Purpose: The CNC lathe uses a power chuck operated by a hydraulic-driven rotating cylinder to grip the lathe stably, which is especially important during high-speed milling. In this paper, we suggest the cause of power chuck failure and then verify its reliability by improving its structure of internal parts. We also perform a life test and a pre/post major performance test on a prototype aluminum chuck, analyze its shape data, and propose shape and scale parameters.Methods: We used ANSYS mechanical software to provide a structural analysis of the prototype chuck body. Constraints were set to fixed conditions below the body with a load of 20 kN equivalent applied to the cylinder thrust. The life data analysis was performed using the Minitap program.Results: The shape and scale parameters of the prototype power chuck were 2.77 and 4,706,474 cycles, respectively.Conclusion: The prototype power chuck life span was analyzed as 521,512 cycles at the lower 95% confidence limit, meaning its reliability showed higher than its warranty life.

Purpose: Failure Mode and Effects Analysis (FMEA) is a widely used technique to assess product reliability by identifying potential failure modes and their effects at the early stages of product development. FMEA techniques have been consistently evolving. In this study, we examine the past and present trends of FMEA, and make recommendations for the future.Methods: Through our Literature Review, we classified FMEA techniques into seven categories (excluding application studies) as follows: FMEA Types; FMEA Format; Implemented Subject; Studies for Identifying and Preventing Omission of Failure Mode; Studies for Inferring Failure Mechanism; Automation for Performing FMEA; and Risk Priority Number (RPN) Assessment.Results: Though FMEA has two primary approaches (hardware and functional), the required industrial standards of FMEA have been developed based only on the functional approach. This approach may not be proper for sub-system or component manufacturers that need to improve their failure analyses through identifying all potential failure modes.Conclusion: We propose applying different analyses approaches depending on the objectives of FMEA implementation. We also propose that concrete procedures for System FMEA, Design FMEA, and Process FMEA be required.

Purpose: Testing a hydraulic winch system by matching the field operating conditions is difficult due to the many operating factors that the system must control simultaneously. This study used different approaches to mimic the lifetime of the winch system to reduce the test time.Methods: We investigated the load condition of a hydraulic winch under field conditions and analyzed its failure mode and mechanism. In addition, we established a reliable assessment system for field conditions that could be reproduced and tested in the laboratory.Results: We applied an acceleration life test to overcome the difficulties of test time that could not be solved by the failure test. In addition, we established a reliability evaluation system for field conditions that could be reproduced and tested in a laboratory.Conclusion: The acceleration factor was calculated using the force to pull the hydraulic winch from the wire, and the accelerated life test time was applied to perform a reliability assessment.

Purpose: The accuracy of reliability prediction for the Active Electrically Scanned Array (AESA) type antenna is limited due to the antenna’s complex structural and functional characteristics. This study focuses on those characteristics to achieve a more accurate reliability prediction.Methods: A design analysis of the AESA antenna preceded the reliability prediction portion of this study. The antenna’s functional diagram was schematized through structural and functional analysis. Also, because the AESA had a redundancy of multiple Transmit Receive Modules (TRM), we calculated the failure acceptance criteria by basing it on the failure characteristic and the required performance on detection range.Results: Based on the functional diagram and the failure acceptance criteria, several reliability analysis methods derived from the k-out-of-n model were applied to calculate the reliability metric of Mean Time Between Failure (MTBF) for the AESA antenna.Conclusion: The concepts and results of each reliability analysis method were discussed and compared. Through the consideration of each method, the most appropriate analysis method was suggested.

