This study investigates the effect of thermo-mechanical treatment on the damping capacity of the Fe-20Mn-12Cr- 3Ni-3Si alloy with deformation induced martensite transformation. Dislocation, αʹ and ε-martensite are formed, and the grain size is refined by deformation and thermo-mechanical treatment. With an increasing number cycles in the thermo-mechanical treatment, the volume fraction of ε-martensite increases and then decreases, whereas dislocation and α'-martensite increases, and the grain size is refined. In thermo-mechanical treated specimens with five cycles, more than 10 % of the volume fraction of ε-martensite and less than 3 % of the volume fraction of αʹ-martensite are attained. Damping capacity decreases by thermomechanical treatment and with an increasing number of cycles of thermo-mechanical treatment, and this result shows an opposite tendency for general metal with deformation induced martensite transformation. The damping capacity of the thermomechanical treated damping alloy with deformation induced martensite transformation greatly affect the formation of dislocation, grain refining and α'-martensite and then ε-martensite formation by thermo-mechanical treatment.

This study investigates the effect of fatigue stress on the damping capacity in a damaged Fe-22Mn-12Cr-3Ni-2Si- 4Co damping alloy under fatigue stress. α’ and ε-martensite forms by fatigue stress in the damaged Fe-22Mn-12Cr-3Ni-2Si- 4Co damping alloy under fatigue stress. The α’ and ε-martensite forms with the specific direction and surface relief, or they cross each other. With an increasing fatigue stress, the volume fraction of α’-martensite and ε-martensite increases. With an increasing fatigue stress, the damping capacity increases with an increase in the volume fraction of ε-martensite. The increase in the damping capacity in the damaged Fe-22Mn-12Cr-3Ni-2Si-4Co alloy under fatigue stress strongly affects the increase of ε-martensite formed by fatigue stress, but the damping capacity of the damaged Fe-22Mn-12Cr-3Ni-2Si-4Co damping alloy under fatigue stress is strongly controlled by a large amount of α’-martensite.

이 연구의 목적은 일반 콘크리트의 감쇠비를 높이기 위한 재료 및 방법을 제안하고, 제안된 재료 및 방법으로 제작한 시험체의 감쇠비를 측정하여 폴리우레탄 혼입량의 영향을 조사하는 것이다. 이를 위하여 폴리우레탄으로 골재를 코팅한 후 공극을 시멘트 페이스트로 채우는 방법을 개발하였고, 폴리우레탄의 함유량에 따라 시험체를 제작하고 충격가진시험을 실시하였다. 시험체 제작을 통해 골재 무게대비 폴리우레탄의 양이 15%를 넘는 경우 폴리우레탄 층이 형상되는 것을 확인하였다. 실험결과 이 연구에서 제안한 재료 및 방법으로 제작한 시험체는 일반 콘크리트에 비하여 8.7배 높은 감쇠비를 나타내었으며, 폴리우레탄 층이 골재의 크기보다 두꺼운 경우 감쇠비가 20.08%까지 나타났다. 골재 무게대비 폴리우레탄의 양이 10%에서 20% 범위에서 사용되는 경우 강성은 일반 콘크리트 대비 51%에서 65% 감소하는 것으로 나타났다.

This study was carried out to investigate the effect of grain size on the damping capacity of the Fe-26Mn-4Co-2Al damping alloy. α’ and ε-martensite were formed by cold working, and these martensites were formed with a specific direction and surface relief. With an increase in grain size, the volume fraction of α’ and ε-martensite increased by decrement the austenite phase stability. This volume fraction more rapidly increased in cold-rolled specimen than in the specimen that was not cold-rolled. The damping capacity also increased more with the augmentation an increased grain size and more rapidly increased in cold-rolled specimen than in the specimen that was not cold rolled. The effect of grain size on the damping capacity was larger in the cold-rolled specimen than the specimen that was not cold-rolled. Damping capacity linearly increased with an increase in volume fraction of ε-martensite. Thus, the damping capacity was affected by the ε-martensite.

