• Title, Summary, Keyword: Stress

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The effect of initial stress induced during the steel manufacturing process on the welding residual stress in multi-pass butt welding

  • Park, Jeong-ung;An, Gyubaek;Woo, Wanchuck
    • International Journal of Naval Architecture and Ocean Engineering
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    • v.10 no.2
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    • pp.129-140
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    • 2018
  • A residual stress generated in the steel structure is broadly categorized into initial residual stress during manufacturing steel material, welding residual stress caused by welding, and heat treatment residual stress by heat treatment. Initial residual stresses induced during the manufacturing process is combined with welding residual stress or heat treatment residual stress, and remained as a final residual stress. Because such final residual stress affects the safety and strength of the structure, it is of utmost importance to measure or predict the magnitude of residual stress, and to apply this point on the design of the structure. In this study, the initial residual stress of steel structures having thicknesses of 25 mm and 70 mm during manufacturing was measured in order to investigate initial residual stress (hereinafter, referred to as initial stress). In addition, thermal elastic plastic FEM analysis was performed with this initial condition, and the effect of initial stress on the welding residual stress was investigated. Further, the reliability of the FE analysis result, considering the initial stress and welding residual stress for the steel structures having two thicknesses, was validated by comparing it with the measured results. In the vicinity of the weld joint, the initial stress is released and finally controlled by the weld residual stress. On the other hand, the farther away from the weld joint, the greater the influence of the initial stress. The range in which the initial stress affects the weld residual stress was not changed by the initial stress. However, in the region where the initial stress occurs in the compressive stress, the magnitude of the weld residual compressive stress varies with the compression or tension of the initial stress. The effect of initial stress on the maximum compression residual stress was far larger when initial stress was considered in case of a thickness of 25 mm with a value of 180 MPa, while in case of thickness at 70 mm, it was 200 MPa. The increase in compressive residual stress is almost the same as the initial stress. However, if initial stress was tensile, there was no significant change in the maximum compression residual stress.

Effects of Chungganhaewooltang on Serum Levels of Histamine and Corticosterone and Immune Response after Immobilization-Stress or Cold-Stress in Mice (청간해울탕(淸肝解鬱湯)이 생취에 Immobilization-Stress 및 Cold-Stress 부하후(負荷後) 혈중(血中)Histamine과 Corticosterone 함량(含量) 및 면역능(免疫能)에 미치는 영향(影響))

  • Kang, Bok-Hwan;Jung, Woo-Suk;Kim, Song-Baeg;Yoo, Sim-Keun
    • The Journal of Korean Obstetrics and Gynecology
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    • v.18 no.4
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    • pp.85-105
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    • 2005
  • Purpose : Investigate the effects of Chungganhaewooltang(CHT) on immobilization-stress or cold-stress in C576BL/6J mice. Methods : Male C57BL/6J 30 mice of weighting 18${\pm}$2g, were divided into sixs groups including the immobilization-stress group(5heads), after immobilization-stress CHT oral administration(500mg/kg) groups(5heads), cold-stress group(5heads) and after cold-stress CHT oral administration(500mg/kg) groups(5heads). then we observed changes in the serum histamine and corticosterone level and changes immune system Results : Immobilization-stress or cold-stress increased the serum level of histamine and corticosterone. CHT decreased the serum level of histamine and corticosterone increased by cold-stress. CHT inhibited the release of histamine from mast cells at the concentration of 0.1 mg/ml. In addition, immobilization-stress or cold-stress decreased the cell viability of murine thymocytes and splenocytes. CHT increased the cell viability of thymocytes decreased by immobilization-stress or cold-stress, but did not affect the cell viability of splenocytes decreased by immobilization-stress or cold-stress. Also immobilization-stress or cold-stress increased DNA fragmentation of thymocytes and splenocytes. CHT decreased DNA fragmentation of thymocytes increased by immobilization-stress or cold-stress, but did not affect DNA fragmentation of splenocytes increased by immobilization-stress or cold-stress. Immobilization-stress increased the population of thymic $CD4^+$ cells. CHT decreased the population of thymic $CD4^+$ cells increased by immobolization-stress. Immobilization-stress or cold-stress decreased the population of $B220^+$ cells and increased the population of $thy1^+$ cells. CHT decreased the population of $thy1^+$ cells increased by immobilization-stress or cold-stress. Immobilization-stress or cold-stress increased the population of splenic $CD4^+$ cells and $CD8^+$ cells. CHT decreased the population of splenic $CD4^+$ cells increased by immobolization-stress or cold-stress. Immobilization-stress or cold-stress decreased the production of ${\gamma}-interferon$(IFN) interleukin(IL)-2 and IL-4. CHT enhanced the production of ${\gamma}-IFN$ decreased by immobilization-stress or cold-stress but did not affect the production of IL-2 and IL-4 decreased by immobilization-stress or cold-stress. Furthermore, Immobilization- stress or cold-stress decreased the phagocytic activity of peritoneal macrophages and the production of nitric oxide. CHT enhanced the phagocytic activity and nitric oxide production decreased by cold-stress. Conclusion : CHT may be useful for the prevention and treatment of stress via suppression of serum histamine and corticosterone level and enhancement of immune response.