Purpose: Passenger train door systems can undergo failure during operation, causing inconveniences such as service delays, breakdowns or even resulting in the human casualties. This study proposes a diagnostic process to predict such failure conditions so they can be avoided in advance.Methods: A door test rig is prepared, in which the motor signals are acquired for different fault modes during the operation test. Various time domain features are extracted and selected using the Fisher Discriminant Ratio and Pearson correlation. Classifications are then performed by the k-Nearest Neighbor (k-NN) method for the door-open and door-close operations, respectively.Results: Overall, the fault modes are identified quite well except for the artificial bearing wear. The result is worse in thedoor-close operation because the high peak current applied near the end to ensure the door closing may have affected the classification accuracy.Conclusion: The proposed fault diagnosis method is easy to implement for the passenger train door system. Once the diagnosis system is trained via the seeded fault modes, it can be applied with accuracy to the fault diagnostics of train door systems, and be used for the efficient maintenance.

Purpose: In this study, we reproduced the vibrational degradation of passenger vehicle engine mounts to address driver complaints about vibration problems that occur when the vehicle is stopped or idling. To address these problems in the development stage, we needed to improve the field correlation and reproducibility of the actual vehicle durability test mode for engine mount degradation.Methods: We analyzed used vehicles in the field, comparing the characteristic change amounts and features of their engine mounts. We used the temperature/aging curve of natural rubber, the material used in engine mounts, to investigate the thermal load of each configuration mode of the actual vehicle test, and then reconstructed the configuration mode to be head loaded to fit the field target.Results: We reproduced the engine mount degradation mode using a high temperature chamber. We applied the thermal load to reproduce the engine mount degradation of 100,000km in the field, and then implemented the mode to verify.Conclusion: Through this study, we determined it was possible to develop other vehicle bushes or mounts that would address the problem of vibrational degradation in the vehicle.

Purpose: This paper evaluates the effects of heat and gamma radiation on the degradation behavior of fluoroelastomer under the normal and the Design-Basis Event (DBE) environments of a nuclear power plant.Methods: Accelerated thermal radiation aging and Loss-of-Coolant Accident (LOCA) tests were performed to simulate normal and DBE environments, respectively. Mechanical and thermal degradation caused by heat and radiation were measured by tensile test and thermogravimetric analysis. Molecular structure analysis was conducted through Fourier transformed infrared (FT-IR) spectroscopy.Results: The mechanical properties were not changed significantly in pre-aging, normal operating conditions. But radiation of the DBE accident environment significantly affected the mechanical properties of fluoroelastomer and molecular structures, such as C = O formation.Conclusion: The changes in mechanical properties were caused by increased crosslink density. The crosslink density increased due to chemical bonds that were scissioned by irradiation, resulting in the formation of free radicals. FT-IR results showed that C = O and C-O bonds were increased with increasing doses of gamma radiation. Because of the unstable molecular structure generated by reactions between free radicals and scissioned molecular and oxidized chemical bonds, polymeric materials were hardened and decreased in thermal stability as gamma radiation doses increased.

Purpose: This paper presents a correction method to improve the accuracy of the estimated RAM value in the proposed stage of the new weapon system using the SEM(structural equation model).Methods: The staff in the field of operation, maintenance, and support of the weapon system evaluates the time required by each field, evaluates the correction between the main variables by using the SEM, and suggests how to use it in estimating the RAM value. Excel and Amos programs are used for descriptive statistical analysis and SEM.Results: A comparative analysis on the calibration method using MIL-HDBK-17 and SEM for RAM value correction is proposed to improve the accuracy of RAM value.Conclusion: RAM data correction items were verified through data verification for the difference of evaluation results according to the staffs in each field, and direct and mediating effects on variables affecting RAM value estimation were verified using SEM.

Purpose: The environment of modern networks is changing. Hardware-centric networks have become a huge part of the Software Defined Network (SDN). This study analyzes the reliability of the virtual network according to its underlying physical structure and suggests methods for improving network reliability.Methods: We analyzed survival characteristics in the virtual network according to the number of physical links. The number of independent paths according to the link number is interpreted as reliability, even when the number of virtual networks changes.Results: As the number of links increases, the average path number increases, and as the number of virtual networks increases, the average path number decreases.Conclusion: To increase network reliability, it is necessary to either restrict the diversity of the virtual network, or, to increase the number of links on the physical network.

