• Title, Summary, Keyword: Fatigue

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Fatigue Characteristics of Non Load-Carrying Fillet Welded Joints According to Post-Processing (용접후처리에 따른 하중비전달형 필렛용접부의 피로특성)

  • Hong, Sung-Wook
    • Journal of the Korean Society of Safety
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    • v.25 no.6
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    • pp.161-168
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    • 2010
  • A series of fatigue tests have been performed on the non-load carrying fillet welded joints in order to quantitatively assess the fatigue characteristics due to the grindings and TIG(Tungsten Inert Gas) welding treatments. From the results of fatigue tests, it has been shown that the fatigue strengths at $2{\times}106$ load cycles were improved in the case of the grinding sand TIG welding treatments, and we could know that it is satisfying fatigue strength prescribed in fatigue design standard in general. Besides, from the results of fracture mechanics approaches, the geometric shape correction factors were the most dominant factors in the initial fatigue crack growth, but as the fatigue crack develops, the finite plate correction factor were became the most dominant factor, and the fatigue life on non-load carrying fillet welded joints could be relatively exactly estimated by using the relations between fatigue crack growth rate and stress intensity factor obtained from finite element analysis and existing proposed formulae.

Study of Fatigue in Patients with Rheumatoid Arthritis (류마티스 관절염환자의 피로에 대한 조사)

  • Park, Jeong-Sook;Cho, Hyea-Myung
    • The Journal of Korean Academic Society of Nursing Education
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    • v.7 no.2
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    • pp.245-253
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    • 2001
  • The aim of this study is to describe degree of fatigue and factors related to fatigue in patients with rheumatoid arthritis. The subjects of the study consist of one hundred fifty-eight outpatients with rheumatoid arthritis at three university hospitals in Taegu between July 10 and August 30, 1999. The instrument used in this study was the Multidimensional Assessment of Fatigue developed by Belza et al.(1995) and revised by Jung, Bok Hee. Kim, Myung Ae(1998). Analysis of data was done by using the descriptive statistics, t-test, ANOVA and Duncan with SPSS program. The major findings can be summarized as follows: 1. Degree of fatigue in patient with Rheumatoid Arthritis was shown the average 22.91 out of the total scores 40. Four subscales of fatigue scores are common fatigue degree 6.37, fatigue timing at the last week 5.92, distress due to fatigue 5.40 and degree of daily activity fatigue 5.22. Among the realms of daily activity fatigue, outdoor activity(6.00), sexual life(5.84), doing the household(5.66), shopping(5.61), other exercise except stroll(5.54) were shown the high degree of fatigue and cooking(4.97), a stroll(4.48), recreation(4.35) showed the low degree of fatigue. 2. There were no significant differences on the total degree of fatigue according to demographic variables. But there were some significant differences on the subscale fatigue scores according to demographic variables. Degree of daily activity fatigue according to sex was shown significant difference (t=-2.358, p=.020), and according to education level was shown significant difference(F=3.938, p=.005) and common fatigue degree according to age was shown significant difference(F=2.853, p=.026). Conclusively fatigue is one of difficult problems for patients with rheumatoid arthritis. Therefore it is necessary to develop some nursing intervention for reducing fatigue of rheumatoid arthritis patients.

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The Effect of Initial α' on Low and High Cycle Fatigue Behavior of STS 304 Stainless Steel (STS 304 강의 저주기 및 고주기 피로에 있어 초기 마르텐사이트의 영향)

  • Lee, Hyun-Seung;Sin, Hyung-Ju;Kim, Song-Hee
    • Journal of Industrial Technology
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    • v.21 no.B
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    • pp.331-339
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    • 2001
  • Zero to tension fatigue tests and strain controlled fatigue tests were carried out to find how initial strain induced martensite, ${\alpha}^{\prime}$ affects low and high cycle fatigue behavior and fatigue crack growth mechanisms. Microscopic study and phase analysis were carried out with TEM, SEM, EDAX, Optical Microscope, Ferriscope, and X-ray diffractometry. The amount of Initial ${\alpha}^{\prime}$ was controlled from 0% to 33% by controlling the temperatures for cold working and heat treatment. Lower contents of initial ${\alpha}^{\prime}$ showed higher fatigue resistance in low cycle fatigue but lower fatigue resistance in high cycle fatigue because it is ascribed to the more transformation of ${\alpha}^{\prime}$ martensite during low cycle fatigue and higher ductility. In high cycle fatigue, fatigue life is attributed to the strength and phase transformation of austenite into ${\alpha}^{\prime}$ during fatigue was negligible. ${\gamma}$ boundary, ${\gamma}/twin$ boundary, and ${\gamma}/{\alpha}^{\prime}$ boundary were found to be the preferred site of fatigue crack initiation.

