• Journal of Applied Reliability
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• v.15 no.4
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• pp.248-255
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• 2015

Purpose : The purpose of this research is to develop the optimized method and process in the reliability-growth target setting, especially for complex and repairable system (or products) such as vehicle and airplane, construction equipment. Method : A reliability-growth test plan specifies a scenario to achieve the planned reliability value (or reliability target). The major elements in test planning are reliability-growth starting time and reliability level at that time, reliability-growth rate and reliability-growth target. All of them except a reliability target can be referred to the previous development data and reference researches. The reliability target level is directly influencing to test period (or time) which is related to test and warranty cost together. There are a few researches about the reliability target setting method and but showing the limitations to consider the views of engineering, business and customer together. There is no research how to handle the target setting process in detail. Result : We develop the optimized method and systematic process in reliability target setting with considering such views. This research also establish the new concept as production capability which means company (or supplier) capability to product its products. Conclusion : In this research result, we apply the new method to a few projects and can set the reasonable test planning. The developing results is showing the good balance between the developing cost and warranty cost at market.

• Journal of Applied Reliability
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• v.13 no.3
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• pp.175-190
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• 2013

This study considers reliability growth management as the excellent method for construction equipment development with the effect on decreasing COPQ(Cost of Poor Quality Cost) of new products. MIL-HDBK-189A(1981) and RADC-TR-84-20(1984) standards provide a general concept of reliability growth management including to reliability growth test, models and FRACAS(Failure Reporting and Corrective Action System). There is no study how to apply reliability growth management to construction equipment(or machine) development. This paper propose the method to apply it to construction equipment development process from the reliability target setting for developing products to launching them at market. It is expecially showing how to set target reliability for new developing equipment and the development risk to reach the reliability target in detail.

• Journal of Applied Reliability
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• v.18 no.3
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• pp.201-207
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• 2018

Purpose: To develop the reliability growth planning for a subsystem of guided weapon system using PM2-Continuous model. Methods: The target MTBF of the subsystem is set by allocating the system target MTBF to the lower level, where ARINC method is applied. Other model parameters such as initial MTBF, management strategy ratio and average fix effectiveness factor are chosen from historical growth parameter estimates. Given the values of model parameters, the reliability growth planning curve using PM2-Continuous model is constructed and the sensitivity analyses are performed for the changes of model parameters. Results: We have developed the reliability growth plan for a subsystem of guided weapon system using PM2-Continuous model. It was found that the smaller the ratio of initial MTBF to target MTBF, the smaller the management strategy ratio, the smaller the average fix effectiveness factor, and the shorter the development test period, the higher reliability growth is required. Conclusion: The result of this study will be used as a basis for establishing the reliability growth plan, the test period setting and the budget appropriation for the similar system entering the system development stage in the future.

• Journal of Applied Reliability
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• v.14 no.4
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• pp.225-229
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• 2014

A one-shot device is defined as a product, system, weapon, or equipment that can be used only once. After use, the device is destroyed or must undergo extensive rebuild. Determining the reliability of a one-shot device poses a unique challenge to the manufacturers and users due to the destructive nature and costs of the testing. This paper presents a reliability growth prediction for a one-shot system. It is assumed that 1) test duration is discrete(i.e. trials or rounds); 2) trials are statistically independent; 3) the number of failures for a given system configuration is distributed according to a binomial distribution; and 4) the cumulative expected number of failures through any sequence of configurations is given by AMSAA model. When the system development is represented by three configurations and the number of trials and failures during configurations are given, the AMSAA model parameters and reliability at configuration 3 are estimated by using a reliability growth analysis software. Further, if the reliability growth predictions do not meet the target reliability, the sample size of an additional test is determined for achieving the target reliability.

• Journal of the Korean Society of Systems Engineering
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• v.16 no.2
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• pp.87-96
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• 2020

In this paper we proposed the test design method of reliability growth management. First, we presented the process for establishing the reliability growth management test design considering the number of failures and the termination test time. Reliability growth analysis of continuous system was performed in accordance with the test design process presented. In case the reliability test result is not met with the reliability target value after more than three failures occurred, the required test times were analyzed that 1,725 hrs for one corrective action, 1,950 hrs for two corrective actions. If the number of failures is less than three, design a reliability demonstration test according to confidence level 80% and 90% was performed using RGA 11 Software. As a result, it is possible to establish the reliability growth management test design with sufficient use of available resources. The results of this study can be used when establishing a test design for assessment of reliability growth management of all continuous systems.

