When weapon system is designed and developed, a reliability is one of important factors to determine the development goal. The reliability analysis of the weapon system and equipment is based on MIL Specification, MIL-HDBK-217F and MIL-HDBK-338B. And the weapon system is operated on various environments by operating concept of the military using the weapon system. This study, at first, present failure rate by PSA comparing with failure rates by PCM, the different reliability analysis method, for same CCA(Circuit Card Assembly). And the study present change of reliability analysis results for CCA on various operation environment condition..

The aim of this paper is to consider the effect of the manufacturing processes on corrosion and centerline cracking of ancient bronze spoons. The ancient bronze spoons in question were made by several steps of forging, in reheated condition with cast ingots. The manufacturing method is similar to that of the modern spoons. The investigations include observations from light and scanning electron microscopes of the microstructure in terms of the crack propagation. Cracks in the centerline are caused by solute segregation in the center-line region; this solute is solidified in the final stage of bronze spoon manufacture. Centerline cracking is also caused by α phase segregation, accompanied by forged overlapping along the longitudinal direction of the spoons. A vertical stripe with cracks along the centerline of the spoon’s width is formed by folding in the wrought process. The overlapping area causes crack propagation with severe corrosion on the spoon surfaces over a period of a thousand years. The failure mechanisms of ancient bronze spoons may be similar to that of modern spoons, and the estimation of the failure mechanisms of ancient spoons can be appropriate to determine failure causes for such modern spoons.

Diesel engines show better thermal efficiency and fuel consumption, but diesel engines typically generate more NOx emissions because of lean-burn conditions. Therefore, it is necessary to reduce the emissions of diesel engines either by efficiently controlling combustion or by employing exhaust gas after-treatment systems. In this study several problems we're observed in a SCR system and Engine control system. The analysis result, new technology SCR is suitable for the vehicle with low temperature operating condition. Through this analysis we can find out more effective repair factors from the various fault in SCR component.

보증데이터의 분석 목적은 크게 세 가지로 분류할 수 있다. 첫째 현상파악이다. 현 상파악은 각 부품별 보증클레임데이터를 이용하여 각부품의 현수준을 분석하는 방법 으로 단변량 분석방법이다. 즉 부품의 현 수명(신뢰도)를 분석할 수 있는 생명표법, 카 랜마이어 방법이 대표적이라고 할 수 있다. 둘째, 고장원인분석이다. 부품의 고장에 다 양한 인자가 영향을 줄 것이다. 생산부터 고객의 사용조건까지 다양할 것이다. 이처럼 단순히 사용시간을 가지고 분석하는 것이 아닌 다양한 원인변수를 통해서 원인을 파 악하는 다변량 방법이다. 셋째, 단변량이 아닌 다변량 수명예측방법으로 그 모형의 구 조에 따라 비례적 위험함수 모형 (proportional hazards)의 가정을 적용하는 COX 모형 과 가속화 시간 (accelerated failure time)을 적용하는 AFT 모형으로 분류할 수 있다. 본 연구에서는 예측에 적합한 AFT모형을 통해서 생존 시간 자체에 대한 설명변수 의 효과를 모형화하고 각 부품의 수명을 예측하고자 한다. 이 방법을 제시하는 이유는 COX모형의 경우 준 모수적 방법으로 위험함수의 모수적 유형을 지정하지 않아도 된 다는 장점을 가지고 있지만, 위험 함수 보다는 설명변수의 효과를 추정에 그 주 목적 이 있기 때문에 모형의 결과를 수명예측에 사용하기에는 부적합하다. 본 논문에서는 다양한 인자를 고려하여 부품의 수명 및 수명에 대한 설명변수의 효 과를 모형화 하여 보증데이터를 분석하는 AFT 모형을 제시 하였고 실제 보증데이터 를 통해서 AFT 모형의 활용성을 확인하였다.

Failure modes and effects analysis (FMEA) is a widely used engineering tool in the fields of the design of a product or a process to improve its quality or performance by prioritizing potential failure modes in terms of three risk factors―severity, occurrence, and detection. In a classical FMEA, the risk priority number is obtained by multiplying the three values in 10 score scales which are evaluated for the three risk factors. However, the drawbacks of the classical FMEA have been mentioned by many previous researchers. As a way to overcome these difficulties, this paper suggests the ELECTRE III that is a representative technique among outranking models. Furthermore, fuzzy linguistic variables are included to deal with ambiguous and imperfect evaluation process. In addition, when the importances for the three risk factors are obtained, the entropy method is applied. The numerical example which was previously studied by Kutlu and Ekmek‡ioğlu(2012), who suggested the fuzzy TOPSIS method along with fuzzy AHP, is also adopted so as to be compared with the results of their research. Finally, after comparing the results of this study with that of Kutlu and Ekmek‡ioğlu(2012), further possible researches are mentioned.