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Low Cycle Fatigue Life Evaluation of External Grooved C-shaped Specimen (외경홈을 지닌 C형 시험편의 저주기 피로수명평가)

  • Lee, Song-In
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.21 no.2
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    • pp.199-208
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    • 1997
  • A local strain approach was applied to an external single and double grooved C-shaped specimen in order to evaluate and predict the fatigue crack initiation life by using low cycle fatigue properties. The low cycle fatigue properties were determined from the strain-controlled fatigue tests using smooth cylindrical axial specimens. Fatigue crack initiation life was evaluated by a life prediction software, FALIPS, based on the local strain approach. The fatigue life was significantly influenced by the mean stress, and SWT parameter represented the fatigue life effectively. The predicted fatigue crack initiation life was then compared to the experimental fatigue life evaluated from the C-shaped fatigue test specimens. A good correlation was found between the experimental and predicted fatigue lives within factors of 2 and 4 for the single and double grooved C-shaped specimens respectively. Also, experimental fatigue life of the double grooved specimen was 10-12 times longer than that of the single grooved specimen.

Fatigue Life Estimation for Flaperon Joint of Tilt-Rotor UAV (틸트 로터 무인항공기의 플랩퍼론 연결부에 대한 피로수명 평가)

  • Kim, Myung Jun;Park, Young Chul;Lee, Jung Jin;Park, Jung Sun
    • Journal of Aerospace System Engineering
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    • v.3 no.2
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    • pp.12-19
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    • 2009
  • The research for the fatigue analysis is regarded greatly as important in aerospace field. Moreover, a study on the fatigue characteristic is very actively progressing. In this study, the fatigue life estimation was performed for Flaperon Joint which has FCL(fatigue critical location) of tilt-rotor UAV. The Flaperon Joint should be taken the various loads by several missions profiles of UAV. The fatigue load spectrum of Flaperon Joint is generated by the standard mission segment for the tilt-rotor UAV, and this spectrum is used for the fatigue test and analysis. The in-house fatigue analysis program is applied to calculate the fatigue life based on Stress-Life(S-N) method. The S-N curve is generated from the S-N data of Mil-Handbook by second order polynomial regression method. Moreover, the coefficient of determination is used to ensure how accuracy it has. In addition, the Goodman equation is used to consider the mean stress effect for evaluating more accurate fatigue life. Finally, the result of fatigue analysis is verified by comparing with the fatigue test result for the Flaperon Joint.

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A Comparison of Self-Reported Fatigue and Fatigue-Regulating Behaviors of Rheumatoid Arthritic Patients and Normal Persons (류마티스관절염 환자와 정상인의 피로도 및 피로조절행위 비교)

  • Jung, Bok-Hee;Kim, Myung-Ae
    • Journal of muscle and joint health
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    • v.6 no.1
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    • pp.51-72
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    • 1999
  • The purpose of this study is to compar self-reported fatigue and fatigue-regulating behaviors of rheumatoid arthritic patients and normal persons. This study collected the data from 75 rheumatoid arthritic patents visited the departments of internal medicine or orthopedics of four general hospitals T-city and K-city by means of direct interview and questionnaires. in this study also collected data from 75 normal persons who had not been exposed to any other disease in T-city and K-city by means of direct interviews anti questionnaires which were conducted by two trained nurses. This experiment was conducted from August 1, 1998 to October 15, 1998. This study used both MAP(Multi-Dimentional Assessment of Fatigue) developed by Belza(1995) to measure fatigue and the measurement developed by Kwon, Young-Eun to investigate fatigue regulating behaviors. The collected materials were analyzed by means of descriptive statistics, t-test, and the ANCOVA according to the SPSS PC+ program. The findings are as follows : 1. There was the statistically significant difference(t =5.07, p=.000), between rheumatoid arthritic patients(32.76 points) and normal persons(25.81 points) in t-test comparison by group about fatigue. A fatigue degree of rheumatoid arthritic patient group was high in five kinds of lower realms such as common fatigue degree, fatigue severity to be experienced, distress due to fatigue, daily fatigue degree, and fatigue timing at the last week by dimension. 2. There was the significant difference in the number of fatigue-regulating behaviors between rheumatoid of fatigue arthritic patients(9.37 times) and normal persons (8.15 times), but there wasn't any significant difference in the efficiency between rheumatoid arthritic patients(2.85 points) and normal persons (2.78 points) This research suggests two kinds of things as follows : 1. It is necessary to develop an educational program for improving efficiency of fatigue-regulating behaviors as well as some nursing arbitration measures for reducing fatigue of rheumatoid arthritic patients. 2. It is necessary for the future studies to continuously grasp characteristics of fatigue by gender variable by selecting more rheumatoid arthritic male patients.