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Relationships between Child′s Self-Regulation and Stress (아동의 자아통제능력과 스트레스와의 관계)

  • 정현희;최경순
    • Journal of the Korean Home Economics Association
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    • v.39 no.9
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    • pp.175-188
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    • 2001
  • The purpose of this study was to examine the relationships between child's self-regulation and stress according to child's sex. The subjects for this study were 380 children of 5-6th grade selected from elementary schools in Busan. Lee, Soon-Kyu's questionnaires(1994) on child's self-regulation and Han, Mi-Hyun's questionnaires(1996) on child's stress were used. Statistical techniques such as Manova, Pearson's correlation, multiple regression, canonical were used. The resets were as follows : (1) According to sex, there were significant differences in child's self-regulation and stress. The girls showed more self-regulation and higher friend-related stress than the boys. The boys showed higher parent-related stress than the girls. (2) Relationships between child's self-regulation and stress showed as follows : The boys who used more impulsive-control perceived lower friend-related stress, lower school-related stress, lower teacher-related stress, and lower surroundings-related stress. And the boys who used more behavioral-control perceived lower school-related stress, lower teacher-related stress, and lower surroundings-related stress. (3) The predicted variable for boy's friend-related stress was impulsive-control. The predicted variables for boy's school-related stress, teacher-related stress and surroundings-related stress were impulsive-control and behavioral-control. (4) Among three dimensions of self-regulation for boy, the effective variables were impulsive-control and behavioral-control. And among six dimensions of stress were surroundings-related stress, school-related stress and friend-related stress. Implications of this study were discussed in terms of child's self-regulation and stress.

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Differences of Perceived Stress Level and Stress Coping Behavior among School Children (일부지역 아동의 스트레스 지각정도와 스트레스 대처 행동의 차이)

  • Kim, Suk
    • The Journal of the Korean Society of School Health
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    • v.16 no.1
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    • pp.55-66
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    • 2003
  • This study was conducted to evaluate the differences of perceived stress level and stress coping behavior for 360 elementary school children in rural area and 360 in urban area. The questionnaire survey was done from December 10 to December 20, 2001. The results were as follows: 1. There was no significant difference of perceived stress level between rural and urban areas, but there were significant difference of stress coping behavior between them. 2. Significant difference of perceived stress level and stress coping behavior among groups of grade was found. 3. There was significant difference of perceived stress level and stress coping behavior between male and female. 4. There was significant difference of stress coping behavior according to perceived stress levels In conclusion, perceived stress level and stress coping behavior in elementary school children were different according to their grade and sex. It is important to teach them proper stress coping method, depending on their grade and sex. But, we have to focus on the development and application of stress self-control program, which enables children to cope with stress for themselves. Based on: 1. Before starting the study, the subjects should be examined about whether they have ever been on stress education program before or not. 2. The educational environments and the development and implementation of teaching program for the proper stress coping method are needed. 3. This study was performed through the questionnaire for perceived stress level and stress coping behavior, but various methods like observation, person-to-person interview should be used for the further in-depth study.

Strength Characteristics of Clay Soil by Preconsolidation Pressure (선행하중(先行荷重)에 의한 점토(粘土)의 강도특성(强度特性))

  • Chon, Yong-Baek;Shin, Young-Gi
    • Journal of the Korean Society of Industry Convergence
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    • v.6 no.3
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    • pp.185-192
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    • 2003
  • This study consolidation undrain Triaxial Compression Tests using constant confining pressure in clay that receive preconsolidation stress that is different and, void ratio, pore water pressure coefficient, shear strength compare with another thing theory and studied analyzing change relation of elastic modules. The summary of analysis is follows: If preconsolidation stress increases in same confining stress in relation of preconsolidation stress and deviator stress, deviator stress is proportional and increased. Can know that excess void pressure is proportional and decreases in size of preconsolidation stress in same confining stress state if preconsolidation stress increases preconsolidation stress and relation of excess void pressure. Also, over consolidated state can assume that this is thing by Dilatancy's effect though excess void pressure decreased remarkably. Preconsolidation stress and relation of stress path can know that shear strength degree increases preconsolidation stress increases, and specially, preconsolidation stress was appear in stress path form of overconsolidated state case of clay that receive at 300, 400, 500kPa in 100, 150kPa's deviator stress.

