• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1997년도 추계학술대회 논문집
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• pp.43-46
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• 1997

Reliability engineering is regarded as the major and important roll for all industry. And advanced manufacturing systems with high sped and intelligent have been developing for betterment of machining ability. In this study, we have systemized evaluation of reliability for machinery system. We proposed the reliability assessment and designed and manufactured reliability test-bed to evaluate reliability. In addition we acquired reliability data using test-bed system and made database to handle reliability data. And also we not only use reliability data by analyzing reliability, but also apply design review method using analyzing critical units of machinery system. Form this study, we will expect to guide and increase the reliability engineering in developing and processing phase of high quality product.

• 전기학회논문지
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• 제57권2호
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• pp.208-213
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• 2008

In order to assess the reliability of the electronics control unit for vehicles, accelerated life test model and procedure are developed. By using this method, failure mechanism and life distribution are analyzed. The main results are as follows : i) the main failure mechanism is degradation failure that is, junction destruction of a semiconductor resin by high temperature. ii) the life distribution of the electronics control unit for vehicles is fitted well to Weibull life distribution and the accelerated life model of that is fitted well to Arrhenius model. iii) at the result of the life distribution, accelerated life test method is developed, and test time for life assessment will be shortened by 5,000 hours by this test method.

• 한국국방경영분석학회지
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• 제10권1호
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• pp.23-39
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• 1984

Consider a failure model for a stochastic system. A shock is any perturbation to the system which causes a random amount of damage to the system. Any of the shocks can cause the system to fail at shock times. The amount of damage at each shock is a function of the sum of the magnitudes of damage caused from all previous shocks. The times between shocks form a sequence of independent and identically distributed random variables. The system must be replaced upon failure at some cost but it also can be replaced before failure at a lower cost. The long term expected cost per unit time criterion is used. Structural relationships of the optimal replacement policy under the appropriate regularity conditions will be developed. And these relationships will provide theoretical background for the algorithm development.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2005년도 봄학술 발표회 논문집(I)
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• pp.175-178
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• 2005

The major object of this paper is to propose a nonlinear finite element analysis(FEA) technique of steel coupling beams-wall connections governed panel shear failure using ABAQUS. Detailed finite element models are created by studying the monotonic load response of the designed steel coupling beams-wall connections. The developed models account for the effect of material inelasticity, concrete cracking, panel shear failure and geometric nonlinearity. In order to verify the proposed FEA model, this study attended experiment considered parameters to the steel beam : face bearing plates, and horizontal ties. And the analytical result attended by the proposed FEA model validated through comparisons with the experimental results. Finally, the study estimated the analytical values compared with ASCE Design Guidelines. At this time, the analysis showed good agreement between the theoretical and experimental results.

• 대한전기학회논문지
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• 제39권3호
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• pp.301-311
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• 1990

A multiple controller structure consisting of a typical feedback controller and an additive redundant controller is proposed for enhancing the reliability of the control system. For the case where the main controller is chosen as a pole assignment controller with input/output measurements and the redundant controller as the Model Reference Adaptive Controller (MRAC) whose reference model is the closed-loop combination of the plant and the main controller, it is proven that the tracking error between the command input and plant output converges to zero under failure in one of the controllers or parameter perturbations of the plant, and further that the reliability measured by Mean Time To Failure (MTTF) is greater than that of the system with only a single main controller. A simulation Example is provided to illustrate reliable operation of the proposed control system against the controller failure.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2005년도 추계학술대회논문집
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• pp.301-305
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• 2005

This paper introduces a novel technique to detect and isolate the failures of multiple actuators connected to a system. Failure of actuator considered in this study could be any type of erroneous input that is different from commanded one. The interaction matrix technique allows the development of input-output equations that are only influenced by one target input. These input-output equations serve as an effective toot to monitor the integrity of each actuator regardless of the status of the other actuators. The method is capable of real-time actuator failure detection and isolation under any type of input excitation. The laboratory experiment using 8-bay NASA truss structure verifies the feasibility of the proposed method.

• 터널과지하공간
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• 제34권4호
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• pp.355-373
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• 2024

일반화된 Hoek-Brown (GHB) 식은 암반공학적 활용에 특화된 비선형 파괴기준식이며 최근 활용 빈도가 증가하고 있다. 그러나 GHB 식은 파괴 시점의 최소주응력과 최대주응력의 관계식이며 GSI≠100이면 파괴면에 작용하는 수직응력과 전단응력의 명시적 관계식 즉, Mohr 파괴포락선식으로 표현이 어렵다는 단점을 가지고 있다. 이 단점으로 인해 GHB 식을 한계평형해석, 상계한계해석, 임계평면법 등과 같은 수치해석기법에 적용하는 것이 쉽지 않다. 이에 따라 최근 GHB Mohr 파괴포락선을 근사적인 해석식으로 표현하려는 연구가 시도되고 있으며 관련 연구에 대한 지속적 관심이 여전히 필요하다. 이 연구에서는 기존 식보다 전단강도 예측 정확도가 높은 근사 GHB Mohr 파괴포락선 수식화 방법을 제시하였다. 개선된 수식화 과정에서는 접선마찰각의 근사 정확도를 높이는 방법과 비선형 GHB 파괴포락선의 접선식을 활용하여 전단강도 근사값의 정확도를 높이는 방법이 이용되었다. 이 논문의 후반부에서는 전단강도 예측 정확성과 계산시간 측면에서 제안된 근사 GHB 파괴포락선들의 장단점을 논의하였다.