Wind tower structure has relatively simple shape compared to other structures, but due to its characteristics, various and irregular environmental loads are applied. These loads cause vibrations at tower, and can cause failure of the structure if over vibration occurs. Vibration occurred at structures is gradually exhausted by damping of the structures, and if high damping is ensured, the failure of the structure due to over vibration can be prevented. In this study, the vibration reduction effects are to be analyzed through FEM analysis by examining the top displacement, bottom moment, and bottom fatigue damage of the structure depending on damping ratio of the wind tower structure.

This paper presents a dynamic crack propagation algorithm with Rayleigh damping effect based on the MLS(Moving Least Squares) Difference Method. Dynamic equilibrium equation and constitutive equation are derived by considering Rayliegh damping and governing equations are discretized by the MLS derivative approximation; the proportional damping, which has not been properly treated in the conventional strong formulations, was implemented in both the equilibrium equation and constitutive equation. Dynamic equilibrium equation including time relevant terms is integrated by the Central Difference Method and the discrete equations are simplified by lagging the velocity one step behind. A geometrical feature of crack is modeled by imposing the traction-free condition onto the nodes placed at crack surfaces and the effect of movement and addition of the nodes at every time step due to crack growth is appropriately reflected on the construction of total system. The robustness of the proposed numerical algorithm was proved by simulating single and multiple crack growth problems and the effect of proportional damping on the dynamic crack propagation analysis was effectively demonstrated.

This study was carried out to investigate the effect of deformation induced martensite on the damping capacity of Fe-26Mn-4Co-2Al damping alloy. α‘ and ε-martensite were formed by cold working, and; deformation induced martensite was formed with according to the specific direction and the surface relief. With an increasing degree of cold rolling, the volume fraction of α‘-martensite increased rapidly, while the volume fraction of ε-martensite decreased after rising to a maximum value at a specific level of cold rolling. Damping capacity was increased, and then decreased with an increasing of the degree of cold rolling. Damping capacity was influenced greatly by the volume fraction of ε-martensite formed by cold working, but the effect of the volume fraction of α‘-martensite have a actually on effect on the damping capacity.

The effect of retained and reversed austenite on the damping capacity in high manganese stainless steel with two phases of martensite and austenite was studied. The two phase structure of martensite and retained austenite was obtained by deformation for various degrees of deformation, and a two phase structure of martensite and reverse austenite was obtained by reverse annealing treatment for various temperatures after 70 % cold rolling. With the increase in the degree of deformation, the retained austenite and damping capacity rapidly decreased, with an increase in the reverse annealing temperature, the reversed austenite and damping capacity rapidly increased. With the volume fraction of the retained and reverse austenite, the damping capacity increased rapidly. At same volume of retained and reversed austenite, the damping capacity of the reversed austenite was higher than the retained austenite. Thus, the damping capacity was affected greatly by the reversed austenite.

지반-기초 상호작용계를 해석할 때 실제로 지반은 다양한 지반종류와 다층으로 형성되어 있으므로 지반 특성의 변화를 고려해야 한다. 초기의 대부분의 상호작용계의 정동적 해석은 지반의 복잡한 성질을 역학적으로 탄성거동을 한다고 가정한 Winkler 지반모델 혹은 지반을 등방성이고 균질한 반무한 탄성체로 가정한 반무한 탄성지반 모델로 보아 수행되었다. 본 연구는 유한 요소법을 이용하여 지반-기초 상호작용계의 동적 거동을 해석하기 위해 기초는 4절점 후판요소를 사용하고 지반은 지반특성을 고려할 수 있도록 8절점 6면체 요소를 사용하였고, 지반의 감쇠효과 및 지반특성을 고려한 지반-기초 상호작용계의 동적 거동을 유한요소법으로 해석하고 지반의 영향범위를 결정하는 것이다.

