• Title/Summary/Keyword: Fatigue-Life

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Comparison of Fatigue Strength Criteria for TiNi/Al6061-T6 and TiNi/Al2024-T4 Shape Memory Alloy Composite (TiNi/Al6061-T6과 TiNi/Al2024-T4 형상기억복합재료에 대한 피로강도기준의 비교)

  • Jo, Young-Jik;Park, Young-Chul
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.33 no.2
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    • pp.99-107
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    • 2009
  • This study produced a design curve and fatigue limit for a variation in volume ratio and reduction ratio of TiNi/Al composites. In many cases, stress-life curve does not indicate fatigue limit, so it was presented by probabilistic-stress-life curve. Goodman diagram was used to analyze the fatigue strength of materials with a finite life determined by repeated load and the fatigue strength of endurance limit with an infinite life. The fatigue experiment was conducted using the scenk-type plane bending specimen in same shape. The result of the fatigue test, which had been conducted under consistent stress amplitude, was examined. (i) The optimal condition for TiNi/Al in accordance with hot pressing (ii) Impacts of fatigue limit caused by a variation in reduction ratio and volume ratio of TiNi/Al composites (iii) Probability distribution for fatigue limit of TiNi/Al2024 and TiNi/Al6061.

Fatigue Life Prediction for Automotive Vibroisolating Rubber Component Using Tearing Energy (찢김에너지를 이용한 자동차용 방진 부품의 내구수명 예측)

  • Moon, Hyung-Il;Kim, Ho;Woo, Chang-Soo;Kim, Heon-Young
    • Transactions of the Korean Society of Automotive Engineers
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    • v.20 no.6
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    • pp.100-106
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    • 2012
  • Recently, the demand to acquire and improve durability performance has steadily risen in rubber components design. In design process of a rubber component, an analytical prediction is the most effective way to improve fatigue life. Existing methods of analytical estimation have mainly used an equation for fatigue life obtained from fatigue test data. However, such formula is rarely used due to costs and time required for fatigue testing, as well as randomness of rubber materials. In this paper, we describe fatigue life estimation of rubber component using only the results from a relatively simple tearing test. We estimated fatigue life of the Janggu type fatigue specimen and the automotive motor mount, and evaluated reliability of the proposed method by comparing the estimated values with actual test results.

The Effect of Ultrasonic Impact Treatment(UIT) for Fatigue Life of Weldment (Ultrasonic Impact Treatment(UIT)효과가 용접재의 피로수명에 미치는 영향)

  • Song, Jun-Hyouk;Lee, Hyun-Woo
    • Transactions of the Korean Society of Automotive Engineers
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    • v.18 no.6
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    • pp.38-45
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    • 2010
  • Welding structures are designed to endure its expected life. The most important factors are life. Especially on welded structure, fatigue strength is critical. So this study performed a research on Box and T shape weldment specimen to examine the influence of welding type. In this experiment, the results indicate Box shape was available in more than T shape. Fatigue tests were performed to evaluate the fatigue strength of the both as-welded and statically pre-loaded specimens by 3 point bending load. Fatigue life can be improved by using Ultrasonic Impact Treatment(UIT) effect. Ultrasonic Impact Treatment(UIT) is excellent for eliminating the tensile residual stresses and generating compressive residual stresses which elevate fatigue strength of welded structures. Also, this shows that welding part has better fatigue life and welding was performed well. In this study, to evaluate the Ultrasonic Impact Treatment(UIT) effect, for welding structure, the experiment was conducted at various levels of stress range between 100MPa and 500MPa. From the test results, it was indicated that fatigue performance was improving by Ultrasonic Impact Treatment(UIT)

Estimation Fatigue Life of Weldments by Notch Stress Approaches (노치응력법에 의한 용접 연결부 피로수명 추정에 관한 연구)

