• 소성∙가공
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• 제5권4호
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• pp.327-336
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• 1996

The effect of dynamic strain aging on high temperature deformation behaviour of the A-Mg alloy was investigated by strain rate change tests and stress relaxation tests between 20$0^{\circ}C$and 50$0^{\circ}C$. Yield point, short stress transient and periodic discontinuities on the stress-strain curve were considered as an evidence of the effect of dynamic strain aging. With this criterion two distinct strain rate-temperature regimes could be manifested. Dynamic strain aging was considered to be effective in the high temperature-low strain rate regime, whereas dynamic recovery was a dominant deformation mechanism in the low temperature-high strain rate regime. It was found that dynamic strain aging in the high temperature deformation was governed by the mechcanism of diffusion-controlled, viscous dislocation movement.

• Computers and Concrete
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• 제15권4호
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• pp.607-642
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• 2015

The stress-strain relationship of concrete in flexure is one of the essential parameters in assessing the flexural strength and ductility of reinforced concrete (RC) columns. An overview of previous research studies revealed that the presence of strain gradient would affect the maximum concrete stress developed in flexure. However, no quantitative model was available to evaluate the strain gradient effect on concrete under flexure. Previously, the authors have conducted experimental studies to investigate the strain gradient effect on maximum concrete stress and respective strain and developed two strain-gradient-dependent factors k3 and ko for modifying the flexural concrete stress-strain curve. As a continued study, the authors herein will extend the investigation of strain gradient effects on flexural strength and ductility of RC columns to concrete strength up to 100 MPa by employing the strain-gradient-dependent concrete stress-strain curve using nonlinear moment-curvature analysis. It was evident from the results that both the flexural strength and ductility of RC columns are improved under strain gradient effect. Lastly, for practical engineering design purpose, a new equivalent rectangular concrete stress block incorporating the combined effects of strain gradient and concrete strength was proposed and validated. Design formulas and charts have also been presented for flexural strength and ductility of RC columns.

• Geomechanics and Engineering
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• 제5권1호
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• pp.57-70
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• 2013

Constant rate of strain (CRS) consolidation tests were conducted for undisturbed Ariake clay samples from three boreholes in Saga Plain of Kyushu Island, Japan. The coefficients of consolidation ($c_{\nu}$) were interpreted from the CRS test results by small- and large-strain theory. Large-strain theory was found to interpret smaller $c_{\nu}$ values and less strain rate effect on $c_{\nu}$ than that by small-strain theory. Comparing the theoretical strain distributions within a soil specimen to those obtained by numerical simulation shows that the small-strain theory can be used only for the dimensionless parameter $c_{\nu}/\dot{\varepsilon}H_0^2{\geq}50$ (where $\dot{\varepsilon}$ is strain rate and $H_0$ is the specimen height), and the large-strain theory can be used for a larger range of strain rates. Applying the criterion to undisturbed Ariake clay with a $c_{\nu}$ value of about $1{\times}10^{-7}\;m^2/s$, it is suggested that the large-strain theory should be adopted for calculating the $c_{\nu}$ value when $\dot{\varepsilon}$ > 0.03%/min.

• Journal of Species Research
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• 제10권4호
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• pp.336-343
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• 2021

In 2020, as a subset study to discover indigenous yeast species in Korea, a total of 22 yeast species were isolated from soil samples collected in Gwangju-si, Gyeonggi-do. Among them, 10 strains were unreported species. From the high 26S rRNA gene sequence similarity and formation of a robust phylogenetic clade with the closest species, it was determined that each strain belonged independent and predefined yeast species. The 22 strains were assigned to the genera Dothiora (1 strain), Sarocladium (1 strain), Tetrapisispora (1 strain) and Torulaspora (2 strains) of the phylum Ascomycota; the genera Erythrobasidium (1 strain), Leucosporidium (4 strains), Ustilentyloma (2 strains), Fellozyma (1 strain), Sampaiozyma (2 strains), Filobasidium (1 strain), Solicoccozyma (2 strains) and Vishniacozyma (4 strains) of the phylum Basidiomycota. This is the first official report of the following species in Korea: Dothiora cannabinae (1 strain), Sarocladium strictum (1 strain), Fellozyma inositophila (1 strain), Filobasidium magnum (1 strain), Solicoccozyma phenolicus (1 strain), Solicoccozyma terreus(1 strain), Vishniacozyma tephrensis(1 strain) and Vishniacozyma victoriae (3 strains). Cell morphology, phenotypic features and biochemical features are described in the Species Description section.

