• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.10a
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• pp.141-142
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• 2006

• Steel and Composite Structures
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• v.21 no.5
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• pp.1017-1029
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• 2016

When a welded circular hollow section (CHS) tubular joint is subjected to brace axial loading, failure position is located usually at the weld toe on the chord surface due to the weak flexural stiffness of the thin-walled chord. The failure mode is local yielding or buckling in most cases for a tubular joint subjected to axial load at the brace end. Especially when a cyclic axial load is applied, fracture failure at the weld toe may occur because both high stress concentration and welding residual stress along the brace/chord intersection cause the material in this region to become brittle. To improve the ductility as well as to increase the static strength, a tubular joint can be reinforced by increasing the chord thickness locally near the brace/chord intersection. Both experimental investigation and finite element analysis have been carried out to study the hysteretic behaviour of the reinforced tubular joint. In the experimental study, the hysteretic performance of two full-scale circular tubular T-joints subjected to cyclic load in the axial direction of the brace was investigated. The two specimens include a reinforced specimen by increasing the wall thickness of the chord locally at the brace/chord intersection and a corresponding un-reinforced specimen. The hysteretic loops are obtained from the measured load-displacement curves. Based on the hysteretic curves, it is found that the reinforced specimen is more ductile than the un-reinforced one because no fracture failure is observed after experiencing similar loading cycles. The area enclosed by the hysteretic curves of the reinforced specimen is much bigger, which shows that more energy can be dissipated by the reinforced specimen to indicate the advantage of the reinforcing method in resisting seismic action. Additionally, finite element analysis is carried out to study the effect of the thickness and the length of the reinforced chord segment on the hysteretic behaviour of CHS tubular T-joints. The optimized reinforcing method is recommended for design purposes.

• International Journal of Internet, Broadcasting and Communication
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• v.13 no.3
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• pp.169-177
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• 2021

Recently, the use of electric and electronic control systems is increasing in the automobile industry. This increase in the electric and electronic control system greatly increases the complexity of designing a vehicle, which leads to an increase in the malfunction of the system, and a safety problem due to the malfunction is becoming an issue. Based on IEC 61508 relating to the functional safety of electrical/electronic/programmable electronics, the ISO 26262 standard specific to the automotive sector was first established in 2011, and a revision was published in 2018. Malfunctions due to system failure are covered by ISO 26262, but ISO/PAS 21448 is proposed to deal with unintended malfunctions caused by changes in the surrounding environment. ISO 26262 sets out safety-related requirements for the entire life cycle. Functional safety analysis includes FTA (Fault Tree Analysis), FMEA (Failure Mode and Effect Analysis), and HAZOP (Hazard and Operability). These analysis have limitations in dealing with failures or errors caused by complex interrelationships because it is assumed that a failure or error affecting the risk occurs by a specific component. In order to overcome this limitation, it is necessary to apply the STPA (System Theoretic Process Analysis) technique.

• Journal of Korean Society for Quality Management
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• v.46 no.2
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• pp.327-338
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• 2018

Purpose: A risk evaluation procedure is proposed for common failure causes in FMEA(Failure Mode and Effects Analysis). The conventional FMEA does not provide a proper means to compare common failure causes with other failure causes. This research aims to develop a risk evaluation procedure in FMEA where common failure causes and other failure causes exist together. Methods: For each common failure cause, the effect of each combination of its resulting failures is recommended to be reevaluated considering their interactive worsening effect. And the probability that each combination of failures is incurred by the same common cause is also considered. Based on these two factors, the severity of each common cause is determined. Other procedures are similar to the conventional method. Results: The proposed procedure enables to compare and prioritize every failure cause. Thus, the common causes, each of which incurring two or more failures, and other causes, each of which is corresponding to one failure, can be fairly compared. Conclusion: A fair and proper way of comparing the common failure causes and other causes is provided. The procedure is somewhat complicated and requires more works to do. But it is worth to do.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.20 no.9
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• pp.28-34
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• 2021

The Fourth Industrial Revolution has led to the development of drones for commercial and private applications. Therefore, the malfunction of drones has become a prominent problem. Failure mode and effect analysis was used in this study to analyze the primary cause of drone failure, and blade breakage was observed to have the highest frequency of failure. This was tested using a vibration sensor placed on drones along the breakage length of the blades. The data exhibited a significant increase in vibration within the drone body for blade fracture length. Principal component analysis was used to reduce the data dimension and classify the state with machine learning algorithms such as support vector machine, k-nearest neighbor, Gaussian naive Bayes, and random forest. The performance of machine learning was higher than 0.95 for the four algorithms in terms of accuracy, precision, recall, and f1-score. A follow-up study on failure prediction will be conducted based on the results of fault diagnosis.

