• Elastomers and Composites
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• 제55권2호
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• pp.81-87
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• 2020

Service life prediction and evaluation of rubber components is the foundational technology necessary for securing the safety and reliability of the product and to ensure an optimum design. Even though the domestic industry has recognized the importance thereof, technology for a systematic design and analysis of the same has not yet been established. In order to develop this technology, identifying the fatigue damage parameters that affect service life is imperative. Most anti-vibration rubber components had been damaged by repeated load and aging. Hence, the evaluation of the fatigue characteristics is indispensable. Therefore, in this paper, we propose a method that can predict the service life of rubber components relatively accurately in a short period of time. This method works even in the initial designing stage. We followed the service life prediction procedure of the proposed rubber components. The weak part of the rubber and the maximum strain were analyzed using finite element analysis of the rubber bushing for the tracked vehicles. In order to predict the service life of the rubber components that were in storage for a certain period of time, the fatigue test was performed on the three-dimensional dumbbell specimen, based on the results obtained by the rubber material acceleration test. The service life formula of the rubber bushing for tracked vehicles was derived using both finite element analysis and the fatigue test. The service life of the rubber bushing for tracked vehicles was estimated to be about 1.7 million cycles at room temperature (initial stage) and about 400,000 cycles when kept in storage for 3 years. Through this paper, the service life for various rubber parts is expected be predicted and evaluated. This will contribute to improving the durability and reliability of rubber components.

• Corrosion Science and Technology
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• 제3권5호
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• pp.209-215
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• 2004

Flexible hydraulic hose assembly that consists of hose and joints is used widely on various construction heavy equipments, agricultural machines, motor vehicles, and industrial heavy machines that require flexibility on hydraulic pipelines. It is classified by the maximum usage pressure which is determined by the winding layers of coiling steel wire and the inner diameter of the hoses. In this paper, we designed and performed an accelerated life test for assessing the reliability of a flexible hydraulic hose assembly. In the proposed accelerated life test, typical impulse pressure testing method is applied with the half omega flexing operation to simulate the practical flexing motion of the hose assembly.

• 대한안전경영과학회지
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• 제12권4호
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• pp.61-66
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• 2010

Organic light emitting diode(OLED) has been developed fast from 1963 when electric light emitting phenomenon was discovered. PMOLED(passive matrix OLED) is producted earlier than AMOLED(active matrix OLED). PMOLED is mainly mounted at sub display, but AMOLED is mounted at main display. Nowadays AMOLED is expanded to PMP(portable multimedia players), navigation and TV market. Even thought OLED's market is opening to many applications, OLED's life is worried until now. If we know about OLED's real life, we need time to test so much time over 20,000hrs. Realistically, there is difficult to test such as long time with products from the information-technology sector having a short life cycle. In this paper, we study about OLED's accelerated test to reduce life test by current. We can design OLED's accelerated life model by the result of test. The model consists of design variables like ratio of light emitting, organic material structure, condition of aging, etc. In conclusion, this model can be applied to study about organic material, machine and manufacturing process etc, and also it's possible to develop a method of manufacturing process & materials, so we need to study on the subject of this paper continuously.

• 한국자동차공학회논문집
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• 제25권2호
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• pp.250-256
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• 2017

Automatic transmission(A/T) is one of a car's core components. The durability of A/T has an effect on the durability of the car. The input shaft of A/T passes the power directly from the engine, so the durability of the input shaft for A/T is likewise vital. In this study, the test method of the input shaft is considered and the load spectrum of A/T is analyzed to secure durability of the input shaft. The shape parameter, T-N curve of the input shaft torsional fatigue test are obtained for life evaluation and analysis. Results of this study can be used to get the basic background of the durability test for A/T components.

• 한국어병학회지
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• 제28권2호
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• pp.71-78
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• 2015

In this study, we conducted to the development of a rapid antimicrobial susceptibility test method using WST-1 which is known to water-soluble tetrazolium salt, in order to rapidly response against bacterial diseases in fish. Eight of antibiotics which are permissioned for marine organism from government were used to rapid antimicrobial susceptibility testing using the WST-1. As a result, a similar tendency was verified compare to conventional antibiotic susceptibility test results. Generally, the antibiotic susceptibility test method required about 3 days (72 hours) for determine the effective antibiotics, however, we have confirmed that the our method using WST-1 was required at least 36 hours in this study. Consequentially, our method will contribute to development of rapid antimicrobial susceptibility testing for bacterial diseases in fish.

