and also, volume fraction of laves phase increased. Consequently, the stress added was accelerated initial precipitation of laves phase.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 2005년도 추계 학술발표회 제17권2호
• /
• pp.595-598
• /
• 2005

Recently, owing to the development of industry and the improvement of building techniques, the concrete structure is becoming larger and higher. In hardening these large concrete, the heat of hydration gives rise to considerable thermal stress depending on the size and environmental condition of concrete, which might cause thermal cracking. Especially, the crack may cause severe damage to the safety and the durability of concrete structure. This study is investigated the thermal properties of concrete according to several binder conditions, such as OPC, Belite rich cement(BRC), slag cement(SC), blast furnace slag (BFS) added cement, fly ash added cement and BFS-fly ash added cement. As a result of this study, the concrete made with BRC, fly ash($25\%$) added cement and BFS($35\%$)-fly ash($15\%$) added cement gets superior effect in the control of heat hydration.

• Nuclear Engineering and Technology
• /
• 제48권4호
• /
• pp.1036-1046
• /
• 2016

We propose a primary water stress corrosion cracking (PWSCC) initiation model of Alloy 600 that considers the stress triaxiality factor to apply to finite element analysis. We investigated the correlation between stress triaxiality effects and PWSCC growth behavior in cold-worked Alloy 600 stream generator tubes, and identified an additional stress triaxiality factor that can be added to Garud's PWSCC initiation model. By applying the proposed PWSCC initiation model considering the stress triaxiality factor, PWSCC growth simulations based on the macroscopic phenomenological damage mechanics approach were carried out on the PWSCC growth tests of various cold-worked Alloy 600 steam generator tubes and compact tension specimens. As a result, PWSCC growth behavior results from the finite element prediction are in good agreement with the experimental results.

• 소성∙가공
• /
• 제16권6호
• /
• pp.463-466
• /
• 2007

Micro-wire made from straightening process invents high added value and it has been adopted many industrial fields. Therefore, many research activities about straightening process are advanced actively. It is known that fine straightness of micro-wire can be obtained by removing residual stress induced during the manufacturing processes. Generally, residual stress is removed or minimized through several drawing processes with heat treatment. In this study, the residual stress at each straightening process is calculated and monitored by finite element analyses and the main reason of stress change is investigated.

• 한국환경보건학회지
• /
• 제23권4호
• /
• pp.9-15
• /
• 1997

This experiment was carried out to examine the roles of selenium in arsenic- and chromium-induced oxidative stress, which results in chromosomal damage, such as sister chromatid exchange (SCE) and chromosomal aberration (CA). For this purpose, the frequency of CA and SCE related to the level of 0xidative stress were analyzed. Selenium decreased the frequency of CA induced by As. In order to evaluate the effect of selenium on clastogenic factors, media from As- and Cr-treated cells were ultrafiltered and added again to cells in the presence or absence of selenium. Selenium decreased the frequency of SCE by As and Cr. This observation indicates the possibility of presence of clastogenic factor. In addition, the clastogenic factor would be involed in oxidative stress since selenium decreased the level of oxidative stress. Thus, it is suggested that selenium may play a role as an anti-clastogenic effector by preventing the oxidative stress, thereby decreasing the frequency of Asand Cr-induced chromosomal damage.

• 한국해양공학회지
• /
• 제26권3호
• /
• pp.39-45
• /
• 2012

This paper investigates the strength characteristics and stress-strain behaviors of waste fishing net (WFN)-added lightweight soil. The lightweight soil, which consisted of dredged soil, crumb rubber, and cement, was reinforced with WFN in order to increase its shear strength. Glue treated WFN was also added to lightweight soil to improve the interlocking between the soil mixture and WFN. Three kinds of test specimens were prepared: unreinforced lightweight soil, reinforced lightweight soil without glue treatment, and reinforced lightweight soil with glue treatment. Several series of laboratory tests were carried out, including flow value tests, unconfined compression tests, and SEM analyses. From the experimental results, it was found that the peak strength of the reinforced lightweight soil with glue treatment was increased by the increased interlocking between the soil mixture and WFN, which was induced from the bonding effect. The stress-strain relation of the reinforced lightweight soil, irrespective of the glue treatment, showed a more ductile behavior than that of the unreinforced lightweight soil.

