• Title, Summary, Keyword: Retardation

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A Stochastic Analysis for Crack Growth Retardation Behavior and Prediction of Retardation Cycle Under Single Overload (단일과대하중하에서 피로균열진전지연거동 및 지연수명의 확률론적 해석)

  • Shim, Dong-Suk;Kim, Jung-Kyu
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.23 no.7
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    • pp.1164-1172
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    • 1999
  • In this study, to investigate the fatigue crack retardation behavior and the variability of retardation cycles, fatigue crack growth tests were conducted on 7075-T6 aluminum alloy under single tensile overload. A retardation coefficient, D was introduced to describe fatigue crack retardation behavior and a random variable, Z to describe the variability of fatigue crack growth. The retardation coefficient was separately formulated according to retardation behavior which is composed of delayed retardation part and retardation part. The random variable, Z was evaluated from experimental data which was obtained from fatigue crack growth tests under constant amplitude load. Using these variables, a probabilistic model was developed on the basis of the modified Forman's equation, and retardation behavior and cycles were predicted under certain overload condition. The predicted retardation curve well agrees with the trend of experimental crack retardation behavior. And this model well predicts the scatter of experimental retardation cycles.

Fatigue Crack Retardation and Retardation Mechanism in Variable Loading (The Effects of Crack Tip Branching in Crack Growth Retardation)

  • Song, Sam-Hong;Kwon, Yun-Ki
    • International Journal of Precision Engineering and Manufacturing
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    • v.3 no.3
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    • pp.76-81
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    • 2002
  • In order to study the fatigue crack and retardation mechanism in variable loading, the effects of crack tip branching in crack growth retardation were examined. The characteristics of crack tip branching behavior were considered with respect to microstructure and crack tip branching angle was examined. Crack tip branching was observed along the grain boundary of finite and pearlite structure. It was found that the branching angle ranges from 25 to 53 degrees. Using the finite element method, the variable of crack driving farce to branching angle was examined. The effective crack driving farce (K$\_$eff/) decreased as the branching angle increased. The rate of decrease was 33% for kinked type and 29% for forked one. It was confirmed that the effect of crack tip branching is a very important factor in crack growth retardation. Therefore, crack branching effect should be considered in building the hypothetical model to predict crack growth retardation.

Disease Related to the Five Retardation, Five Limpness, Five Stiffness (오지(五遲) 오연(五軟) 오경(五硬)과 관련된 현대의학의 질병)

  • Park, Jae-Hyung;Paeck, Eun-Kyung
    • Journal of Physiology & Pathology in Korean Medicine
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    • v.24 no.2
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    • pp.197-205
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    • 2010
  • The association between five limpness(五軟), five stiffness(五硬), five retardation and disease have been repeatedly shown in patient. However, comparative study has been rare. This study arrange disease, which answer to five limpness, five stiffness, five retardation and classify by epiologic diagnosis. We search for scientific journals, medical college texts, theses of a degree and collect case reports. In this study we found that the five retardation(N=56) is showing numerous more than the others. The five stiffness(N=14) is showing rare than the five limpness(N=29). The five limpness is overlapping more than 90% with five retardation. and the five stiffness is overlapping 80% with five retardation. Symptom of five limpness, five stiffness, five retardation is coming out independent and overlapping each others. And generally it accompanies with abnormality in central nervous system.

Fatigue Crack Growth Retardation after Single Overload Cycle in High Strengh Aluminium Weldments (고강도 알루미늄 합금 용접부에 있어서의 피로균열전파에 미치는 과하중 효과)

  • 이택순;김상태;김인식
    • Journal of Welding and Joining
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    • v.6 no.1
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    • pp.46-52
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    • 1988
  • Retardation or delay in fatigue crack growth due to overloads are important for the accurate prediction of fatigue lives of structural materials. In this study, retardation of fatigue crack growth in Al 6061-T6 weldments and heat affected zones (HAZ) after single overload cycle had been investigated. Retardation in both weldments and HAZ was observed. It was concluded that retardation in both weldment and HAZ was greater than in base metal due to microstructural change and crack branching and crack closure were major governing factor in retardation.