  • Yang, Park-Dal-Chi;Song, Joon-Kyu
    • Journal of Ocean Engineering and Technology
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    • v.25 no.5
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    • pp.47-51
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    • 2011
  • This paper analyzes the fatigue-life of welded joints using the notch stress approach. In the notch stress approach, the notch effects are usually approximated by introducing weld-bead parameters for the local detailed weld joints. The actual bead shape is complex and 3-dimensional. It may also greatly influence the fatigue strength. In this study, the welded shape was modeled using a 3D-scanner. The critical distance method was adopted in the evaluation of the fatigue effective notch stress for the weldments. Fatigue life tests were performed to verify the present method of fatigue life estimation for two types of welded plates with longitudinal attachments. The estimated results of the present methods were applied to the results of the experiment. The results of the analysis showed that the scatter of fatigue-life for the experimental data expressed in the nominal stress was significantly reduced by applying the effective fatigue stress of the present study.

The Prediction of Fatigue Life According to the Determination of the Parameter in Residual Strength Degradation Model (잔류강도 저하모델의 파라미터결정법에 따른 피로수명예측)

  • 김도식;김정규
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.18 no.8
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    • pp.2053-2061
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    • 1994
  • The static and fatigue tensile tests have been conduted to predict the fatigue life of 8-harness satin woven and plain woven carbon/epoxy composite plates containing a circular hole. A fatigue residual strength degradation model, based on the assumption that the residual strength for unnotched specimen decreases monotonically, has been applied to predict statistically the fatigue life of materials used in this study. To determine the parameters(c, b and K) of the residual strength degradation model, the minimization technique and the maximum likelihood method are used. Agreement of the converted ultimate strength by using the minimization technique with the static ultimate strength is reasonably good. Therefore, the minimization technique is more adjustable in the determination of the parameter and the prediction of the fatigue life than the maximum likelihood method.

Fatigue analysis of pressure vessel in view of wind and seismic loads (풍력과 지진하중을 고려한 압력용기의 피로해석)

  • 박진용;황운봉;박상철;박동환
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.15 no.2
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    • pp.596-603
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    • 1991
  • Fatigue life prediction of pressure vessel is studied analytically using cumulative damage models and linear elastic fracture mechanics method. The stresses are analyzed by finite element method. During operation, the maximum stress occurs at the outside of neck region while fatigue analysis indicates that the bottom of nozzle part has the shortest fatigue life. Previously proposed fatigue life prediction equation and cumulative damage model are modified successfully by introducing reference fatigue modulus. It is found that the modified life prediction equation and damage model are useful for lower stress level application.

Fatigue Life Predictions for Variable Load Histories (변동하중하의 피로수명예측)

  • 하재선;송지호;이시중
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.12 no.4
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    • pp.760-780
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    • 1988
  • Using the fatigue test results obtained in the SAE Fatigue Cumulative Damage Test Program, prediction methods of fatigue crack initiation life for notched members undergoing random loaming histories were discussed in detail. Conventional fatigue life predictions based on so-called modified Miner's rule were found to be apt to give nonconservative estimate, due to lack of sufficient consideration for stress-interaction effect. A modified .epsilon.-N curve concept was proposed to account for the stress-interaction effect. The predicted fatigue life based on the modified .epsilon.-N curve concept was in good agreement with the experimental results of SAE Test Program. Specifically for the cases when fatigue data was not available at hand, was proposed a procedure to give conservative estimate of fatigue life.

Estimation of Probability Distribution Fit for Fatigue Crack Propagation Life of AZ31 Magnesium Alloy (AZ31 마그네슘합금의 피로균열진전수명에 적합한 확률분포 평가)

  • Choi, Seon-Soon
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.33 no.8
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    • pp.707-719
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    • 2009
  • The variables relating to the fatigue behavior have uncertainty and are random. The fatigue crack propagation is, thus, stochastic in nature. In this study, fatigue experiments are performed on the specimen of the magnesium alloy AZ31. The data of the fatigue life are scattered even in the same experimental condition. It is necessary to determine the probability distribution of the fatigue crack propagation life for the reliability analysis as well as the design and maintenance of structural components. Therefore the statistics and the probability distribution for the fatigue crack propagation life are investigated and the best fit probability distribution of that is proposed in this paper.

