• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 1997.10a
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• pp.127-131
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• 1997

In systematic and orderly estimation of fatigue strength of the spot welded lap joints, because the influence of residual stress of fatigue crach initiation and growth is not negligible, there need to estimate fatigue strength considered residual stress at near spot weld part of the lap joints. Therefore, in this thesis, peformed stress distribution and residual stress analysis at near the spot weld part by F.E.M and X-ray diffraction method, and obtained the maximum principal stress considered residual stress at nugget edge by superposing residual stress at nugget edge by superposing their results. From the results obtained above, we could find that fatigue strength of the IB-type spot welded lap joints was rearranged by the maximum principal stress considered residual stress at nugget edge and was entirely low about 13 percents compare with that neglected residual stress.

• Journal of Korean society of Dental Hygiene
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• v.14 no.2
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• pp.139-145
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• 2014

Objectives : The purpose of the study is to investigate the clinical practice stress reduction and to improve clinical practice satisfaction in dental hygiene students. Methods : The subjects were 354 dental hygiene students in Gwangju and Jeonnam. A self-reported questionnaire was filled out from June 3 to 21, 2013. The questionnaire included stress management in the clinical practice. Results : As for clinical practice stress, there was a significant relevance between satisfaction in major and clinical practice. Clinical practice stress coping had a significant relevance to clinical practice satisfaction and clinical practice stress. Conclusions : In order to reduce clinical practice stress in dental hygiene students and to enhance clinical practice satisfaction, it is important to develop clinical practice stress management program and to develop the appropriate measurement tool for stress.

• The Journal of Korean Society for School & Community Health Education
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• v.16 no.1
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• pp.27-38
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• 2015

Objectives: The purpose of this study is to develop programs that help students adjust to school and provide basic data for the students who have difficulty adjusting to school by analyzing the influence of elementary school students' stress and their relationship with parents on school adjustment. Methods: The study surveyed fourth graders in 3 elementary schools in G district. The researcher used convenience sampling to select the 3 elementary schools. The combined 158 students were selected for the analysis, and the survey was conducted for a month in September 2011. The stress monitoring tool used in the 5th year of Korean Youth Panel Survey was mobilized to measure levels of stress among the participants. To measure the parent-child relationship, the Korean Parent-Child Relationships Scale was used. For the measurement of school adjustment, a tool designed to identify the school adjustment of elementary school students was used. The SPSS 21 software and a two-sided test under the significance level of ${\alpha}=0.05$ were used to analyze data. The regression analysis was also used to identify the relative influence of the stress and parent-child relationship on children's adjustment to school. Results: The regression analysis has found the following: the higher peer stress (B=-0.175) and parental strictness (B=-0.159) grow, the lower the level of school adjustment gets; the higher the level of intimacy between parent and child gets, the higher the level of school adjustment grows; and intimacy between parent and child (${\beta}=0.400$) has the largest influence on the child's school adjustment. Conclusions: For elementary school students to be well adjusted to school, their stress and relationships with their parents should be managed. In particular, using the programs that can reduce stress from peers and increase parent-child intimacy will be effective in helping students adjust to school.

• Transactions of Materials Processing
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• v.23 no.6
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• pp.380-385
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• 2014

An analysis procedure is proposed to improve the prediction accuracy of springback as well as to evaluate the structural stability of the tooling used for fabricating a side sill part from UHSS. The analysis couples the stamping analysis and the subsequent analysis of the tool structural. The deformation and stress results for the tool structure are obtained from the proposed analysis procedure. The results show that the amount of deformation and stresses are so high that the tool structure must be reinforced and the tooling design must consider structural stability. Springback is predicted with CAE in order to compare the prediction accuracy between the given tool geometry and the geometry from the structural analysis. The simulation results with the deformed tool can predict the experimental springback tendency accurately.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2002.10a
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• pp.36-40
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• 2002

The development of feed drive system with high speed and accuracy has been a major issue in the machine tool industry. Linear motors can be used as the efficient tool to achieve fast feed mechanism and high accuracy. However. a high speed feed drive system with linear motors can generate heat problems such as the variation of temperature distribution and the resultant thermal stress. In this paper, the important heat sources and the resultant thermal errors are presented. The thermal deformation characteristics of the machine tool with linear motors were identified, which are thermal expansion of linear scale, shrinkage, expansion and bending in the machine tool structure.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.16 no.6
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• pp.94-102
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• 2007

Applications of bonded dissimilar materials such as large scale integration (LSI) packages, ceramics/metal and resin/metal bonded joints, are very increasing in various industry fields. It is very important to analyze the thermal stress and stress singularity at interface edge in LSI. In order to investigate stress singularities on the bonded interface edges and delamination of die pad and resin in the IC package. In this paper, stress singularity factors(${\Gamma}_i$) and stress intensity factors($K_i$) considering thermal stress in the IC package were analyzed by using the 2-dimensional elastic boundary element method(BEM).

• Journal of the Korean Society for Precision Engineering
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• v.14 no.8
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• pp.73-81
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• 1997

The hard turning process defined as a single point turning of materials harder than $H_{R}$C 58 differs from conventional turning because of hardness of the work materials and cutting toos needed in the process. In hard turning, tool life is very short, of the order of a few minutes, during which the cutting tool is subjected to the extremes of stress and temperature. In this regard, it is well known that CBN tool is proper for this process in spite of expensive cost. In this research, we studied the feasibility of the use of the low cost cutting tool such as a aTiN coated tool. To this end, a new cooling system was designed with an air-oil method for reducing tool temperature, which is based on the principle of air vortex flow. That is, the outlet temperature of the air becomes aver 20 .deg. C lower than atmosphere temperature by entering pressurized air of 5kgf/c $m^{2}$ into the inlet. This cooled air ejected to the top of the cutting tool lowered tool temperature, which reduced the wear of a TiN coated tool by the 30% of CBN tool life with respect to the same cutting length.h.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.33 no.7
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• pp.693-699
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• 2009

This paper shows mechanical properties and behaviors of macro- and micro-structures on friction stir welded specimen with 6061-T6 aluminum alloy plate. It apparently results in defect-free weld zone jointed at welding conditions like the traverse speed of 267mm/min, tool rotation speed of 2500rpm, pin inserted depth of 4.5mm and tilting angle of $2^{\circ}$ with tool dimensions such as tool pin diameter of 5mm, shoulder diameter of 15mm and pin length of 4.5mm. The tensile stress ${\sigma}_T=228MPa$ and the yield point ${\sigma}Y=141MPa$ are obtained at the condition of traverse speed of 267mm/min and tool rotation speed of 2500rpm. With the constant rotation speed, the higher traverse speed become, the higher tensile stress and yielding point become. Vickers hardness for welding zone profile were also presented.

• Journal of the Korean Professional Engineers Association
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• v.22 no.2
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• pp.10-18
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• 1989

New Materials such as fine ceramics have attracted much attention as structural materials. The industrial needs of machining such materials will be emphasized more and more in the future. The objective of this study is to supply useful knowledges for improvement by cooled cutting of sintered diamond tool. This study treats with experimental analysis of tool wear, surface roughness and thermal stress which will lead to the machinability of fine ceramics.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2011.06a
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• pp.1357-1358
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• 2011