• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2001년도 추계학술대회 논문집
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• pp.285-288
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• 2001

Hypereutectic Al-25Si-X alloys, expected to be applied to the cylinder-liner-part of the engine-block of an automobile due to the excellent wear resistance, low density and low thermal expansion coefficient has been fabricated through a spray forming process. The obtained microstructure of the hypereutectic Al-25Si-X alloy appeared to consist of Al matrix and equiaxed Si particles of average diameter of $5-7{\mu}m$. To characterize the deformation behavior of this alloy, a series of load relaxation and compression tests have been conducted at temperatures ranging from RT to $500^{\circ}C$. The strain rate sensitivity parameter (m) of this alloy has been found to be very low (0.1) below foot and reached 0.2 at $500^{\circ}C$. During the deformation above 300'c in compression, strain softening has been observed. The diagram of extrusion pressure vs. ram-speed has been constructed, providing the extrusion condition of Al-25Si-X alloys.

• 한국산학기술학회논문지
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• 제11권10호
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• pp.4012-4017
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• 2010

이 연구에서는 팩 말뚝과 모래다짐말뚝의 전단강도 특성을 비교하기 위해 모래-팩-점토 복합토 및 모래-점토 복합토를 인위적으로 치환율($a_s$) 10%, 20%로 재성형하여 구속압력을 변화시켜가며 삼축압축시험(CU Test)을 실시하였다. 시험결과 모래-점토 복합토에 비해 모래-팩-점토 복합토의 강도가 치환율 10% 및 20% 모두에서 훨씬 크게 측정되어 모래다짐말뚝보다 팩말뚝이 큰 지지력을 갖는다는 것을 확인하였다.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2001년도 춘계학술대회 논문집
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• pp.20-23
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• 2001

Hypereutectic Al-25Si alloy, which is expected to be applied to the cylinder-liner-part of the engine-block of an automobile due to its excellent wear resistance, low density and low thermal expansion coefficient, has been fabricated through a spray forming process. The obtained microstructure of the hypereutectic Al-25Si alloy appeared to consist of Al matrix and equiaxed Si particles of average diameter of 5-7 mm. To characterize the deformation behavior of this alloy, a series of load relaxation and compression tests have been conducted at temperatures ranging from RT to $500^{\circ}C$. The strain rate sensitivity parameter (m) of this alloy has been found to be very low (0.1) below $400^{\circ}C$ and reached maximum value of about 0.2 at $500^{\circ}C$. During the deformation above $300^{\circ}C$ in compression, strain softening has been observed. The diagram of extrusion pressure vs. ram-speed has been constructed. The extrusion has been successfully conducted at the temperatures of $300^{\circ}C$ and above with the ratio of area reduction of 28 and 40 in this study.

• Earthquakes and Structures
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• 제18권5호
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• pp.581-598
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• 2020

This paper aims to investigate the seismic behavior and influence parameters of the large-scaled thin-walled reinforced concrete (RC) tubular columns in air-cooled supporting structures of thermal power plants (TPPs). Cyclic loading tests and finite element analysis were performed on 1/8-scaled specimens considering the influence of wall diameter ratio, axial compression ratio, longitudinal reinforcement ratio, stirrup reinforcement ratio and adding steel diagonal braces (SDBs). The research results showed that the cracks mainly occurred on the lower half part of RC tubular columns during the cyclic loading test; the specimen with the minimum wall diameter ratio presented the earlier cracking and had the most cracks; the failure mode of RC tubular columns was large bias compression failure; increasing the axial compression ratio could increase the lateral bearing capacity and energy dissipation capacity, but also weaken the ductility and aggravate the lateral stiffness deterioration; increasing the longitudinal reinforcement ratio could efficiently enhance the seismic behavior; increasing the stirrup reinforcement ratio was favorable to the ductility; RC tubular columns with SDBs had a much higher bearing capacity and lateral stiffness than those without SDBs, and with the decrease of the angle between columns and SDBs, both bearing capacity and lateral stiffness increased significantly.