• 한국식품영양과학회지
• /
• 제28권1호
• /
• pp.161-166
• /
• 1999

CaCl2 and water soluble degraded chitosan mixtures were used as coagulants for extending the shelf life of tofu. Microbial counts, pH, and turbidity in tofu immersion solution were analyzed during the periods of storage at 4oC and physico chemical properties of tofu were determined by rheological properties, color and yield. There was no significant difference in moisture content and yield between tofu made with and without chitosan. Failure stress and stress relaxation values were reduced when chitosan was added to CaCl2, but there was no significant change among contents of chitosan added to tofu. The pH values were decreased at the beginning and then slowly increased after 14 days storage. The changes in turbidity were increased during storage, but the change in 2.0g degraded chitosan mixture with 7.0g CaCl2 coagulant(2.0:7.0 ratio) was lower than others and initial turbidity was lower as much as chitosan added to coagulant. These data showed that the water soluble degraded chitosan had a good anti microbial effect and increases the shelf life of tofu.

• 생명과학회지
• /
• 제9권5호
• /
• pp.537-547
• /
• 1999

This study was designed to investigate the effects of sea tangle (Laminaria japonica) extract (Dasi-Ex group: dry base 4.0%) and fucoidan-added (Fuco-I, II, III group: fucoidan of 1.0%, 2.0%, 3.0% added to Dasi-Ex) beverages on the anti-stress action. ICR male mice (20$\pm$2g) were fed basic experimental diets and given free through water bottle filled with these beverages instead of water for 18 days including sociopsychological stress. Body weight gains were consistently lower in Dasi-Ex and Fuco-I,II,III groups compared with control group, expecting in a inhibitory effect of obesity. Dasi-Ex group resulted in a significant decrease of 25% in serum corticosterone (CS) secretion, while Fuco-I,IIand IIIgroups resulted in a marked decreases of 45~55% in serum CS secretion compared with control group. Noradrenaline (NA) secretions were significantly increased about 15% in Dasi-Ex group, and 20~22% in Fuco-I,II,III groups compared with control group. Significant differences in brain MHPG-SO4 levels of Dasi-Ex group could not be obtained, but Fuco-I,II,III groups resulted in a marked decreases of 20~25% in brain MHPG-SO4 ratio of brain, but Fuco-I,II and III groups resulted in a marked increases of 45~60% in NA/MHPG-SO4 ratio of brain compared with control group. These results suggest that fucoidan beverage may play a effective role in a ridding of the sociopsychological stress by pivotal anti-stress effect of fucoidan.

• 한국세라믹학회지
• /
• 제31권6호
• /
• pp.609-616
• /
• 1994

Investigation for the high strength grouts using ordinary cement mortar, melamine formaldehyde condensate (MFC) with various admixtures was carried out. The physical properties of the grouts were investigated through the observation of the microstructure and the application of fracture mechanics. When the lime stone and fly ash was added with 6 wt% to the grouts, the compressive strength was about 72 MPa, 69 MPa respectively, and the flexural strength was about 11.9 MPa, 11.4 MPa respectively, the Young's modulus was about 4.3 GPa, 3.9 GPa, and the critical stress intensity was about 7.3 ×10-1MNm-1.5, 6.8×10-1MNm-1.5 respectively. When the silica fume was added with 6 wt% to the grouts, the compressive strength and the flexural strength were 81 MPa, 12.3 MPa, Young's modulus was 4.8 GPa and the critical stress intensity was about 8.4×10-1MNm-1.5.

• 한국안전학회지
• /
• 제34권2호
• /
• pp.7-14
• /
• 2019

A palladium can adsorb hydrogen and detect leaking hydrogen through changes in color and electrical resistance. This study is to evaluate the structural behavior of carbon fiber adding palladium composite materials used in the hydrogen storage vessel. A multi-scale analysis technique was used to analyze accurately the behavior of each material in relation to the microscopic composition. The multi-scale analysis is more proper and precise for composite materials because of considering the individual microscopic structure and properties of each material for composite materials. Also the crack evaluation was performed by XFEM analysis to confirm the reinforcement performance of aluminum as a liner of the hydrogen vessel. The results show that the addition of the palladium material increased the macroscopic stress, but microscopically the carbon fiber stress was reduced. It means the performance improvement of the palladium added carbon fiber/Al composite.