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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Journal of the Korean Society of Safety
Journal Basic Information
Journal DOI :
The Korean Society Safety
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Volume & Issues
Volume 15, Issue 4 - Dec 2000
Volume 15, Issue 3 - Sep 2000
Volume 15, Issue 1 - Mar 2000
Selecting the target year
Determination of the Threshold Stress Intensity Factor in Fatigue Crack Growth Test
Journal of the Korean Society of Safety , volume 15, issue 3, 2000, Pages 1~6
In fatigue crack growth test, it is important not only to analyze characteristics of fatigue crack growth but also to determine the threshold stress intensity factor,
. which is the threshold value of fatigue crack growth. Linear regression analysis using fatigue test data near the threshold is suggested to determine the
in the standard test method but the
can be affected by a fitting method. And there are some limitations on the linear regression analysis in the case of small number of test data near the threshold. The objective of this study is to investigate differences of the
due to regression analysis method and to evaluate the relative error range of the
in same fatigue crack growth test data.
Effects of Laser Welding Speed on the Tensile and Forming Characteristics of Tailored Blanks
Journal of the Korean Society of Safety , volume 15, issue 3, 2000, Pages 7~13
Forming characteristics of tailored blank are mostly effected by the welding method. Recently, laser welding is widely used for the tailored blank. However, tensile and forming characteristics vary due to welding conditions such as welding speed, heat flux etc. The objective of this paper is to evaluate the effect of welding speed on the tensile and forming characteristics of laser welded tailored blank. For this purpose, tailored blank specimens with different welding speed were prepared and tensile tests were performed. Also forming tests such as LDH and OSU test, were performed to evaluate the effect of welding speed on the forming characteristics. Finally, forming limit diagrams were obtained for different welding speed.
Numerical Prediction of Phase Change within the Molten Steel with Thin Slab Casting
Journal of the Korean Society of Safety , volume 15, issue 3, 2000, Pages 14~22
A numerical analysis has been performed on the two-dimensional rectangular gallium melting problem using the enthalpy method. The major advantage of this method is that the physical domain is discretized with fixed grids without transforming variables and the interface conditions of phase change are accounted for the definition of suitable source terms in the governing equations. But in the fixed method, there is some ambiguity in defining the porosity constant which has no physical interpretation. If the velocity correction is included in the momentum equation, for the appropriate range of porosity constant, the realistic predictions are obtained. The object of the present work is to predict the phase change within the molten steel with thin riser slab using the modified enthalpy-porosity method. The computational procedures for predicting velocity and temperature are based on the finite volume method and the non-staggered grid system. The influence of natural convection on the melting process is considered. A comparison with the experimental results shows that the modified method is better than the previous one.
An Experimental Study on the Safely of Portable Butane Gas Range
Journal of the Korean Society of Safety , volume 15, issue 3, 2000, Pages 23~29
The objective of this paper is to study burst through the influence of overheating to affect a seamed container using the cookers with different materials and bottom sizes. Following result are drawn from this study; When bottom size of the roast meat had 24cm diameter, the upper part temperature of a seamed container was increased over
. Therefore the cooker material without regard to cooker size had a great influence on the temperature of seamed container. For the natural stone plate which had bottom length 65cm, a seamed container was burst at the cooker temperature
, the surface temperature of a burner
. the upside temperature of seamed container
, the downside temperature of seamed container
and ambient temperature
. For the cooker of the same bottom area, the stone plate had greater influence on effect of temperature than aluminium cooker. Overheating had a great influence on the seamed container if the bottom or upside diameter of a cooker had been larger than a trivet.
