• Journal of the Korean Society of Manufacturing Process Engineers
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• v.13 no.5
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• pp.50-56
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• 2014

A technique based on the finite element method (FEM) is used in the simulation of metal cutting process. This offers the advantages of the prediction of the cutting force, the stresses, the temperature, the tool wear, and optimization of the cutting condition, the tool shape and the residual stress of the surface. However, the accuracy and reliability of prediction depend on the flow stress of the workpiece. There are various models which describe the relationship between the flow stress and the strain. The Johnson-Cook model is a well-known material model capable of doing this. Low-alloy steel is developed for a dry storage container for used nuclear fuel. Related to this, a process analysis of the plastic machining capability is necessary. For a plastic processing analysis of machining or forging, there are five parameters that must be input into the Johnson-Cook model in this paper. These are (1) the determination of the strain-hardening modulus and the strain hardening exponent through a room-temperature tensile test, (2) the determination of the thermal softening exponent through a high-temperature tensile test, (3) the determination of the cutting forces through an orthogonal cutting test at various cutting speeds, (4) the determination of the strain-rate hardening modulus comparing the orthogonal cutting test results with FEM results. (5) Finally, to validate the Johnson-Cook material parameters, a comparison of the room-temperature tensile test result with a quasi-static simulation using LS-Dyna is necessary.

• Research in Community and Public Health Nursing
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• v.32 no.1
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• pp.73-85
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• 2021

Purpose: The purpose of this qualitative study is to explore the adaptation process of correctional officers' job stress. Methods: Participants collected were fourteen officers who had experienced the adaptation process of job stress. Data were collected through individual in-depth interviews until the point of theoretical saturation from May to August, 2017. Transcribed interview contents were analyzed using Corbin and Strauss' grounded theory method. Results: A total of 98 concepts, 27 subcategories, and 10 categories were identified through the open coding. As a result of axial coding based on the paradigm model, the job stress adaptation process centering phenomenon of correctional officers was revealed as 'repeat-mark hardening', and the core category was extracted as 'endurance in hardening' consisting of a three-step process: enduring, understanding prisoner management procedures, and rebuilding. The rebuilding was considered as the key phase to escape the repeat-mark hardening and the participants utilized various strategies such as finding fun elsewhere, restoring confidence, accepting values of the prison officer in this phase. Conclusion: The results of this study suggest that the adaptation process of correctional officers' job stress can be a process that endurance the hardening. Therefore, it is necessary to develop systematic practical education and vocational motivation programs.

• The Korean Journal of Community Living Science
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• v.14 no.2
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• pp.107-117
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• 2003

The purpose of this study was to investigate university freshmen' stress coping strategy and psychological wellbeing to appling ecological family life welfare model. Based on Bronfenbrenner's ecological perspective, “ecological family welfare model”, which includes person(individual attributes), context(family backgrounds), process(mechanism of development), and time (the specific period), was suggested as a new research paradigm for family welfare life research. The questionnaire study was done for 171 freshmen of an university in Pusan. The results show the suggested research model was significant and effective to explain the mechanism of stress coping strategy and psychological wellbeing. Individual attributes(i. e., attachment style) and family context have an impact on family cohesion and adaptability which in turn affect stress coping strategies which then affect individual psychological wellbeing.

• Structural Engineering and Mechanics
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• v.5 no.6
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• pp.817-837
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• 1997

In the present contribution an interface crack model is introduced which is capable of modelling crack initialisation and growth in aluminium as well as in Fibre Metal Laminates. Interface elements are inserted in a finite element mesh with a yield function which bounds all states of stress in the interface. Hardening occurs after a state of stress exceeds the yield stress of the material. The hardening branch is bounded by the ultimate stress of the material. Thereafter, the state of stress is reduced to zero while the inelastic deformations grow. The energy dissipated by the inelastic deformations in this process equals the fracture energy of the material. The model is applied to calculate the onset and growth of cracking in centre cracked plates made of aluminium and GLARE$^{(R)}$. The impact of the model parameters on the performance of the crack model is studied by comparisons of the numerical results with experimental data.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.11 no.1
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• pp.125-133
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• 2012

This study aims at structural analysis with fatigue on the shock absorber mount of automobile. Two kinds of mount as original model 1 and reinforced model 2 are applied. Among the cases of nonuniform fatigue loads at both models, 'SAE bracket history' with the severest change of load becomes most unstable but 'Sample history' becomes most stable. In case of 'SAE bracket history' or 'SAE transmission', the maximum fatigue life at model 2 is 5 to 6 times as much as model 1 and the minimum damage at model 2 is decreased 5 to 6 times as much as model 1. In case of 'Sample history' as slow fatigue loading history, the minimum damage at model 2 becomes same as model 1 but the maximum fatigue life at model 2 is decreased more than 17 times as much as model 1. In case of 'Sample History' with the average stress of -$10^4MPa$ to $10^4MPa$ and the amplitude stress of 0MPa to $10^4MPa$, the possibility of maximum damage becomes 3%. This stress state can be shown with 5 times more than the damage possibility of 'SAE bracket history' or 'SAE transmission'. Safe and durable design of shock absorber can be effectively improved by using this study result on mount frame.

