Microstructural evolution in the thickness direction of an oxygen free copper processed by accumulative rollbonding (ARB) is investigated by electron back scatter diffraction (EBSD) measurement. For the ARB, two copper alloy sheets 1 mm thick, 30 mm wide and 300 mm long are first degreased and wire-brushed for sound bonding. The sheets are then stacked and roll-bonded by about 50% reduction rolling without lubrication at an ambient temperature. The bonded sheet is then cut to the two pieces of the same dimensions and the same procedure was repeated on the sheets up to eight cycles. The specimen after 1 cycle showed inhomogeneous microstructure in the thickness direction so that the grains near the surface were finer than those near the center. This inhomogeneity decreased with an increasing number of ARB cycles, and the grain sizes of the specimens after 3 cycles were almost identical. In addition, the aspect ratio of the grains decreased with an increasing number of ARB cycles due to the subdivision of the grains by shear deformation. The fraction of grains with high angle grain boundaries also increased with continuing process of the ARB so that it was higher than that of the low angle grain boundaries in specimens after 3 cycles. A discontinuous dynamic recrystallization occurred partially in specimens after 5 cycles.

In this study, the weldability of ADC12 FSW joints obtained by the load control type of the FSW machine is examined. The higher the tool plunge downforce the wider the range of the optimum FSW conditions is obtained. However, there is a limit of optimum range with increasing the tool plunge downforces. The three different types of defects are formed in ADC12 FSW joints, depending on the welding conditions. One is a large mass of flash due to the excess heat input, another is a cavity or groove-like defects caused by insufficient heat input and the other is a cavity caused by the abnormal stirring. As for the abnormal stirring, it is very clearly seen that the shape of the top part on the advancing side in the stir zone is completely different. For this type of defect, the effect of the tool plunge downforce is not significant, though the size of the defect due to insufficient heat input significantly is decreased with the increasing downforce

Main topics in this study is a new structural detail for connection between H-Steel or SRC column and flat plate slab. We carried out to evaluate the punching shear performance of H-steel or SRC column + RC slab system for vertical load and lateral load. From the test results structural characteristics - yield moment, yield rotation, maximum moment, deformation capabilities ect. - are obtained and evaluated. In this paper as a shear reinforcement for supporting region of plate closed stirrup type and shear band are used, and their test results are compared.

An experimental study was carried out to evaluate the punching shear performance of H-steel column + RC slab system for vertical load. Three specimens were constructed for interior column-slab system. All specimens were the same configuration and material properties except for columns such as RC column+flat plate slab and H-Steel column+flat plate slab. From the test results structural characteristics (maximum proof stress, maximum displacement, deformation capabilities and so on) are obtained and evaluated.

The effects of printed circuit board electroless nickel immersion gold (ENIG) and organic solderability preservative (OSP) surface finishes on the electromigration reliability and shear strength of Sn-3.5Ag Pb-free solder bump were systematically investigated. In-situ annealing tests were performed in a scanning electron microscope chamber at 130, 150, and 170˚C in order to investigate the growth kinetics of intermetallic compound (IMC). Electromigration lifetime and failure modes were investigated at 150˚C and 1.5×105A/cm2, while ball shear tests and failure mode analysis were conducted under the high-speed conditions from 10 mm/s to 3000 mm/s. The activation energy of ENIG and OSP surface finishes during annealing were evaluated as 0.84 eV and 0.94 eV, respectively. The solder bumps with ENIG surface finish showed longer electromigration lifetime than OSP surface finish. Shear strengths between ENIG and OSP were similar, and the shear energies decreased with increasing shear speed. Failure analysis showed that electrical and mechanical reliabilities were very closely related to the interfacial IMC stabilities.

The contact mechanism of devices is usually researched at electrode contacts. However, the contact between a dielectric and channel at the MOS structure is more important. The graphene was used as a channel material, and the thin film transistor with MOS structure was prepared to observe the contact mechanism. The graphene was obtained on Cu foil by the thermal decomposition method with H2 and CH4 mixed gases at an ambient annealing temperature of 1000˚C during the deposition for 30 min, and was then transferred onto a SiO2/Si substrate. The graphene was doped in a nitrogen acidic solution. The chemical properties of graphene were investigated to research the effect of nitric atoms doping. The sheet resistance of graphene decreased after nitrogen acidic doping, and the sheet resistance decreased with an increase in the doping times because of the increment of negative charge carriers. The nitric-atom-doped graphene showed the Ohmic contact at the curve of the drain current and drain voltage, in spite of the Schottky contact of grapnene without doping.

