• 한국신뢰성학회지:신뢰성응용연구
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• 제15권4호
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• pp.241-247
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• 2015

Purpose : The demand for higher fuel economy vehicles has helped develop fuel-efficient vehicles such as a CVVL called continuous variable valve lift. Existing CVVL has been applying DC type motor to control intake valve, but recently some car parts manufacturers have been developing a BLDC type CVVL motor for improvements of endurance performance. The purpose of this study is to find the potential failure mechanism of the CVVL BLDC moto in early stage of development based on the design properties and design the accelerated life test model. Methods : CVVL BLDC is consist of brushs, coil, magnetic, PCB, bearing and so on. Each component has a latent failure mechanism caused by temperature, humidity, vibration. By analysis result of the failure mechanism, thermal fatigue is the most important factor of a durability of CVVL BLDC motor. So, we designed a new accelerated life test model for guarantee of the CVVL BLDC motor. Results : A crack occurred on via hole in test using the conditions we designed, so we did change the design to avoid this failure. The via hole dimension is changed a little larger, as a result we achieve improvements in reliability of the CVVL BLDC motor. By applying various kinds and extreme level of stresses, we can find the operating limits of products. Conclusion : In thesis, We analyzed the failure mechanism of CVVL BLDC and designed an accelerated life test method to give a guarantee for reliability. Based on the test results, we could improve the reliability of developments by change of design.

• 한국인터넷방송통신학회논문지
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• 제14권5호
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• pp.215-221
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• 2014

본 논문에서는 RF 고전력 스트레스에 의한 SAW 디바이스의 신뢰성 분석을 위하여 향상된 내전력 시험시스템 및 시험방법을 제안하고 고장분석을 통해 고장메카니즘을 분석하였다. 광학현미경, SEM(Scanning Electron Microscope) 및 EDX(Energy Dispersive X-ray Spectro-scopy)장비를 이용하여 고장 분석한 결과, SAW 디바이스의 고장메카니즘은 고전류 밀도 및 고온 조건에서 줄열에 의한 Electromigration으로 분석하였다. Electromigration은 IDT전극에 void와 hillock을 생성하고, 그 결과로 전극이 단락과 단선되어 삽입손실이 증가하는 것이다. 제안된 내전력 시험시스템과 방법을 이용하여 450MHz CDMA용 SAW 필터의 가속수명시험을 수행하고, 아이링 모델과 와이블 분포를 이용하여 SAW 필터의 $B_{10}$수명은 98,500시간으로 추정하였다.

• Hip & pelvis
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• 제35권3호
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• pp.175-182
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• 2023

Purpose: This study aims to compare patients in whom fixation failure occurred via cut-out (CO) or cut-through (CT) in order to determine patient factors and radiographic parameters that may be predictive of each mechanism. Materials and Methods: This retrospective cohort study includes 18 patients with intertrochanteric (IT) hip fractures (AO/OTA classification 31A1.3) who underwent treatment using a single lag screw design intramedullary nail in whom fixation failure occurred within one year. All patients were reviewed for demographics and radiographic parameters including tip-to-apex distance (TAD), posteromedial calcar continuity, neck-shaft angle, lateral wall thickness, and others. Patients were grouped into cohorts based on the mechanism of failure, either lag screw CO or CT, and a comparison was performed. Results: No differences in demographics, injury details, fracture classifications, or radiographic parameters were observed between CO/CT cohorts. Of note, a similar rate of post-reduction TAD>25 mm (P=0.936) was observed between groups. A higher rate of DEXA (dual energy X-ray absorptiometry) confirmed osteoporosis (25.0% vs. 60.0%) was observed in the CT group, but without significance. Conclusion: The mechanism of CT failure during intramedullary nail fixation of an IT fracture did not show an association with clinical data including patient demographics, reduction accuracy, or radiographic parameters. As reported in previous biomechanical studies, the main predictive factor for patients in whom early failure might occur via the CT effect mechanism may be related to bone quality; however, conduct of larger studies will be required in order to determine whether there is a difference in bone quality.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1999년도 학회창립 10주년 기념 1999년도 가을 학술발표회 논문집
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• pp.609-612
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• 1999

This study presents the plastic analysis for the flexural and shear strength of RC beams related to anchorage failure. Five failure mechanisms based on the upper bound solution were constructed and the ultimate strength equations were formulated from them. The parametric study herein was carried out to observe the variation of the controlling failure mechanism depending on the parameters in the ultimate strength equations. The results of the parametric study show that controlling failure mechanism and ultimate strength are determined through the interaction of each parameter. This indicated that respective structural configuratins must be treated in a unified manner. Additionally this study proposes the scope of the parameter to induce the flexural of RC deep beams.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1999년도 봄 학술발표회 논문집(I)
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• pp.750-755
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• 1999

When the RC frame structures subjected to the seismic load, brittle shear failure of vertical members induces brittle collapse of whole structures. Failure mechanism like this is not desirable. So shear strengthening method to avoid this failure mechanism is needed. Recently, strengthening method using continuous fiber sheet is studied and used widely which have high elastic and high strength characteristics. In this study, RC columns which is strengthened by carbon fiber sheet in the form of tape or whole sheet were tested under the cyclic load. The parameter of this test is the amount of strengthening. As the amount of strengthening increase, strength, ductility and energy capacity increase. The failure mode of test results are shear and bond-split failure.

