• Journal of the Korean Society of Manufacturing Process Engineers
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• v.11 no.1
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• pp.88-94
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• 2012

An axle drive shaft with double joint shaft, cross kit and yoke has an important role by transferring power and changing steering angle between axle and wheel in power train system. It has been used widely in the heavy machinery requiring a high reliability in the power train system. At fatigue failures of the axle drive shaft with the long span, a relatively high stress concentration at a snap ring groove on the drive shaft brings to significant fatigue damages under repeated loading condition. As Peterson's suggestions on this study, a relief groove in the vicinity of the snap ring groove is applied by decreasing the stress concentration and improving the fatigue life of axle drive shaft. By using FEM analysis, the decreasing effect of the stress concentration and extended fatigue life are due to the change of design parameters related with size and location of the relief groove. The relief groove with the design parameters such as d/b=2.0 and r/h=1.2 enables to decrease the stress concentration of 22.3% and increase the fatigue life more than 3 times by comparing with no relief groove application.

• Research in Community and Public Health Nursing
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• v.17 no.4
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• pp.521-529
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• 2006

Purpose: This study was to measure the degree of job stress and job satisfaction and the relationship between job stress and job satisfaction of 119 relief squads. Methods: The subjects were 170 members of 119 relief squads in the Fire Department of D City, and data were collected from 1 April to 20 April, 2006 through a survey using a questionnaire composed of questions on general characteristics (11 items), job stress (6 items) and job satisfaction (20 items). Collected data were analyzed through frequency, percentage, t-test, ANOVA and Pearson's correlation using the SPSS program. Results: The average item score for job stress was 2.77. Role sharing with peers was highest as 3.05. There were significant differences in the degree of job stress according to religion, working period and applying motive. The average item score for job satisfaction was 2.93. Group conflict was highest as 3.18. There were significant difference in the degree of job satisfaction according to religion, working period and applying motive. There were significant differences in the negative correlation between role-sharing with peers among the job stress factors and decision-making factor (r=.53), group conflict factor (r=.58), role implementation factor (r=.63) and personal social-culture factor (r=.53) among the job satisfaction factors. Also, there were significant differences in the negative correlation between co-workers among the job stress factors and decision-making factor (r=.607), group conflict factor (r=.51) and personal social-culture factor (r=.45) among the job satisfaction factors. Conclusion: It is important to develop various methods of job stress management to increase job satisfaction in 119 relief squads.

• Proceedings of the KSME Conference
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• 2004.11a
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• pp.250-255
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• 2004

In this paper, we established baseline information and insight on residual stress relief mechanism associated with furnaced and local PWHT(post weld heat treatment) operation. Based on FEM analysis results, we suggested that furnaced PWHT stress relief mechanism was based on creep relaxation and local PWHT stress relief mechanism involved complicated interactions between plasticity and creep. In case of furnaced PWHT, significant stress relaxation was occurred in the early stage of PWHT. In case of local PWHT, stress relaxation magnitude was increased as PWHT time increased. Finally, We have proposed that detailed furnaced and local PWHT procedure, and qualification criteria to support current codes of practices.

• Journal of Welding and Joining
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• v.14 no.3
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• pp.48-57
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• 1996

A study was made to examine the characteristics of base metal and stress relief cracking(SRC) of heat affected zone(HAZ) for HY-100 and Cu-bearing HSLA-100 steels. The Gleeble thermal/mechanical simulator was used to simulate the SRC/HAZ. The details of mechanical properties of base plate and SRC tested specimens were studied by impact test, optical microscopy and scanning electron microscopy. The specimens were aged at $650^{\circ}C$ for HSLA-100 steel and at $660^{\circ}C$ for HY-100 steel and thermal cycled from $1350^{\circ}C$ to $25^{\circ}C$ with a cooling time of $\Delta$t_${800^{circ}C/500^{circ}C}$=21sec. corresponds to the heat input of 30kJ/cm. The thermal cycled specimens were stressed to a predetermined level of 248~600MPa and then reheated to the stress relief temperatures of $570~620^{\circ}C$. The time to failure$(t_f)$ at a given stress level was used as a measure of SRC susceptibility. The strength, elongation and impact toughness of base plate were greater in HSLA-100 steel than in HY-100 steel. The time to failure was decreased with increasing temperature and/or stress. HSLA-100 steel was more susceptible to stress relief cracking than HY-100 steel under same conditions. It is thought to be resulted from the precipitation of $\varepsilon$-Cu phase by dynamic self diffusion of solute atoms. By the precipitation of $\varepsilon$-Cu phase, the differential strengthening of grain interior relative to grain boundary may be greater in the Cu-bearing HSLA-100 steel than in HY-100 steel. Therefore, greater strain concentration at grain boundary of HSLA-100 steel results in the increased SRC susceptibility. The activation energies for SRC of HSLA-100 steel are 103.9kcal/mal for 387MPa and 87.6kcal/mol for 437MPa and that of HY-100 steel is 129.2kcal/mol for 437MPa.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2022.04a
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• pp.125-126
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• 2022

Office workers at the architectural design office are under job stress for various reasons such as excessive working hours, friction with the site, and unpredictability of work. This can increase not only the negative image of office workers in the construction industry, but also the avoidance of young manpower in the future. This study investigated the specific purpose of each activity as a problem of job stress relief activities in the architectural design office, and the specific purpose and goal setting of each activity as a way to improve job stress relief activities.