A Numerical Analysis on the Characteristics of Spray by Swirl Injector in Gas Turbine Combustor
Journal of the Korean Society of Safety , volume 15, issue 3, 2000, Pages 30~39
The present paper deals with the numerical simulation for the spray characteristics with swirling turbulent flows and dilution flows from swirl injectors in a simplified can type of gas turbine combustor. The main objective is to investigate the characteristics of swirling turbulent flows with dilution flows and to provide the qualitative results for the spray characteristics such as the droplet distribution and Sauter Mean Diameter(SMD). The gas-phase equations based on Eulerian approach were discretized by Finite Volume Method, together with SIMPLE algorithm and the Reynolds -Stress-Model. The liquid-phase equations based on Lagrangian method were used to predict the droplet behavior. The results of preliminary test are generally in good agreement with experimental data, and show that the anisotropy exists in the primary zone due to swirl velocity and injected air from primary injector, and then gradually decays due to turbulent mixing and consequently near-isotropy occurs in the region between primary and dilution zones. For the spray characteristics, it is indicated that the swirling flows of primary jet region increase the droplet atomization. In addition, it is showed that the swirling flows at the inlet region lead the air-fuel mixture to be distributed near the igniter and can significantly affect the spray behavior in the primary jet region.
A Study on the Fatigue Crack Propagation Behavior by the Variation of Heat Treatment Temperature and Thickness in Mild Steel
Journal of the Korean Society of Safety , volume 15, issue 3, 2000, Pages 40~44
The fatigue and tensile test were carried out with Mild steel using the Dump Frame of commercial car. The specimens were heat-treated at
and worked 4.5, 6.0, 8.0mm thickness in order to look over the mechanical properties and fatigue life by heat treatment and thickness from the tensile test result, the yield strength of the heat treated specimens was increased about 35% more than that of the non-heat treated specimen. The fatigue life of non-heated specimen was decreased 15% but that of heat treated specimens at
were decreased 16.38% and 13.16% respectably according to increasing the thickness from 4.5 to 8.0mm.
A Study on the Safely of Vibration Characteristics on the Various Configuration of Tube
Journal of the Korean Society of Safety , volume 15, issue 3, 2000, Pages 45~51
This paper studies the effect of vibrational characteristics of the various tubes analyzed though experiment. By an experiment analysis we found out that the factor of system vibration is fluid-structure interaction of tube line. In fluid-filled tube system we study on the influence that the natural frequency of system and the frequency of wave motion produce upon through three experiments. Three experiments are modal test on each tube, FRF in continuous system, and vibrating tests when the system is driving on. From the results of the experimental studies, we obtained that the natural frequencies of system are very important than wave induced vibrations. and according to the variation of configuration, the frequencies are different each other. And we found that though fluid passed away through the tube, the tendency of system vibration level was similar with the mode shape at the simple system
A Numerical Study on Effects of Flow Through Openings on Convection
Journal of the Korean Society of Safety , volume 15, issue 3, 2000, Pages 52~56
The finite control volume method was utilized to investigate the effects of flow through openings on convection in an enclosure. Flow patterns and temperature distribution were compared for non-dimensional inflow velocity U=20, 40, 60 at Ra=
, respectively. The inflow velocity influenced temperature distribution in the enclosure significantly and lowered temperature on the top wall. The flow through openings forced the position of the highest temperature on the top wall to move toward the outflow opening.
Simulation of Stress Corrosion Crack Growth in Steam Generator Tubes
Journal of the Korean Society of Safety , volume 15, issue 3, 2000, Pages 57~65
The stress corrosion crack growth is simulated assuming a small axial surface crack inside a S/G tube. Internal pressure and residual stresses are considered as applied forces. Stress intensity factors along crack front, variation of crack shape and crack growth rate are obtained and discussed. It is noted that the aspect ratio of the crack is not depend on the initial crack shape but depend on the residual stress distribution.
