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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Journal of the Korean Society of Safety
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Journal DOI :
The Korean Society Safety
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Volume & Issues
Volume 14, Issue 4 - Dec 1999
Volume 14, Issue 3 - Sep 1999
Volume 14, Issue 2 - Jun 1999
Volume 14, Issue 1 - Mar 1999
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Nonlinear Rocking Vibration Characteristics for Rigid Block Subjected to Horizontal Sinusoidal Excitation
Journal of the Korean Society of Safety , volume 14, issue 4, 1999, Pages 3~12
This research concentrates on the influence of non-linearities associated with impact for the nonlinear rocking behavior of rigid block subjected to one dimensional sinusoidal excitation of horizontal direction. The transition of two governing rocking equations, the abrupt reduction in the kinetic energy associated with impact, and sliding motion of block. In this study, two type of rocking vibration system are considered. One is the undamped rocking vibration system, disregarding energy dissipation at impact and the other is the damped rocking system, including energy dissipation and sliding motion. The response analysis using non-dimensional rocking equation is carried out for the change of excitation parameters and friction coefficient. The chaos responses were discovered in the wide response region, particularly, for the case of high excitation amplitude and their chaos characteristics were examined by the time history, Poincare map, power spectra and Lyapunov Exponent of rocking responses. The complex behavior of chaos response, in the phase space, were illustrated by Poincare map. The bifurcation diagram and Poincare map were shown to be effective in order to understand chaos of rocking system.
A Study on the Effect of Heat-treatment on the Fatigue Strength of SCM420 Spur Gears
Journal of the Korean Society of Safety , volume 14, issue 4, 1999, Pages 13~19
This study deals with effects of heat-treatment on the bending fatigue of SCM420 spur gears. The test gears are heat-treated by two different treatments. After carburization, one group of the test gears is quenched directly, while another group is furnace cooled, reheated then quenched. The fatigue test at a constant stress amplitude is performed by using an electrohydraulic serve-controlled pulsating tester. The S-N curves are obtained and illustrated. By comparing the estimated strength with the experimental results, the validity of the previous experimental formula, presented by the authors for estimating the fatigue strength of carburized gears, was discussed for these tested gears.
A Study for the Prediction Fatigue Limit in a Case Hardening Material
Journal of the Korean Society of Safety , volume 14, issue 4, 1999, Pages 20~27
The standard of the allowed stress in designing components such as shafts used in machinery and aircraft should be determined. It is very important to estimate fatigue strength of a component analytically, because service stress of the components is usually under the level of its fatigue limit. Improving the fatigue strength of each component in machinery is essential for high performance, lightness, and endurance. Surface treatment of components is widely used for these purpose. In this research, the fatigue behaviors of SCM415 steel and carbonitried SCM415 steel are examined. In the analysis of the fatigue behaviors of the carbonitrided SCM 415 steel, we propose a modified fatigue strength evaluation model and modified formulae.
Analysis of Stress Intensity Factors for Circular arc Cracks by Boundary Element Method
Journal of the Korean Society of Safety , volume 14, issue 4, 1999, Pages 28~36
In this paper, A circular arc crackered plate in biaxially stretched sheets was investigated in the boundary element method. The applications of fracture mechanics have traditionally concentrated on crack problems under an mode I, straight crack. However, many service failures occur from growth of cracks subjected to mixed mode loadings. A rectangular plate with arc crack or slanted central crack, under biaxial tensile loading, was treated analytically and also solved numerically. The Results from BEM applying different loading conditions, crack length (a/W), arc angle(
) are presented and discussed. The stress intensity factors are evaluated by the techniques of the J-integral. The decomposition method, used to decouple the stress intensity factors in mixed mode problems, is implemented by a considering a small circular contour path around each crack tip. The BIE method was successfully applied to a circular arc crackerd plate problem, also slanted centre cracked plate under mixed mode.
An Improvement of the Vortex Particle Method
Journal of the Korean Society of Safety , volume 14, issue 4, 1999, Pages 37~42
Modifications were made in the vortex particle method by reducing the number of numerical parameters and adapting more accurate integration schemes. The method was applied to 0.15, 0.2 and 0.25 rectangles where the original method yielded poor results. Structure of vortex formation and its shedding in the wake was clearly shown, and vortex shedding was more regular than that without the modifications, while the time-averaged drag coefficients were nearly the same. It was confirmed the modified method could be used in the viscous vortex particle method.