This paper is the sequel of a companion paper (I. Performance Evaluation) evaluating the relation between the seismic performance of steel intermediate moment frames (IMFs) and the rotation capacity of connections. The evaluation revealed that the seismic performance of IMFs having the required minimum rotation capacity suggested in the current standards did not meet the seismic performance criteria presented in FEMA 695. Therefore, thepresent study evaluates the causes of the vulnerable seismic performance for steel IMFs and proposes alternatives to satisfy the seismic performance suggested in FEMA 695. To that goal, the results of nonlinear analysis, which are the pushover analysis and the incremental dynamic analysis, are examined and evaluated. As a result, high-rise IMF systems are seen to have the lower collapse margin ratio after connection fracture than row-rise IMF systems and, the actual response isfound to compared tothedesign drift ratio acting on design load design. Finally, the minimum design load values are proposed to meet the seismic performance suggested in FEMA 695 for IMF systems having vulnerable seismic performance.

The current AISC341-10 standard specifiesa value of 0.02 radian for the minimum rotation capacity of connections for the intermediate steel moment frame system. However, despite of the advances realized in the domains of performance evaluation method and analysis method, research onthe minimum rotation capacity of the intermediate steel moment frame systemsatisfying the seismic performance has not been conducted in detail. In this study, the intermediate moment frame systemisdesigned with respect to current standards and the seismic performance in accordance with the rotational capacity of connections is evaluated using the seismic performance evaluation method presented in FEMA-P695. The minimum rotation capacity of intermediate steel moment frames required to satisfy seismic performance as well as the major design values affecting the seismic performance of moment frame areestimated. To that goal, the design parameters are selected and various target frames are designed. The analysis models of the main nonlinear elements are also developed for evaluating seismic performance. The resultsshow that the 20-story structure doesnot meet the seismic performance even if it satisfies the rotation capacity of 0.02 radian.

This study describes the development of innovative connections between steel beams and concrete-filled tube columns that utilize a combination of low-carbon steel and super-elastic shape memory alloy components. The intent is to combine the recentering behavior provided by the shape memory alloys to reduce building damage and residual drift after a major earthquake with the excellent energy dissipation of the low-carbon steel. The analysis and design of structures requires that simple yet accurate models for the connection behavior be developed. The development of a simplified 2D spring connection model for cyclic loads from advanced 3D FE monotonic studies is described. The implementation of those models into non-linear frame analyses indicates hat the recentering systems will provide substantial benefits for smaller earthquakes and superior performance to all-welded moment frames for large earthquakes.

The flat plate slab system have many good features, which are design flexibilities, saving of story-height and economy of construction etc. But the study of flat plate slab system for H-steel column have been rare both at home and abroad. Recently high-rise residential and commercial buildings have been constructed in urban areas in Korea. The suggested dowel connection system is more likely to adoptable because it remarkably contribute to save inter story height and also to have many advantages compared with conventional steel works such as H-Steel frame + Deck plate slab system. This study aims at developing design method and program for connection between H-Steel column and flat plate slab system, which contribute to save significantly inter-story height.

This study presents an experimental study of the structural behavior for steel plate-concrete column-to-steel girder connections. Experiments were carried out to investigate the moment-rotation characteristics, failure behavior and ultimate moment capacity of these connections. The results of this experimental study involving three welded moment-resisting connections subjected to cyclic loading are presented. The specimens were fabricated at full scale to evaluate their hysteretic behavior. A description of the test specimens, the details of the joint, the test system and the testing methods are described. The test results showed that the structural behavior of these composite connections was influenced by the connection details.

Recently, applied areas of nonferrous materials have been expanded in terms of efficiency of materials used and cost reduction. And, in accordance with compactness and accuracy of parts, the need of joining of dissimilar materials is raised. Accordingly, this study aimed at finding out the optimal welding current value(6.3～6.5kA) considering tensile strength, fracture test and welding residue after joining with various welding conditions by means of copper pipe(Φ7.0 × t0.5) and aluminium pipe(Φ7.0 × t0.7) using an eutectic diffusion bonding machine.

For the artistic column used by Glass Fiber Reinforced Plastic(GFRP), the connection of steel with GFRP were needed. Due to the fabricating characteristics of hand laminating, GFRP surfaces had to be connected. Because there were no existed data of these connection, experimental study has to be followed so that the structural strength and buckling mode could be investigated. In this paper, therefore, the axial tests of steel with GFRP were performed. The connection of GFRP's surfaces could be also tested as well. As a result, it could be figured out that the strength of these connections were determined by the adhesive strength.

Tapered double cantilever beam (TDCB) specimens are the most commonly used test configurations to measure the fracture toughness of composites and adhesive joints. The material used in this study is aluminum alloy. For the impact analysis, load and displacement applied from pin onto end block as well as the crack energy release rate are calculated and compared with the finite element analysis results. The energy release rate increases with the velocity increases. As TDCB model with the same condition as experiment is simulated and analyzed, the fracture behavior can be estimated with the analysis result similar to experiment. The simulation results can be agreed with experimental graph and all experimental data at this study can be verified. These experimental results can be applied into real field effectively. It is found that the energy release rates measured from impact tests on the specimens can be predicted by the finite element model suggested in this study.