A Trial for Improvement of Energy Efficiency of Plasma Reactor by Superposing Two Heterogeneous Discharges - Characteristics of Surface and Corona Discharge Combined Plasma Reactor -
Journal of the Korean Society of Safety , volume 15, issue 3, 2000, Pages 66~70
In order to cope with environmental problems caused by harmful gases emitted from various industrial sources, a new technology which employs discharge plasma formed in ordinary atmospheric pressure has been intensively investigated in many industrialized nations. Although a plenty of useful outcomes and suggestions have been made public by scientists in this field, few commercial products which effectively decompose pollutant gases have appeared as yet. This is partly because that the energy efficiency of a most effective plasma reactor has not reached a satisfactory level in comparison with those of devices using conventional technologies. In an attempt to solve the problem mentioned above, we noticed to combine heterogeneous electrical discharges. This concepts is based on that each plasma reactor has its specific spatial region in which chemical reaction are active and by electrically affected with another reactor of different type, the activated region would increase - which may lead to cutting down the energy consumption. To prove this concept experimentally, two different discharge equipments, a plane ceramic-based surface discharge electrode and a corona electrode with tungsten needle may, are selected and combined to fabricate a hybrid plasma reactor. The results are summarized as follows; (1) Ozone concentration generated in the plasma region drastically increases when the positive corona discharge is added to the surface discharge. The rate of increase of ozone depends on the frequency of the surface discharge. The negative corona, however, does not contribute to the improvement of the ozone generation. (2) NO(nitrogen monoxide) decomposition rate also improves by simultaneously applying the surface and the positive corona discharges. The effect of the corona superposition is more evident when the level of the surface discharge is moderate. (3) By adjusting the corona level, the net energy efficiency during NO decomposition improves in comparison with the simple surface discharge reactor.
Prediction of Temperature Dependence of Lower Explosive Limits for Paraffinic Hydrocarbons
Journal of the Korean Society of Safety , volume 15, issue 3, 2000, Pages 71~77
The aim of this study is to investigate the temperature dependence of the lower explosive limit(LEL) at elevated temperature. The temperature dependence of the lower explosive limit is one of the significant indices of flammability and combustibility. By using the literature data, the new equations for predicting the temperature dependence of the lower explosive limits for paraffinic hydrocarbons are proposed. The values calculated by the proposed equations were a good agreement with the literature data. It is hoped eventually that this proposed equations will support the use of the prediction for the lower explosive limit and the flash points of the flammable mixtures.
Flash Point of p-xylene and Epoxy Resins Mixtures
Journal of the Korean Society of Safety , volume 15, issue 3, 2000, Pages 78~82
The flash point is an important property and hazardous index of a flammable liquid. The flash points are used by virtually all the environmental, health, and safety organizations in both government and industry to classify flammable liquids for safety and transportation regulations. The basics of all flash points behavior are concerned with the vapor pressure and explosive limits. The flash points of pure components and the mixture of solvents can be calculated with the use of the laws of Raoult, Dalton and Le Chatelier. In this paper, experimentally determined lower flash points of a p-xylene and epoxy resin system were compared with the calculated values by using Raoults law. Calculated lower flash points were in reasonable agreement with the observed values.
Combustion Characteristics of Immobilized Aromatic Organic Solvent in Sands
Journal of the Korean Society of Safety , volume 15, issue 3, 2000, Pages 83~87
Combustion characteristics of immobilized benzene and toluene in sands were studied. Experiments were performed by burning benzene and toluene immobilized on sands(particle size 0.1~0.5mm) to measure combustion rate and combustion temperature. The longer time from ignition to extinguishment was resulted from the larger particle size exhibited the higher mass burning rate. Of aromatic compounds tested the relative magnitude of facilitation of combustion was benzene and toluene. Combustion temperature of benzene and toluene without regard to the types of benzene and toluene was not increased with smaller sand. However, with larger sands, combustion temperature of benzene and toluene were increased by 50~
and the highest combustion temperature was obtained with larger sands.
Prediction of the Noise Levels for a Plant
Journal of the Korean Society of Safety , volume 15, issue 3, 2000, Pages 88~95
The level of noise produced by machinery and its arrangement insides a factory is indicated to be a maximum of 96.1 dB(A). The maximum level of noise from a commoner's house outside the factory is shown to be 62.9 dB(A), which exceeds 60 dB(A), the permitted limit of noise level in a time period of day. us study has predicted the level of noise reduction according to a step by step prevention plan by considering the characteristics of the causes of noise, the permitted limit of noise levels, problems and economical efficiency attendant upon the noise prevention measures. Establishing target levels of noise each of the three steps of the noise prevention plan. The predicted level of noise at the place of a commoner's house in accordance with the first step is 50.0 - 59.0 dB(A), and can satisfy the permitted limit of noise in a time period of the day. In taking prevention measures for the second step, the noise level is 50.7 - 53.6 dB(A) which is less than 55 dB(A) in a time period of the evening, the permitted limit of noise in a time period of night., and it can meet 47.4 - 50.3 dB(A) in the third step.