Analysis of Elastic-Plastic Stress Fields near the Crack Tip under Tension-Compression Loading
Journal of the Korean Society of Safety , volume 14, issue 4, 1999, Pages 43~52
In this study, theoretical stress field analysis near the crack tip under tension-compression loading was performed. The results of the theoretical stress analysis were compared to the results of Finite Element Method(FEM). From this study, generation of tensile residual stress at crack tip was proved after 1-cycle of tension-compression loading, and the fracture toughness and the fracture load of a structure can be decreased by the residual stress.
Development of Precise Shearing Mechanism on Thin Sheet for Laser Welding (Analysis of Precise Shearing Process using FEM
Journal of the Korean Society of Safety , volume 14, issue 4, 1999, Pages 53~59
Recently, Tailor Welded Blank (TWB) is widely used in automotive industry since the transformation characteristic of its material can be changed. However, clearance between welding surfaces becomes the important factor which affect the quality of the laser weld, causing difficulties in preparing the sheet. The objective of this paper is to systematically evaluate the effects of previously presented fracture criterion and shearing condition on precise mechanical shearing simulation result. For this purpose, a parametric study was peformed to investigate the effect of finite element size and fracture criterion on simulation result. Also, in order to predict the optimum shearing condition, effect of shearing conditions such as clearance and punch radius on the shear plane shape was evaluated.
Study on Optimization Technique for Design of the Road Tunnel Ventilation System
Journal of the Korean Society of Safety , volume 14, issue 4, 1999, Pages 60~70
In this study, the computer code for the optimal design of road tunnel ventilation system based on one-dimensional analysis of the air flow was developed. The control volume method was used to calculate the air velocities and the concentration distribution of pollutants(CO, NOx, Particulate) for various tunnel ventilation system. This code was validated by comparing the calculation results to the practical design data for the road tunnel ventilation system. The calculation results were in accord with the practical design data.
A Study of Vibration Characteristics of Exposed Gas Pipeline under Vehicle Loading
Journal of the Korean Society of Safety , volume 14, issue 4, 1999, Pages 71~77
Exposed gas pipeline in underground, especially subway construction site, has been continuously vibrated by vehicle above ground. Because this vibration can cause unexpected damages to pipeline, we had measured and analyzed the vibration. This paper presents results of the vibration analysis of exposed gas pipeline and the results are as follows. The major vertical vibration frequency of pipeline was about 13 Hz and the other frequency components disappeared when the vibration transmitted to I-beam and wire rope. Existence of wooden casement had not affect vibration of exposed gas pipeline. The results of modal analysis by experimental and analytical methods have good agreement and it is also shown that exposed pipeline has possibility of resonance at second mode.
The Development and Performance Evaluation of the Air-preheating Heat Exchanger for Ultra-high Temperature Applications
Journal of the Korean Society of Safety , volume 14, issue 4, 1999, Pages 78~84
A compact air-preheating type heat exchanger was developed and tested for the ultra-high temperature heat recovery applications. For the direct use of exhaust gases up to
, the heat exchanger adopted a ceramic core with high strength and low thermal expansion coefficient less than
. The ceramic core was fabricated by special extrusion and bonding techniques. To minimize thermal stresses in the core, spring-loaded sealing mechanism was designed and successfully installed. 1-pass air flow scheme was adopted for the compactness and cost-savings. The pressure test for the ceramic core showed no failure under 35 kPa and less than 3% leak under 7 kPa. Flue gas simulation system was developed to investigate the performance of the heat exchanger. The test results showed normal operations of the heat exchanger up to
of exhaust gases and relatively high heat recovery efficiencies of 31～39% depending upon exhaust gas temperatures..
Rollover Propensity Analysis of A Jeep Vehicle
Journal of the Korean Society of Safety , volume 14, issue 4, 1999, Pages 85~92
Vehicle rollover is an important issue for the traffic safety. Rollover can occur from the driver's action, the vehicle characteristics, or the road condition. This study is about the rollover propensity analysis of a jeep vehicle using the steering and braking maneuver, which is the combined result by the driver and the vehicle. Simple equations of roll motion is used to analyze the roll motion and a special purpose vehicle dynamics program is used to simulate the rollover of the jeep vehicle. From the simulation, an incipient rollover motion of the vehicle was found. However, the more complete rollover propensity analysis would require further investigation using roll dynamic sensitivity study.
