• Title, Summary, Keyword: fatique

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The Influence on the Corrosion Fatigue Crack Propagation in Changing of the Second Phase Hardness of Dual Phase Steel (複合組織鋼의 第2相 硬度變化가 腐蝕疲勞 크랙傳播에 미치는 影響)

  • 오세욱;김웅집
    • Journal of Welding and Joining
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    • v.11 no.2
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    • pp.42-52
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    • 1993
  • The corrosion fatigue fracture behaviour of dual phase steel was investigated in 3% NaCl solution at 302MPa and 137MPa. Fatigue test was conducted by cantilever type of self-made rotary bending fatigue testing machine. The fatigue strength increased with increasing the hardness of 2nd phase. Corrosion pit originated at the boundary of the 2nd phase. The size and number of corrosion pits were influenced by the 2nd phase hardness, and pits remained constant in size just after they were transited into cracks. The life of crack initiation was effected by stress level. The shape of relation of .DELTA. K and da/dN has smaller scattering in it in 3% NaCl solution than that in air. The higher the 2nd phase hardness is, the greater the corrosion fatigue life becomes. Corrosion fatigue fracture behaviour was primarily effected by mechanical factor in case of high stress(302MPa), but by electro-chemical reaction in a lower stress(137MPa). As stress level got lower and hardness of the 2nd phase got higher, the roughness of fracture surface increased.

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A Study on Fatigue Crack Propagation Analysis and Fatigue Strength Evaluation for Bulk Carrier (살물선의 피로균열 전파해석과 피로강도 평가에 대한 연구)

  • 엄동석;김충희
    • Journal of Welding and Joining
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    • v.11 no.4
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    • pp.112-124
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    • 1993
  • It has been reported that fatigue damage sometimes occurred at the stress concentrated and dynamic loaded structural members of bulk carrier. In this paper, studies on fatigue strength of hull structures are reviewed, and the program for evaluating fatigue strength is developed. And the fatigue crack initiation and propagation on the end part of cargo hold frame of bulk carrier were calculated by FEM stress analysis and the fatigue strength evaluation program. These method can be applied not only to the crack initiation life but also to crack propagation life for the hull structural members at the hull design stage and be effective as the guideline to prevent the crack initiation or to estimate the fatigue strength for repairing of the fatigue damaged structures of real ships.

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A Study on the Subjective Symptoms of VDT Syndrome in Radiological Technologist Using Computer Keyboard (컴퓨터 단말기를 사용하는 방사선사의 VDT 증후군에 관한 연구)

  • Lee, Byoung-Nam;Lee, Kang-Woo
    • Korean Journal of Digital Imaging in Medicine
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    • v.5 no.1
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    • pp.138-149
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    • 2002
  • During the period from may to June 2000, a questionnaire study was carried out on 65 male radiological technologist who had been engaged at VDT work, to find out correlation their symptoms to VDT syndrome factors, work environment and condition. The results were as follows : 1. The mean age was 41.0 years, the mean relay working time was 3.75 hours and the mean duration of using computer monitor was 5.9 years, the satisfactory of working was 44.6% the others 55.4%, among these, 3.1% had symptoms before using the VDT and the others had not. 2. The prevalence of symptoms was the highest on wholebody tired, followed by eye, neck, low back, in decreased order and the lowest was fatique of wrist. 3. There was not significant correlation of symptoms to age, but significant to working time, working duration. 4. There was not significant correlation of symptoms to satisfactory. 5. Working desk, monitor, illuminations, temperature, and noise were significantly related to symptoms. 6. There was significant relation of symptoms to CT, MRI workers.

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Structural Safety Assessment of Independent Spherical LNG Tank(2nd report) - Fatigue Crack Propagation Analysis Based on the LBF Theory - (독립구형 LNG 탱크의 구조안전성 평가(제2보) - LBF 이론에 의한 피로균열 진전해석 -)

  • In-Sik Nho;Yong-Yun Nam;Ho-Sup Lee
    • Journal of the Society of Naval Architects of Korea
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    • v.30 no.4
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    • pp.74-82
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    • 1993
  • The present paper deals with the structural safety assessment techniques for independent type B spherical LNG tank against fatique crack initiation and propagation, which contains fellowing 3 steps. 1) Prediction of long term distribution of wave induced stresses and fatique crack intiation life using cumulative damage theory which were described at the 1st report. 2) Surface crack propagation analysis to verify that initial defects cannot penetrate tank plate. 3) Passing-through fatigue crack propagation analysis was performed based on LBF(Leak Before Failure ) theory.

