• Transactions of the Korean Society of Mechanical Engineers A
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• 제41권5호
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• pp.337-343
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• 2017

As a shop practice, a strength estimation method for die cast parts is suggested, in which various defects such as pores can be allowed. The equivalent porosity is evaluated by combining the stiffness data from a simple elastic test at the part level during the shop practice and the theoretical stiffness data, which are defect free. A porosity equation is derived from Eshelby's inclusion theory. Then, using the Mori-Tanaka method, the porosity value is used to draw a stress-strain curve for the porous material. In this paper, the Hollomon equation is used to capture the strain hardening effect. This stress-strain curve can be used to estimate the strength of a die cast part with porous defects. An elastoplastic theoretical solution is derived for the three-point bending of a die cast beam by using the plastic hinge method as a reference solution for a part with porous defects.

• The Journal of the Korea Contents Association
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• 제10권4호
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• pp.206-215
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• 2010

This study was designed to investigate the effects of mild hypothermia and Aquatic exercise on function Activity after experimental Spinal Cord Injury(SCI) rats. Experimental groups were divided into the control group (non-treatment after SCI induction), group I(hypothermia after SCI induction), group II(exercise after SCI induction), group III(hypothermia and exercise after SCI induction). After operation, rats were examined neurological motor behavior test at 3, 7, 14, 21 days and Immunohistochemical assessment at 3, 7, 21 days.Each other 14 days were a statistically significant difference between control group and group II, III(p<.001) in BBB scale, between control group and group III(p<.05) in grid walk test. In mmunohistochemical assessment, there was appeared highest express in group III. Based on these results, mild hypothermia and exercise was effected functional Activity after SCI.

• Journal of the KSME
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• 제22권1호
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• pp.53-61
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• 1982

최근년의 철도차량의 동향을 살펴보면, 고속경량화와 더불어 차체강도 및 진동특성 등이 중요 시됨에 따라 안전운행을 위하여 제작된 차량의 실제강도가 설계치의 허용범위내에 있어야 하 므로, 우리나라에서도 차량안전성차량을 위하여 전기제한 스트레인 게이지를 이용한 능력해석을 개발하여 성능평가에 도입할 수 있게 되었다. 본 연구에서는 선진외국과 같은 방식의 스트레인 게이지 법을 사용하여 전동객차의 차체 및 대동수 측정에는 가속도계와 스트레인 게이지를 transducer 로 사용하여 진동특성을 기록 및 분석하고, 안정성을 평가하였다.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 한국항해항만학회 2005년도 춘계학술대회 논문집
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• pp.55-60
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• 2005

Plate that have cutout inner bottom and girder and floor etc. in hull construction absence is used much, and this is strength in case must be situated, but establish in region that high stress interacts sometimes fatally in region that there is no big problem usually by purpose of weight reduction, a person and change of freight, piping etc.. Because cutout's existence gnaws in this place, and, elastic buckling strength by load causes large effect in ultimate strength. Therefore, perforated plate elastic buckling strength and ultimate strength is one of important design criteria which must examine when decide structural elements size at early structure design step of ship. Therefore, and, reasonable elastic buckling strength about perforated plate need design ultimate strength. Calculated ultimated strength change several aspect ratioes and cutout's dimension, and thickness in this investigation. Used program applied ANSYS F.E.A code based on finite element method.

• Journal of the Korea Concrete Institute
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• 제21권4호
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• pp.523-530
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• 2009

For designing concrete structures, engineers are provided data from unidirectional flexure test in most cases. But real structural components such as pavements and deck panel are subjected to multiaxial stress throughout their body. Therefore, biaxial flexure test for concrete may be considered as a gage of the performance of concrete in service. In this paper, we propose the optimum biaixial flexture test (BFT) to measure the biaxial flexural strength of concrete. This method are an improved version of the ring-on-ring test which have been used extensively in the fields of ceramics and biomaterials. The optimum geometry of the test specimen was determined by using a three-dimensional finite element analysis. A series of test data obtained from the proposed test method is provided to show that the proposed optimum biaxial flexure test method can be used to identify the biaxial tensile strength of concrete.

