• 대한치과보철학회지
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• 제38권4호
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• pp.526-543
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• 2000

Finite element analyses were performed to study effects on stress distribution generated in jaw bone for various shapes of dental implants: plateau type, plateau with small radius of curvature, triangular thread screw type in accordance with ISO regulations and square thread screw filleted with small radius partially. It was found that square thread screw filleted with small radius was more effective on stress distribution than other dental implants used in analyses. Additional analyses were performed on the implant with square thread screw filleted with small radius for very-ing design parameters, such as the width of thread end, the height of the thread of the implant and load direction, to determine the optimum dimensions of the implant. The highest stress concentration occurred at the region in jaw Pone adjacent to the first thread of the implant. The maximum effective stress induced by a 15 degree oblique load of 100 N was twice as high as the maximum effective stress caused by an equal amount of vertical load. Stress distribution was more effective in the case when the width of thread end and the height of thread were p/2 and 0.46p, respectively, where p is the pitch of thread. At last, using tensile force calculated from the possible insert torque without breading bone thread, finite element analysis was performed on the implant to calculate pre-stress when the primary fixation of the implant was operated in jaw bone. The maximum effective stress was 136.8 MPa which was proven to be safe.

• Geomechanics and Engineering
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• 제33권4호
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• pp.369-380
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• 2023

The aim of this paper is to investigate stress analysis of semi-infinite soils consisting of two layers with twin rectangular tunnels under static loads. The region close to the ground surface and tunnel modelled within finite elements. In order to use a more realistic model, the far region is modelled within infinite elements. The material model of the layered soil is considered as elastic and isotropic. In the finite element solution of the problem, two dimensional (2D) plane solid elements are used with sixteen-nodes rectangular finite and eight-nodes infinite shapes. Finite and infinite elements are ordered to be suitable for the tunnel and the soils. The governing equations of the problem are obtained by using the virtual work principle. In the numerical process, the five-point Gauss rule is used for the calculation of the integrations. In order to validate using methods, comparison studies are performed. In the numerical results, the stress distributions of the two layered soils containing twin rectangular tunnels presented. In the presented results, effects of the location of the tunnels on the stress distributions along soil depth are obtained and discussed in detail. The obtained results show that the locations of the tunnels are very effective on the stress distribution on the soils.

• 한국지반공학회논문집
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• 제27권5호
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• pp.17-31
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• 2011

본 연구에서는 흙막이 굴착 공사시 지하수저하에 의한 주변 지반의 공학적 거동에 관한 수치해석 연구내용을 다루었다. 먼저 2차원 간극수압-응력 연계해석을 통하여 굴착공사가 지반침하 거동에 미지는 영향을 알아보았으며 그 결과를 토대로 벽체 수평변형, 벽체배변 변형, 소성변형률 분포, 유효응력분포 및 버팀보 축력분포 등을 분석을 수행하였다. 한편 다양한 지층조건과 초기 지하수위 조건에 대한 매개변수 연구를 통하여 주변지반 및 버팀보의 거동을 분석하였으며 해석 결과를 토대로 특정조건의 최대 지반변형범위를 제안하였다.

• International Journal of Precision Engineering and Manufacturing
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• 제6권1호
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• pp.65-72
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• 2005

Drilling process is one of the most common, yet complex operations among manufacturing processes. The performance of a drill is largely dependent upon drilling forces, Many researches focused on the effects of drill parameters on drilling forces. In this paper, an effective theoretical model to predict thrust and torque in drilling is presented. Also, with the predicted forces, the stress analysis of the drill tool is performed by the finite element method. The model uses the oblique cutting model for the cutting lips and the orthogonal cutting model for the chisel edge. Thrust and torque are calculated analytically without resorting to any drilling experiment, only by tool geometry, cutting conditions and material properties. The stress analysis is performed by the commercial FEM program ANSYS. The geometric modeling and the mesh generation of a twist drill are performed automatically. From the study, the effects of the variation of the geometric features of the drill and of the cutting conditions of the drilling on the drilling forces and the stress distributions in the tool are calculated analytically, which can be applicable for designing optimal drill geometry and for improving the drilling process.

• Computers and Concrete
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• 제21권4호
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• pp.451-461
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• 2018

Present study is mainly concerned about the idea of innovative utilization of bamboo in modern construction. Owing to its compatible mechanical properties, a beneficial effect of its use in reinforced concrete (RC) frame infills has been observed. In this investigation, finite element analyses have been performed to examine the failure pattern and stress distribution pattern through the infills of a moment resisting RC frame. To validate the pragmatic use of bamboo reinforced components as infills, earthquake loading corresponding to Nepal earthquake had been considered. The analysis have revealed that introduction of bamboo in RC frames imparts more flexibility to the structure and hence may causes a ductile failure during high magnitude earthquakes like in Nepal. A more uniform stress distribution throughout the bamboo reinforced wall panels validates the practical feasibility of using bamboo reinforced concrete wall panels as a replacement of conventional brick masonry wall panels. A more detailed analysis of the results have shown the fact that stress concentration was more on the frame components in case of frame with brick masonry, contrary to the frame with bamboo reinforced concrete wall panels, in which, major stress dispersion was through wall panels leaving frame components subjected to smaller stresses. Thus an effective contribution of bamboo in dissipation of stresses generated during devastating seismic activity have been shown by these results which can be used to concrete the feasibility of using bamboo in modern construction.