Prediction of Fatigue Design Life in Magnesium Alloy by Failure Probability (파손확률에 따른 마그네슘합금의 피로설계수명 예측)

  • Choi, Seon-Soon
    • Journal of the Korean Society of Manufacturing Technology Engineers
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    • v.19 no.6
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    • pp.804-811
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    • 2010
  • The fatigue crack propagation is stochastic in nature, because the variables affecting the fatigue behavior are random and have uncertainty. Therefore, the fatigue life prediction is critical for the design and the maintenance of many structural components. In this study, fatigue experiments are conducted on the specimens of magnesium alloy AZ31 under various conditions such as thickness of specimen, the load ratio and the loading condition. The probability distribution fit to the fatigue failure life are investigated through a probability plot paper by these conditions. The probabilities of failure at various conditions are also estimated. The fatigue design life is predicted by using the Weibull distribution.

The correlation analysis between fatigue and health promoting life style among a rural college students (일 지역 대학생의 피로와 건강증진 생활양식과의 관계분석)

  • Jang Hee-Jung
    • Journal of Korean Academy of Fundamentals of Nursing
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    • v.6 no.3
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    • pp.477-492
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    • 1999
  • The disease patterns among the Korean was shifted from acute and infectious diseases to chronic diseases. According to the these disease patterns trends, people have concerned about the health promotion and health behaviors. Pender's(1996) revised health promotion model(HPM) is consist of three categories; Individual characteristics and experiences, Behavior-specific cognitions and affect, behavioral outcome. Of these categories, individual characteristics and experiences, this category of variables is considered to be of biological, psychological and socio-cultural personal factors, especially, individual fatigue. Futhermore. these variables constitute a critical core for nursing intervention, as they are subject to modification through nursing actions. But there is no few the research of the relationship between the fatigue and health promotion. Therefore, the purpose of this study is to investigate the correlation between the fatigue and health promoting life style among a rural college students. Additionally, this descriptive correlational study identified the relation of demographic factors and fatigue, health promoting life style. From June 20 to 26, 1998, a convenience sample of 270 college students completed the questionnaire of the fatigue and health promoting life style profile which were developed by the Yoshitake(1978) and Walker, et al.(1987), respectively. The descriptive correlational statistics, mean, t-test, ANONA, Pearson correlation coefficient were used to analyze the data gathered with SAS pc+ program. The results were as it follows: 1. The average fatigue score of the subjects was $64.93{\pm}12.89$. Fatigue scores by subcategory were physical symptoms($23.5{\pm}4.87$). psychological symptoms($22.11{\pm}4.66$) and neuro-sensory symptoms($19.32{\pm}5.14$). With the respect to the demographic characteristics of the subjects, there were statistically significant differences between the demographic factors and fatigue, especially, sex(t==3.69 p<0.01), major(t=-2.89 p<0.01). the experience of family illness(t=2.76 p<0.01). 2. The average health promoting life style item score of the subjects was $2.33{\pm}0.33$. In the subcategories, the highest degree of performance was self-actualization(2.94), following interpersonal support(2.81). stress management(2.33), exercise(2.20), nutrition(2.10), and the lowest degree was health responsibility(1.73). There were the significant differences on the learning of health education(t=2.00 p<0.01). religion(F=3.01, p<0.05), circle activity(t=2.07, p<0.05), nutrition control(t=5.25, p<0.01) of demographical factors with the health promoting life style. 3. The correlation between the fatigue and health promoting life style made statistically no significance(r=-0.09731, p>0.05). But there was negative significant relationship between health promoting life style and psychological symptom as a fatigue subcategory(r=-0.15721, p<0.05). The self-actualization showed negative significant correlation with all fatigue subcategory. The health responsibility showed significant relationship with total fatigue(r=0.13050. p<0.05). For further research, it suggests to replicate the correlational and causal study between the fatigue and the health promoting life style using the another fatigue scale which is able to measure the subjective and objective fatigue degree. And it needs to develop the nursing intervention program for maintaining and promoting the health behavior as well as for decreasing the college students's fatigue.

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