• 한국강구조학회 논문집
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• 제14권2호
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• pp.349-356
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• 2002

현재 우리나라 스틸하우스 건설에 사용하는 구조재는 SGC41 강종으로 제작된 보통 C-형강이나 Lip-C-형강이 주를 이루고 있으나 이 분야의 선진국가에서는 좌굴 강도가 높고 시공성이 좋은 고유의 단면 형상을 개발하여 사용하고 있다. 본 연구에서는 정량이면서 강도 및 강성이 높고 다양한 시공상 장점이 있는 고강도 신형상 박판냉간성형단면의 압축부재로서의 구조적인 고동과 성능을 연구하기 위하여 재료실험 및 압축실험을 수행하고 해석치와 비교하여 보았다.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2000년도 추계학술대회 논문집
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• pp.171-177
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• 2000

It is essential to understand the creep behavior, which shows how long the characteristics of material maintains because press joined molding GMT-Sheet for recycle is usually used in the severe environment. In this study, we predict joining strength of GMT-Sheet for recycle, when lap length was changed. and we will investigate how compression ratio have an effect on creep behavior in press joined molding. The result of experiment of forming condition concerned with joining problem of GMT-Sheet is as followings joining efficiency. of GMT-Sheet, increases as lap joint length I, increases. Increase of compression ratio causes decrease o f joining efficiency after of GMT-Sheet joining. As the result of creep test, GMT-Sheet is easily damaged in high temperature range, because it is sensitive to the temperature

• Steel and Composite Structures
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• 제18권5호
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• pp.1259-1277
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• 2015

The present study is focused on the behavior and design of perforated steel storage rack columns under axial compression. These columns may exhibit different types of behavior and levels of strength owing to their peculiar features including their complex cross-section forms and perforations along the member. In the present codes of practice, the design of these columns is carried out using analytical formulas which are supported by experimental tests described in the relevant code document. Recently proposed analytical approaches are used to estimate the load carrying capacity of axially compressed steel storage rack columns. Experimental and numerical studies were carried out to verify the proposed approaches. The experimental study includes compression tests done on members of different lengths, but of the same cross-section. A comparison between the analytical and the experimental results is presented to identify the accuracy of the recently proposed analytical approaches. The proposed approach includes modifications in the Direct Strength Method to include the effects of perforations (the so-called reduced thickness approach). CUFSM and CUTWP software programs are used to calculate the elastic buckling parameters of the studied members. Results from experimental and analytical studies compared very well. This indicates the validity of the recently proposed approaches for predicting the ultimate strength of steel storage rack columns.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 추계학술대회 논문집
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• pp.649-652
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• 2005

It is reported that semi-solid forming process takes many advantages over the conventional forming process, such as long die lift, good mechanical properties and energy saves. Rheology material has a thixotropic, pseudo-plastic and shear-thinning characteristic. Therefore, general plastic or fluid dynamic analysis is not suitable for the behavior of rheology material. So it is difficult for a numerical simulation of the rheology process to be performed because complicated processes such as the filling to include the state of the free surface and solidification in the phase transformation must be considered. Moreover, it is important to predict the deformation behavior for optimization of net shape forging process with semi-solid materials and to control liquid segregation for mechanical properties of materials. In this study, so, molecular dynamics simulation was performed for the control of liquid segregation in compression experiment as a part of study on analysis of rheology forming process.

• Steel and Composite Structures
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• 제35권2호
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• pp.159-169
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• 2020

Sandwich composite wall consists of concrete core attached by two external steel faceplates. It combines the advantage of steel and concrete. The appropriate composite action between steel faceplate and concrete core is achieved by using adequate mechanical connectors. This research studied the compressive behavior of the sandwich composite walls using steel trusses to bond the steel faceplates to concrete infill. Four short specimens with different wall width and thickness of steel faceplate were designed and tested under axial compression. The test results were comprehensively evaluated in terms of failure modes, load versus axial and lateral deformation responses, resistance, stiffness, ductility, strength index, and strain distribution. The test results showed that all specimens exhibited high resistance and good ductility. Truss connectors offer better restraint to walls with thinner faceplates and smaller wall width. In addition, increasing faceplate thickness is more effective in improving the ultimate resistance and axial stiffness of the wall.

• 대한기계학회논문집A
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• 제20권3호
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• pp.796-805
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• 1996

A fabrication process using Semi-Solid Material(SSM) for casting alloy has been studied to demonstrate the possibility for mass production with controlled solid fraction. The SSM was fabricated under the various solid fractions and preheating temperatures of mold. The behaviour of a semi-solid global microstructure has been investigated under the various heating and die temperatures for solid fraction. The effect of reheating time on the globularization of SSM microstructure has been investigated in detail. And the behavior of SSM which has the solid fraction 0.5 was observed under compression. The stress strain relationship was also obtained for the compression test of semi-solid materials. The rheological behaviour of semi-solid with globule microstructure was investigated as a function of the compression velocity under isothermal holing conditions.