A Study on Method of CAD/CAM Separate and Relief Modeling to Reduce Lead Time in Die Manufacturing
Journal of the Korean Society of Safety , volume 14, issue 4, 1999, Pages 93~99
A try was carried out to reduce lead time of die manufacturing. That is to make manual machining and finishing work time shorter by improving CAD/CAM modeling methods, so called with "separate modeling" and "relief modeling". The manual machining and finishing manual work time were reduced adapting the novel CAD/CAM modeling methods. Ultimately we accomplished much reduction of the lead time of die manufacturing.f die manufacturing.
The Effect of Pressurized Hydrogen on the Aging and Partial Discharge Activity in Generator Winding Insulations
Journal of the Korean Society of Safety , volume 14, issue 4, 1999, Pages 100~107
The purpose of the study is to investigate the effect of H
pressure on partial discharge (PD) activity and aging rate in turbine generator winding insulations. A series of field tests and laboratory tests were peformed to investigate the effect of
pressure on PD activity. Field tests were conducted at two unit turbine generators in two conditions, in
pressure and in air atmosphere. Obtained results are as follows ; 1)
and maximum partial discharge are reduced with increase of
pressure and partial discharge inception voltage. 2) The reduction ratio of
pressure is higher than one of PD magnitude. 3) Partial discharge pulses suffer from attenuation and distortion when transmitted along windings, because of the complex L-C network between windings. From the result, partial discharge pulses are subjected to resonance phenomena in a generator winding.
A Fuzzy Controller for Robust Control of Induction Motor Drive System
Journal of the Korean Society of Safety , volume 14, issue 4, 1999, Pages 108~113
This paper presents a study on fuzzy speed and flux controller used in a vector control of a CRPWM(Current Ragulated PWM) induction motor drive. In this paper, an approach for an easier design of the fuzzy controller is presented in order to obtain the desired value for the response time with minimal overshoot and to improve the steady state performance for speed step commands. The fuzzy controller is constructed only upon the knowledge of the motor behaviour and the desired speed response, and provides fast and robust control by reducing the effects of nonlinearities, parameter changes and load disturbance. The results of applying the fuzzy logic controller to an IM drive system are compared with those obtained by application of a conventional PI controller. The fuzzy controller provided a better response than the PI controller.
A Study on Chemical Cleaning of Electrolytic Facilities with Sea Water
Journal of the Korean Society of Safety , volume 14, issue 4, 1999, Pages 114~119
When NaOCl was generated and put into sea-water cooling machine in order to overcome the biological hindrances against sea-water cooling machine, it was converted into metallic ion, particularly Ca and Mg, as a hydrate in sea-water and is to stick to electrolyte as a side reaction. This phenomena make the distance between the electrolytes narrow to decrease the flow rate, which induces the local vortex flow which erodes the pole plate. Moreover, this increases the resistance of the electrolyte as well as voltage to decrease the electrolytic efficiency, which has curtailed a chlorine yield and caused a pole plate cut. We are able to overcome these problems by chemical cleaning and intend to extend the life-time of electrolyte and to increase output of the sea-water electrolysis facilities by studying optimal policy regarding chemical cleaning of electrolytic cell. Cleaning time of electrolytic facilities is determined when both increase in electrolytic efficiency and decrease in pole-plate voltage are 10%. At this time as operating current of electrolytic facilities is high, operating time is diminished. Whereas, parameter of end point determination according to cleaning is Mg ionic concentration in solution. When we use Cleaner as a 7wt% HCl, cleaning time is about 80min proper. We are able to maintain pole plate performance by protecting against pole plate cut by means of electrolytic by-product, improve operating rate of facilities, and cut down on maintenance expenditure after acidic cleaning.
A Study on Estimation and Management of Loss Due to Catastrophic Accident
Journal of the Korean Society of Safety , volume 14, issue 4, 1999, Pages 120~125
This study evaluated the effect of the accidents caused by fire, explosion, and toxic gas release by using SuperChems, quantitative hazardous material release modeling software, which estimates the potential area of damage. According to the loss severity, the appropriate risk management principles can be applied. Risk management is divided into the two methods which are risk control and risk financing. Risk control includes risk avoidance, risk spreading and diversification, and risk reduction. Risk financing includes risk retention and risk transfer. The results of this study can help the related company determine the appropriate reserve fund and the amount to be insured against the third party losses according to the estimated loss severity.
