• Journal of Korean Neurosurgical Society
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• 제38권4호
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• pp.259-264
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• 2005

Objective : The vertebroplasty is an excellent procedure in spine compression fracture, but there are some problems such as cement leakage and difficulties in bone biopsy. Recently, the osteoplasty system is developed to solve these problems, so we will report the usefulness of the osteoplasty system. Methods : From January 2003 to November 2003, there are 9patients with simple osteoporotic spine compression fracture, 2 compression fracture patients combined with suspicious spinal metastasis, 1patient with suspicious primary bone tumor, and 2patient with infection on spine. All patients were treated using the osteoplasty system. Results : All 11 compression fracture patients were relived the back pain after the osteoplasty and there is no complication. The bone biopsies in 3 suspicious cancer patients were also effectively performed using the osteoplasty system; negative result in 2patients and positive result in 1patient. The culture result of spontaneous discitis was no growth for 48hours. The spine tuberculosis was confirm using the osteoplasty system. Conclusion : The osteoplasty system has distinguished advantages in comparison with the vertebroplasty. That is, the risk of cement leakage is lower than vertebroplasty because of low pressure delivery system. And we can obtain the specimen effectively in bone biopsy because of large cannula. In conclusion, we emphasize that the osteoplasty system is a more useful procedure in spine compression fracture especially in the patient needed bone biopsy for diagnosis.

• 한국압력기기공학회 논문집
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• 제11권1호
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• pp.69-73
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• 2015

The study investigated effects of residual stresses and Charpy impact energy on brittle fractures of the butt weld between the valve and the piping, and of the valve body in nuclear power plants via a linear elastic fracture mechanics approach in the ASME B&PV Code, Sec.XI and finite element analysis. Weld residual stress in a butt weld between close check valve and piping, and residual stress in the valve due to casting process were assumed to be proportional to yield strength of base metal. Operating stresses in the butt weld and the valve body were calculated using approximate engineering formulae and finite element analysis, respectively. Applied stress intensity factors were calculated by assuming postulated cracks with specific sizes and then by substituting the residual stresses and the operating stresses into engineering formulae presented in the ASME B&PV Code, Sec.III. Plane strain fracture toughness was derived by using a correlation between Charpy V-notch impact energy and fracture toughness. Structural integrity of the weld and the body against brittle fracture was assessed by using the applied stress intensity factors, plane strain fracture toughness and the linear elastic fracture mechanics approach. As a result, it was identified that the structural integrity was maintained with decreasing the residual stress levels and increasing the Charpy V-notch impact energy.

• Nuclear Engineering and Technology
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• 제21권3호
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• pp.165-170
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• 1989

준 동적 파괴가 일어나는 변형율속도 조건에서 A533B-1 원자로 압력용기강의 파괴인성 및 파괴저항특성에 미치는 변형율속도의 영향을 균열선단의 강 소성역 관찰 및 파면의 미세거칠기측정을 통해 연구하였다. 1/2T-CT 파괴시편에서 약 1.5mm 이하의 균열진전에 대해서는 소성일로 부터 구한 J와 수정 J가 거의 일치하였다. 파면의 미세거칠기로부터 구한 국부 변형율은 1.8-2.0 정도의 값을 나타내어 거시적으로 측정된 값보다 높은 값을 보여주었다. 이들 방법은 모두 변형율속도가 증가함에 따라 파괴인성은 증가하나 tearing modulus는 큰 변화가 없음을 보여주었다.

• 대한금속재료학회지
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• 제47권9호
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• pp.533-541
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• 2009

Materials used for a reactor pressure vessel(RPV) are required high strength and toughness, which determine the safety margin and life of a reactor. Ni-Mo-Cr low alloy steel shows better mechanical properties than existing RPV steels due to higher Ni and Cr contents compared to the existing RPV steels. The present study focuses on effects of Ni, Cr contents on the cleavage fracture toughness of Ni-Mo-Cr low alloy steels in the transition temperature region. The fracture toughness was characterized by a 3-point bend test of precracked Charpy V-notch(PCVN) specimens based on ASTM E1921-08. The test results indicated that the fracture toughness was considerably improved with an increase of Ni and Cr contents. Especially, control of Cr content was more effective in improving fracture toughness than manipulating Ni content, though Charpy impact toughness was changed more extensively by adjusting Ni content. These differences between changes in the fracture toughness and that in the impact toughness were derived from microstructural features, such as martensite lath size and carbide precipitation behavior.

