• 한국철도학회:학술대회논문집
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• 한국철도학회 2007년도 춘계학술대회 논문집
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• pp.395-403
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• 2007

Railroad track consists of relatively simple structures such as rail, sleeper, ballast. Roadbed shares vertical pressure by train load which passed through rail to ballast as base that supports the track. For evaluating stress and displacement of roadbed due to the railroad load is an important role on the track as a basic data for estimation of the durability and design of the roadbed thickness. GEOTRACK program applied multi-layered theory was developed for analyzing railroad track structure. GEOTRACK program is a sort of numerical analysis program which has advantage that can analysis component of track by simple method. In this study, this program was used to preform the numerical analysis by changing track conditions and roadbed conditions such as tie, reinforced roadbed, dynamic wheel load, Resilient modulus and so on. Further detail will be presented on the paper.

• 한국자동차공학회논문집
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• 제11권2호
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• pp.140-147
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• 2003

Full scale durability test in the laboratory is an essential of any fatigue life evaluation of components or structures of the automotive vehicle. Component testing is particularly important in today's highly competitive industries where the design to reduce weight and production costs must be balanced with the necessity to avoid expensive service failure. Generally, hydraulic road simulator is used to carry out the fatigue test and the vibration test. In this paper, the link unit which is able to realize the 3 element forces such as vertical force, lateral force, and longitudinal force that are applied to the road simulator is designed. Also, the designed link is verified with kinematics and inverse-kinematics. From this results, the designed factor satisfied the maximum stroke so that it satisfied the requirements for 3-axial road simulator.

• 한국자동차공학회논문집
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• 제7권8호
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• pp.262-271
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• 1999

To design suspension system and estimate its durability , the loading history of each suspension part exposed to various operation conditions should be known from either measurement or computations. Based on these results, stress analysis is carried out to obtain the optimal shape and to reduce the production cost through the proper selection of manufacturing process. In this paper, first the measurement of 3-directional accelerations of wheel center using an accelerometer are undertaken from a vehicle running on Belgian road. Then the data measured from experiments are pre-processed with filtering . Based on the pre-processed data the methodology for determining the dynamic loading to each suspension part is developed by simply modeling the suspension system with ADAMS software. Eventually , it is expected that dynamic loadings can be used for the dynamic stress and fatigue analyses.

• Journal of Magnetics
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• 제18권4호
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• pp.473-480
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• 2013

A new concept design of electromagnetic energy harvester is proposed for powering a tire pressure monitoring sensor (TPMS). The thin coil strap is attached on the circumferential surface of a rim and a permanent magnet is placed on the brake caliper system. When the wheel rotates, the relative motion between the magnet and the coil generates electrical energy by electromagnetic induction. The generated energy is stored in a storage unit (rechargeable battery, capacitor) and used for TPMS operation and wireless signal transmission. Innovative layered design of the strap is provided for maximizing energy generation. Finite Element Method (FEM) and experiment results on the proposed design are compared to validate the proposed design; further, the method for design improvement is discussed. The proposed design is excellent in terms of durability and sustainability because it utilizes the everlasting rotary motion throughout the vehicle life and does not require material deformation.

• 한국신뢰성학회지:신뢰성응용연구
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• 제17권3호
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• pp.197-206
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• 2017

Purpose: Clarify the cause of the noise by the front wheel strut insulator, which is located in close proximity to the driver's seat. Methods: The improvement mechanism was confirmed through failure analysis and reproduction test of the joint generation mechanism. In addition, the main factors were analyzed through principal test. Results: This paper describes the mechanism of occurrence of noise due to deterioration and hardness increase of rubber, deformation on severe road surface, foreign matter and water inflow in cold weather. Conclusion: We found that the insulator and body deformation can be minimized without increasing the thickness of the body and the insulator and reinforcing the body by dispersing the input load by applying load distribution structure instead of the local forming structure of the insulator in the insulator robust structure.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2006년도 추계학술대회 논문집
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• pp.494-507
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• 2006

The major objective of this study is to investigate the dynamic behaviors of track due to the deterioration characteristics of ballast for servicing tracks by the field test. The durability of ballast plays an important role in the track behaviour. To estimate the deterioration characteristics of ballast, several tests have been carried out by several scholars. The deterioration characteristics of ballast is one of the most important factor in the dynamic behaviour of track and its life. In this paper abrasion/breakage characteristics of ballast is studied to predict the effect of physical ballast characteristics on ballast track. To reveal deterioration characteristics of ballast, the field test were carried out. The deterioration characteristics, studied in this paper, is applied to the dynamic behaviour of track in various conditions.

