• Journal of the Korean Crystal Growth and Crystal Technology
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• v.10 no.5
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• pp.367-372
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• 2000

The film-type specimen of poly ethylene terephthalate (PET) was stepwise elongated under tension with various speed range of about 0.5~500 mm/min, and then the necking behavior during its plastic deformation was observed. When elongated at the speed range of about 20~100 mm/min, stress oscillation was apparently occurred in the stress-strain curve. When elongated at the speed range of about 200~500 mm/min, stress oscillation was not did. The transparent/opaque zone and cross-section area in the specimen elongated at the speed of about 50 mm/min were examined using the optical microscopy and scanning electron microscopy. The corrosion characteristic of the specimen elongated at the speed of about 50 mm/min in 3.8 M NaOH alkali solution was examined using the optical microscopy.

• Journal of Biosystems Engineering
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• v.9 no.2
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• pp.89-96
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• 1984

This study was intended to search the thermal properties of rice which are necessary in preventing qualitative and quantitative losses in the drying and milling processes. First, the coefficient of cubical thermal expansion of brown rice was measured, which is required for analyzing the internal stress of rice, and then theoretical thermal and moisture stresses were calculated. The results are summarized as follows: 1. The coefficient of cubical thermal expansion of brown rice was about $2.81{\times}10^{-4}/^{\circ}C$ in the temperature range of $10^{\circ}C-60^{\circ}C$. 2. When the shape of brown rice was assumed to be a sphere or a cylinder, maximum thermal stress due to temperature change of $20^{\circ}C-60^{\circ}C$ was in the range of $25-100kg/cm^2$. And maximum moisture stress was in the range of $450-650kg/cm^2$ when the drying temperature was $35^{\circ}C$, initial and final moisture contents of brown rice were 20% and 14% (w.b.), and the moisture diffusion coefficient was assumed to be $6.79{\times}10^{-4}cm^2/hr$. 3. Consequently, it was concluded that crack formation in a rice kernel is mainly caused by moisture stress.

• Transactions of the Korean Society of Mechanical Engineers
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• v.9 no.1
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• pp.1-9
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• 1985

In-plane tension fatigue tests (R = 0.05) were carried out to investigate the initiation and propagation behaviors of micro-surface-fatigue cracks on smooth surfaces of a mild steel. Also, the investigations of saturated cyclic strain which can be obtained by the fatigue tests have been made via the cyclic strain intensity factor, .DELTA. $K_{\epsilon}$/, for the purpose of unifying two approaches of the study of fatigue; the one approach is based on the fracture mechanics concept and the other on lowcycle fatigue concept. Some of the results are as follows; The growth rate, d(2a)/dN, of small cracks cannot be represented by one straight line as a function of .DELTA.K for various of the nominal stress range, .DELTA..sigma., and is higher than that of a larger through crack. The rearrangement of the d(2a)/dN by .DELTA..epsilon..root..pi.s( = .DELTA. $K_{\epsilon}$/) with the stress range .DELTA..epsilon. in .DELTA.K replaced by .DELTA..epsilon., strain range, gives one straight line of the .DELTA. $K_{\epsilon}$-d(2a)/dN relation for various values of stress range .DELTA.$_{\epsilon}$../.X>../.

• Korean Journal of Metals and Materials
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• v.49 no.7
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• pp.541-548
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• 2011

Thermomechanical fatigue (TMF) behavior of heat resistant austenitic stainless steel was evaluated in the temperature range from 100$^{\circ}C$ to peak temperatures of 600 to 800$^{\circ}C$; The fatigue lives under TMF conditions were plotted against the plastic strain range and the dissipated energy per cycle. In the expression of the inelastic strain range versus fatigue life, the TMF data obtained at different temperature ranges were located close to a single line with a small deviation; however, when the dissipated energy per cycle, calculated from the area of the stress-strain hysteresis loops at the half of the fatigue life, was plotted against the fatigue life, the data showed greater scattering than the TMF life against the inelastic strain range. A noticeable stress relaxation in the stress-strain hysteresis curve took place at the peak temperatures higher than 700$^{\circ}C$, but all specimens in this study exhibited cyclic hardening behavior with TMF cycles. Recrystallization occurred during the TMF cycle concurrent with the formation of fine subgrains in the recrystallized region, which is considered to cause the cyclic hardening of the steel.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 1997.10a
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• pp.120-126
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• 1997