A progressive failure analysis procedure for composite laminates is completed in here. An anisotropic plastic constitutive model for fiber-reinforced composite material is implemented into computer program for a predictive analysis procedure of composite laminates. Also, in order to describe material behavior beyond the initial yield, the anisotropic work-hardening model and subsequent yield surface are implemented into a computer code, which is Predictive Analysis for Composite Structures (PACS). The accuracy and efficiency of the anisotropic plastic constitutive model and the computer program PACS are verified by solving a number of various fiber-reinforced composite laminates with and without geometric discontinuity. The comparisons of the numerical results to the experimental and other numerical results available in the literature indicate the validity and efficiency of the developed model.

A progressive failure analysis procedure for composite laminates is developed in here and in the companion paper. An anisotropic plastic constitutive model for fiber-reinforced composite material, is developed, which is simple and efficient to be implemented into computer program for a predictive analysis procedure of composites. In current development of the constitutive model, an incremental elastic-plastic constitutive model is adopted to represent progressively the nonlinear material behavior of composite materials until a material failure is predicted. An anisotropic initial yield criterion is established that includes the effects of different yield strengths in each material direction, and between tension and compression. Anisotropic work-hardening model and subsequent yield surface are developed to describe material behavior beyond the initial yield under the general loading condition. The current model is implemented into a computer code, which is Predictive Analysis for Composite Structures (PACS), and is presented in the companion paper. The accuracy and efficiency of the anisotropic plastic constitutive model are verified by solving a number of various fiber-reinforced composite laminates with and without geometric discontinuity. The comparisons of the numerical results to the experimental and other numerical results available in the literature indicate the validity and efficiency of the developed model.

PURPOSES: The purpose of this study is to verify the causes of surface scaling at L-shoulder concrete structure. METHODS : From the literature reviews, mechanisms of frost damage were studied and material properties including strength, air void, spacing factor and scaling resistance of L-shoulder concrete structure were analyzed using core specimens taken by real fields. RESULTS : The spacing factor of air void has relatively high correlation of surface conditions : lower spacing factor at good surfacing condition and vice versa. If the compressive strength is high, even thought spacing factor does not reach the threshold value of reasonable durability, the surface scaling resistance shows higher value. Based on these test results, the compressive strength also provide positive effect on the surface scaling resistance. CONCLUSIONS: The main causes of surface scaling of L-shoulder could be summarized as unsuitable aid void amount and poor quality of air void structure. Secondly, although the compressive strength is not the governing factor of durability, but it shows the positive effect on the surface scaling resistance.

An accident related with elevators can cause death or serious injury of operators or passengers. This kind of a fatal accident is due to a failure of elevator. The reduction of failures of elevators is important to reduce the occurrence of elevator accident. Thus, this paper presents the results of analysis for the failure of elevators using the failure data of elevator. The results of analysis can be used to make a maintenance process of elevators.

In aerospace industry, MTBF (Mean Time Between Failure) and MFTBF (Mean Flight Time Between Failure) are generally used for reliability analysis. So far, especially to Korean military aircraft, MFTBF of avionic equipments is predicted by MIL-HDBK-217 and MIL-HDBK-338, however, the predicted MFTBF by military standard has a wide discrepancy to that of real-world operation, which leads to overstock and increase operation cost. This study analyzes operational data of avionic equipments. Operational MFTBF, which is calculated from operational data, is compared with predicted MFTBF calculated conventionally by military standard. In addition, failure rate trend is investigated to verify reliability growth in operational data, the investigation shows that failure rate curve from operational data has somewhat pattern with decreased failure rate and constant failure rate.

Thermo-mechanical fatigue cracks on the turbine housing of turbochargers are often observed in currently developed gasoline engines for them to adopt lightness and higher performance levels. Maximum gas temperatures of gasoline engines usually exceed 950℃ under engine test conditions. In order to predict thermo-mechanical failures by simulation method, it is essential to consider temperature-dependent inelastic materials and inhomogeneous temperature distributions undergoing thermal cyclic loads. This paper presented the analytical methods to calculate thermal stresses and plastic strain ranges for the prediction of fatigue failures on the basis of motoring test mode, which is commonly used for accelerated engine endurance test. The analysis results showed that the localized critical regions with large plastic strains coincided well with crack locations from a thermal shock test.