• 한국신뢰성학회지:신뢰성응용연구
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• 제6권2호
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• pp.173-186
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• 2006

This paper presents a study on the failure mechanism for optical engine of Projection TV. The lenses of which optical engine composes are failed by various environmental conditions, that is, thermal effect, moisture effect, mechanical shock or chemical effect. By surveying on actual TV working condition, the major factor of failure was turned out the thermal effect. Because the actual surface temperature of optical engine rose at max. $51^{\circ}C$ during it worked, the relative humidity around optical engine was kept at less than 20% that is difficult to do chemical reaction with humidity. Therefore we can make a conclusion that the major failure of optical engine resulted from thermal effect.

• Geomechanics and Engineering
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• 제11권2호
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• pp.253-267
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• 2016

The stability of surrounding rock will be poor when the tunnel is excavated through nearly horizontal stratum. In this paper, the instability mechanism of local nearly horizontal stratum in super-large section and deep buried tunnel is revealed by the analysis of the macro failure and micro fracture. A structural model is proposed to explain the mechanics of surrounding rock collapse under the action of stress redistribution and shed light on the macroscopic analytical approach of the stability of surrounding rock. Then, some highly effective formulas applied in the tunnel engineering are developed according to the theory of mixed-mode micro fracture. And well-documented field case is made to demonstrate the effectiveness and accuracy of the proposed analytical methods of mixed-mode fracture. Meanwhile, in order to make the more accurate judgment about yield failure of rock mass, a series of comprehensive failure criteria are formed. In addition, the relationship between the nonlinear failure criterion and $K_I$ and $K_{II}$ of micro fracture is established to make the surrounding rock failure criterion more comprehensive and accurate. Further, the influence of the parameters related to the tension-shear mixed-mode fracture and compression-shear mixed-mode fracture on the propagation of rock crack is analyzed. Results show that ${\sigma}_3$ changes linearly with the change of ${\sigma}_1$. And the change rate is related to ${\beta}$, angle between the cracks and ${\sigma}_1$. The proposed simple analytical approach is economical and efficient, and suitable for the analysis of local nearly horizontal stratum in super-large section and deep buried tunnel.

• 한국지반공학회지:지반
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• 제13권6호
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• pp.139-146
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• 1997

기초파괴는 일반적으로 변형이 집중되어 하나 또는 그 이상의 파괴면이 발생되어, 기초의 관입과 더불어 파괴면은 점진적으로 형성된다. 본 논문의 목적은 수치적으로 기초의 극한지지력 및 진행성 파괴거동을 파악할 수 있는가 하는 가능성을 검토하는데 있다. 대변형이론과 변형률 연화이론을 사용하여 비배수 상태인 점토지반의 기초에 대한 진행성 파괴거동에 대하여 분석하였다. 본 논문에서는 기초의 진행성 파괴과정과 완전한 하중 변위곡선을 해석하기 위한 수치해석 방법에 대하여 논하였다. 해석결과, 띠기초의 피크 이후의 지반파괴거동 및 진행성 파괴과정에 대한 명확한 수치적 해석가능성을 보여주었다.

• Geomechanics and Engineering
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• 제13권1호
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• pp.63-77
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• 2017

The failure mechanism of a deep hard rock tunnel under high geostress and high geothermalactivity is extremely complex. Uniaxial compression tests of granite at different temperatures were conducted. The complete stress-strain curves, mechanical parameters and macroscopic failure types of the rock were analyzed in detail. The brittleness index, which represents the possibility of a severe brittleness hazard, is proposed in this paperby comparing the peak stress and the expansion stress. The results show that the temperature range from 20 to $60^{\circ}C$ is able to aggravate the brittle failure of hard rock based on the brittleness index. The closure of internal micro cracks by thermal stress can improve the strength of hard rock and the storage capacity of elastic strain energy. The failure mode ofthe samples changes from shear failure to tensile failure as the temperature increases. In conclusion, the brittle failure mechanism of hard rock under the action of thermal coupling is revealed, and the analysis result offers significant guidance for deep buried tunnels at high temperatures and under high geostress.

• 한국방재학회:학술대회논문집
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• 한국방재학회 2007년도 정기총회 및 학술발표대회
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• pp.263-266
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• 2007

In this paper, analysis results on the failure of slope behind a Plant Complex of Gimhae due to typhoon Rusa in 2002 are introduced. The left side of the slope was reinforced by soil nails and the right side of the slope was going to construct slope reinforcement works. In the slope failure, the damage area is about $34,000m^2$, the lower width of slope failure is about 230m, the upper width of slope failure is about 50m, and the height of slope failure is about 120m. The elevation of a bedrock in the right side of the slope was lower than the left side of the slope. Due to the depth of weathered soils and weathered rocks in right side of the slope was thick, it will be expected that the effects of pore-water pressure during the rainfalls are large. For the analysis of the failure mechanism, 3-dimensional numerical analysis was carried out by FLAC-3D.