This paper examines the crack growth behavior of 7075-T651 aluminum alloy under high-low block loading condition. The cantilever beam type specimen with a chevron notch is used in this study. The crack growth and closure are investgated by compliance method. The applied initial stress ratios are R=-0.5, R=0.0 and R=0.25 Crack length($\alpha$), effective stress intensity factor range(ΔKeff), ratio of effective stress intensity factor range(U) and crack growth rate(d$\alpha$/dN) etc. are inspected fracture mechanics estimate.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.57 no.3
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• pp.332-337
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• 2008

We analyzed carbonization pattern and crystal structure of polyvinyl chloride wire by thermal stress. Copper that is oxidized at normal temperature is a reddish brown. If under the thermal stress range of 500 to 700 [$^{\circ}C$], carbonization and exfoliation occurrence. Section structure of electric wire is same as arrangement of particle in metallograph analysis. But, as thermal stress increases, size of particle is enlarged. Electric wire displays elongation structure in SEM image analysis and elongation structure collapses when receive thermal stress at 300 [$^{\circ}C$]. In EDX analysis, we get the spectra of CuL, CuK, OK, and ClK. FT-IR analysis was shown new spectra with in range of $1,440{\sim}1,430\;[cm^{-1}]$, 1,340 [$cm^{-1}$], 1,240 [$cm^{-1}$].

• Journal of Mechanical Science and Technology
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• v.18 no.1
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• pp.114-121
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• 2004

In order to investigate the corrosion fatigue characteristics in the weld of multi-pass welded A 106 Gr B steel pipe, corrosion fatigue tests were performed under the various stress ratios and 3.5 wt% NaCl solution at room temperature. The corrosion fatigue characteristic curves were represented using crack closure concept. The obtained results are as follows : when the load frequency is 1.0 Hz, the crack opening point is transited in the region of $K_{max}$=20∼32 MPaㆍ $m^{1}$2/. In the low stress intensity factor range, the crack opening point is higher than that in air. However, in the high stress intensity factor range, it is lower than that in air. In the cases of 0.1 Hz and 0.01 Hz, the crack opening point gradually decreases to $K_{min}$ with $K_{max}$ increase.rease.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.7 no.2
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• pp.54-61
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• 1998

This paper examines the crack growth behavior of 7075-T651 aluminum alloy for small tensile overload under high-low block loading condition. The cantilever beam type specimen with a chevron notch is used in this study. The crack growth and closure are investigated by compliance method. The applied initial stress ratios are R=-0.5 R=0.0 and R=0.25 Crack length, effective stress intensity factor range, ratio of effective stress intensity factor range and crack growth rate etc, are inspected with fracture mechanics estimate.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.11 no.6
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• pp.1-8
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• 2012

This study investigates stress and deformation due to static and dynamic vibration analysis about various types of bike handles installed with smart phone depositories. When force is applied on the side of handle at the models of type 1, 2, 3 and 4, the maximum equivalent stress is highest at type 2. The stress or deformation becomes lowest among these 4 model types. At vibration analysis, type 1 becomes safest within the range of 500Hz and type 3 becomes stable within the range of 100Hz. The result of this study can be applied with the design of bike handle installed with smart phone depository. The damage or deformation due to vibration can be prevented when the bike falls down. This result can be widely utilized to investigate and predict the durability.

• International Journal of Advanced Culture Technology
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• v.10 no.3
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• pp.18-24
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• 2022

This study attempts to provide basic data for the development of manpower maintenance programs by checking the degree of job stress and emotional burnout for nurses working in a university hospital and identifying factors affecting emotional burnout. Data were obtained through a structured questionnaire survey conducted on 187 nurses. The average score for job stress of nurses was 2.50 (range 1 to 4) and emotional burnout was 3.29 (range 1 to 5). The factors affecting emotional burnout were occupational climate, job demand, job insecurity, and lack of reward, which accounted for 44% of explanatory power. In order to reduce the emotional burnout of nurses, the management of medical institutions needs administrative and financial support. Further, it is necessary to improve the organizational culture regarding job assignment through job analysis, employment security, and a performance-based reward system.