• Journal of Ship and Ocean Technology
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• 제9권1호
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• pp.64-71
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• 2005

In probabilistic design, the challenge is to estimate the uncertainty propagation, since outputs of subsystems at lower levels could constitute inputs of other systems or at higher levels of the multilevel systems. Three uncertainty propagation estimation techniques are compared in this paper in terms of numerical efficiency and accuracy: root sum square (linearization), distribution-based moment approximation, and Taguchi-based integration. When applied to reliability-based design optimization (RBDO) under uncertainty, it is investigated which type of applications each method is best suitable for. Two nonlinear analytical examples and one vehicle crashworthiness for side-impact simulation example are employed to investigate the unique features of the presented techniques for uncertainty propagation. This study aims at helping potential users to identify appropriate techniques for their applications in the multilevel design.

• Computers and Concrete
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• 제7권3호
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• pp.221-237
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• 2010

In this study 72 different high strength concrete (HSC) mixes were produced according to the Taguchi design of experiment method. The specimens were divided into four groups based on the range of their compressive strengths 40-60, 60-80, 80-100 and 100-125 MPa. Each group included 18 different concrete mixes. The slump and air-content values of each mix were measured at the production time. The compressive strength, splitting tensile strength and water absorption properties were obtained at 28 days. Using this data the Genetic Programming technique was used to construct models to predict mechanical properties of HSC based on its constituients. These models, together with the cost data, were then used with a Genetic Algorithm to obtain an HSC mix that has minimum cost and at the same time meets all the strength and workability requirements. The paper describes details of the experimental results, model development, and optimization results.

• Composites Research
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• 제30권1호
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• pp.35-40
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• 2017

본 연구에서는 천연섬유 복합재료의 홀 가공 인자를 최적화 하기 위하여, 진공 인퓨전 성형공정을 이용하여 천연섬유 복합재료를 제조하였으며 보강재로는 아마섬유를 사용하였다. 그 후 가공에 적합한 드릴을 설계하고, 선정된 가공조건에 따라 홀 가공을 수행하였다. 실험횟수를 최소화하기 위하여 다구찌 실험계획법을 사용하였으며, 홀 가공 후 가공면내 거칠기를 측정하고 거칠기비 분석을 통하여 그 결과를 비교하였다. 실험결과 천연섬유 복합재료의 가공 시 절삭저항을 분산할 수 있는 새로운 드릴을 설계하였다. 이 드릴을 사용할 경우 가공중의 절삭저항이 분산되었으며, 표면거칠기가 최소화된 천연섬유 복합재료를 얻을 수 있었다. 또한 홀 가공에 적합한 최적의 드릴 회전속도 및 이송속도를 선정하였다.

• 공업화학
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• 제10권6호
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• pp.949-953
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• 1999

반도체 봉지재에 쓰이는 EMC(Epoxy Molding Compound)는 고농도의 충전제를 함유하고 있는데, 이 충전제의 양과 성질에 따라 유동 특성이 크게 달라진다. 본 연구에서는 충전제의 농도, 입자모양, 크기에 따른 EMC(에폭시/실리카)의 점도변화 특성을 조사하였고, 이를 Mooney 식을 사용하여 예측하여 보았다. Mooney 식에 포함되어 있는 최대 충전율과 형상인자 중 최대 충전율은 Ouchiyama의 충전 모델과 Taguchi의 방법을 이용하여 구하였고, 형상인자는 실험자료를 이용하여 구하였다. 구해진 Mooney 식은 EMC의 점도 거동을 잘 예측하였다.

• 한국세라믹학회지
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• 제40권1호
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• pp.93-97
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• 2003

치과용 재료를 포함한 생체재료로 각광을 받고 있는 알루미나-유리복합체에 사용되는 유리침투재의 적정 조성은 열팽창계수가 중요 인자로, 적합한 열팽창계수를 가지는 적정 조성 유리 개발을 효율적으로 달성하기 위하여 다구치 실험계획법을 도입하였다. 이러한 방법을 이용하여 유리 침투재의 열팽창에 가장 많은 영향을 미치는 알칼리 산화물과 알칼리 토류 산화물의 영향을 관찰하였다. 치과용 유리침투재의 제성분들을 고려할 때 유리의 열팽창계수에 미치는 영향은 $Na_2$O≫K$_2$O≫MgO≒CaO의 순서로 $Na_2$O의 영향력은 MgO, CaO의 약 8배로 나타났으며 $K_2$O의 영향력은 MgO, CaO의 약 4배로 계산되었다. 또 각 인자간의 교호작용(interaction affects) 중 $K_2$O-CaO의 교호 작용이 가장 유의하게 나타났으며 각 인자와 교호 작용의 수준별 기여율을 계산하여 특성 조성의 열팽창 특성치를 예측하였다.