In aerospace industry, MTBF(Mean Time Between Failure) and MFTBF((Mean Flight Time Between Failure) are generally used for reliability analysis. So far, especially to Korean military aircraft, MFTBF of avionic equipments is predicted by MIL-HDBK-217 and MIL-HDBK-338, however, the predicted MFTBF by military standard has a wide discrepancy to that of real-world operation, which leads to overstock and increase operation cost. This study analyzes operational data of avionic equipments. Operational MFTBF, which is calculated from operational data, is compared with predicted MFTBF calculated conventionally by military standard. In addition, failure rate trend is investigated to verify reliability growth in operational data, the investigation shows that failure rate curve from operational data has somewhat pattern with decreased failure rate and constant failure rate.

This study was carried out to investigate artificial insemination (AI) failure status and frozen semen characteristics in Korean proven bulls‘ number (KPN) semen used for AI of Hanwoo cows in Gangwon East region (Gangneung, Donghae, Taebaek, Samcheok, Sokcho, Yangyang, Goseong). Among semen used for AI, AI failure rate showed lowest at KPN506 (27.6%), whereas highest at KPN593 (77.2%). Correlations of AI failure in between Korean proven bulls semen and cows was 0.2941, which means that AI failure rate of Korean proven bulls semen may have respectable effect on reproduction of Hanwoo cow. In addition, present study was conducted to investigate spermatozoal viability rate, ruptured acrosome rate and active mitochondria in frozen Korean proven bulls semen with flow cytometry. The semen of KPN593 showed significantly (p<0.05) higher viability rate in KPN593 (30.49%) than that in KPN637 (37.34%). Furthermore, percentage of ruptured acrosome was lower in KPN637 as 21.37% than in KPN637 (21.37%), but it was not statistically significant. In conclusion, these results indicate that choice of Korean proven bulls semen may correlate positively with conception rate in Hanwoo cow. Therefore, KPN with high AI failure rate might be avoid to increase conception rate and characteristics of frozen semen might be evaluated before its use for AI.

Reliability tools such as QFD and FMEA identify voice of customer related to product design, its use, how failures may occur, the severity of such failures, and the probability of the failure occurring. With these identified items, a development team can

A space launch vehicle system represents a typical example of large-scale multi-disciplinary systems, consisting of subsystems such as mechanical structure, electronics, control, telecommunication, propulsion, material engineering etc. Mission assurance for launch success is needed over the lifecycle of a space vehicle development program and through launch. This study suggests a comprehensive approach to analyzing failure spaces of space system failures, especially launch failures, from viewpoints of latent conditions and active failures in Reason's Model. First it reviews methods to identify process failure spaces using systems engineering process as latent conditions and explains their analysis results. Second it reviews literatures to identify physical failure spaces, deficiency areas of launch vehicles itself, as active failures and explains their analysis results.

BGA test sockets failed earlier than the expected life-time due to abnormal signal delay, shown especially at the low temperature (-50˚C). Analysis of failed sockets was conducted by EDX, AES, and XRD. A SnO layer contaminated with C was found to form on the surface of socket pins. The formation of SnO layer was attributed to the repeated Sn transfer from BGA balls to pin surface and instant oxidation of fresh Sn. As a result, contact resistance increased, inducing signal delay. Abnormal signal delay at the low temperature was attributed to the increasing resistivity of Sn oxide with decreasing temperature, as manifested by the resistance measurement of SnO2.

The likelihood of failure for the stress corrosion cracking (SCC) of caustic cracking, which affect to a risk of facilities, was analyzed through the risk based-inspection using API-581 BRD. We found that SCC of the caustic cracking was occurred above 5 % NaOH concentration, and the technical module subfactor (TMSF) was maximized for above 50 % concentration. The heat traced and monitoring were not sensitive to the TMSF with NaOH concentration and temperature. But the steam out was more of less affect minimum value of the TMSF. Also, the inspection number, the inspection effectiveness, and the year since inspection were very sensitive to the TMSF with NaOH concentration and temperature. Therefore, the plan of next inspection will be established with compositively considering those at once.