• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.17 no.12
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• pp.1169-1176
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• 2005

In this paper, thermal reliability of a closed type BLDC (Brushless DC) motor for high speed axial fan was analyzed by the accelerated life test. The closed type BLDC (Model No. MB1-8855-J01) motor was controlled by PCB module, which was composed of various electrical components. The failure of the closed type BLDC motor happened in PCB module due to high temperature. Failure mechanism of the closed type BLDC motor appears to be electrolyte dry out of capacitor. The accelerate life test was performed in temperature stress of $85^{\circ}C\;and\;105^{\circ}C$, respectively The failure data from the accelerated life test were analyzed and the life in each stress level was estimated with 960h and 261 h. At last, both life expression according to operating temperature of PCB module and life of the closed type BLBC motor in normal condition $(50^{\circ}C)$ were suggested.

• Journal of the Korean Institute of Gas
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• v.16 no.3
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• pp.29-34
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• 2012

Investigating safer ways to design and use to prevent a loss of life and property by failure of the structures are necessary and assessing total fatigue life with initiation and propagation of fatigue crack accurately through fatigue analysis is very important. The object of this study is to examine the initial life and propagation life when the fatigue crack is introduced from the root which is likely to appear in LOP(Lack of Penetration) cruciform fillet welded structure including bridges, ships and gas storage facilities which are impossible to be fully penetrated and to measure the rate of fatigue life until the final cleavage failure. As the result, each rate of fatigue life for fatigue failure is somewhat different in the range of 5% according to the thickness of material, however, the overall rate of initial life is in the range of 34~39% and propagation life showed the range of 61~66%.

• Journal of the Korean Statistical Society
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• v.11 no.2
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• pp.77-87
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• 1982

The choice if constants that define a life testing procedure is considered in terms of the test termination time (censoring time) and the number of items to be tested subject to a given range of variance of the expected life time, where the failure time of life testing is exponentially distributed.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.4
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• pp.2401-2406
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• 2015

Pipelines are used by large heavy industries to deliver various types of fluids. Since this is important to maintain the performance of large systems, it is necessary to accurately predict remaining life of the corroded pipeline. However, predicting the remaining life is difficult due to uncertainties in the associated variables, such as geometries, material properties, corrosion rate, etc. In this paper, a statistical method for predicting corrosion remaining life is proposed using Bayesian inference. To accomplish this, pipeline failure probability was calculated using prior information about pipeline failure pressure according to elapsed time, and the given experimental data based on Bayes' rule. The corrosion remaining life was calculated as the elapsed time with 10 % failure probability. Using 10 and 50 samples generated from random variables affecting the corrosion of the pipe, the pipeline failure probability was estimated, after which the estimated remaining useful life was compared with the assumed true remaining useful life.

• IE interfaces
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• v.15 no.1
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• pp.64-72
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• 2002

Broaching machine is widely used for machining inner shaped slots in the work-pieces, and provides vertical motion (usually hydraulically powered) between tool and work-piece. In this study, we modelled the tool life process and investigated economic tool life of broaching machine. Tool life process is divided into wear-process and succeeding failure process. Wear process is defined as machining wear and failure process as 'chipping' occurred by random shock. We modelled wear process as linear regression function for products amounts and assumed failure process as Poisson process. Economic tool life is defined as the number of lots which minimizes average tool related cost per lot and analyzed by using age replacement policy technique. As tool-related cost factors, we consider tool replacement cost, tool maintenance cost and quality costs of products. The results of this study can be applied to analyze life process of general machining tools.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.1 s.173
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• pp.38-51
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• 2000

The study on the mechanical behavior of a spot-welded specimen is largely divided into the quasi-static overload failure analysis and the fatigue failure prediction. The main issue in an overload analysis is to examine the critical loads, thereby providing a generalized overload failure criterion. As the welding spot forms a singular geometry of an external crack type, fatigue failure of spot-welded specimens can be evaluated by means of a fracture parameter. In this study, we first present the limit loads of 4 representative types of single spot-welded specimens in terms of the base metal yield strength and specimen geometries. Recasting the load vs. fatigue life relationships experimentally, obtained here, we then predict the fatigue life of spot-weld specimens with a single parameter denoted the equivalent stress intensity factor. This crack driving parameter is demonstrated to successfully describe the effects of specimen geometry and loading type in a comprehensive manner. The suggested fatigue life formula for a single spot weld can play a key, role in the design and assessment of spot-welded panel structures, in that the fatigue strength of multi-spots is eventually determined by the fatigue strength of each single spot.

• Journal of Information Technology Applications and Management
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• v.24 no.2
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• pp.71-80
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• 2017

Software reliability is one of the most elementary and important problems in software development In order to find the software failure occurrence, the instantaneous failure rate function in the Poisson process can have a constant, incremental or decreasing tendency independently of the failure time. In this study, we compared the reliability performance of the software reliability model using the parameters of Pareto life distribution with the intensity decreasing pattern and the shape parameter of Erlang life distribution with the intensity increasing and decreasing pattern in the software product testing. In order to identify the software failure environment, the parametric estimation was applied to the maximum likelihood estimation method. Therefore, in this paper, we compare and evaluate software reliability by applying software failure time data. The reliability of the Erlang and Pareto life models is shown to be higher than that of the Pareto lifetime distribution model when the shape parameter is higher and the Erlang model is more reliable when the shape parameter is higher. Through this study, the software design department will be able to help the software design by applying various life distribution and shape parameters, and providing basic knowledge using software failure analysis.

• Journal of Veterinary Clinics
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• v.24 no.2
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• pp.260-263
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• 2007

A 9-month-old, intact female mixed dog was referred to Veterinary Medical Teaching Hospital of Gyeongsang National University with symmetrically enlarged and protruded upper jaw. The patient was diagnosed as acute renal failure due to ethylene glycol poisoning and was treated for 1 month in a local animal hospital. In spite of treatment, the patient proceeded to chronic renal failure. Also, the patient's upper jaw begun to enlarge continuously. To evaluate this upper jaw, radiographic examination was performed. Skull radiographs revealed thickening of maxilla, decreased bone opacity, cortical thinning, loss of lamina dura and periodontal space in the maxilla. Diagnosis of rubber jaw syndrome is based on clinicial signs, radiographic findings and laboratory evidence of chronic renal failure due to ethylene glycol poisoning.

• Transactions of Materials Processing
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• v.3 no.2
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• pp.147-155
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• 1994

The service life of tools in metal forming technology is to a large extent limited by wear and fatigue fracture of the active elements. This presents a basic request for tool cost minimization and reduction of extensive machine down time, caused by premature tool failure. Currents developments are dominated by steps to reduce the causes of tool failure. A main problem of forming technology remains the insufficient reliability of tools due to a large and incalculable life time fluctuation. Only a systematic investigation of the failure mechanisms and operational loading of tools can lead to future improvements in tool layout, that is optimization of tool usage.

• Proceedings of the Korean Reliability Society Conference
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• 2011.06a
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• pp.41-48
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• 2011

In order to assess the reliability of the Tire Pressure Sensor for automobiles, 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, PCB destruction and battery Discharge by high temperature. ii) the life distribution of the Tire Pressure Sensor 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