• The Journal of Korean Academy of Orthopedic Manual Physical Therapy
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• v.19 no.1
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• pp.9-20
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• 2013

Background: This study was conducted to provide preventive measure for the musculoskeletal disorders in automobile parts manufacturing workers. Method: The author surveyed to the musculoskeletal symptoms prevalence and its related factors from 10th to 17th April 2011 with structured self administered questionnaires. 223 out of 225 collected questionnaires were used for final analysis, excluding 2 questionnaires with no valid response. Based on the diagnostic criteria of NIOSH (National Institute for Occupational and Health), an investigation was made into the prevalence of musculoskeletal symptoms as well as into the factors related to individual items. Results: The prevalence of musculoskeletal symptoms according to the criteria of NIOSH was the highest in the shoulder (52.9%), followed by the neck (39.%), the hand/wrist (35%), the waist (29.6%), the arm/elbow (24.7%), and the leg/food (23.8%). One-way analysis showed that among general characteristics, age was the musculoskeletal risk factor with the greatest effect. Whereas among work-related characteristics, significant risk factor didn't find. Yet it was shown that among ergonomic work postures, high degree of musculoskeletal risk was shown by the posture involving frequent and repetitive movement of the arm and the hand/wrist and also by the posture involving standing for a long time. Multiple regression analysis showed that musculoskeletal risk was 1.795 times higher in those age 50 and over than in those under age 50; 1.67 times higher in the high risk stress group than in the low risk stress group; and 1.131 higher in the group involving the repetitive use of the hand/arm than in the other groups (p<.05). Conclusion: The prevalence and stress score of automobile parts manufacturing workers were higher than other occupation workers. Among general characteristics, drinking and smoking were shown to be related to stress score; while age was shown to have significant effect on musculoskeletal risk.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.23 no.11 s.170
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• pp.2087-2095
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• 1999

One of the main causes of unwanted dimensional changes in precision metal mold casting parts is excessive and irregular residual stresses induced by temperature gradients and plastic deformation in the solidifying shell. Residual stresses can also cause stress cracking, and lower the fatigue life and fracture strength of the casting parts. In the present study, aluminum alloy casting system with metal mold equipped with electrical heating elements and water cooling units was designed and the casting specimens were produced to quantify the effects of different cooling conditions on the development of residual stresses. The layer removal method was used to measure the biaxial residual stresses in casting specimens produced from the experiments. The experimental results agreed with Tien-Richmond's theoretical model for thermal stress development for the solidifying metal plate.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.776-779
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• 2003

To reduce the storage space of spent fuel used at the atomic power plants in the over the world, the uranium elements contained in the spent fuel is being extracted and effectively stored. For this, the spent fuel are oxidized and deoxidized. In this study, it is produced the heat-resisting methods about the spent fuel management technology research and test facility for the spent fuel waste for spent fuel minimized. The first considered processes in the facility are the electrolytic metal reduction reactor process. Since the electrolytic metal reduction reactor is operated at the high temperature range, we have to consider the heat-resisting methods for the devices. For the heat-resisting methods, we have searched and analyzed technical reference for the heat-resisting methods. We have calculated thermal stress and strain of each devices by the commercial analysis software, ANSYS. D.S. It is experimented for inspecting confidence rate of analysis results. By using the results, we have analyzed the problems of parts and determined the heat-resisting material, commercial parts, and the size of parts and O-ring. Based on these results, it is produced the heat-resisting methods of magnesia filter, cathode, and reactor for the electrolytic metal reduction reactor.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.31 no.1
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• pp.32-40
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• 2008

According to the statistic of industrial disaster in 2006 presented by the Ministry of Labor, there were 10,235 people with occupational diseases adding 2,740 more people (36.6%) compared to the previous year. Concerning the occupational diseases, 1,607 people had brain-cardiovascular diseases comprising more than 15% of all occupational diseases, and excessive workload and occupational stress seemed to play important parts. According to Korean Society of Occupational Stress, among 7,000 workers at 254 businesses in Korea, 73% of them were reported to be exposed to potential occupational stress and 22% of them were reported to be under severe stress. The increase of occupational stress among workers comes from excessive competition caused by business restructuring, promotion competition, annual salary system and so forth. Occupational stress threatens the heath and even the life of workers and lowers business competitiveness. Using the Korean occupational stress reduction model to the workers at small and medium businesses in Incheon area, therefore, the project intends to measure the level of stress among office workers and examine its relatedness to the VTD subjective symptoms. In addition, the project intends to present some methods to reduce occupational stress and increase business efficiency at work by studying and analyzing the various elements that workers use to reduce their occupational stress.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.5 s.176
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• pp.1103-1114
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• 2000