• Geomechanics and Engineering
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• v.5 no.3
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• pp.241-261
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• 2013

The bearing mechanism of pile during installation and loading process which controls the deformation and distribution of strain and stress in the soil surrounding pile tip is complex and full of much uncertainty. It is pointed out that particle crushing occurs in significant stress concentrated region such as the area surrounding pile tip. The solution to this problem requires the understanding and modeling of the mechanical behavior of granular soil under high pressures. This study aims to investigate the sand behavior around pile tip considering the characteristics of sand crushing. The numerical analysis of model pile loading test under different surcharge pressure with constitutive model for sand crushing is presented. This constitutive model is capable of predicting the dilatancy of soil from negative to positive under low confining pressure and only negative dilatancy under high confining pressure. The predicted relationships between the normalized bearing stress and normalized displacement are agreeable with the experimental results during the entire loading process. It is estimated from numerical results that the vertical stress beneath pile tip is up to 20 MPa which is large enough to cause sand to be crushed. The predicted distribution area of volumetric strain represents that the distributed area shaped wedge for volumetric contraction is beneath pile tip and distributed area for volumetric expansion is near the pile shaft. It is demonstrated that the finite element formulation incorporating a constitutive model for sand with crushing is capable of producing reasonable results for the pile loading problem.

• Proceedings of the KSR Conference
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• 2005.05a
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• pp.385-390
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• 2005

A specimen with residual stress due to welding was analyzed by three-dimensional cohesive zone model. The residual stress distribution was calculated by simulating welding process, and cohesive elements were located along crack propagation planes. Crack growth is possible since two planes of the cohesive element are separated beyond a maximum load carrying capacity. Stress fields around a crack tip are compared for specimens with and without residual stresses. Load-displacement curves and crack growth behaviors are also examined.

• Journal of Korean Academy of Nursing
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• v.16 no.2
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• pp.36-43
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• 1986

The main purpose of this study was to explore the effect of the stress of hospitalization on the sleep pattern. Additionaly, this study was also to demonstrate how Johnson's nursing model may be applied to as nursing process. 104 hospitalized patients on surgical and medical wards were asked to rate 49 stress producing events associated with experience of hospitalization and sleep pattern scale. Five university hospitals were used as the setting for this study. Data for the study were collected by patient interview during hospitalization, self-reports and review of charts. For the analysis of the data, the pearson's correlation analysis of covariance and regression analysis were used. The results of this study were stated as follows; 1. The mean of the hospital stress scores was 111.261(S.D.=26.160). This means that the level of the hospitalization stress is high. The mean of the sleep pattern scores was 12.204(S.D. =2.615) This means that the characteristic's of the sleep pattern is poor. 2. The relationship between the hospitalization stress and sleep pattern was statistically significant at .01 level. 3. The effect of the hospitalization stress influenced strongly on the sleep pattern after sex, trait anxiety as covariates controlled. 4. The hospitalization stress revealed a 12% pre-diction as an influenced factor for the sleep pattern. Therefore, It can he said that the hospital stress did contribute significantly to the characteristics of the sleep pattern. Johnson's model can he also said that it is useful for the the assessment and diagnosis in nursing process.

• Transactions of Materials Processing
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• v.13 no.2
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• pp.168-173
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• 2004

Microforming can be a good application for bulk metallic glasses. It is important to simulate the deformation behaviour of the bulk metallic glasses in a supercooled liquid region for manufacturing micromachine parts. For these purposes, a correct constitutive model which can reproduce viscosity results is essential for good predicting capability. In this paper, we studied deformation behaviour of the bulk metallic glasses using the finite element method in conjunction with the fictive stress constitutive model which can describe non-Newtonian as well as Newtonian behaviour. A combination of kinetic equation which describes the mechanical response of the bulk metallic glasses at a given temperature and evolution equations fur internal variables provide the constitutive equation of the fictive stress model. The internal variables are associated with fictive stress and relation time. The model has a modular structure and can be adjusted to describe a particular type of microforming process. Implementation of the model into the MARC software has shown its versatility and good predictive capability.

• Journal of the Korea Safety Management & Science
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• v.1 no.1
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• pp.123-134
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• 1999

There are several models for process quality assurance by quality system (ISO 9000), process capability analysis, acceptance control chart and so on. When a high level process capability has been achieved, it takes a long time to monitor the process shift, so it is sometimes necessary to develop a quicker monitoring system. To achieve a quicker quality assurance model for high-reliability process, this paper presents a model for process quality assurance when the fraction nonconforming is very small. We design an acceptance control chart based on variable quality characteristic and time-censored accelerated testing. The distribution of the characteristics is assumed to be normal or lognormal with a location parameter of the distribution that is a linear function of a stress. The design parameters are sample size, control limits and sample proportions allocated to low stress. These paramaters are obtained under minimization of the relative variance of the MLE of location parameter subject to APL and RPL constraints.