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FATIGUE LIFE ESTIMATION OF IMPLANT USING A FINITE ELEMENT METHOD (유한요소법을 이용한 치아 임플랜트 피로수명 예측)

  • Han In-Sook;Son Jung-Hun;Yang Young-Soo;Lee Seung-Young
    • The Journal of Korean Academy of Prosthodontics
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    • v.44 no.4
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    • pp.414-420
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    • 2006
  • Purpose : The purpose of this study is to use finite element analysis to predict the fatigue life of an implant system subjected to fatigue load by mastication (chewing force). The reliability and the stability of implant system can be defined in terms of the fatigue strength. Not only an implant is expensive but also it is almost impossible to correct after it is inserted. From a bio-engineering standpoint, the fatigue strength of the dental implant system must be evaluated by simulation (FEA). Material and Methods Finite element analysis and fatigue test are performed to estimate the fatigue strength of the implant system. Mesh of implant is generated with the actual shape and size. In this paper, the fatigue strength of implant system is estimated. U-fit (T. Strong, Korea, internal type). The stress field in implant is calculated by elastic-plastic finite element analysis. The equivalent fatigue stress, considering the contact and preload stretching of a screw by torque for tightening an abutment, is obtained by means of Sine's method. To evaluate the reliability of the calculated fatigue strength, fatigue test is performed. Results: A comparison of the calculated fatigue strength with experimental data showed the validity and accuracy of the proposed method. The initiation points of the fatigue failure in the implant system exist in the region of high equivalent fatigue stress values. Conclusion: The above proposed method for fatigue life estimation tan be applied to other configurations of the differently designed and improved implant. In order to prove reliability of prototype implant, fatigue test should be executed. The proposed method is economical for the prediction of fatigue life because fatigue testing, which is time consuming and precision-dependent, is not required.

A Survey on the Relationship between the Fatigue due to Schoolwork and Dietary (식품섭취(食品攝取)와 학업피로(學業疲勞)의 관계(關係)에 대(對)한 조사(調査))

  • Lee, Dong-Suk
    • Korean Journal of Food Science and Technology
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    • v.6 no.3
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    • pp.158-162
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    • 1974
  • The writer has undertaken a survey, against 467 urban university women students, of the fatigue due to their schoolwork and has intended to clarify the relationship between the fatigue and dietary. As a result, the following described conclusion was obtained: (1) The fatigue due to their schoolwork was found in an order of mental fatigue >physical fatigue> neuro-sensory fatigue among which their schoolwork was proved as a typical mental works. (2) It was found, in comparison of the health condition with the fatigue from schoolwork, that the frequencies of mental and neurosensory fatigue in which physical fatigue is excluded had a significant difference. (3) In an analysis of the fatigue rate in relation with the daily dietary, it was found that fatigue rate of the group which takes meat, egg, fish and milk every day showed a significantly lower rate over the group which takes these food occasionally.

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A Study on the Fatigue Behaviors of Cr-Mo-V Alloy for Steam Turbine at High Temperature Difference (터빈용 Cr-Mo-V강의 고온 환경변화에 따른 피로거동에 관한 연구)

  • Song, Sam-Hong;Kang, Myung-Soo
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.21 no.1
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    • pp.173-179
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    • 1997
  • The high temperature fatigue tests were performed using the specimens taken from Cr-Mo-V steel, widely used as thermal power plant turbine materials for examination fatigue behavior of materials in power plants which have been operated for long periods. The fatigue tests at high temperature were performed at the various temperature and applied stress. The results obtained are summarized as follows : The fatigue crack length increases and the fatigue life decreases with temperature and applied stress according to the same number of stress cycle. The fatigue crack propagation and the fatigue life were much influenced by temperature and applied stress.

A Study on the Prediction of Fatigue Damage in 2024-T3 Aluminium Alloy Using Neural Networks (신경회로망을 이용한 AI 2024-T3합금의 피로손상예측에 관한 연구)

  • Cho, Seok-Swoo;Jang, Deuk-Yul;Joo, Won-Sik
    • Journal of the Korean Society for Precision Engineering
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    • v.16 no.7
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    • pp.168-177
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    • 1999
  • Fatigue damage is the phenomena which is accumulated gradually with loading cycle in material. It is represented by fatigue crack growth rate da/dN and fatigue life ratio $N/N_{f}$. Fracture mechanical parameters estimating large crack growth behavior can calculate quantitative amount of fatigue crack growth resistance in engineering material. But fatigue damage has influence on various load, material and environment. Therefore, In this study, we propose that artificial intelligent fatigue damage model can predicts fatigue crack growth rate da/dN and fatigue life ratio $N/N_{f}$ simultaneously using fracture mechanical and nondestructive parameters.

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