• Nuclear Engineering and Technology
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• 제54권7호
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• pp.2386-2394
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• 2022

In this paper, smooth and notched bar tensile tests of austenitic stainless steel 304 are performed, covering four different multi-axial stress states and six different strain rate conditions, to investigate the effect of the stress triaxiality and strain rate on fracture strain. Test data show that the measured true fracture strain tends to decrease with increasing stress triaxiality and strain rate. The test data are then quantified using the Johnson-Cook (J-C) fracture strain model incorporating combined effects of the stress triaxiality and strain rate. The determined J-C model can predict true fracture strain overall conservatively with the difference less than 20%. The conservatism in the strain-based acceptance criteria in ASME B&PV Code, Section III, Appendix FF is also discussed.

• 한국정밀공학회지
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• 제21권4호
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• pp.148-153
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• 2004

It is well-known that the mechanical behavior of fiber-reinforced composites under hydrostatic pressure environment is different from that of atmospheric pressure environment. It is also known that the mechanical behavior of fiber-reinforced composites is affected by a strain rate. In this work, we investigated the effect of strain rate on the compressive elastic modulus, fracture stress, and fracture strain of carbon/epoxy composites under hydrostatic pressure environment. The material used in the compressive test was unidirectional carbon/epoxy composites and the hydrostatic pressures applied was 270㎫. Compressive tests were performed applying three strain rates of 0.05％/sec, 0.25％/sec, and 0.55％/sec. The results showed that the elastic modulus increased with increasing strain rate while the fracture stress was little affected by the strain rate. The results also showed that the fracture strain decreased with increasing strain rate.

• 대한수의학회지
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• 제18권1호
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• pp.27-31
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• 1978

In order to identify unknown Babesia spp. which was isolated from Korean cattle, the morphology of Korean strain was compared with that of Babesia bigemina (Kochinda strain) and Babesia spp. (Miyake strain). Immunofluorescent technique was used to identify the serological character of the parasites. The results obtained were summarized as follows: 1. Korean strain was morphologically very similar to Babesia spp.(Miyake strain) which mostly showed parallel-bigeminate forms, while B. bigemina (Kochinda strain) was mostly round and oval forms. 2. By the indirect fluorescent antibody technique: a) Anti-Babesia spp. and Korean Babesia spp. sera showed a higher antibody titers with Babesia spp. (Miyake strain) antigen (1:500) than with B. bigemina (Kochinda strain) antigen (1:50). b) Anti-Babesia bigemina sera showed a lower titer with Babesia spp. antigen (1:50) than with B. bigemina antigen (1:250). 3. On the basis of morphological and serological confirmantions, a Babesia strain isolated from a Korean cattle was very similar, if not identical, to Miyake strain of Babesia spp.

• 반도체디스플레이기술학회지
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• 제13권4호
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• pp.33-36
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• 2014

In this paper, a carbon strain gauge for large strain was developed. The carbon strain gauge was fabricated by forming PCB and antenna pattern using Cu/Ni/Au film and carbon resistor pattern using screen printing process on plastic film substrate. It was possible to develop low-cost disposable strain gauge since the carbon paste was cheap and the fabrication process was simple. The wireless communication type carbon strain gauge was fabricated by integrating signal processing circuit, antenna and power all together on the same substrate as a strain gauge. The wireless communication type carbon strain gauge has a merit of being available immediately at the spot without any particular system.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2005년도 하계학술대회 논문집 Vol.6
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• pp.274-275
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• 2005

The tensile strain dependency of critical current in YBCO coated conductors was examined at 77K and in the self magnetic field. A commercially available YBCO sample with Cu stabilizer layer was supplied. There existed a peak in the relation between the Ie and tensile strain, and the reversible variation of $I_c$ with applied tensile strain was found. In the neutral axis Ni alloy RABiTS-$Y_2O_3$/YSZ/$CeO_2$ buffered YBCO tape, the $I_c$ recovered reversibly until the applied strain reached to about 0.5%, representing that a significant residual compressive strain induced during cooling to 77 K influenced the axial strain tolerance of YBCO conductors. To investigate the strain and stress influence on the $I_c$, the stress-strain characteristics of YBCO conductors measured at 77 K were discussed.

• 소성∙가공
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• 제13권7호
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• pp.594-599
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• 2004

In the sheet metal forming operations, the strain measurement of sheet panel is an essential work which provides the formability information needed in die design, process design, and product inspection. To measure efficiently complex geometry strains, the 3-dimensional automative strain measurement system, which theoretically has a high accuracy but practically has about 3～5％ strain error, is often used. For eliminating the strain error resulted in measuring the strains of formed panels using an automated strain measurement system, the position error calibration method is suggested, which computes accurate strains using the grids with accurate nodal coordinates. The accurate nodal coordinates are calculated by adding the nodal coordinates measured by the measurement system and the position error found using the multiple regression method as a function of the main error parameters obtained from the analysis of strain error in a standard cube. For the verification, the strain distributions of square and dome cups obtained from the position error calibration method are compared with those provided by the finite element analysis and ASAME.