• Transactions of Materials Processing
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• v.8 no.6
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• pp.620-625
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• 1999

A finite element analysis is performed to predict the recrystallized volume fraction and the mean grain size in hot compression of Al-5wt%Mg alloy. In the analysis, a modeling equation of flow stress is assumed as a function of strain, strain rate, and temperature. And the influence of above varibles on flow stress is quantified by using Zener-Hollomon Parameter. In the modeling equation, effects of strain hardening and dynamic recrystallization on microstructure of Al-5wt%Mg alloy are investigated. The predicted results of recrystallized volume fraction and mean grain size are in good agreement with those of microstructures obtained from hot compression tests.

• 한국방재학회:학술대회논문집
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• 2008.02a
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• pp.273-276
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• 2008

Equivalent linear method indirectly reflects a variation of shear modulus(G/Gmax) and damping ratio $(\xi)$ by selects mean value of every response analysis. Existing equivalent linear method does not properly consider variation of shear strain along frequencies and uses mean value. Real dynamic soil behavior is affected by shear stiffness and damping ratio. Modified equivalent linear method is developed to consider variation. Modified equivalent linear method can reflects high strain at low frequency and low strain at high frequency by using an easement curve. This study presents propriety of method by case study.

• Korean Journal of Occupational Health Nursing
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• v.17 no.2
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• pp.216-223
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• 2008

Purpose: This study was performed to evaluate the worker's job stress status in the workplace of a local area. Method: Data were collected from October to December, 2007. The subjects were 208 workers at 2 work sites in Busan Metropolitan area, who were examined using Job-Strain-Model Questionnaire. Data were analyzed by SPSS 12.0 Win Program to get the percentage, mean, standard deviation, t-test, ${\chi}^2$-test, ANOVA. Results: The results of this study were as follows: In the mean sub-factors job stress level, the mean of job demand was $28.7{\pm}4.4$(median 29.0), the mean of job discretion was $54.7{\pm}8.2$(median 54.0), the mean of social support was $21.8{\pm}2.9$(range:8-32). This study's subjects were appeared as active group with relatively higher score of job demand and job discretion than the average value of those. There was no statistically significant difference of general characteristics among the different job strain groups. There was statistically significant difference with of social supports among the different job strain groups. Conclusion: In conclusion, the subjects of this study's were active group. Thus, it is suggested that it is be necessary to repeated the education of the job task work for active group with high score of job demand and job discretion.

• Asian Pacific Journal of Cancer Prevention
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• v.13 no.4
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• pp.1447-1452
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• 2012

Aim: To evaluate the differential diagnostic potential of lesion stiffness assessed by the sonoelastographic strain index ratio (SR) and elastographic color scoring system (UE) for breast lesions. Materials and Methods: Three hundred and forty two breast masses (158 benign and 184 malignant) from 325 consecutive patients (mean age 44.2 years; range 16-81)who had been scheduled for a sonographically guided core biopsy were examined proposed by Itoh et al, with scoring 1-3=benign and 4-5=malignant. Strain and area ratios of each lesion were calculated within the same machine. Histological diagnosis was used as the reference standard. The area under the curve (AUC) and cut-off point were obtained by receiver operating curve and the cross table Fischer Test was carried out for assessing diagnostic value. Sensitivity, specificity, PPV, NPV, accuracy and false-discovery rates were compared. Results: The mean strain ratios for benign and malignant lesions were 1.87 and 7.9 respectively. (P<0.0001). When a cutoff point of 3.54 was used, SR had a sensitivity of 94.6%, a specificity 94.3%, a PPV of 95.1%, an NPV of 93.7% and an accuracy of 94.4%. The AUC values were 0.90 for the 5 point scoring system (UE) and 0.96 for the strain index ratio. The overall diagnostic performance was SR method was better (P<0.05). Conclusions: Strain ratio measurement could be another effective predictor in elastography imaging besides 5 the point scoring system for differential diagnosis of breast lesions.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.40 no.12
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• pp.1027-1035
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• 2016

In this study, a strain-controlled fatigue test of widely-used 316L stainless steel with excellent corrosion resistance and mechanical properties was conducted, in order to assess its fatigue life. Low cycle fatigue behaviors were analyzed at room temperature, as a function of the strain amplitude and strain ratio. The material was hardened during the initial few cycles, and then was softened during the long post period, until failure occurred. The fatigue life decreased with increasing strain amplitude. Masing behavior in the hysteresis loop was shown under the low strain amplitude, whereas the high strain amplitude caused non-Masing behavior and reduced the mean stress. Low cycle fatigue life prediction based on the cyclic plastic energy dissipation theory, considering Masing and non-Masing effects, showed a good correlation with the experimental results.