• 한국군사과학기술학회지
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• 제10권3호
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• pp.173-180
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• 2007

In this paper, we have proposed a simple finite element model for separation mode analysis on the roadwheel and track assembly of main battle tank and established a contact stress-based mechanism which could explain the initiation and growth of separation defect occurred during the test of padreplacable track. It was proved that the longitudinal contact shear stress component on the pin hole region of the track shoe body which is parallel to the driving direction is consistent with the crack initiation at the bonding surface between track shoe and wheel-side rubber. The longitudinal shear stress increased locally near the separated region after the separation initiated. So we could assume that the local stress concentration accelerates the separation growth according to the shear mode.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2016년도 제50회 동계 정기학술대회 초록집
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• pp.397-397
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• 2016

Triboelectric nanogenerators (TENG) can produce power from ambient mechanical sources and have strong points of high output performance, light weight, low cost, and easy manufacturing process. It is expected that TENG can be utilized in the fields of wireless electronics and self-powered devices in the world which pays attention to healthcare and the IoT. In this work, we focus on scavenging ambient rotational energy by using a durably designed TENG. In previous studies regarding harvesting rotation mode energy, the devices were based on sliding mechanism and durability was not considered as a major issue. However friction by rotation causes reliability problems due to wear and tear. Therefore, in this study, we convert rotary motion to linear motion utilizing a cam by which we can then utilize contact-mode TENG and improve device reliability. In order to increase output performance, bumper springs were used below the TENG and the optimum value for the bumper spring constant was analyzed theoretically. Furthermore, the inserting a soft substrate was proposed and its effect on high output was determined to be due to an increase in the contact area. By increasing the number of cam noses, the output frequency was shown to increase linearly. For the purpose of maximum power transfer, the input impedance of the device was determined. Finally, to demonstrate the use of the C-TENG as a direct power source, it was installed on a commercial bicycle wheel and connected to 180 LEDs. In conclusion we present a rotational motion TENG energy scavenger system designed for enhanced durability and optimized output by appropriate choice of spring constants and substrate.

• 한국주조공학회지
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• 제38권2호
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• pp.48-54
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• 2018

To improve the durability of the turbocharger, it is important to suppress cracking of the turbine housing; therefore, we investigated the initiation and growth of these cracks. First, we initiated a crack in the turbine housing using endurance experiments. After the endurance test, cracks mainly occurred in the valve seat, the nozzle area, and the scroll part of the turbine housing. The results of a fracture analysis of the cracks showed that cracks in the valve seat were initiated by fatigue fracture. This seems to be caused by the accumulation of mechanical and thermal stresses due to vibration of the turbine wheel and high-temperature exhaust gas. Also, cracks in nozzle and scroll area were initiated by intergranular corrosion due to the exhaust gas. Thus, although there are differences in the cause of initiation according to the site, a concentric waveform was observed in all fracture planes. This phenomenon indicates that cracks gradually grow due to repeated stress changes, and the main causes are the temperature difference of the exhaust gas and the vibration caused by the turbine shaft.

• Composites Research
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• 제21권1호
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• pp.40-45
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• 2008

자동차용 유압브레이크 고무호스 어셈블리 제품은 자동차에 장착되어 실제로 사용 중에 가압, 굽힘, 비틀림, 열하중 등의 복합적인 스트레스를 받는다. 고무호스의 재질은 EPDM(ethylene-propylene diene monomer)고무와 PVA(polyvinyl acetate)섬유 보강층 그리고 중간고무로 NR(natural rubber)고무가 사용되고 있다. 고무호스 어셈블리 제품의 내구성과 파괴 메커니즘을 조사하기 위해 굽힘과 비틀림의 반복하중 사이클 수가 10만, 20만, 30만, 40만, 최종파열 사이클 수까지 되도록 시험하였다. 유압브레이크 고무호스의 초기크랙 발생을 알아보기 위해 제품 시험편을 다이아몬드 휠커터를 이용하여 수직 절단하여 폴리싱한 후 광학현미경과 주사형 전자현미경(SEM)으로 단면을 관찰하였다. 40만 사이클의 피로하중을 받은 시험편을 보면 외면고무와 PVA섬유 사이의 계면을 따라 길이 1mm의 층간분리가 일어났으며, 이러한 손상은 외면고무의 표피층으로 균열을 진전시켜 고무호스를 최종적으로 찢어지게 하는 것이다.