• 한국산학기술학회논문지
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• 제16권7호
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• pp.4398-4404
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• 2015

스테인리스 강판은 동적기계구조물을 제작하기 위한 구조용 재료로 널리 사용된다. 또한 이들을 일체화 시키는 방법으로 가스용접을 많이 사용하게 되는데 가스용접에는 다양한 종류에 의해 구조물을 일체화 시킨다. 따라서 부재와 부재를 연결하는 용접부에 대한 응력분포 및 피로강도평가는 구조물의 건전성 및 수명을 연구하는데 매우 중요한 요소가 된다. 그래서 본 연구에서는 피로시험에 의해서 얻어지는 ${\Delta}P-N_f$ 관계를 유한요소해석법에 의해서 최대주응력으로 ${\Delta}{\sigma}-N_f$ 관계로 나타내어 피로설계기준을 정하였고, 이 결과를 이용해서 확률론적 통계해석기법을 적용해서 가속식을 추정하여 임의의 목표수명을 예측할 수 있는 신뢰성설계기술기법을 제시하고자 하였다.

• 대한기계학회논문집A
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• 제36권8호
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• pp.889-895
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• 2012

탄소섬유강화(CFRP) 복합재료는 높은 비강성과 비강도 특성을 갖고 있기 때문에 항공기, 자동차 등의 경량화가 요구되는 분야에서 금속재를 대체하여 사용 빈도가 급격히 증가하고 있다. 그 중 항공기의 경우, 동체가 고온 다습한 환경 조건에 노출되는 경우가 많기 때문에 CFRP를 이용한 항공기의 건전성 확보를 위하여 실제 환경에서의 강도 특성을 연구할 필요가 있다. 본 논문에서는 CFRP시험편을 $75^{\circ}C$의 물에 장기간 침지하였으며. 이 시험편을 이용해 침지 기간별로 인장강도를 평가하였다. 또한, SEM을 이용하여 흡습 기간에 따른 파단면의 파괴양상을 분석하였으며 300일간 침지된 시험편에 대해 응력비 R=0.1 조건으로 피로시험을 수행하여, 침지하지 않은 시험편에 비해 피로수명이 크게 저하되는 것을 확인하였다.

• 대한조선학회논문집
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• 제44권4호
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• pp.417-424
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• 2007

With regard to corrosion fatigue crack initiation life (Nc), it has been treated ambiguously for the member which doesn't have stress concentration area. In this research, in order to clarify the corrosion fatigue crack initiation life (Nc), corrosion fatigue tests were carried out. Reasonable and universal corrosion fatigue crack initiation life (Nc) was defined and corrosion fatigue crack initiation/propagation model was suggested also. As the fatigue crack which emanates from the pit is usually small, accordingly it is treated as a small crack. In addition, the observation of the corrosion fatigue fracture surfaces using SEM was conducted. And the fracture mechanics analysis using an intrinsic crack model was conducted for the treatment of the small crack. Finally, the followings were obtained. When there is no clear stress concentration point which seems to fall into a corrosion fatigue crack initiation life, the significance of the definition and suggestion of the moment of the reasonable and universal corrosion fatigue crack initiation life (Nc), at which the fatigue crack propagation rate becomes faster than the corrosion pit growth rate so that the fatigue crack initiates from the pit and propagates in earnest, has been clarified.

• 대한기계학회논문집
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• 제17권9호
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• pp.2271-2279
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• 1993

In the case of life prediction on the structures and machines after long service, it is natural to consider a degradation problems. Most of degradation data form practical structures are isolated data obtained at the time of periodical inspection or repair. From such data, it may be difficult to obtain the degradation curve available and necessary for life prediction. In this paper, for the purpose of obtaining a degradation curves, developed the simulate degradation method and fatigue test and Charpy impact test were conducted on the degraded, simulate degraded and recovered materials. Fatigue life prediction were conducted by using the relationship between fracture transition temperature (DBTT : vTrs) obtained from the Charpy impact test through the degradation process and fatigue crack growth constants of m and C obtained from the fatigue test.