• 한국환경과학회지
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• 제16권10호
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• pp.1169-1177
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• 2007

The main objective of this research was to evaluate the effects of process variables which were forming ability, flow displacement, effective stress, effective strain, fluid vector and products defects on manufactured artificial lightweight aggregate made of both incinerated sewage sludge ash and clay by means of the numerical analysis of a rigid-plastic finite element method. CATIA (3D CAD program) was used for an extrusion metal mold design that was widely used in designing aircraft, automobile and metallic molds. A metal forming analysis program (ATES Co.) had a function of a rigid-plastic finite element method was used to analyze the program. The result of extrusion forming analysis indicated clearly that a shape retention of the manufactured artificial light-weight aggregate could be maintained by increasing the extrusion ratio (increasing compressive strength inside of extrusion die) and decreasing the die angle. The stress concentration of metal mold was increased by increasing an extrusion ratio, and it was higher in a junction of punch and materials, friction parts between a bottom of the punch and inside of a container, a place of die angle and a place of die of metal mold. Therefore, a heat treatment as well as a rounding treatment for stress distribution in the higher stress concentration regions were necessary to extend a lifetime of the metallic mold. A deformity of the products could have made from several factors which were a surface crack, a lack of the shape retention and a crack of inside of the products. Specially, the surface crack in the products was the most notably affected by the extrusion ratio.

• 대한간호학회지
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• 제48권1호
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• pp.109-121
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• 2018

Purpose: This study was conducted to examine the longitudinal effects of parenting stress and parental control attitudes on problem behaviors in preschool children, using a latent growth model. Methods: Participants were 1,724 pairs of parents and 1,724 preschool children who had completed the panel survey on Korean children ($5^{th}{\sim}7^{th}$ survey panels). Results: An analysis of the multivariate latent growth model of parenting stress, parental control attitudes, and children's problem behaviors suggested that the parents' intercepts for parenting stress influenced their intercepts for parental control attitudes (father: ${\beta}=.21$, p<.001; mother: ${\beta}=.55$, p<.001). In addition, the slopes for fathers' parenting stress was the only aspect that affected the slopes for mothers' parental control attitudes (${\beta}=.77$, p<.001). Moreover, both the intercepts and slopes of parenting stress and parental control attitudes significantly affected the children's problem behaviors. Conclusion: This study is significant as it provides longitudinal evidence of the impact of parenting stress and parental control attitudes on children's problem behaviors. The findings suggest that accurately assessing changes in parenting stress and parental control attitudes and developing intervention programs to reduce them will be effective in reducing problem behaviors in children.

• 수산해양교육연구
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• 제29권3호
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• pp.732-745
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• 2017

The purpose of this study was to analyze the influence of collective self-esteem on teachers' job stress. For the study, 223 teachers in elementary school, junior high school, and high school were selected and data on teachers' background variables, collective self-esteem, and job stress were collected. The relationship between variables was analysed by using multiple regression analysis. The results were as follows: The job stress of teacher was significantly different according to teacher's gender, school level, and career experience. When the influence of background variables was controlled and multiple regression analysis was performed, the group self-esteem of teachers had a great influence on mitigating the perception of job stress. Particularly, it was shown that private collective self-esteem and importance to identity are the most important factors in mitigating job stress perception among the sub-variables of collective self-esteem. These results showed that it is an important task for our society to find an effective way to elevate the teacher's collective self-esteem. Teachers' collective self-esteem is expected to play a positive role not only in mitigating job stress but also in enhancing self-fulfillment and personal self-esteem of teacher.

• Smart Structures and Systems
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• 제16권2호
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• pp.367-382
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• 2015

This paper aims to conduct the reliability-based assessment of the welded joint in the orthotropic steel bridge deck by use of a mesh-insensitive structural stress (MISS) method, which is an effective numerical procedure to determine the reliable stress distribution adjacent to the weld toe. Both the solid element model and the shell element model are first established to investigate the sensitivity of the element size and the element type in calculating the structural stress under different loading scenarios. In order to achieve realistic condition assessment of the welded joint, the probabilistic approach based on the structural reliability theory is adopted to derive the reliability index and the failure probability by taking into account the uncertainties inherent in the material properties and load conditions. The limit state function is formulated in terms of the structural resistance of the material and the load effect which is described by the structural stress obtained by the MISS method. The reliability index is computed by use of the first-order reliability method (FORM), and compared with a target reliability index to facilitate the safety assessment. The results achieved from this study reveal that the calculation of the structural stress using the MISS method is insensitive to the element size and the element type, and the obtained structural stress results serve as a reliable basis for structural reliability analysis.

• 한국치위생학회지
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• 제14권1호
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• pp.67-74
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• 2014

Objectives : The purpose of the study was to investigate the effective coping management of stress towards self-efficacy in students of dental hygiene department. Methods : A self-reported questionnaire was filled out by the students of dental hygiene department in Daegu from April to May, 2013. Descriptive statistics and frequency analysis, t-test, ANOVA and correlation analysis were analyzed using SAS (version 9.2) for statistics. Results : The overall stress coping score was 2.54. Problem-focused coping was 2.50, and social support-seeking coping was 2.60 in active coping. Emotional coping was 2.29, and hopeful thinking coping was 2.76 in passive coping. The level of self-efficacy according to general characteristics varied significantly depending on grade, satisfaction with major, subjective health status and smoking status. The stress coping methods according to general characteristics varied significantly depending on academic achievement and satisfaction with major. The results showed that the level of self-efficacy was associated with stress-coping methods. Conclusions : Self-efficacy of students of dental hygiene department was associated with stress coping methods. It is necessary to develop the programs for stress coping to increase self-efficacy.