• Journal of People, Plants, and Environment
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• v.24 no.1
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• pp.63-73
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• 2021

Background and objective: This study was conducted to investigate the effects and preferences of horticultural therapy programs for stress relief according to MBTI personality types (Judging and Perceiving types) of female undergraduate students. Methods: The participants were divided into 15 Judging and 15 Perceiving types based on lifestyle preferences of the MBTI personality test, and a total of 30 participants participated in the horticultural therapy programs for 6 sessions. Results: Both Judging and Perceiving types showed a significant decrease in stress after participating in the horticultural therapy programs. Among the 8 life stress subfactors, Judging types showed significant stress relieving effects in 5 subfactors (relationship with the opposite sex, relationship with family, economic problems, future problems, value problems), while Perceiving types showed stress relieving effects in only 3 subfactors (relationship with family, economic problems, future problems). However, the changes in stress relief of 8 subfactors were not significantly different between the two personality types. The most preferred program for the Judging types was 'Making a flower basket', while the most preferred ones for the Perceiving types were 'Planting monstera', and 'Making preserved lemons with marigold', suggesting that the preferences varied depending on personality types. Conclusion: Therefore, it is necessary to develop suitable horticultural therapy programs for different subjects based on their personality types to enhance the effect of the programs on the subjects.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.33 no.6
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• pp.282-287
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• 2023

The effect of stress relief heat treatment temperature and duration time on the microstructure, residual stress and Vickers hardness of additively manufactured Ti-6Al-4V alloy using laser powder bed fusion process was clarified. As a result of stress relief heat treatment for 240 minutes at 823 K and 60 minutes or more at 873 K, residual stress was decreased less than 30 MPa without grain growth and phase transformation which causes dimensional distortion and deterioration of mechanical properties. In addition, hardness was increased with increasing heat treatment temperature and duration time. It was deduced that the refinement of acicular martensitic α' phase due to the increasing duration time of isothermal heat treatment at 773~873 K, which was not detected by XRD and phase map analysis using SEM-EBSD, probably increases the hardness.

• Journal of Power System Engineering
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• v.14 no.1
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• pp.47-52
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• 2010

In this study, Finite Element Analysis have been adopted to analyze reducing stress effect and used to induce the sensitivity of design parameter on various techniques which was used for reducing stress. And so it can be utilized as a data to design on similar model. The effect of reducing stress with respect to change of relief groove radius can be increased by 27.3~18.2 % more than radius of fillet. And if a shoulder fillet radius is larger, additional reducing stress by relief groove radius is not obtained. And there was only little effect on reducing stress by changing the center point of groove radius along horizontal direction. In the case that undercut radius is 1.5mm, Max. Equivalent stress is reduced by 5.71% under bending force and 11.11% under torsion. The best effect of reducing stress at undercut model was yielded when the undercut radius is a forth of difference of stepped shaft radius.

• Geomechanics and Engineering
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• v.8 no.4
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• pp.495-510
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• 2015

The applications of water jet cutting (WJC) in coal mine have progressed slowly. In this paper, we analyzed the possibility and reasonableness of WJC application to pressure relief in hard coal seam, simulated the distributive characteristics of stress and energy fields suffered by hard coal roadway wallrock and the internal relationships of the fields to the instability due to WJC (including horizontal radial slot and vertical annular slot) on roadway wallrock. The results showed that: (1) WJC can unload hard coal seam effectively by inducing stress release and energy dissipation in coal mass near its slots; its annular slots also can block or weaken stress and energy transfer in coal mass; (2) the two slots may cause "the beam structure" and "the small pillar skeleton", and "the layered energy reservoir structure", respectively, which lead to the increase in stress concentration and energy accumulation in coal element mass near the slots; (3) the reasonable design and optimization of slots' positions and their combination not only can significantly reduce the scope of stress concentration and energy accumulation, but also destroy coal mass structure on a larger scale to force stress to transfer deeper coal mass.

• Journal of the Society of Naval Architects of Korea
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• v.48 no.3
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• pp.238-245
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• 2011

Welding inevitably introduces the residual stresses which affect the fatigue strength of the joint structure. The mitigation of fatigue strength depends on the residual stress magnitude and distribution. Stress relief analyses are of practical interest for all cyclic loaded welded structures, such as ships and offshore structures. In order to estimate the effects of relaxation of residual stresses in the welded structure, this paper presents a finite element analysis procedure and experimental results for the welded structure. Cruciform specimens joint by MAG welding have been tested to measure the released stress. Relieved welding residual stresses obtained by finite element analysis are compared with those measured by experiment.