Wear Properties of Biocompatible Ti Implant due to Nitrogen Ion Implantation
Journal of the Korean Society of Safety , volume 14, issue 4, 1999, Pages 126~134
In this study, plasma source ion implantation was used to improve the wear properties of biocompatible titanium implant. In order to observe the effect of ion energy and dose on wear property of titanium implant, pin-on-disk type wear tests in Hank's solution were carried out. The friction coefficient of ion implanted specimens were increased from 0.47 to 0.65 under high energy and ion dose conditions. As increasing ion energy and ion dose, the amount of wear was reduced.
A Study on Utilization Method of Paper Ash in Industrial Waste
Journal of the Korean Society of Safety , volume 14, issue 4, 1999, Pages 135~141
This study is an experimental study to investigate the possibility of the utilization of paper ash as the cover, liner in waste disposal landfill and other construction materials. The sample used in these tests was obtained from Daehan paper mill. A series of tests were peformed to evaluate basic properties, compaction, permeability, compressive strength, consolidation, leaching, and CBR of paper ash. In order to investigate the soil engineering properties of paper ash, the test results were compared with those obtained of fly ash. The results of unconfined compression tests show that paper ash had a larger strength than the fly ash. Also, the maximum dry unit weight of paper ash was approximately 59～76.9% less than that of the fly ash. It was found from the results of leaching test that paper ash is classified as non-detrimental general wastes according to the waste management law
A Study on the Collapse Accidents of the Temporary Structures
Journal of the Korean Society of Safety , volume 14, issue 4, 1999, Pages 142~147
Formwork is a temporary structure that supports its own weight and that of the freshly placed concrete as well as construction live loads including materials, equipments, and workmen. In designing and building formwork, the contractor should plan for economical construction without sacrificing quality or safety. But these temporary structures sometimes collapse during the concrete placing. Among the accidents and failures that occur during concrete construction, many are formwork failures, which usually happen at the time concrete is being placed. Generally some unexpected events cause one member to give way, then others become overloaded or misaligned and the whole formwork structure collapses. In this study, formwork failure events from 1994 to 1997 are analyzed using the structural analysis program. So the causes of the respective formwork failure are explored. Therefore, the present study provides a firm base to design the temporary structures such as formwork.
Geometrically Nonlinear Dynamic Analysis of Suspension Bridges Considering Construction Sequences
Journal of the Korean Society of Safety , volume 14, issue 4, 1999, Pages 148~157
Dynamic structural behavior in long span bridges, especially cable structures, is very sophisticated due to their flexibility and structural members are sequentially erected in each construction step. In this study, the consistent mass matrix for dynamic analysis is formulated and computational program considering construction sequences is developed where structural members can be builded or removed by command language and automatically reanalyzed in the moment when structural system is changed. The dynamic analysis, i.e. eigenvalue and time series analysis and the geometrically nonlinear analysis considering construction sequence are conducted to the Namhae Bridge. The analytical results are satisfactory compared with measuring values and the developed computational program can successfully be applied to design and safety check.
The Characteristics for Seepage Behaviour of Soil Structure by Modeling Tests
Journal of the Korean Society of Safety , volume 14, issue 4, 1999, Pages 158~167
In parallel flow condition, to estimate the stability of the extended embankment constructed on a permeable foundation ground, a laboratory model test was performed due to extended materials and water level increasing velocity of a flood period. A laboratory model test was peformed for different permeability coefficients (
) using seepage. The fluctuation of water level occurring to an extended embankment was analyzed by laboratory model tests as vary the increasing velocity of water level with 0.6cm/min, 1.2cm/min, 2.4cm/min respectively. In analysis results, the increase of water level into embankment occurs rapidly because seepage water moving along with a permeable soil flow into embankment. The larger the permeability coefficient of an extended part is the longer initial seepage distance, and the exit point of downstream slope is gradually increased and then shows unstable seepage behavior as occurring partial collapse. As the increasing velocity of water level increase, the initial seepage line is formed low, and the discharge increases. Therefore, the embankment extended by a lower permeable soil than existing embankment shows stable seepage behavior because an existing embankment plays a role as filter for an extended part.