Dynamic Analysis of Rectangular Liquid Storage Containers Considering Fluid-Structure Interaction effects
Journal of the Korean Society of Safety , volume 15, issue 3, 2000, Pages 96~101
The effects of internal fluid motion have to be considered in the analysis of liquid storage containers. Therefore this thesis developed a three-dimensional boundary element-finite element method for the analysis of rectangular liquid storage containers. The irrotational motion of inviscid and incompressible ideal fluid is modeled by using boundary elements and the motion of structure by finite elements. Coupling is performed by using compatibility and equilibrium conditions along the interface. Dynamic response characteristics of rectangular liquid storage containers such as sloshing motion, hydrodynamic pressure, displacement by fluid-structure interaction are investigated.
Bond Characteristics of PS Strand around the End Zones of High Strength Pretensioned Prestressed Concrete Members
Journal of the Korean Society of Safety , volume 15, issue 3, 2000, Pages 102~107
The extensive use of pretensioned prestressed concrete in the modem construction industry, together with wider application of pretensioned components for structural purposes requires some important consideration on the adequate transfer of prestress force into the concrete, especially around the end zones of pretensioned member. The main objective of this paper is to study the effects of various important parameters on the bond characteristics of prestressing strand around the end zone of high strength pretensioned concrete members. To this end, a comprehensive experimental program has been set up. The principal test variables considered were strand diameter, concrete strength, concrete cover size. The present study provides valuable test data for the realistic and accurate determination of transfer length, which can be efficiently used for improving the design equation of transfer length in pretensioned prestressed concrete members.
Comparison and Selection of Standing / Sedentary Work Posture for A Light Assembly Work
Journal of the Korean Society of Safety , volume 15, issue 3, 2000, Pages 108~114
The work posture impose additional stress upon human workers so that it should be carefully considered in designing works. However, we have a lot of manufacturing plants which convert their standing workplace to sedentary one. To confirm the validity of that trend, the authors conducted an experimental study, and compared the results. The results of the EMG and the self-cognitive symptoms, in general, showed a correspondent trend that the sedentary work posture was rated more comfortable. At the beginning of the work, complaint of the lowerback was higher whereas that of the lower leg and the feet went higher as the time elapsed. If the weight of workpiece were heavier than 500g, increasing rate of bodily discomfort in the sedentary posture were greater than that of the standing posture. In the meanwhile, the standing posture was consistently superior to the sedentary posture in its performance. Thus, in conclusion, for a light assembly work, sedentary work posture would be recommendable because bodily discomfort would be larger irrespective of the small increase of performance increase.
A Study on Tracking Position Control of Pneumatic Actuators Using Neural Network
Gi Heung Choi ;
Journal of the Korean Society of Safety , volume 15, issue 3, 2000, Pages 115~123
Pneumatic actuators are widely used in a variety of hazardous working environments. Any process that involves pneumatic actuation is also recognized as "eco-friendly". In most cases, applications of pneumatic actuators require only point-to-point control. In recent years, research efforts have been directed toward achieving precise position tracking control. In this study, a tracking position control method is proposed and experimentally evaluated for a linear positioning system. The positioning system is composed of a pneumatic actuator and a 3-port proportional valve. The proposed controller has an inner pressure control loop and an outer position control loop. A PID controller with feedback linearization is used in the pressure control loop to nullify the nonlinearity arising from the compressibility of the air. The position controller is also a PID controller augmented with the friction compensation by a neural network. Experimental results indicate that the proposed controller significantly improves the tracking performance.rformance.