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Crack Retardation byt Load Reduction During Fatigue Crack Propagation (피로균열전파 동안 하중감소에 의한 균열지연)

  • Kim, Hyun-Soo;Nam, Ki-Woo;Ahn, Seok-Hwan;Do, Jae-Yoon
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.27 no.12
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    • pp.2004-2010
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    • 2003
  • Fracture life and crack retardation behavior were examined experimentally using CT specimens of aluminum alloy 5083. Crack retardation life and fracture life were a wide difference. between 0.8 and 0.6 in proportion to ratio of load reduction. The wheeler model retardation parameter was used successfully to predict crack growth behavior. By using a crack propagation rule, prediction of fracture life can be evaluated quantitatively. A statistical approach based on Weibull distribution was applied to the test data to evaluate the dispersion in the retardation life and fracture life by the change of load reduction.

Analysis of Minerals in the Hair of Mental Retardation

  • Lee, Ju-Young;Choi, Won-Chul
    • Journal of Environmental Health Sciences
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    • v.31 no.3
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    • pp.187-191
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    • 2005
  • Several heavy metals are known to give some kinds of mental retardation although abnormal X-chromosome is closely connected with genetic disease such as mental retardation. This study dealt with the influence of minerals in the hair of mental retardation people. Minerals were analyzed by Inductively Coupled Plasma Mass Spectrometer (Sciex Elan 6100, Perkin-Elmer corporation, Foster, CA, USA). The nutritional elements such as Ca, Na, K were higher level (p<0.01) in normal group than in the mental retardation group. The toxic elements such as Cd (p<0.01) and As were higher level in the mental retardation group than in normal group. But Pb is not significant difference among the all groups including normal group.

Clinical study on the correlation between five kinds of flaccidity in infants(五軟), five kinds of retardation(五遲) and Autistic disorder (자폐장애와 오지(五遲).오연(五軟)과의 상관성에 관한 임상적 연구)

  • Park, Jae-Hyung;Park, Jae-Hyun;Paeck, Eun-Kyung;Yun, Young- Ju;Jeong, Seul-Ki;Lim, Ja-Seong;Lyu, Yeoung- Su;Kang, Hyung-Won
    • Journal of Oriental Neuropsychiatry
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    • v.16 no.2
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    • pp.25-34
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    • 2005
  • Background and Objectives There was no clinical data except literary study on mutual correlation with autistic disorder in Western medical diagnosis and five kinds of flaccidity in infants(五軟), five kinds of retardation(五遲) in Oriental medical diagnosis. This study was performed to investigate the correlation of five kinds of flaccidity in infants(五軟), five kinds of retardation(五遲) to the children with autistic disorder and to set the time table for clinical diagnosis of developmental retardation by making a comparative study of normal developmental children so we can treat the children with autistic disorder in good time. Method We made the comparative study of interview sheets recorded by parents of total 163 children who were diagnosed as autistic disorder who visited HaeMa Oriental Medical Clinic with interview sheets recorded by parents of generally accepted normal developmental children(263) and then we took statistics. Results : 1. There was significant correlation with speech and walking among five kinds of flaccidity in infants(五軟), five kinds of retardation(五遲) in autistic disorder statistically and clinically in comparison with normal children. 2. There wasn't significant correlation with growth time of tooth among five kinds of flaccidity in infants(五軟), five kinds of retardation(五遲) on diagnosis of autistic disorder in comparison with normal children. 3. There was significant correlation with retardation of times going to toilet by oneself (it does not consist in five kinds of flaccidity in infants(五軟), five kinds of retardation(五遲).) in both of autistic disorder. Conclusion Autistic disorder was significantly correlated with the faculty of speech(語遲), retardation in walking out(行遲) of five kinds of flaccidity in infants(五軟), five kinds of retardation(五遲). We need to concrete the index of diagnosis, because it is so difficult to measure times and register retardation in tooth eruption(齒遲), retardation in hair-growing(髮遲), debility of neck and nape(頭項軟), flaccidity of extremities(手軟) and flaccidity of muscle(肌肉軟). And we can also use times going to toilet by oneself as one of diagnostic criteria because of its significant correlation. It is required to make early diagnosis of five kinds of flaccidity in infants(五軟), five kinds of retardation(五遲) using these criteria, and to treat them early by oriental medicine.

