• 제목/요약/키워드: stress condition

검색결과 4,074건 처리시간 0.028초

선박용 스프링강의 피로수명에 미치는 쇼트피닝의 영향 (A Effect of Shot Peening for Fatigue Life of Spring Steel for Vessel Application)

  • 유형주;박경동
    • Journal of Advanced Marine Engineering and Technology
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    • 제29권4호
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    • pp.426-435
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    • 2005
  • The lightness of components required in automobile and machinery industries is requiring high strength of components. Therefore this requirement is accomplished as the process of shot-peening method that the compressive residual stress is made on the metal surface as one of various improvement methods. Special research is, therefore, needed about compressive residual stress on the metal surface in the process of shot-peening method. Therefore, in this paper the effect of compressive residual stress of spring steel(JISG SUP-9) by shot-peening on fatigue crack growth characteristics in environmental condition(temperature) and mechanical condition(shot velocity, stress ratio) was investigated with considering fracture mechanics. By using the methods mentioned above, the following conclusions have been drawn. (1) The fatigue crack growth rate(da/dN) of the shot-peened material was lower than that of the un-peened one. In high temperature range. fatigue crack growth rate decreased with increasing temperature range, while fatigue crack growth rate increased by decreasing temperature in low temperature. (2) Fatigue life shows more improvement in the shot-peened material than in the un-peened material. And compressive residual stress of surface on the shot-peen processed operate resistance force of fatigue crack propagation.

변형률 의존성을 고려한 쌍곡선 모델의 개발 (Developement of Hyperbolic Model Considering Strain Dependency)

  • 이용안;김유성
    • 한국지반공학회:학술대회논문집
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    • 한국지반공학회 2008년도 춘계 학술발표회 초청강연 및 논문집
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    • pp.644-655
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    • 2008
  • Conventional hyperbolic model does not satisfactorily predict the overall stress-strain behaviors of various geomaterials. Tatsuoka and Shibuya(1992) suggest the generalized hyperbolic equation(GHE) considering strain dependency and calculated performance is in good agreement with precise triaxial compression test results of stress-strain relations over wide range of strains before peak stress condition in some cases, but GHE model also does not satisfactorily predict stress-strain relations as strain goes on state of peak stress in most cases. For improve a weak point of the GHE, in this study, modified form of generalized hyperbolic equation (MGHE model) is proposed which can predict highly nonlinear stress-strain behavior for various geomaterials from small strain to peak stress condition.

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The Subsurface Stress Field Caused by Both Normal Loading and Tangential Loading

  • Koo Young- Phi;Kim Tae-Wan;Cho Yong-Joo
    • Journal of Mechanical Science and Technology
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    • 제19권11호
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    • pp.1967-1974
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    • 2005
  • The subsurface stress field caused by both normal loads and tangential loads has been evaluated using the rectangular patch solution. The effect of tangential loading on the subsurface stress field has been investigated in detail for both the cylinder-on-cylinder contact and a spur gear teeth contact. For the cylinder-on-cylinder contact, the subsurface stress fields are moved more to the direction of tangential loads and the positions where the maximum stress occur are getting closer to the surface with the increasing tangential loads. The subsurface stress fields of the gear teeth contact are expanded more widely to the direction of tangential loads with the increasing tangential loads. The friction coefficient of a gear teeth contact is low because they are operated in a lubricated condition, and therefore surface tractions in the EHL condition hardly affect on the subsurface stress field.

영양소 섭취가 사회심리적 스트레스에 미치는 영향 (Effect of the Nutrient intakes on Psychosocial Stress)

  • 김미경;신동순;왕수경
    • 한국식생활문화학회지
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    • 제10권5호
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    • pp.405-417
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    • 1995
  • This research was designed to see the relationship among nutrient intake, food intake frequency and psychosocial stress in ordinary life. The subjects were 190 males and 263 females of university students in urban areas. There were significant correlations between nutrient intake and stress value, and between food intake frequency and stress value. In male, the more they consumed energy, protein and carbohydrate, the higher they had stress in several categories. But in female the results were reversed. Their stress values were lower when they have consumed protein source food frequently. And in general, stress values of female were higher than those of male. From these results, we conclude that nutrient intake tends to be decresed with increase stress in less stressful condition, but to be increased in more stressful condition.

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PENALIZED NAVIER-STOKES EQUATIONS WITH INHOMOGENEOUS BOUNDARY CONDITIONS

  • Kim, Hongchul
    • Korean Journal of Mathematics
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    • 제4권2호
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    • pp.179-193
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    • 1996
  • This paper is concerned with the penalized stationary incompressible Navier-Stokes system with the inhomogeneous Dirichlet boundary condition on the part of the boundary. By taking a generalized velocity space on which the homogeneous essential boundary condition is imposed and corresponding trace space on the boundary, we pose the system to the weak form which the stress force is involved. We show the existence and convergence of the penalized system in the regular branch by extending the div-stability condition.

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원전 정상가동조건 적용 방식이 원자로 압력용기 상부헤드 관통 노즐의 용접 잔류응력에 미치는 영향 (Effect of Normal Operating Condition Analysis Method for Weld Residual Stress of CRDM Nozzle in Reactor Pressure Vessel)

  • 남현석;배홍열;오창영;김지수;김윤재
    • 대한기계학회논문집A
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    • 제37권9호
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    • pp.1159-1168
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    • 2013
  • 가압형 경수로 원자로의 압력용기 상부헤드 관통노즐 J-groove 용접부 주변에서 일차수응력부식균열(PWSCC)로 인한 냉각수 누설사례가 발생하고 있다. 본 연구에서는 PWSCC 의 주요 원인 중 하나인 용접 잔류응력을 유한요소 해석을 이용해 평가하고 원자력 발전소의 정상가동 조건을 해석에 반영하는 방법이 용접잔류응력 분포에 미치는 영향에 대한 분석을 수행하였다. 또한 반복되는 원자력 발전소의 가동 주기가 용접잔류응력 분포에 미치는 영향을 확인하여 정상가동조건에서의 정확한 용접 잔류응력을 예측할 수 있는 방법을 분석하였다.