Recent attempt to enhance the safety against collision reshaped the simple shell structures into the integrated complex shell structures. Moreover, due to various regulations continuously tightened for environment protection, weight reduction of automobiles becomes an increasingly important issue. Auto parts lightening is mainly accomplished by more reasonable design, adoption of lighter materials and miniaturization of the auto bodies. Focusing on the locally enhanced design approach among the above three ways, we here attempt to develop a patching optimization method, and also to determine the thicknesses of an integrated shell structure, both bringing a specified amount of stress relaxation. We first select a cross member as a patching optimization model. Based on the finite element stress calculations, we relieve the stress of cross member by patching in two ways-nonuniform thickness patching and optimized uniform thickness patching, the latter of which is more effective in a practical point of view for the preset amount of stress relaxation. Selecting a box type subframe as another finite element analysis model, we then determine the thickness of each part by axiomatic design approach for a preset amount of stress relaxation. The patching methodology and the axiomatic approach adopted in this work can be applied to the other complex shell structures such as center member and lower control arm.

• Journal of the Korean Society for Precision Engineering
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• v.20 no.5
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• pp.148-155
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• 2003

Most manufacturing processes such as welding, cutting and molding generate residual stresses on the surface of manufactured parts. Between compressive and tensile residual stresses, the tensile residual stress is harmful to the surface integrity, which results in reduced fatigue life and causes other structural failures when the service stresses are superimposed on the residual stresses. In the research, the residual stresses in the hardened tool steel (SKD11) were measured using hole-drilling method. The specimens were prepared through hard turning. Most of residual stresses in the machined surface were compressive.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.10 no.3
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• pp.28-32
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• 2011

The safety of transporting equipment in a cryogenic condition is one of important problems under the circumstances that the application weight of natural gas is gradually increasing. As a larger disaster may be generated by leakage of oil or gas from valves in case of fire occurrence of a ship, the present research applied a numerical analysis method on thermal stress distribution and deformation, etc. to the design of ball valves satisfying fire safety test's specification(API607) to prevent this. In addition, the present research progressed fire safety tests and compared the test result with numerical analysis results. The Max stress by parts was confirmed through thermal analysis of major parts to evaluate safety. The fire safety test was progressed according to the regulation of API607.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.05a
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• pp.961-966
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• 2003

In recent, the design of diaphragm which is representative disturbed region in PSC box girder bridge have been performed according to the empirical method or beam theory. But, these methods couldn't be described the behavior of the end diaphragm, and placed reinforcements accurately. As the compressive stress transferred by the web concentrated on the lower parts of diaphragm, it was demonstrated that the basic assumption of 2-D strut-and-tie model for the diaphragm that the compressive stress acts on the upper parts of the diaphragm is wrong. Meanwhile, in this research, after analyzing the variables of end diaphragm, the 2-D strut-and-tie models appropriate to each cases are proposed. And, the problems of 2-D strut-and-tie model were analyzed, so 3-D strut-and-tie model is proposed as well. There is no codes which include the demonstration of safety of 3-D strut-and-tie model. Hence, for nodes, the stresses at the elements which included the singular node in strut-and-tie model were investigated using the finite element analysis. And, the stress states of strut has one direction, so effective stresses were considered at the stage, dimensioning of the model. From the results, 3-D strut-and-tie model could predict the behavior of end diaphragm accurately, and design of reinforcement could be performed economically.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.21 no.2
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• pp.217-222
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• 1997

A simple finite element approach to predicting deformed shape and load-deflection curve of elastomers is presented in this paper. The method is based on several simplifications in deformation pattern and material behavior. The conventional updated Lagrangian approach is employed together with material data obtained by a simple tension test. The presented approach is verified through comparison of predicted results with experimental ones and applied successfully to shape design of various elastomers for shock, vibration and noise control. The advantage of the presented approach lies in easiness, simplicity and accuracy enough for engineering application.

• Journal of Welding and Joining
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• v.33 no.4
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• pp.50-56
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• 2015

In general, discontinuity of metallurgical and structural points of weld zone could decline the fatigue strength. For the lightweight trend, the AHSS application in automotive chassis is in-progress. However, there are few research reports on AHSS welds fatigue strength in especially automotive chassis parts. Therefore, in this study, we evaluated the effects of the factors affecting the AHSS welding fatigue strength. As the result, the stress concentration of weld bead is the most important factor for welding fatigue strength. For the enhancement of welding fatigue strength, we focused on reducing the stress concentration of the welding beads. So, we applied and proved the plasma welding process and GTAW (Gas Tungsten Arc Welding) dressing method. It was verified by uniaxial fatigue specimen, fatigue performance increased from 40 to 60% by applying TIG dressing method compared to the conventional GMAW (Gas Metal Arc Welding). These results could be recommended the enhancement of fatigue performance of AHSS.