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A Study on the Effect of the Overload Ratio on the Fatigue Crack Growth Retardation (과대하중비가 균열성장지연에 미치는 영향에 관한 연구)

  • Kim, Kyung-Su;Kim, Sung-Chan;Shim, Chun-Sik;Park, Jin-Young;Cho, Hyung-Min
    • Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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    • pp.306-311
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    • 2003
  • A growing fatigue crack is known to be retarded on application of an overload cycle. The retardation may be characterized by the total number of cycles involved during retardation and the retarded crack length. The overload ratio plays an important role to influence the retardation behavior. The objective of the present investigation is to study the effect of different overload ratio on the retardation behavior. For DENT(double edge notched tension) specimens and ESET(eccentrically-loaded single edge crack tension) specimens, fatigue crack growth tests are conducted under cyclic constant-amplitude loading including a single tensile overloading with different overload ratios. The proposed crack retardation model predicts crack growth retardation due to a single tensile overloading. The predictions are put into comparison with the experimental results to confirm the reliability of this model.

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The Prediction of Crack Growth Retardation Behavior by Crack Tip Branching Effects (Fatigue Behavior in variable Loading Condition) (균열가지 효과를 고려한 균열 성장 지연 거동 예측 (변동하중하에서의 피로거동))

  • 권윤기
    • Journal of The Korean Society of Manufacturing Technology Engineers
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    • v.8 no.2
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    • pp.126-136
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    • 1999
  • We studied on crack growth retardation in single overloading condition. Crack tip branching which as the second mechanism on crack growth retardation was examined. Crack tip branching was observed to kinked type and forked type. It was found that the branching angle range was from 25 to 53 degree. The variations of crack driving force with branching angle were calculated with finite element method The variation of {{{{ KAPPA _I}}}}, {{{{ KAPPA _II}}}} and total crack driving force(K) were examined respectively So {{{{ KAPPA _I}}}}, {{{{ KAPPA _II}}}} and K mean to mode I, II and total crack driving force. Present model(Willenborg's model) for crack growth retardation prediction was modified to take into consideration the effects of crack tip branching When we predicted retardation with modified model. it was confirmed that predicted and experimental results coincided with well each other.

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Retardation Analysis of Plastic Optic Lens according to Injection Speed Variation (사출속도 변화에 따른 플라스틱 광학렌즈의 위상차 해석)

  • Park, Soo-Hyun;Kim, Tae-Kyu;Kwak, Tae-Soo
    • Journal of the Korean Society of Manufacturing Process Engineers
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    • v.14 no.2
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    • pp.93-98
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    • 2015
  • This study focuses on simulation technology in the injection molding process for plastic optic lenses. The CAE program 3D TIMON was used to predict retardation, flow patterns and warpage deformation. The results were compared to the results of optic lenses as measured using the WPA-100 retardation measurement device with injection molding CAE for retardation predictions. According to the analysis and measured results, the distributions of retardation between the CAE results and the measurement results were similar. It was also confirmed that varying the injection speed had an effect on the injection pressure, warpage deformation and retardation distribution. As the injection speed increases, the injection pressure also increases and warpage deformation decreases. However, as the injection speed increases, the retardation distribution deteriorates.