• Journal of Korean Society for Quality Management
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• v.45 no.4
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• pp.981-994
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• 2017

Purpose: In this study, the reliability growth management procedures for armed vehicle is suggested and an illustrative case study of launcher system is given. Methods: Crow-AMSAA model is adopted to manage reliability growth of armed vehicle using failure data acquired from development test phase to field operation phase. Between the development test phase and the production phase, the suggested reliability growth procedures for armed vehicle entails accelerated life test of the selected module whose design is changed to improve its reliability for assuring the target system reliability. And it can be verified through estimating the system reliability based on the failure data of field operation phase. Results: It is shown that the proposed reliability growth management procedures are effective for armed vehicle based on the case study of launcher system. After estimating the reliability of launcher system at every development test, some items are selected to change their designs for improving reliability. Accelerated life test is performed to prove the reliability improvement and finally it is verified through the field operation. Conclusion: The reliability growth management procedures for armed vehicle is suggested and the case study of launcher system shows it can be effective for managing the reliability growth of the armed vehicle.

• Journal of Information Technology Applications and Management
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• v.13 no.4
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• pp.1-12
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• 2006

Many software reliability growth models(SRGM) have been proposed since the software reliability issue was raised in 1972. The technology to estimate and grow the reliability of developing S/W to target value during testing phase were developed using them. Most of these propositions assumed the S/W debugging testing efforts be constant or even did not consider them. A few papers were presented as the software reliability evaluation considering the testing effort was important afterwards. The testing effort forms which have been presented by this kind of papers were exponential, Rayleigh, Weibull, or logistic functions, and one of these 4 types was used as a testing effort function depending on the S/W developing circumstances. I propose the methology to evaluate the SRGM using least square estimator and maximum likelihood estimator for those 4 functions, and then examine parameters applying actual data adopted from real field test of developing S/W.

• Journal of Applied Reliability
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• v.16 no.2
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• pp.162-170
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• 2016

Purpose: The purpose of this study was to analyze the failure modes of an auto transfer switch (ATS), determine the most common failure mechanisms, and iterate the design to improve reliability. Methods: We carried out failure mode and effect analysis (FMEA) to determine the failure modes and mechanisms. We identified the parts or modules that required improvement via two-stage quality function deployment based on FMEA, and improvements to reliability were monitored using the Gomperz growth model. Results: The main failure modes of the ATS were damage to, and deformation of, the stator / movable element due to repetitive movements. Five iterations of design modification were carried out, and the mean time to failure (MTTF) increased to 14,539 cycles, corresponding to 85% of the target MTTF. The Gompertz growth model indicates that the 10th iteration of design modification is expected to achieve the target MTTF. Conclusion: We improved the reliability of mechanical parts via failure mode analysis, and characterized the iterative improvements in the MTTF using the Gompertz growth model.

• Journal of Korean Society for Quality Management
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• v.21 no.2
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• pp.131-139
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• 1993

The newly proposed model of the future reliability results in earlier fault-fixes having a greater effect than the fault which make the greatest contribution to the overall failure rate tend to show themselves earlier, and so are fixed earlier. The suggested model allows a variety of reliability measures to be calculated. Predictions of total execution time(debugging time) is to achieve a target reliability. This model could also apply to computer-hardware reliability growth resulting from the elimination of design error and fault.

• Magazine of the Korean Society of Agricultural Engineers
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• v.34 no.1
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• pp.66-77
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• 1992

A prototype probabilistic approach to thickness design for asphalt pavement surface course was developed using first-order second moment probability model. The tensile strain (load effect) developing at the bottom of surface layer due to the wheel load and the critical strain (resistance) of asphalt concrete were used as random variables for pavement reliability analysis. Based on the parameters for load effect and resistance data collected from reference and field, simulated data were generated by Monte Carlo method for reliability evaluation of the pavement for a typical rural highway. Thickness of pavement surface course was defined in terms of target reliability of the pavement, growth factor of traffic, design life of pavement and resistance of the asphalt concrete to be placed on the pavement. According to these rationales, prototype thickness design chrats were sugested through example studies. From these, similar design charts can be developed for many pavements if appropriate data and target reliability are determined.