• 대한기계학회논문집A
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• 제32권9호
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• pp.707-712
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• 2008

The fatigue characteristics of a material or a structure are generally derived from fatigue tests of standard specimens. However, test results of standard specimens are different from those of real structures or components. Therefore, to calculate more accurate fatigue life, the geometrical effect and surface condition must be considered by comparing test results of standard specimens with those of real structures or components. Thus the object of this paper is to evaluate the fatigue characteristics of a real waterwork pipe. Also, to evaluate fatigue characteristic based on life distribution, the statistical fatigue characteristics were analyzed by the normal distribution and related data of P-S-N curve.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2005년도 춘계학술대회 논문집
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• pp.239-245
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• 2005

Through the fatigue test of plastic gears using polyacetal polymer, this research aims at providing basic data for not only specifying operation conditions of plastic gears, but also designing dimensions of plastic gears with giving fatigue life and the estimated equation of fatigue life of plastic gears. That is, from the fatigue life curves, the estimated equation of fatigue life of plastic gears is taken out. For the estimated equation of fatigue life of plastic gears, this research provides two test methods; one is preserving non-limited temperature of tooth flank, the other is preserving limited temperature of tooth flank. As results, how the temperature of tooth flank affects the fatigue life is shown. In addition, based on the endurance limit, the essential factors of the unit load and K-factor are determined, which are needed in the design of gear by bending strength and surface durability.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2005년도 추계학술대회논문집
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• pp.143-146
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• 2005

In modern automotive control modules, mechanical failures of surface mounted electronic components such as microprocessors, crystals, capacitors, transformers, inductors, and ball grid array packages, etc., are mai or roadblocks to design cycle time and product reliability. This paper presents a general methodology of failure analysis and fatigue prediction of these electronic components under automotive vibration environments. Mechanical performance of these packages is studied through finite element modeling approach fur given vibration environments in automotive application. Using the results of vibration simulation, fatigue lift is predicted based on cumulative damage analysis and material durability information. Detailed model of solder/lead joints is built to correlate the system level model and obtain solder strains/stresses. The primary focus in this paper is on surface-mount interconnect fatigue failures and the critical component selected for this analysis is 80 pin plastic leaded microprocessor.

• 대한조선학회논문집
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• 제30권2호
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• pp.132-140
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• 1993

LNG선은 극저온의 위험한 화물을 안전하게 격납, 운송해야 하기 때문에 일반 선박에 비해서 고도의 구조설계/해석 기술이 요구된다. 따라서 본고에서는 독립형 LNG탱크의 총체적인 구조안전성 평가과정을 다루었으며 구체적으로 다음과 같은 연구내용들을 포함한다. 1) 파랑하중의 직접계산, 선체 및 탱크의 응력해석 그리고 통계해석과정을 포함하는 파랑 응력의 장기분포해석. 2) S-N approach에 의한 피로강도 평가. 3) 피로균열 전파해석 및 LBF개념에 의한 구조안전성 평가. 본 제1보에서는 (1)(2)항에 중점을 두어 시설계 LNG선에 대한 예제계산을 수행하였으며 나머지 부분은 이어지는 제2보에서 상세히 다루어질 예정이다.

• 비파괴검사학회지
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• 제33권1호
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• pp.20-25
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• 2013

열화 정도를 예측하기 위한 비파괴기법으로 초음파기법이 널리 적용되고 있다. 초음파 속도와 감쇠 특성은 일반적으로 금속재료의 물성 변화에 따라 변화하기 때문에 초음파 속도와 감쇠 특성을 이용하여 금속재료의 열화 정도를 간접적으로 예측할 수 있다. 따라서, 본 연구에서는 반복하중으로 인하여 피로파괴 발생 가능성이 높은 볼트, 리벳 접합의 구조용재 및 선박 차량에 사용되고 있는 Al6061-T6을 피로수명의 0%, 55%, 70%, 85%인 시험편을 제작하였고, 가공된 시험편의 감쇠 특성을 이용하여 측정된 열화 이미지로 Al6061-T6의 건전부와 열화부를 판단하였으며, 건전부와 열화부의 감쇠 특성 차이를 계산하여 Al6061-T6의 열화 진행 정도를 평가하였다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 추계학술대회
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• pp.160-165
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• 2004

An effective integrity evaluation system is essential to manage the fitness for service issues on infra-structure because the evaluation processes usually take long times and are detrimental for productivity point of view. In this paper, the key structures and procedures of four integrity evaluation programs which have been developed based on currently available codes and standards are described. The proposed programs are not only flexible to adopt advances in fitness for purpose type assessment methodologies but also convenient for field engineers. The developed programs which will be unified as an integrity evaluation system are expected to play a prominent role for integrity evaluation of major infra-structure.