• International Journal of Safety
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• v.2 no.1
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• pp.1-6
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• 2003

In this paper, several different fracture criteria using the Eftis and Subramanian's stress solutions [1] are compared with the printed experimental results under different loading conditions. The analytical results of using the solution with non-singular term show better than without non-singular in comparison with the experimental data. And maximum tangential stress criterion (MTS) and maximum tangential strain energy density criterion (MTSE) can get useful results for several loading conditions.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.21 no.2
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• pp.199-208
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• 1997

A local strain approach was applied to an external single and double grooved C-shaped specimen in order to evaluate and predict the fatigue crack initiation life by using low cycle fatigue properties. The low cycle fatigue properties were determined from the strain-controlled fatigue tests using smooth cylindrical axial specimens. Fatigue crack initiation life was evaluated by a life prediction software, FALIPS, based on the local strain approach. The fatigue life was significantly influenced by the mean stress, and SWT parameter represented the fatigue life effectively. The predicted fatigue crack initiation life was then compared to the experimental fatigue life evaluated from the C-shaped fatigue test specimens. A good correlation was found between the experimental and predicted fatigue lives within factors of 2 and 4 for the single and double grooved C-shaped specimens respectively. Also, experimental fatigue life of the double grooved specimen was 10-12 times longer than that of the single grooved specimen.

• International Journal of Naval Architecture and Ocean Engineering
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• v.11 no.2
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• pp.671-678
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• 2019

In this paper, the low cycle fatigue failure and ratcheting behavior, as well as their interaction of AH32 steel were experimentally investigated under uniaxial cyclic loading. The effects of mean stress, stress amplitude and stress ratio on the low cycle fatigue life and ratcheting strain were discussed. It was found that the ratcheting strain increased while the fatigue life decreased with the increase of mean stress and stress amplitude, and the increasing stress ratio would result in smaller ratcheting and larger fatigue life. Two kinds of failure modes, i.e. low cycle fatigue failure due to crack propagates and ratcheting failure due to large plastic strain will take place respectively. Based on the experimental results, considered the effect of ratcheting on fatigue life, a model with the maximum stress and ratcheting strain rate was proposed. Comparison with the experimental result showed that the new model provided a good prediction for AH32 steel.

• Journal of Microbiology and Biotechnology
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• v.22 no.5
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• pp.614-621
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• 2012

Silver nanoparticles production by the green chemistry approach was investigated using an isolated marine actinomycetes strain. The isolated strain was identified as Streptomyces albidoflavus based on chemotaxonomic and ribotyping properties. The strain revealed production of silver nanoparticles both extracellular and intracellularly. Surface Plasmon Resonance analysis with the function of time revealed that particle synthesis by this strain is reaction time dependent. The produced particles were spherical shaped and monodispersive in nature and showed a single surface plasmon resonance peak at 410 nm. Size distribution histograms indicated production of 10-40-nm-size nanoparticles with a mean size of 14.5 nm. FT-IR spectra of nanopartilces showed N-H, C-H, and C-N stretching vibrations, denoting the presence of amino acid/peptide compounds on the surface of silver nanoparticles produced by S. albidoflavus. Synthesized nanoparticles revealed a mean negative zeta potential and electrophoretic mobility of -8.5 mV and -0.000066 $cm^2/Vs$, respectively. The nanoparticles produced were proteinaceous compounds as capping agents with -8.5 mV zeta potential and revealed antimicrobial activity against both Gram-negative and -positive bacterial strains. Owing to their small size, these particles have greater impact on industrial application spectra.

• Transactions of the Korean Society of Automotive Engineers
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• v.12 no.4
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• pp.181-190
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• 2004

The interest of the fatigue life of rubber components such as engine mounts is increasing according to the extension of warranty period of the automotive components. Automotive engine mounts get damaged due to thermal and mechanical loadings. This paper discusses a fatigue life prediction of the 3-dimensional dumbbell specimens for natural rubber compound considering the effects of maximum strain and heat aging temperature. Displacement controlled fatigue life tests were performed using specimens with different levels of maximum strain and various hardness. The basic mechanical properties test and the fatigue test of aged rubber specimen under normal and elevated temperature were executed. A procedure to predicted the fatigue life of vulcanized natural rubber material based on the maximum strain method was proposed, and then this curve was in good agreement with fatigue test data less than 200% error range.