파손확률에 따른 마그네슘합금의 피로설계수명 예측

최선순,Choi, Seon-Soon 한국생산제조학회 2010 한국생산제조학회지 Vol.26 No.1

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.

평균응력이 AZ31 마그네슘합금의 렌덤진전균열크기 확률분포에 미치는 영향

최선순,이억섭,Choi, Seon-Soon,Lee, Ouk-Sub 한국생산제조학회 2009 한국생산제조학회지 Vol.25 No.1

In this paper the mean stress effects on the probability distribution of the random grown crack size at a specified loading cycle are studied through the fatigue crack propagation tests, which are conducted on the specimens of magnesium alloy under four different stress ratios. Through 80 replicates the probability distributions of the grown crack size are obtained. The goodness-of-fit for probability distributions of the random grown crack size are investigated by Anderson-Darling test and the best fit for those probability distributions is found to be a 3-parameter Weibull distribution. The effects of the mean stress on the probability distribution of the random grown crack size are also estimated.

AZ31 마그네슘합금 시편의 두께가 피로균열진전거동의 확률분포에 미치는 영향

최선순,Choi, Seon-Soon 한국생산제조학회 2009 한국생산제조학회지 Vol.26 No.3

As the variables affecting the fatigue behavior have uncertainty, the fatigue crack propagation is stochastic in nature. 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 under the different thicknesses of specimen. The effects of specimen thickness on the probability distribution of the fatigue crack propagation life and the crack size are estimated experimentally. The probability distribution of the crack size and the fatigue life for different specimen thicknesses are investigated by Anderson-Darling test and the best fit for those probability distributions are also presented.

최대하중조건에 따른 Mg-Al-Zn 합금의 확률변수 잔차를 이용한 확률론적 피로균열전파모델 평가

최선순(Seon Soon Choi) 대한기계학회 2015 大韓機械學會論文集A Vol.39 No.1

본 논문의 주 목적은 최대하중조건을 변화시키면서 확률변수의 잔차를 이용하여 확률론적 피로균열전파모델들을 평가하고, Mg-Al-Zn 합금의 피로균열성장거동의 변동성을 묘사하기에 적합한 확률론적 모델을 제시하는 것이다. 평가에 사용된 모델은 피로균열성장의 변동성을 나타내기 위하여 실험적 피로균열전파모델인 Paris-Erdogan 모델, Walker 모델, Forman 모델과 수정 Forman 모델에 확률변수를 도입한 모델이다. 최대하중조건에 따른 Mg-Al-Zn 합금의 피로균열전파거동의 확률적 변동성을 묘사하기에 적합한 모델은 ‘확률론적 Paris-Erdogan 모델’과 ‘확률론적 Walker 모델’임을 밝혔으며, 최대하중조건이 피로균열성장의 확률적 변동성에 미치는 영향 또한 고찰하였다. The primary aim of this paper is to evaluate the probabilistic fatigue crack propagation models using the residual of a random variable and to present the probabilistic model fit for the probabilistic fatigue crack growth behavior in Mg-Al-Zn alloys under maximum load conditions. The models used in this study were prepared by applying a random variable to empirical fatigue crack propagation models such as the Paris-Erdogan model, Walker model, Forman model, and modified Forman model. It was verified that the good models for describing the stochastic variation of the fatigue crack propagation behavior in Mg-Al-Zn alloys under maximum load conditions were the ‘probabilistic Paris-Erdogan model’ and ‘probabilistic Walker model’. The influence of the maximum load conditions on the stochastic variation of fatigue crack growth is also considered.

통계적인 경계조건이 마그네슘합금 AZ31의 피로신뢰성에 미치는 영향

최선순(Seon Soon Choi),이억섭(Ouk Sub Lee) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.5

The fatigue crack propagation is stochastic in nature, because the variables affecting the fatigue behavior are random and have uncertainty. In this study, fatigue experiments are conducted on the specimens of magnesium alloy AZ31 for varying boundary conditions having different statistical characteristics. The effects of these varying boundary conditions on the fatigue failure life are systematically investigated. The reliability estimation for these fatigue failure lives is also performed.