Performance and Posture Evaluation of Ergonomic Keyboard
Journal of the Korean Society of Safety , volume 14, issue 4, 1999, Pages 168~175
The objective of this research is to review the ergonomic keyboard developed to prevent musculo-skeletal disorders from being occurred during keyboard work. It was studied by comparing it with the traditional keyboard after analyzing and comparing the typing performance and work advantages both the two keyboards. Twelve male subjects with no history of musculo-skeletal disorders participated in the experiment. The quantitative data such as typing speed, accuracy, performance time, and the number of typing errors were obtained from the HTT software that was adjusted for this experiment. RULA worksheet and the degrees of extension and ulnar deviation on right and left wrist were used to analyze the upper body postures. The experiment results showed that the typing performance of the ergonomic keyboard decreased a little, but no significant difference statistically, compared with that of the traditional keyboard. On the work posture, the ulnar deviation during typing decreased in case of the ergonomic keyboard. But, the wrist extension was increased unexpectedly. Therefore, it can be regarded as these results occur due to the shape of wrist rest and the overall height of keyboard on a table. As a result, the reconsideration and redesign on the ergonomic keyboard are requested.
A Study of Analysis on Variation of the Rate of Injury according to the Job Type Using Safe-T-Score on the Small Sized Companies
Journal of the Korean Society of Safety , volume 14, issue 4, 1999, Pages 176~181
The objective of this study is to compare and analyze the industrial injury-values of all the industries through yearly accident rate and frequency rate based on the governmental documentation of industrial injuries. The samples for this study are chosen from the companies with less than 200 employees under charge of the Kangnung Ministry of Labor during the period of 1995-97. Safe-T-Score is used for statistic control on the qualitative comparison of the present and the past industrial injury-rates. In the comparison of the past and the present industrial injury-rate by means of Safe-T-Score, this study shows that there does not exist any remarkable improvement, whereas the document of the Ministry of labor reports that the rate is decreasing greatly. Therefore, this study proposes some solutions to reduce industrial disasters and points out the necessity of more practical and effective methods to analyze the industrial disaster.
An Effective Plan for Product Liability and Product Safety by the Hazard Analysis
Journal of the Korean Society of Safety , volume 14, issue 4, 1999, Pages 182~191
Product liability(PL) and product safety(PS) is one of the most costly and confusing problems facing manufacturing today. Accordingly, this paper presents an integral process for product safety and product liability resulting from a defective product and proposes countermeasures of PL and PS for the four types of risk based on severity and frequency. Finally, we have presented a framework and practical procedure to provide the manufacturer with useful way of analyzing the risk potential of consumer products.
An Analysis of Physical Load of the Shipping Work in Cold Storage Warehouses
Journal of the Korean Society of Safety , volume 14, issue 4, 1999, Pages 192~198
Work-related musculoskeletal disorders constitute a major source of employee disability and lost wages. Cumulative Trauma Disorders(CTD) refers to a category of physical conditions which result from chronic musculoskeletal injury. Assessment of CTD risk in industry at early stage allows for early control, a safe environment, and a healthier workforce. In this study, the physical load of the shipping work in the cold storage warehouse were especially investigated. Employees were working with almost unnatural posture in a very restricted work space. The questionnaire and biomechanical analysis were used to evaluate the physical load. Results from analyses showed that they were sufficiently exposed to CTD due to repetition and unnatural posture. Based on the analysis, ways for improving working conditions are proposed. The analysis and proposals in this paper will serve as a basic tool for designing/redesigning working environment such as improvement of tools and equipments, design of times for work/rest cycle.
A Framework for Assessing Seismic Safety Using Reliability Physics
Moo-Sung Jae ;
Journal of the Korean Society of Safety , volume 14, issue 4, 1999, Pages 199~203
A framework for assessing seismic safety is suggested in this paper. The concepts of requirement and achievement are used in this framework. The quantified correlation between requirement and achievement derived from two competing variables results in the unconditional frequency of exceeding a damage level. This framework can be applied to any other external safety assessment of nuclear power plants.
Volume Holographic Optical Fingerprint Identification for Secure Entry System
S.H. Lee ; M.S. Park ; W.S. Shin ;
Journal of the Korean Society of Safety , volume 14, issue 4, 1999, Pages 204~210
We propose an optical fingerprint identification system using volume hologram for database of matched filter. Matched filters in VanderLugt correlator are recorded into a volume hologram that can store data with high density, transfer them with high speed, and select a randomly chosen data element. The multiple reference fingerprint photographs of database are prerecorded in a photorefractive material in the form of Fourier transform images, simply by passing the image displayed in a spatial light modulator through a Fourier transform lens. The angular multiplexing method for multiple holograms of database is achieved by controlling the reference directions with a step motor. Experimental results show that the proposed system can be used for secure entry systems to identify individuals for access to a restricted area, security verification of credit cards, passports, and other IDs.