Purpose: This paper proposes using the new extended two-phase warranty model for a repairable system.Methods: Jung et al. [7, 11] discusses the two-phase warranty policy. Under the two-phase warranty, the warranty period is divided into two non-overlapping subintervals, one of which is for a replacement warranty, and the other for a minimal repair warranty. We propose using the new extended warranty model under the two-phase warranty system.Results: We calculated the expected total warranty cost from the manufacturer’s point of view during the warranty period for the new extended two-phase warranty model.Conclusion: Given the cost structures incurred during the warranty cycle of the system, we formulated the expected total warranty cost and provided numerical examples to illustrate the proposed extended warranty model.

Purpose: This paper reports on a simulator whose development considered the operational characteristics of a desalination plant while evaluating its performance.Methods: An availability simulator was developed and its performance evaluated through comparative analysis with results achieved both mathematically and with a widely used commercial software. For performance evaluation, we generated example systems including well-known basic structures and conducted an experiment on it.Results: Experimental results showed that the developed software produced results close to the known inherent availability derived from a commercial software. The known operational characteristics of the seawater desalination plant further verified the accuracy of the produced results.Conclusion: We have proposed practical considerations and developed a simulator for a desalination plant. It is expected that the proposed method and the developed software will contribute to advance the plant"s Operation and Maintenance (O&M) performance.

Purpose: This study developed a manufacturing technique for a composite material heat dissipation filler by using the sputtering method, and then verified its application in terms of heat dissipation performance and reliability.Methods: We used the sputtering method to develop a ceramic deposition on the bead surface that was based on the optimal design of the magnetic array of ceramic cathode, followed by manufacturing a composite heat dissipation prototype. The product holder system was developed to improve the efficiency of the ceramic material during the sputtering process.Results: Test results by Laser Flash Apparatus (LFA) indicated that “SR+AIN” had the best thermal conductivity out of four types. Standards and/or user requirements were verified by demonstrating eight types of reliability tests to the Chip-On-Flex (COF) Printed Circuit.Conclusion: The thermal conductivity test revealed 15% improved efficiency. The new composite heat dissipation filler using the sputtering method is expected to improve reliability and reduce the production cost.

Purpose: Maintenance data for Korean traffic signal controller(TSC) shows that the replacement life is shorter than 10 years required. To investigate the causes, Korean and international TSC reliability standards are compared and MTBF of TSC is evaluated.Methods: Reliability test items of Korean, US, European, and Japanese TSC standards are compared as well as their test conditions. In addition, failures rates of main control unit CPU boards of 2 main control unit are evaluated based on MIL-HDBK-217F.Results: Domestic’s TSC requires 20 items compared to the European standard that defines 35 items. After installing and operating a new product of TSC, the actual way-out period was analyzed at 8.4 years until the replacement. This is a very short TSC endurance of 10 years. Thyristor LSU had no official tests with surge current applied. Corrective action is necessary to ensure that the confirmation procedure is carried out to improve such safety.Conclusions: Korean TSC standard requires less test items than EU, US and Japan. Some important tests like solar test, salt spray test, gas test and storage test are not specified. MTBFs of 2 CPU boards are evaluated to be less than 10 years.

Purpose: Fault data on automobile brakes are applied to reliability and statistical analysis methods to derive the brake acceleration factor and acceleration factor for automobiles. Based on these results, a brake acceleration life test design is proposed.Methods: The factors influencing brake failure are derived from literature review. The wear data are extracted by two-mixture Weibull distribution analysis based on three levels of failure data to determine if the factor affects the failure of brake parts. The extracted wear data are analyzed to confirm the acceleration and determine the acceleration factor and the acceleration factor.Results: Acceleration life tests can be designed from existing vehicle brake life tests by reflecting the derived acceleration factors and acceleration factors.Conclusion: With the reduction in the proposed testing time compared with the existing one, a more reliable design can be achieved. The proposed analytical process can be useful in deriving the acceleration factor for the design of an accelerated life test for non-brake car parts