• Journal of the Korean Society for Railway
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• v.10 no.5
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• pp.546-553
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• 2007

The objective of the present paper is to evaluate the effect of the evolution of contact surface profile by fretting wear on the contact stress distribution and fatigue crack initiation site of press-fitted shaft by means of an analytical method based on experimental data. A finite element analysis was performed to analyze the stress states of press-fitted shaft, considering the worn contact surface profiles of shaft. The evolutions of contact stress as wearing of contact surface were analyzed by finite element analysis and fatigue crack nucleation sites were evaluated by fretting fatigue damage parameter (FFDP) md multiaxial fatigue criteria. It is found that the stress concentration of a contact edge in press-fitted sha손 decreases rapidly at the initial stage of total fatigue life, and its location shifts from the contact edge to the inside due to fretting wear as increasing of fatigue cycles. Thus the transition of crack nucleation position in press-fitted shaft is mainly caused by stress change of a contact edge due to the evolution of contact surface profile by fretting wear. Therefore, it is suggested that the nucleation of multiple cracks on fretted surface of press fits is strongly related to the evolution of surface profile at the initial stage of total fatigue life.

• Journal of Aerospace System Engineering
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• v.11 no.2
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• pp.16-22
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• 2017

This paper investigates fretting wear damage in aerospace, biomedical, and nuclear components. Experimental parameters are identified that affect fretting wear damage. The parameters observed in industries are directly compared. The magnitudes of frequency, relative displacement, and normal force are found to differ depending on the contacting components where fretting wear occurs. In addition, recent solutions to minimize fretting wear damage are reviewed. The solutions include depositing of a low-friction coating, surface treatment, selection of substrate material, and optimal design of contact geometries. This comparative study suggests useful methods and solutions for analyzing fretting wear damage and for designing tribo-components.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.37 no.7
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• pp.642-652
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• 2009

Most of lap jointed aircraft structures encounter the fretting damages, which provoke fretting cracks prematurely and lead to significant reduction of fatigue life. In the case of ageing aircrafts especially, this fretting fatigue problem is a fatal threat for the safety and airworthiness. Recently, as the service life extension program(SLEP) of ageing aircrafts has become a hot issue, the prediction of fretting fatigue life is also indispensable. On these backgrounds, a series of experimental tests of fretting fatigue on bolted lap joint specimens, were performed. And the fretting crack initiation and propagation life of each specimen were evaluated using existing and newly proposed prediction models with the fretting parameters obtained from the FEA results for elasto-plastic contact stress analyses. The validations of prediction models were also discussed, comparing the prediction results with experimental test ones.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.35 no.7
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• pp.601-611
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• 2007

Most of mechanically jointed aircraft structures are always encountered the fretting damages on the contact surfaces between two jointed structural members or at the edges of fastener holes. The partial slip and contact stresses associated with fretting contact can lead to severe reduction in service lifetime of aircraft structures. Thus a critical need exists for predicting fretting crack initiation in mechanically jointed aircraft structures, which requires characterizing both the near-surface mechanics and intimate relationship with fretting parameters. In this point of view, a series of fretting fatigue specimen tests for 2024-T351 Al-alloy, have been conducted to validate a mechanics-based model for predicting fretting fatigue life. And included in this investigaion were elasto-plastic contact stress analyses using commercial FEA code to quantify the stress and strain fields in subsurface to evaluate the fretting fatigue crack initiation.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.2
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• pp.167-175
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• 2014

If volumetric flaws such as bearing pad fretting flaws and debris fretting flaws are detected in the pressure tubes of pressurized heavy water reactors during in-service inspection, the initiation of fatigue cracks and delayed hydrogen cracking from the detected volumetric flaws shall be assessed by using elastic stress concentration factors in accordance with CSA N285.8-05. The CSA N285.8-05 presents only an approximate formula based on linear elastic fracture mechanics for the debris fretting flaw. In this study, an engineering formula considering the geometric characteristics of the debris fretting flaw in detail was derived using two-dimensional finite element analysis and Kinectrics, Inc.'s engineering procedure with slight modifications. Comparing the application results obtained using the derived formula with the three-dimensional finite element analysis results, it is found that the results obtained using the derived formula agree well with the results of the finite element analysis.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.8
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• pp.951-956
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• 2011

Inconel alloys are generally used as steam generator tubes in nuclear power plants. These alloys are highnickel chromium alloys that exhibit excellent resistance to aqueous corrosion. In this paper, the effects of elevated temperatures such as an operating temperature of $320^{\circ}C$ on the fretting fatigue behavior of inconel 600 and 690. We observed that the plain and fretting fatigue limits at $320^{\circ}C$ were slightly lower than those at room temperature. The frictional forces varied depending on the number of load cycles. After each test, we studied the fretting fatigue mechanisms via SEM observations. These results can be used for structural integrity evaluations at elevated temperatures and for studying fretting damage in steam generator systems.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.8 no.4
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• pp.713-720
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• 2007

Grating is an installed structure on the road for drain. This paper proposes a new product which can prevent the accumulation of earth and sand through the improvement of Grating structure. There were usually harmful insects and bad smell because of accumulated garbage in the frame of previous product. The whole thing of the existing. This study is to separate grating from body. Also body structure consists of frame and box for collecting sewage. Thus, earth and sewage are prevented from accumulating in the drain main hole. The contents of this study is designed safely after structure analysis and vibration shape analysis about new products.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.1
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• pp.49-54
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• 2010

Fretting wear behavior under elastic deformable contacts was experimentally examined by using a simulated dual cooled fuel rod and its supporting structure. As this fuel rod has larger outer diameter than the typical solid rod to accommodate sufficient internal flow, new supporting structure geometries should be designed and their reliabilities (i.e. vibration characteristics, fretting wear resistance, etc.) are also examined with both analytical and experimental methods. In this study, the supporting structure characteristics and fretting wear behaviors are analyzed and examined by using one of the supporting structure candidates which has an embossing shape. The supporting structure characteristics were examined by using a specially designed test rig and their results were compared with that of analytical method. Based on the test results, the relationship between the supporting structure characteristics and their fretting wear behaviors was discussed in detail.

• Proceedings of the Korean Society of Computer Information Conference
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• 2015.07a
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• pp.9-10
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• 2015

최근 임베디드 소프트웨어는 전자기기뿐만 아니라 의료기기, 자동차, 항공 등 광범위하게 적용되고 있다. 임베디드 소프트웨어의 규모가 커지는 만큼 비중도 높아지고 있어 임베디드 소프트웨어 테스팅의 비중도 높아지고 있다. 따라서 본 논문에서는 디버깅 도구인 GDB를 테스팅에 과정에 연계하여 현재 실행중인 프로세스에서 겸사하고자 하는 단위 소프트웨어의 스택 프레임으로부터 정보를 얻어 단위 테스팅 수행이 가능한 구조를 제안한다. 이를 통해 별도의 코드를 수정하지 않고도 단위 테스팅이 가능해지며 런타임 테스팅과 자동 단위 테스팅이 가능해진다.

• Proceedings of the KSME Conference
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• 2005.11a
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• pp.112.2-112.2
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• 2005