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The Effect of Different dietary Patterns (between Non-Vegetarian and Vegetarian) on Protein Nutritional Status during Short-term (식사 Pattern의 차이가 단백질 영양상태에 미치는 영향)

  • 박귀선;김정임
    • Journal of the East Asian Society of Dietary Life
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    • v.7 no.1
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    • pp.1-11
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    • 1997
  • The purpose of this study was to describe the protein nutritional status of female collegians between nonvegetarian diet groups(14) and vegetarian diet groups(19). Daily intake, protein were calculated from food direct measurement. Urea/creatinine, muscle mass, fatique conditions and hematological parameter were calculated. Blood samples were analyzed for total protein, albumin ammonia, urea, uric acid, creatinine, BUN contents. The results obtained are summarized as following : 1) On total dietary intake, especially Fe, vitamin C, niacin intake, vegetarian groups were higher than non vegetarian groups. 2) On composition of EAA(essential amino acids), vegetarians were highter than non vegetarian of leucine contents, but were lower lysine and threonine contents. 3) On urea / creatinine excretion, vegetarians were higher than non begetarians. Muscle mass were non signicant, fatique condition, vegetarians were normal state. 4) Non vegetarians were increased serum albumin total protein, uric acid, ammonia but vegetarians were decreased BUN, ammonia after experimental diet intake. 5) In process of time after meal, non vegetarians were increased serum albumin total protein, BUN, but vegetarians were decreased ammonia.

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Fatique Analysis of RC Beams Strengthened by Steel Plate or Carbon Fiber Sheet (강판 및 탄소섬유 sheet로 보강된 철근콘크리트 보의 피로해석)

  • Sim, Jong-Sung;Hwang, Eui-Seung;Bae, In-Hwan;Jang, Sang-Hoon
    • Proceedings of the Korea Concrete Institute Conference
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    • pp.703-708
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    • 1997
  • In this study, the fatigue tests are performed on simply-supported R/C beams strengthened with steel plate and CFS (Carbon fiber sheet). Analysis results by Weibull distribution are compared with the test data. The unknown Weibull distribution parameters are estimated based on observations recorded in fatigue test. Safety factors for the number of cycles and the stress level are obtained. S-N-P curves are also generated from these testes and probabilities of failure.

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A Study on the Extraction of the Preferable Luminance Distribution in VDT Workspaces (VDT작업공간의 적정휘도분포 추출에 관한 연구)

  • 정진현;이진숙
    • The Proceedings of the Korean Institute of Illuminating and Electrical Installation Engineers
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    • v.9 no.3
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    • pp.59-66
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    • 1995
  • In this study through a series of the experiments, 1) the preferable luminance values of the CRT screens, 2) the preferable luminance ratios between the CRT screens and its surrounding surfaces are determined. The results are evaluated by the level of satisfaction, and re-examined by the work performance (number of types, rate of errors) and the level of eye fatique (number of blinks, near point distance)

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The Analysis of the Dietary Factors Related to Climacteric Symptoms in Middle-aged Women (중년 여성의 식사섭취 상태와 갱년기 증상 관련 요인 분석)

  • Kim, Soon-Kyung;SunWoo, Jae-Gun
    • Korean Journal of Community Nutrition
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    • v.12 no.1
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    • pp.25-39
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    • 2007
  • The purpose of this study was to investigate the dietary intakes in middle-aged women(pre and postmenopausal) and relation to climacteric symptoms. We conducted the anthropometric measurements, climacteric symptoms survey, and dietary intake to assess the nutrient intakes. Also, dietary quality indices were evaluated. The subjects, over 40 years old, were 168 middle aged women(pre=74, postmenopausal=94), mean age was $48.9{\pm}3.6yr$. The anthropometric measurements showed that 59% of subjects were overweight and obese. Climacteric symptoms that were answered 'yes' in 50% plus in the subjects, were dry eyes, forgetfulness, difficult concentration, large joint pain(shoulder), fatique, backache, dry skin, joint pain(ankle and knee), dry mouth, dizziness, depression and lonesomeness, snore, morning stiffness, and hot flash. Some symptoms showed significant difference between pre and postmenopausal groups. The average energy intake was 1602.1 Kcal, which was 82% of the Korean EER. The subjects had lower vitamin A, riboflavin, folic acid, Fe, Zn and Ca intake than Korean RI. The lowest nutrient intake was Ca. The mean of food intake was 1294.2 g and MAR of diet quality indices was 0.83. In relation to dietary factors with climacteric symptoms, significant correlations have been found between total protein, animal protein, lipid, cholesterol and niacin intake and 'fatique', energy, carbohydrate, thiamin, vitamin B6, folic acid, vitamin C, Na, K and Fe intake and 'dry skin', Ca intake and 'difficult concentration'. Our results indicate that dietary factors(food and nutrients intake, INQ, NAR, MAR) may effect the prevention and reduction of some climacteric symptoms in middle aged women.

Relationship between Rolling Motion and Microstructural Change in Rolling Element (구름계의 미소조직 변화와 구름운동의 상호관계)

  • 차금환;김대은
    • Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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    • pp.163-167
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    • 1996
  • The life of rolling elements depends on various factors such as operating conditions and material properties. In this work, the effect of microstructure on the rolling behavior is investigated. Specially, the deformations in the substrate regions before and after rolling are compared. It is found that rolling action causes severe flow of material in the direction opposite to the rolling direction in the case of dry rolling direction. With lubrication, the deformation is more severe at the subsurface region rather than at the surface.

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