AZ31 마그네슘합금의 피로균열진전수명에 적합한 확률분포 평가

최선순(Seon Soon Choi) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.5

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.

AZ31 마그네슘합금 시편의 두께가 피로균열진전거동의 확률분포에 미치는 영향

최선순(Seon-Soon CHOI) 한국생산제조학회 2009 한국생산제조학회지 Vol.18 No.4

As the variables affecting the fatigue behavior have uncertainty, the fatigue crack propagation is stochastic in nature. 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 under the different thicknesses of specimen. The effects of specimen thickness on the probability distribution of the fatigue crack propagation life and the crack size are estimated experimentally. The probability distribution of the crack size and the fatigue life for different specimen thicknesses are investigated by Anderson-Darling test and the best fit for those probability distributions are also presented.

AZ31 마그네슘합금의 피로균열진전수명에 적합한 확률분포 평가

최선순(Seon Soon Choi) 대한기계학회 2009 大韓機械學會論文集A Vol.33 No.8

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.

Mg-Al-Zn 합금의 Paris-Erdogan 법칙에 따른 피로거동 파라미터의 확률론적 특성

최선순(Seon Soon Choi) 대한기계학회 2011 大韓機械學會論文集A Vol.35 No.4

본 연구의 주목적은 마그네슘합금의 피로균열성장거동을 지배하는 파라미터들의 확률론적 특성을 규명하는 것이다. 피로균열전파실험은 AZ31 마그네슘합금의 CT 시편을 이용하여 통계적으로 수행하였으며, 시편두께, 하중비, 최대하중 등의 여러 가지 실험조건으로 실온에서 진행하였다. 이 실험을 통하여 획득한 통계적 피로 데이터를 이용하여 피로거동 파라미터의 확률적 변동성 해석과 함께 확률분포 적합성을 고찰하였다. 균열성장속도계수는 확률적으로 매우 큰 변동성을 나타내는 파라미터로 밝혀졌으며, 반면에 균열성장속도지수는 매우 작은 변동성을 나타냄으로써 재료상수로 볼 수 있을 것이다. 피로거동 파라미터인 균열성장속도계수와 균열성장속도지수에 가장 적합한 확률분포는 3-파라미터 Weibull 분포이며, 2-파라미터 Weibull 분포는 균열성장속도계수의 경우에만 양호한 적합성을 나타낸다는 것을 규명하였다. The primary aim of this study is to investigate the probabilistic characteristics of the fatigue parameters that describe the fatigue crack growth behavior in magnesium alloy. Statistical fatigue crack propagation experiments have been performed on rolled AZ31 magnesium alloy CT specimens with different specimen thickness, load ratio, and maximum load at ambient temperature in a laboratory. Using the statistical fatigue data obtained from these experiments, the goodness-of-fit of the probability distribution of the fatigue behavior parameters is evaluated in this study by performing statistical analyses. The crack growth rate coefficient is a fatigue parameter having a very large COV(Coefficient of Variation), but the variation of a crack growth rate exponent is not substantial. It is considered that a crack growth rate exponent can be a material constant. It is also found that the best fit probability distribution of the parameters such as the crack growth rate coefficient and crack growth rate exponent for a magnesium alloy is a three-parameter Weibull distribution, and two-parameter Weibull distribution is a good distribution only for the crack growth rate coefficient.

마그네슘합금의 피로균열전파거동에 미치는 평균응력 효과

최선순(Seon Soon CHOI) 한국자동차공학회 2010 한국자동차공학회 부문종합 학술대회 Vol.2010 No.5

The fatigue crack propagation experiments have been conducted on CT specimens of the magnesium alloy under constant amplitude loading at ambient temperature in laboratory air. In this study the fatigue crack propagation behaviors are investigated for different load ratios in order to estimate the effect of mean stress in magnesium alloy.