• 한국진공학회지
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• 제7권2호
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• pp.161-168
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• 1998

Taguchi가 제안한 강건설계 및 연구자의 주관에 의존하는 통상적인 실험방법을 병 행하여 CH4/H2 유도결합 고밀도 플라즈마를 이용한 InP 소재의 반응성이온에칭에 있어 공 정변수들이 식각특성에 미치는 영향을 분석하고 적정조건을 도출하였다. 연구 결과 ICP전력 은 표면거칠기와 측벽수직도, bias 전력은 식각속도와 수직도에, CH4분율은 수직도와 식각 속도, 석영창과 시료 사이의 거리는 표면 거칠기에 영향을 주는 변수로 작용하였고, 식각속 도에 가장 크게 영향을 주는 변수는 공정압력임을 알 수 있었다. 결과적으로 ICP Power 700W, bias Power 150W, 시편/coil 거리 14cm, 압력 7.5mTorr, 15% $CH_4$의 적정조건에서 시간당 약 3.1$\mu\textrm{m}$의 식각속도와 미려한 표면을 얻어, 기존의 반응성 이온 식각(RIE)과 비교하 여 1.5배 이상의 식각속도를 얻을 수 있었다.

• Steel and Composite Structures
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• 제36권4호
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• pp.463-480
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• 2020

Although detailed shell analysis is suitable to predict the ductile crack initiation life of steel members, such detailed method adds time expense and complexity. In order to simply predict the ductile crack initiation life of stiffened steel bridge piers, a total of 33 cases are simulated to carry out the parametric analyses. In the analysis, the effects of the width-to-thickness ratio, slenderness ratio, plate thickness and so on are considered. Both shell analyses and beam analyses about these 33 cases are conducted. The plastic strain and damage index obtained from shell and beam analyses are compared. The modified factor β_s is determined based on the predicted results obtained from both shell and beam analyses in order to simulate the strain concentration at the base corner of the steel bridge piers. Finally, three experimental results are employed to verify the validity of the proposed method in this study.

• 한국재료학회지
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• 제25권7호
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• pp.322-329
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• 2015

The magnitude of wear should be at a minimum for numerous automobile and aeronautical components. In the current work, composites were prepared by varying the cenosphere content using the conventional stir casting method. A uniform distribution of particles was ensured with the help of scanning electron microscopy (SEM). Three major parameters were chosen from various factors that affect the wear. A wear test was conducted with a pin-on-disc apparatus; the controlling parameters were volume percentages of reinforcement of 5, 10, 15, and 20%, applied loads of 9.8, 29.42, and 49.03 N, and sliding speeds of 1.26, 2.51, and 3.77 m/s. The design of the experiments (DOE) was performed by varying the different influencing parameters using the full factorial method. An analysis of variance (ANOVA) was used to analyze the effects of the parameters on the wear rate. Using regression analysis, a response curve was obtained based on the experimental results. The parameters in the resulting curve were optimized using the Genetic Algorithm (GA). The GA results were compared with those of an alternate efficient algorithm called Neural Networks (NNs).

• 품질경영학회지
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• 제42권4호
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• pp.579-590
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• 2014

Purpose: Ball milling is a popular process for obtaining fine powders in the part and material industry. One of important issues in the ball milling is to produce particles with a uniform size. Although many factors affect uniformity of particles, this paper focuses on the choice of ball diameter. Consider a ball milling where balls can be taken with three different diameters. The purpose of this paper is to find a ball mix which minimizes the average particle size. Methods: Ball diameters are selected as 10mm, 3mm, and 0.5mm. In order to find an optimum mixing ratio, the method of mixture experiments is employed in this paper. Taguchi's signal-to-noise ratio (SNR) for smaller-the-better type is also used to analyze experimental data. Results: According to the experimental result, SNR is maximized when the ball mix is taken as either 7:3:0 or 6:4:0. Such mixing ratios can be technically validated in terms of porosity reduction. Conclusion: The ball mixing technique presented in this paper provides a useful way to improve the production efficiency with a low cost.

• Journal of Welding and Joining
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• 제23권6호
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• pp.43-48
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• 2005

This work was carried out to obtain sound welds and to select a most suitable binary metal joint among three different dissimilar binary metal combinations such as Zr-4/Ta, Mo/Ta and Ti/Ta(seal tube/sensor sheath) joints fur the instrumented nuclear fuel irradiation test. To do this, Taguchi experimental method was employed to optimize the experimental data. In addition, metallography, micro-focus x-ray radiography and hardness test were conducted to examine the welds. From the weld bead appearance, penetration depth and bead width as well as weld defects standpoint, Zr-4/Ta joint is suggested for the circumferential joining between a seal tube and a sensor sheath. The optimized welding parameters based on Zr-4/Ta joint are suggested as well.