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Family Stress, Work Stress and Psychological Well-being in Employed Men and Women (기혼 취업여성과 남성의 가족 및 직업 스트레스와 심리적 복지)

  • 이형실
    • Journal of Korean Home Management Association
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    • v.19 no.2
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    • pp.143-152
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    • 2001
  • The purpose of this study was to investigate the effects of family stress on work stress and to examine the effects of family and work stress on psychological wellbeing in employed men and women. The analyses of the present study were based on a sample of 263 full-time employed men and 258 full-time employed women aged 30-49 in dual-earner families. There were significant gender differences in marital stress, parenting stress and psychological well-being with women reporting higher levels of stress. However, employed men and women experienced similar levels of work stress. The results from regression analyses showed that stress in the family domain contributed significantly to work stress. Both marital stress and parenting stress were significantly related to higher levels of work stress fro employed men and women. The findings of this study indicated that higher levels of marital stress and work stress were predictive of psychological well-being for men and women in dual-earner couples. Among employed women, marital stress and work stress were more highly related to psychological well-being than among employed men.

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A Study on the Development of Stress Optic Law Considering Residual Stress in Photoelastic Experiment(II) -Application of Stress Optic Law Considering of Residual Sterss- (잔류응력을 고려한 광탄성실험의 광응력법칙 개발에 관한 연구 (2) -잔류응력을 고려한 광응력법칙의 응용-)

  • 서재국;황재석;최선호
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.19 no.8
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    • pp.1810-1821
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    • 1995
  • Photoelastic experiment has been used to analyze stress of structure and stress in the vicinity of crack tip etc.. Model experiment such as photoelastic experiment has been restricted by problem of residual stress in the photoelastic model material. They are generated by molding, cutting and time effects etc.. They produce some errors in the results of photoelastic experiment data. In this paper, stress optic law considering residual stress already developed by authors was applied to the stress concentration problem and fracture mechanics. Although the specimen was bad with residual stress, we could obtain good results by using the stress optic law considering residual stress. It was found that the stress optic law of photoelastic experiment could be applied to the stress analysis of bimaterial.

A study on the fatigue crack growth behavior of aluminum alloy weldments in welding residual stress fields (용접잔류응력장 중에서의 Aluminum-Alloy용접재료의 피로균열성장거동 연구)

  • 최용식;정영석
    • Journal of Welding and Joining
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    • v.7 no.1
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    • pp.28-35
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    • 1989
  • The fatigue crack growth behavior in GTA butt welded joints of Al-Alloy 5052-H38 was examined using Single Edge Notched(SEN) specimens. It is well known that welding residual stress has marked influence on fatigue crack growth rate in welded structure. In the general area of fatigue crack growth in the presence of residual stress, it is noted that the correction of stress intensity factor (K) to account for residual stress is important for the determination of both stress intensity factor range(.DELTA.K) and stress ratio(R) during a loading cycle. The crack growth rate(da/dN) in welded joints were correlated with the effective stress intensity factor range(.DELTA.Keff) which was estimated by superposition of the respective stress intensity factors for the residual stress field and for the applied stress. However, redistribution of residual stress occurs during crack growth and its effect is not negligible. In this study, fatigue crack growth characteristics of the welded joints were examined by using superposition of redistributed residual stress and discussed in comparison with the results of the initial welding residual stress superposition.

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A Study of the Development of the Stress Optic Law of Photoelastic Experiment Considering Residual Stress

  • Suh, Jae-guk;Hawong, Jai-sug;Shin, Dong-chul
    • Journal of Mechanical Science and Technology
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    • v.17 no.11
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    • pp.1674-1681
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    • 2003
  • Photoelastic experiment has two significant problems. The first problem is manufacturing a model specimen for complicated shapes of structures. The second problem is residual stress contained in the photoelastic model material. In this paper, the stress optic law that can be effectively used on photoelastic model materials with residual stress is developed. By using the stress optic law as developed in this research, we can obtain good results in photoelastic experiments using model material in which residual stress is contained. It is assured that the stress optic law developed in this research is useful. Therefore, it is suggested that the stress optic law considering residual stress can be applied to the photoelastic experiment for the stress analysis of the composite materials or bi-materials in which the residual stress is easily contained.

Redistribution of Welding Residual Stress and its Effects on Fatigue Crack Propagation (피로균열이 진전할 때 용접잔류응력의 재분포와 그 영향)

  • 이용복;조남익
    • Journal of Welding and Joining
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    • v.13 no.4
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    • pp.155-162
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    • 1995
  • Redistribution of residual stress and its effects during fatigue crack propagates from tensile residual stress region in weldment are investigated. Tests are performed by using welded CCT specimens of structual rolling steel (SS400) and it makes fatigue crack propagate from tensile residual stress region. For this study tension-tension loading type is selected by external loading condition and magnetizing stress indicator is used correctly to measure redistribution of residual stress according to fatigue crack growth and number of loading cycles. From this result, it is proved that redistribution of residual stress is mainly consist of residual stress released by fatigue crack growth. When fatigue crack propagates from tensile residual stress region residual stress are redistributed and it makes fatigue crack growth rate largely increase. Fatigue crack growth rate is low in case of redistributed residual stress compare with initial distributed residual stress.

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