• 한국산학기술학회논문지
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• 제16권5호
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• pp.2993-2999
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• 2015

강 제조 회사들은 연속주조금형의 표면을 보호하기 위해 Ni-B 또는 Ni-Co 합금 도금을 적용하고 있으며, 도금 층에 균열이 생기게 하는 황을 함유한 사카린 윤활제를 사용하고 있다. 균열 및 인장 응력을 유발하는 것은 Ni-S 화합물로 여겨진다. Ni-Mn-B 삼원합금은 Ni-S 화합물이 형성되기 이전에 Mn-S 화합물을 형성하여 균열을 억제하기 위해서 개발되었으나, Ni-Mn-B 합금 도금에 관한 국내나 해외 기준이 없다. 그리하여 새로이 개발된 Ni-Mn-B 도금을 평가하기 위한 신뢰성 평가기준을 개정하려한다. 가속수명시험을 개발하기 위해 FMEA(고장형태 영향분석)가 사용되어 도금의 주요 파괴 원인을 분석하였다. Ni-Mn-B 신뢰성 기준은 가속수명시험 방법을 포함하였고, 기본 성능 시험과 환경시험, 가속수명시험으로 분류되었으며, 80% 신뢰수준으로 B10수명 1 000시간을 보장하도록 고안되었다.

• Smart Structures and Systems
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• 제29권6호
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• pp.799-805
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• 2022

Permanent magnet synchronous motors (PMSMs) are widely used in systems requiring high control precision, efficiency, and reliability. Predicting the remaining useful life (RUL) with health monitoring of PMSMs prevents catastrophic failure and ensures reliable operation of system. In this study, a model-based method for predicting the RUL of PMSMs using phase current and vibration signals is proposed. The proposed method includes feature selection and RUL prediction based on a particle filter with a degradation model. The Paris-Erdogan model describing micro fatigue crack propagation is used as the degradation model. An experimental set-up to conduct accelerated life test, capable of monitoring various signals was designed in this study. Phase current and vibration data obtained from an accelerated life test of the PMSMs were used to verify the proposed approach. Features extracted from the data were clustered based on monotonicity and correlation clustering, respectively. The results identify the effectiveness of using the current data in predicting the RUL of PMSMs.

• 한국산학기술학회논문지
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• 제7권3호
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• pp.393-397
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• 2006

신제품에 대한 개발 주기가 짧아지고 있는 현시점에서 제품의 수명을 예측하고 평가하기 위한 방법으로 가속 수명시험과 시험을 통해 관측된 고장 데이터의 분석에 대한 관심이 증대되고 있다. 이에 따라 가속 수명시험을 위한 시험 조건과 고장 데이터의 정확한 분석을 위한 고장 데이터의 최적 분포 결정 방법에 대한 관심 또한 증대되고 있다. 따라서 본 논문에서는 고장 데이터를 기반으로 신뢰성 예측을 할 때 사용하는 분포 함수 결정을 위한 방법으로 관측된 고장 데이터만의 분포를 고려하는 Anderson-Darling 방법과 관측된 고장 데이터의 수명-스트레스 관계식을 적용하여 고장 데이터의 분포를 결정하는 Likelihood Function 방법을 비교한다. 두 가지 방식을 비교한 결과 각 방식에 의해 선택되는 최적분포가 다르며, 따라서 각 방식에 의해 선택된 최적 분포에 의해서 예측되는 수명도 다름을 알 수 있다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회A
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• pp.1740-1743
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• 2007

In this study, two types of fatigue tests were conducted. First, cyclic bending tests were performed using the micro-bending tester. A four-point bending test method was adopted, because it induces uniform stress fields within a loading span. Second, thermal fatigue tests were conducted using a pseudo power cycling machine which was newly developed for a realistic testing condition. The pseudo-power cycling method makes up for the weak points in a power cycling and a chamber cycling method. Two compositions of solder are tested in all test condition, one is lead-free solder (95.5Sn4.0Ag0.5Cu) and the other is eutectic lead-contained solder (63Sn37Pb). In the cyclic bending test, the solder that exhibits a good reliability can be reversed depending on the load conditions. The lead-contained solders have a longer fatigue life in the region where the applied load is high. On the contrary, the lead-free solder sustained more cyclic loads in the small load region. A similar trend was detected at the thermal cycling test. A three-dimensional finite element analysis model was constructed. A finite element analysis using ABAQUS was performed to extract the applied stress and strain in the solder joints. A constitutive model which includes both creep and plasticity was employed. Thermal fatigue was occurred due to the creep. And plastic deformation is main damage for bending failure. From the inelastic energy dissipation per cycle versus fatigue life curve, it can be found that the bending fatigue life is longer than the thermal fatigue life.

• 한국자동차공학회논문집
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• 제12권4호
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• pp.181-190
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• 2004

The interest of the fatigue life of rubber components such as engine mounts is increasing according to the extension of warranty period of the automotive components. Automotive engine mounts get damaged due to thermal and mechanical loadings. This paper discusses a fatigue life prediction of the 3-dimensional dumbbell specimens for natural rubber compound considering the effects of maximum strain and heat aging temperature. Displacement controlled fatigue life tests were performed using specimens with different levels of maximum strain and various hardness. The basic mechanical properties test and the fatigue test of aged rubber specimen under normal and elevated temperature were executed. A procedure to predicted the fatigue life of vulcanized natural rubber material based on the maximum strain method was proposed, and then this curve was in good agreement with fatigue test data less than 200% error range.