• Journal of Applied Reliability
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• v.13 no.4
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• pp.299-307
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• 2013

The value of blood sugar is measured by a personal blood glucose meter which consists of two parts: a glucose strip and a blood glucose meter. A personal blood glucose meter makes use of electric media which are composed of glucose oxidase and electron. This study is to propose a method of reliability demonstration test derived from field data analysis and FMEA(Failure Mode and Effect Analysis). Detailed Conditions for reliability demonstration test are selected from the comparison of various failure mechanisms. The most dominant failure mechanism is wear-out which is caused by strip insertion/extraction. The testing device that can reproduce the failure mechanism of strip insertion/extraction is made to conduct reliability demonstration test. Using the testing device, it is confirmed that target lifetime of selected devices is more than 2 years.

• Steel and Composite Structures
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• v.26 no.3
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• pp.265-272
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• 2018

A detailed study was carried out on the tensile properties of the single-lap joint of a steel panel bolted/bonded to a composite laminate with a flanging. Finite element model (FEM) was established to predict the strength and to analyze the damage propagation of the hybrid joints by ABAQUS/Standard, which especially adopted cohesive elements to simulate the interface between the laminate and adhesive. The strength and failure mode predicted by FEM were in good agreement with the experimental results. In addition, three influence factors including adhesive thickness, bolt preload and bolt-hole clearance were studied. The results show that the three parameters have effect on the first drop load of the load-displacement curve, but the effect of bolt-hole clearance is the largest. The bolt-hole clearance should be avoided for hybrid joints.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2009.10a
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• pp.223-226
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• 2009

Various database and analysis system has been used for the cost effective maintenance of distribution facility but it is not effective because of the lack of interconnection among these systems. In order to overcome this problem this paper proposes reliability centered maintenance system based on the on-line monitoring of distribution system through intelligent distribution equipment. This system is made by the interconnection of distribution automation system, asset management system, failure analysis system and failure mode effect analysis system.

• Journal of the Korean Dietetic Association
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• v.21 no.1
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• pp.25-36
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• 2015

In this study, we attempted to improve hospital food delivery service quality and customer satisfaction by using FMEA (Failure Mode and Effect Analysis), which is applied to the quality control of products in manufacturing plants. Subjective food delivery service quality improvement was judged based on a 5-point likert scale. Traditional FMEA uses an RPN (Risk priority number) to evaluate the risk level of a component or process. The RPN index was determined by calculating the product of severity, occurrence, and detection indexes. In our results, total RPN value (P<0.01) significantly decreased after FMEA introduction, whereas customer satisfaction (P<0.001) and food delivery service quality (P<0.001) significantly increased. Specifically, foodservice errors (P<0.01) and loss cost (P<0.01) were significantly improved by FMEA introduction. Taken together, we suggest that FMEA reduces critical activities and errors in foodservice delivery caused by simple priority selection.

• Journal of the Korean Institute of Intelligent Systems
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• v.25 no.2
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• pp.174-179
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• 2015

Failure Mode and Effects Analysis (FMEA) has been used by Dynamic Positioning (DP) system for risk and reliability analysis. However, there are limitations associated with its implementation in offshore project. 1) since the failure data measured from the SCADA system is missing or unreliable, assessments of Severity, Occurrence, Detection are based on expert's knowledge; 2) it is not easy for experts to precisely evaluate the three risk factors. The risk factors are often expressed in a linguistic way. 3) the relative importance among three risk factors are rarely even considered. To solve these problems and improve the effectiveness of the traditional FMEA, we suggest a Fuzzy-FMEA method for risk and failure mode analysis in Dynamic Positioning System of offshore. The information gathered from DP FMEA report and DP FMEA Proving Trials is expressed using fuzzy linguistic terms. The proposed method is applied to an offshore Dynamic Positioning system, and the results are compared with traditional FMEA.