• Journal of the Korea Institute of Building Construction
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• 제24권2호
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• pp.193-202
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• 2024

This research delves into the evaluation of the suitability of ultrasonic pulse velocity as a diagnostic tool for early detection of frost damage in concrete. The investigation involves the measurement of compressive strength and ultrasonic pulse velocity concerning the depth of freezing for individual mortar specimens, followed by an analysis of their microstructure and their interrelation. The findings indicate a consistent decrease in both compressive strength and ultrasonic pulse velocity with increasing freezing depth. Furthermore, a correlation between compressive strength and ultrasonic pulse velocity concerning the depth of early frost damage is established. Consequently, the study asserts the potential of utilizing the ultrasonic pulse velocity method for early detection of frost damage in concrete, with prospects for quantifying the depth of damage through further research endeavors.

• Proceedings of the Korean Society for Rock Mechanics Conference
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• 한국암반공학회 2001년도 춘계학술발표회 논문집
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• pp.97-108
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• 2001

절리가 발달한 암반의 거동평가를 위한 해석적 방법은 연속체 모델과 불연속체 모델을 사용하는 방법으로 대별할 수 있으며, 연속체 모델을 사용할 경우에는 유한요소법이나 유한차분법을 이용하는 방법이 주종을 이루고 있다. 불연속체 모델은 개별 블록들의 움직임을 일일이 계산하므로 매우 매력적인 방법이지만 현재의 지반조사 기술수준으로는 지반내의 절리발달사항을 정확히 파악하기가 매우 어려우며, 컴퓨터의 계산용량이 너무 과다해지는 단점이 있다. 따라서, 불연속면을 포함한 암반을 연속체로 가정한 편재절리 모델(ubiquitous joint model)을 이용한 연구가 요구된다. 한편, 터널의 경우는 사면의 경우와는 달리 파괴면의 형상을 사전에 가정하기 어렵기 때문에 한계평형법에 기초한 해석법 등을 적용하여 안전율을 구하기가 곤란하다. 이러한 이유에서 터널을 대상으로 한 수치해석은 안전율을 구하기보다는 안정성을 평가하는 데만 제한적으로 사용되어 왔다. 본 논문에서는 편재절리모델을 이용한 절리암반터널의 거동 평가기법과 수치해석에 의해 터널의 안전율을 구하는 방법을 제시하는 데에 그 목적이 있다. 이를 위해 터널의 안전율 구하는 방법을 강도감소기법에 근거하여 제시하였다.

• Journal of the Earthquake Engineering Society of Korea
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• 제7권5호
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• pp.67-73
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• 2003

The present seismic analysis of Road-Bridge Design Standard is on a basis of load-based analysis which lets structures have the strength over load. In this study, the capacity spectrum method, a kind of displacement based method, which is evaluated by displacement of structure, is presented as an alternative to the analysis method based on load. Seismic capacity is performed about the existing reinforced concrete pier which has already secured seismic design by capacity spectrum method. As a result. capacity spectrum method could realistically evaluate the non-elastic behavior of structures easily and quickly and the displacement of structures for variable ground motion level. And it could efficiently apply to an evaluation of seismic capacity about the existing structure and a verification of design for capacity target of the new structure.

• Journal of the Korean Recycled Construction Resources Institute
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• 제7권4호
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• pp.316-322
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• 2019

A probabilistic approach considering uncertainties was employed to investigate the effects on the material characteristics and strength of nuclear bio-logical shield concrete walls, when exposed to long-term radiation during the entire service life. Time-dependent compressive and tensile strengths were estimated by conducting the neutron fluence analysis. For the contaminated concrete, individual compressive and tensile failure probabilities can be possibly evaluated by not only establishing limit-state function withthe predefined critical values but also performing Monte Carlo Simulation. Nuclear power plant types similar to the Kori Unit 1, which was shut off permanently in 2017 after the 40-year operation, were herein selected for an illustrative purpose. Consequently, the probability-based performance assessment and prediction of contaminated concrete walls were well demonstrated.

• Journal of the Korea institute for structural maintenance and inspection
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• 제20권4호
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• pp.111-119
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• 2016

Rebound hammer test, SonReb method and concrete core test are most useful testing methods for estimate the concrete compressive strength of deteriorated concrete structures. But the accuracy of the NDE results on the existing structures could be reduced by the effects of the uncertainty of nondestructive test methods, material effects by aging and carbonation, and mechanical damage by drilling of core. In this study, empirical procedure for verifying the in-situ compressive strength of concrete is suggested through the probabilistic analysis on the 268 data of rebound and ultra-pulse velocity and core strengths obtained from 106 bridges. To enhance the accuracy of predicted concrete strength, the coefficients of core strength, and surface hardness caused by ageing or carbonation was adopted. From the results, the proposed equation by KISTEC and the estimation procedures proposed by authors is reliable than previously suggested equation and correction coefficient.