신문사 근로자들의 스트레스와 건강상태에 관한 연구 (A Study on the Stress and the Health Status of Newspaper Employees)

  • 김진희
    • 한국직업건강간호학회지
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    • 제10권1호
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    • pp.41-54
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    • 2001
  • This study was designed to assess the relationship between occupational stress and health status in a study group of 197 workers employed in four newspaper publishing companies, using a self-adminstrative questionnaire. The types of occupation of them were reporters(79), clerical workers(54), and engineers (64). The studies on workers' health have been focused mainly on the physical, chemical, and biological diseases in our country. Therefore, the study of mental health, especially of occupational stress, is to be carried out. I consider stress as a factor having an effect on the health status of the newspaper employees, who have been well known to have high stress due to time pressures. I expect that this research will be helpful not only for understanding of health status by occupation, but also for making clear the issues that have been raised continuously from the previous researches. The results of this study are as follows; 1. The mean values of stress by occupation were statistically significant; the reporters had the highest stress symptom scores, and the engineers had the lowest levels of stress. The mean values of stress symptoms were higher in the workers who had long working hours. 2. The health status by occupation showed significant differences in gastrointestinal systems and in depression. The clerical workers were healthier than the engineers in gastrointestinal systems, and the reporters were more depressed than the engineers in depression. 3. The health status by the general characteristics, there was a statistical significance as for a gender, marital status, and absenteeism in the gastrointestinal systems. The men, the married, and the workers who had not been absent were more healthy. Only absenteeism had an effect on the problems in optical-dermal systems and in oro-fecal systems. Gender, marital status, absenteeism, and working hours were related with health status : the men. the married, the workers who had not been absent, and the workers who had longer working hours were more healthy. In mental stability, gender had a significant effect : the men were more healthy than the women. In general condition, the men, the older, the married, and the workers who had not been absent were more healthy. 4. Stress level had an effect on the health status in the respiratory systems, optical-dermal systems, oro-fecal system, depression, mental stability, general condition, and health condition. The workers who perceived more stress had more problems in their health status. 5. In the results of the multiple regression analyses, age in the respiratory systems, absenteeism in the optical-dermal systems, occupation and absenteeism in the gastrointestinal systems and in the oro-fecal systems, gender in depression and in mental stability, gender, age, absenteeism, and working hours in the general condition, absenteeism in the health condition had an effect on the health status of the workers.

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탄성유체윤활 및 접선하중 상태에서 캠-롤러 접촉표면의 내부 응력장 (Subsurface stress field beneath the cam-roller contact surface under elastohydrodynamic lubrication and tangential loading)

  • 김형자;김영대;박경동;구영필
    • 한국윤활학회:학술대회논문집
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    • 한국윤활학회 2004년도 학술대회지
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    • pp.261-268
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    • 2004
  • For cam and roller-follower contacting surfaces, the effect of tangential loading on the subsurface stress field at an elaso-hydrodynamic lubrication condition has been studied numerically. As tangential load increases, the subsurface stress field extended more widely to the direction of the tangential load. The positions of the maximum shear stress and the maximum effective stress are getting closer to the surface with the increasing tangential load. The tangential load at the elasto-hydrodynamic lubrication condition is of little consequence to the subsurface stress field.

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열화특성치가 와이블분포를 따르는 경우 두 가지 스트레스 변수를 고려한 가속열화시험의 최적 설계 (Optimal Design of Accelerated Degradation Tests with Two Stress Variables in the Case that the Degradation Characteristic Follows Weibull Distribution)

  • 임헌상;김용수
    • 한국신뢰성학회지:신뢰성응용연구
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    • 제13권2호
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    • pp.87-98
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    • 2013
  • Accelerated degradation tests (ADTs) measuring failure-related degradation characteristic at the accelerated condition are widely used to assess the reliability of highly reliable products. Often, however, little degradation could be observed even in single-stress ADTs due to the high reliability of test unit, and as a result poor estimate of the reliability may be obtained. ADTs with multiple stress variables can be employed to overcome such difficulties. In this paper, optimal ADT plans with two stress variables are developed assuming that the degradation characteristic follows Weibull distribution by determining the stress levels, the proportion of test units allocated to each stress level such that the asymptotic variance of the maximum likelihood estimator of the q-th quantile of the lifetime distribution at the use condition is minimized.

Thermal stress analysis for high pressure and temperature pipelines in ultra steam turbine (UST) system

  • 최대건
    • 대한조선학회지
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    • 제52권2호
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    • pp.19-24
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    • 2015
  • A reliable assessment and analysis of the condition of high pressure and temperature steam pipelines requires defining stress state, which will take into consideration not just the impact of internal pressure and temperature but all applied loads. For that, usage of modeling and numerical methods for calculation and analysis of stress state is essential. The main aim of piping stress analysis is to check the design of piping layout, which will allow simple, efficient and economical piping supports and provide flexibility to the piping system for loads and stresses. The piping stress analysis is carried out using CAESER II software. By using this software we can evaluate stresses, stress ratios, flange condition, support loads, element forces and displacements at each node and points. In this paper, only the maximum and minimum displacement results are tabulated, which is also shown in detail by an example of main steam pipelines of UST Main Engine System [1].