• Geomechanics and Engineering
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• 제30권6호
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• pp.503-515
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• 2022

The permeability coefficient is an essential parameter for the study of seepage flow in fractured rock mass. This paper discusses the feasibility and application value of using readily available RQD (rock quality index) data to estimate mine water inflow and grouting quantity. Firstly, the influence of different fracture frequencies on permeability in a unit area was explored by combining numerical simulation and experiment, and the relationship between fracture frequencies and pressure and flow velocity at the monitoring point in fractured rock mass was obtained. Then, the stochastic function generation program was used to establish the flow analysis model in fractured rock mass to explore the relationship between flow velocity, pressure and analyze the universal law between fracture frequency and permeability. The concepts of fracture width and connectivity are introduced to modify the permeability calculation formula and grouting formula. Finally, based on the on-site grouting water control example, the rock mass quality index is used to estimate the mine water inflow and the grouting quantity. The results show that it is feasible to estimate the fracture frequency and then calculate the permeability coefficient by RQD. The relationship between fracture frequency and RQD is in accordance with exponential function, and the relationship between structure surface frequency and permeability is also in accordance with exponential function. The calculation results are in good agreement with the field monitoring results, which verifies the rationality of the calculation method. The relationship between the rock mass RQD index and the rock mass permeability established in this paper can be used to invert the mechanical parameters of the rock mass or to judge the permeability and safety of the rock mass by using the mechanical parameters of the rock mass, which is of great significance to the prediction of mine water inflow and the safety evaluation of water inrush disaster management.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집A
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• pp.61-66
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• 2001

Fracture behaviors of pipes with local wall thinning is very important for the integrity of nuclear power plant. In pipes of energy plants, sometimes, the local wall thinning may result from severe drosion-corrosion damage. However, effect of local wall thinning on strength and fracture behaviors of piping system were not well studied. In this paper, the monotonic bending tests were performed of full-scale carbon steel pipes with local wall thinning. A monotonic bending load was applied to straight pipe specimens by four-point loading at ambient temperature without internal pressure. From the tests, fracture behaviors and fracture strength of locally thinned pipe were manifested systematically. The observed failure modes were divided into four types; ovalization, ovalization+cracking, local buckling and local buckling+cracking. Also, maximum load was successfully evaluated.

• 한국군사과학기술학회지
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• 제16권4호
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• pp.449-455
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• 2013

When a missile is launched, a fracture-type canister cover should be properly broken by a collision with a missile or inner pressure of a canister. The fracture performance of a canister cover should be evaluated by a test using a real missile; however, it is unrealistic due to high cost and time restriction in a design stage. In this study, a test technique is newly developed to predict fracture performance of a canister cover. The test was design to have same kinetic energy with a real missile test when the cover is collide with a missile. The effectiveness of the suggested test technique was proved by comparing the test result with that of a real missile test.

• Design & Manufacturing
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• 제15권1호
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• pp.41-47
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• 2021

The Fine Blanking process is an effective precision shearing process that can obtain a smooth cutting surface and high product precision through a single blanking process. It is widely used in various manufacturing fields. However, shearing through this fine blanking process is only intended to minimize burrs, die rolls and fracture surfaces and does not completely remove them. Therefore, it is necessary to study the minimization of burrs, die rolls and fracture surfaces in the fine blanking process. In this study, a study was conducted on the relationship between the fracture surface and process conditions that occurred during product production using the fine blanking process. For this purpose, the shape of the V-ring indenter, the distance to the punch, and the pressure force, clearance, shear rate, and physical properties of the material were selected as process and design variables, and the relationship with the fracture surface according to each process and design condition was tested. It was analyzed through the Experimental Design Method.

• 한국정밀공학회지
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• 제33권7호
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• pp.559-564
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• 2016

The objectives of this paper are to develop a finite element analysis model to analyze press-fitted and bending load conditions in a press-fitted assembly, and propose a hub shape optimization method to minimize contact pressure near the shaft contact edge. Numerical asymmetric-axisymmetric finite element models have been developed to predict contact stress on press-fitted shafts. The global optimization method, genetic algorithm, local optimization method, and sequential quadratic programming were applied to a press-fitted assembly to optimize the hub contact edge geometry. The results showed that the maximum contact pressure with the optimized hub shape decreased more than 60 % compared to conventional hubs and the maximum contact stress affecting fatigue life was reduced about 47 %. Hub shape optimization can be useful to increase the load capability of press fits in terms of wear and fatigue behavior.

• 한국실천공학교육학회논문지
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• 제2권1호
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• pp.126-134
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• 2010

공업계 고등학교의 금속재료 교과목 중에 재료시험법은 과학기술이 급격히 발전하는 것에 비해 교육수준이 시대에 뒤떨어지고 있다. 특히 기존의 파단면 해석방법보다 훨씬 진일보된 장비와 기술력으로 해석이 가능한 Fractography기법 도입의 필요성이 부각되고 있다. 이런 Fractography의 중요성과 해석방법을 중수로 압력관 재료를 이용하여 파단면의 특성을 정성적으로 해석을 통하여 입증하였다. 추후 공업계 고등학생들의 전문성을 늘이고, 자긍심을 함양하기 위해서 이런 최신 교과내용을 포함해야 할 것이다. 이런 교과내용을 현존하는 과학기술과 맞추는 작업은 주무행정기관에 의해 이루어지기 전에 일선 교사들의 자발적인 참여에 의해 수행될 필요성이 있다고 생각된다.