In recent years, the construction of high-rise buildings are promoted. According to these, there are many needs about new technologies to strengthen the building performance and high-strength steel is regarded as one of these for promoting building performance. In Korea, high-strength steels which stress are over 600MPa are on market and in aborad, super high-strength steels over 1000MPa are developing and they expected to promote the building performance. But there are still doubts about applying high-strength steel members because of size effect and worry of brittle fracture. In this reports, we propose results of performance and analysis tests for use with general steel. We propose the characteristic of high-strength steels first and next the results of performance test to show they satisfy the performance that designers expect. And last, we compare the results of test and analysis for acquire the alanysis reliability in non-linear analysis with high-strength steels.

A5J32-T4 and A5052-H32 dissimilar aluminum alloy plates with thickness of 1.6 and 1.5 mm were welded by friction stir lap welding (FSLW). The FSLW were studied using different probe length tool and various welding conditions which is rotation speed of 1000, 1500 rpm and welding speed of 100 to 600 mm/min and material arrangement, respectively. The effects of plunge depth of tool and welding conditions on tensile properties and weld nugget formation. The results showed that three type nugget shapes such as hooking, void, sound have been observed with revolutionary pitch. This plunge depth and material arrangement were found to effect on the void and hooking for- mation, which in turn significantly influenced the mechanical properties. The maximum joint efficiency of the FSLWed plates was about 90% compared to base metal, A5052-H32 when the A5052-H32 was positioned upper plate and plunge depth was positioned at near interface between upper and lower plates.

알루미늄 폼을 볼트나 너트를 이용하여 체결한다면 경량성이 감소되므로 접착제로 접합하는 것이 가 장 효율적이다. 이런 알루미늄 폼 접착 구조물에 대한 충격 피로 특성과 접착 합면에 대한 파괴인성 연 구는 매우 부족하며 또한 중요하다. 이에 따라 본 연구에서는 알루미늄 폼으로 만들어진 DCB모델을 접 착제로 접합한 후 두께를 변수로 하여 25mm 부터 45mm까지 10mm차이를 두어 실험과 컴퓨터 시뮬레 이션을 통하여 수행하였다. 실험은 MTS사의 인장 시험기를 사용하여 강제 변위 100mm를 주어 변위에 따른 전단력을 알아보았고, 실험과 똑같은 조건하에 ANSYS를 이용하여 유한요소해석을 수행하였다. 실험과 유한요소해석 값을 비교하여 접착제로 접합된 알루미늄 폼 구조물의 접착 합면에 대한 파괴인성을 고찰하였다.

Aluminum foam has many superb properties such as light weight, impact absorption and thermal resistance by comparing with original metallic materials. Composite materials made of aluminum foam have used at various fields as automotive bumper, shock absorption, vessel and aircraft. But it is inefficient to join aluminum foam with bolt and nut because of the property of light weight. In this study, this approach is investigated by joining aluminum foam with adhesive. Impact fatigue and failure toughness at the commissure of adhesive structure are studied by simulation analysis. This study aims to investigate the shear strength evaluation at shear mode of adhesively bonded joint with double cantilever beam(DCB) made of aluminum foam.

최근 진행되고 있는 건축 프로젝트는 기존의 정형적인 구조계획에서 벗어나 점차 복합적이고 다양한 형태를 지향하고 있다. 이와 같은 새로운 건축 트렌드 속에서, 비정형 건축물의 구조 시스템을 효율적으로 현실화하여 골조의 직교성을 해체시키는 기술에 대한 연구의 필요성이 대두되고 있다. 비정형 건축물의 중요한 구조적 특징 중 하나로 경사기둥의 빈번한 적용을 들 수 있다. 경사기둥은 접합된 보에 추가적으로 모멘트와 축력을 전달하므로, 이러한 현상이 골조 및 보-기둥 접합부의 거동에 어떠한 영향을 미치는지를 실험 혹은 해석을 통해 검증할 필요가 있다. 그러나 수직기둥-보 접합부에 비하면 경사기둥-보 접합부에 대한 연구는 현재까지 충분한 연구가 이루어지지 않고 있는 실정이다. 따라서 본 연구에서는 비선형해석 및 유한요소해석을 사용하여 경사기둥을 포함한 보-기둥 접합부의 성능을 평가하였다. 경사기둥을 포함한 철골모멘트 골조의 비선형정적해석을 통하여 골조 전체의 거동을 분석하였고, 경사기둥-보 접합부 모델의 유한요소해석을 통해 좌굴거동 및 취성파단 잠재성을 검토하였다.