• Journal of the korean Society of Automotive Engineers
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• v.13 no.6
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• pp.101-108
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• 1991

During torsional fatigue of externally cracked cylindrical specimen, crack face rubbing may occur. At this time, normal contact forces arise when shear displacements cause the crack faces to be wedged open due to mismatch of the fracture surface asperities. These normal forces, in turn, generate friction force which act in opposition to the applied shear stresses and reduce the effective stress intensity factor. The premise of the proposed work is that friction and wedging can be studied by measuring the shear and normal displacement across the crack mouth. We have measured the crack mouth compliance using the new biaxial extensometer.

• Structural Engineering and Mechanics
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• v.37 no.3
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• pp.257-265
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• 2011

Plant-specific analyses of 5 types of domestic reactors in Korea are performed to assure the structural integrity of the reactor pressure vessel (RPV) during transients which are expected to initiate pressurized thermal shock (PTS) events. The failure probability of the RPV due to PTS is obtained by performing probabilistic fracture mechanics analysis. The through-wall cracking frequency is calculated and compared to the acceptance criterion. Considering the fluence at the end of life expected by surveillance test, the sufficient safety margin is expected for the structural integrity of all reactor pressure vessels except for the oldest one during the pressurized thermal shock events. If the flaw with aspect ratio of 1/12 is considered to eliminate the conservatism, the acceptance criteria is not exceeded for all plants until the fluence level of $8{\times}10^{19}\;n/cm^2$, generating sufficient margin beyond the design life.

• Journal of the Society of Naval Architects of Korea
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• v.29 no.2
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• pp.79-91
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• 1992

This paper develops the compliance approach to the problem of load sharing between a cracked plate and a patch used to bridge the crack. The theory is validated by using calculated stress intensity factors for the patched and unpatched case to reduce experimentally observed growth rates to common base, Calculations are then made on the effect of patch dimension on fatique life technique. The optimum design of the patch considered the life expectancy and fracture strength of the cracked structure can be performed simply by using this technique.

• International Journal of Precision Engineering and Manufacturing
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• v.9 no.4
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• pp.66-70
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• 2008

The propagation of a mixed-mode crack in soda-lime silica glass is modeled by movable cellular automata (MCA). In this model, a special fracture criterion is used to describe the process of crack initiation and propagation. The results obtained using the MCA criterion are compared to those obtained from other crack initiation criteria, The crack resistance curves and bifurcation angles are determined for various loading angles. The MCA results are in close agreement with results obtained using the maximum circumferential tensile stress criterion.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2007.04a
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• pp.99-104
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• 2007

In this paper a dynamic behavior(natural frequency) of a cracked cantilever beam with tip mass and follower force is presented. In addition. an analysis of the flutter and buckling instability of a cracked cantilever beam subjected to a follower compressive load is presented. Based on the Euler-Bernouli beam theory, the equation of motion can be constructed by using the Lagrange's equation. The vibration analysis on such cracked beam is conducted to identify the critical follower force for flutter ins stability based on the variation of the first two resonant frequencies of the beam. Besides. the effect of the crack's intensity and location on the flutter follower force is studied. The crack section is represented by a local flexibility matrix connecting two undamaged beam segments. The crack is assumed to be in the first mode of fracture and to be always opened during the vibrations.

• Proceedings of the KSR Conference
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• 2004.10a
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• pp.595-600
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• 2004

The EMU wheel is one of the most important component for the vehicle safety. For the tensile, fracture toughness and crack propagation tests, several specimens were collected from actual wheels. FEM ,analysis also was performed on the crack that was assumed to be 15 mm in depth under the wheel tread surface. The stress intensity factors $K_{I}$ and $K_{II}$ at the crack tip under the stress ($P_{max}$ = 911.5 MPa) due to a rolling contact were analyzed for crack growth characteristics. As a result, the perpendicular crack was found to be more dangerous compared to the parallel one.

• Journal of Ocean Engineering and Technology
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• v.2 no.1
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• pp.116-124
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• 1988

해양구조물의 원통조인트에 대한 피로 수명 산출이 전통적으로 실험적 방법에만 의존해 왔음은,원통조인트의 구조가 복잡하여 용접부위 균열의 응력확대 계수 계산이 거의 불가능 했든 것이 주 원인이었다. 최근에 유한요소 3차원 모델을 이용한 계산방법이 개발되어 심히 구조적으로 복잡한 표면 균열의 응력확대계수 산출이 용이하게 되었다. 해양 구조물의 원통조인트에 대한 피로 수명 산출법을 개발하기 위한 연속되는 3부작의 제1부로서 본 논문은 X형 원통 조인트 용접주위 표면 균열의 응력확대 계수 거동을 분석하고 있다. 분석결과를 이용하여 응력확대계수를 엄격한 방법에 의해 계산하였다. 계산된 응력확대계수를 구조적인 관점에서 해석하고 있다.

• Journal of the Korean Society of Safety
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• v.25 no.6
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• pp.161-168
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• 2010

A series of fatigue tests have been performed on the non-load carrying fillet welded joints in order to quantitatively assess the fatigue characteristics due to the grindings and TIG(Tungsten Inert Gas) welding treatments. From the results of fatigue tests, it has been shown that the fatigue strengths at $2{\times}106$ load cycles were improved in the case of the grinding sand TIG welding treatments, and we could know that it is satisfying fatigue strength prescribed in fatigue design standard in general. Besides, from the results of fracture mechanics approaches, the geometric shape correction factors were the most dominant factors in the initial fatigue crack growth, but as the fatigue crack develops, the finite plate correction factor were became the most dominant factor, and the fatigue life on non-load carrying fillet welded joints could be relatively exactly estimated by using the relations between fatigue crack growth rate and stress intensity factor obtained from finite element analysis and existing proposed formulae.

• Journal of the Korean Society of Safety
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• v.25 no.6
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• pp.1-8
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• 2010

P-PIE program is developed for evaluating failure probability of pipes in nuclear power plants based on the existing PRAISE program. In the program, crack growth due to fatigue loading and stress corrosion can be considered and the probability of fracture or leakage of pipes can be calculated. Crack growth simulation is performed based on stress intensity factor and a damage parameter and failure of a pipe is determined based on J integral or net section yielding. Using the developed program the failure probabilities of tubes in a domestic nuclear power is obtained and discussed.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2005.05a
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• pp.191-196
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• 2005

The effects of shot peening on the fatigue strength of SK-5M steel is investigated by experiment. The shot peening process is investigated optimum peening condition by changing impeller speed and exposure time. Bending fatigue test is accomplished to investigate the effect of optimum peening condition on the fatigue characteristics. As exposure time is increased, fatigue life in high stress is increased in early stage, become the maximum from 60 to 100 seconds, and then is decreased. Observing fracture surface through SEM after fatigue test, we can see clear configuration of cracks and peening layer.