• 산업경영시스템학회지
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• 제38권4호
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• pp.142-148
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• 2015

Due to advancements in technology and manufacturing capability, it is not uncommon that life tests yield no or few failures at low stress levels. In these situations it is difficult to analyse lifetime data and make meaningful inferences about product or system reliability. For some products or systems whose performance characteristics degrade over time, a failure is said to have occurred when a performance characteristic crosses a critical threshold. The measurements of the degradation characteristic contain much useful and credible information about product or system reliability. Degradation measurements of the performance characteristics of an unfailed unit at different times can directly relate reliability measures to physical characteristics. Reliability prediction based on physical performance measures can be an efficient and alternative method to estimate for some highly reliable parts or systems. If the degradation process and the distance between the last measurement and a specified threshold can be established, the remaining useful life is predicted in advance. In turn, this prediction leads to just in time maintenance decision to protect systems. In this paper, we describe techniques for mapping product or system which has degrading performance parameter to the associated classical reliability measures in the performance domain. This paper described a general modeling and analysis procedure for reliability prediction based on one dominant degradation performance characteristic considering pseudo degradation performance life trend model. This pseudo degradation trend model is based on probability modeling of a failure mechanism degradation trend and comparison of a projected distribution to pre-defined critical soft failure point in time or cycle.

• Structural Engineering and Mechanics
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• 제63권1호
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• pp.23-35
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• 2017

A nonlinear static procedure considering work-energy principle and global failure mechanism to estimate base shears of reinforced concrete (RC) frame-type structures is presented. The relative energy equation comprising of elastic vibrational energy, plastic strain energy and seismic input energy is obtained. The input energy is modified with a factor depending on damping ratio and ductility, and the energy that contributes to damage is obtained. The plastic energy is decreased with a factor to consider the reduced hysteretic behavior of RC members. Given the pre-selected failure mechanism, the modified energy balance equality is written using various approximations for modification factors of input energy and plastic energy in scientific literature. External work done by the design lateral forces distributed to story levels in accordance with Turkish Seismic Design Code is calculated considering the target plastic drift. Equating the plastic energy obtained from energy balance to external work done by the equivalent inertia forces considering, a total of 16 energy-based base shears for each frame are derived considering different combinations of modification factors. Ductility related parameters of modification factors are determined from pushover analysis. Relative input energy of multi degree of freedom (MDOF) system is approximated by using the modal-energy-decomposition approach. Energy-based design base shears are compared with those obtained from nonlinear time history (NLTH) analysis using recorded accelerograms. It is found that some of the energy-based base shears are in reasonable agreement with the mean base shear obtained from NLTH analysis.

• 한국임상수의학회지
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• 제17권2호
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• pp.340-345
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• 2000

The purpose of the present study was to evaluate the possibility of application of pediatric hemodialysis system to dogs weighing less than 6 kg. Six healthy dogs (B .W, 3-6 kg) were used_ Experimental end-stage renal failure was induced by bilateral nephrectomy or bilateral ligation of ure-ters. Hemodialysis was performed when blood urea nitrogen (BUN) value increased over 90 mg/dl and every other day thereafter. Daily investigated parameters included clinical clinical signs such as vomiting, fecal appearance and activity and laboratory data such as PCV, WBC, RBC, BUN, creatinine, Ca, P, $Na^+ Cl^-and K^+$During hemodialysis treatment, BUN and creatinine values were measured hourly. Severe vomiting and inappetence were shown 2 days after infliction of kidney disorder and melena and mucous faces were observed 3 days. The signs were not corrected by hemodialysis treatment. Avel- age hemodialysis treatment time was $5.5 {\times} 0.7$,/TEX> hours until BUN value decreased to normal range. Abnor- mal hematological and electrolytes values were reduced within normal levels after hemodialysis treatments. The complications oft hemodialysis included vomiting, nausea, obstruction of intravascular catheter, tremor, seizure, temporary visual loss and continued decrease in PCV It is suggested that pediatric hemedialysis system can be applied to acute renal failure and acute toxicity. Further works on improvements in maintaining patency of catheter and in managing the complications of hemo- dialysis should be conducted.