벼상자육묘(箱子育苗)에서 살균제(殺菌齊)와 생장조절제처리(生長調節劑處理)가 묘생육(苗生育) 및 생리장해(生理障害)에 미치는 영향(影響)을 구명(究明)코자 삼강(三綱)벼와 낙동(洛東)벼를 공시(供試)하여 시험(試驗)하였던 결과(結果)를 요약(要約)하면 다음과 같다. 살균제처리(殺菌齊處理)에서 삼강(三綱)벼는 Metalaxyl과 SF8002 처리구(處理區)가, 낙동(洛東)벼는 SF8002와 Metalaxyl처리구(處理區)가 초장(草長)과 3엽(葉) 및 4엽(葉)이 뚜렷한 신장교과(伸長效果)를 보였다. 건물중(乾物重)은 Metalaxyl구(區)가 가장 무거웠고 엽수(葉數)와 묘충실도(苗充實度)는 Dachigaren청리구(廳理區)가 양호(良好)하였으며, 살균제처리구(殺菌齊處理區)가 무처리(無處理)에 비(比)해 입고병발생(立枯病發生)이 적었다. 생장조절제처리구(生長調節劑處理區)에서 삼강(三綱)벼에서는 BA처리구(處理區)가, 낙동(洛東)벼에서는 GA，처리구(處理區)가 초장(草長)이 가장 길었으며, ABA(處理區)가 초장(草長)이 가장 작았고, ABA와 CCC처리구(處理區)가 신근발근력(新根發根力)이 왕성(旺盛)했다. 살균제(殺菌齊)+생장조절제처리구(生長調節劑處理區)에서 살균제(殺菌齊)+GA, 구(區)와 Metalaxyl+생장조절제처리구(生長調節劑處理區)가 초장(草長)이 가장 길었으며, Isoprothiolane+생장조절제처리구(生長調節劑處理區)가 초장(草長)이 가장 짧았다. Dachigaren+IAA 처리구(處理區)가 건물중(乾物重)과 묘충실도(苗充實度)가 양호(良好)하여 묘소질(苗素質)이 좋았으며, 살균제(殺菌齊)+생장조절제처리구(生長調節劑處理區)가 무처리(無處理)보다 입고병발생(立枯病發生)이 적었다. 또한 삼강(三綱)벼에서는 Metalaxyl+IAA 처리구(處理區)가 낙동(洛東)벼에서는 Dachigaren+IAA 처리구(處理區)가 지상부재생력(地上部再生力)이 양호(良好)했다.

Recently, because of the increased needs for damped structure, a lot of buildings equipped with damping systems are designed. In this research, in order to reduce the base shear down to the desired, additional damping ratio of damping device for each period was determined with seismic response spectrum

Recently, because of the increased needs for damped structure, a lot of buildings equipped with damping systems are designed. In this research, in order to reduce the base shear down to the desired, additional damping ratio of damping device for each period was determined with seismic response spectrum.

In this paper, the vibration control effect of the exterior-installation Kagome damping syste (EKDS) was investigated by applying the Kagome dampers to a 15-story frame apartment building structure. The numerical analysis results of a structure with exterior-installation Kagome damping system up to the third story showed that the application story should be higher than second story to effectively reduce the base shear and the maximum drift of the uppermost story. When the exterior-installation Kagome damping system was installed up to the fifth story, the application story should be higher than third story and for obtaining the target performance.

본 논문에서는 효과적인 제진설계를 구현하기 위한 설계기술 개발의 일환으로 최근 제안된 Exo-type 감쇠시스템을 활용하여 15층과 20층의 연구 대상 건물을 대상으로 감쇠시스템의 최적 강성비와 적용된 감쇠장치의 최적 항복비에 따른 철근콘크리트 라멘조 건물의 제진 효과를 검토해 보았다. 해석결과, Exo-type 감쇠시스템을 3개층 적용 시에는 대상 건물 15층과 20층 모두 밑면전단력과 최상층 최대응답변위 감소라는 관점에서 유효한 제진효과를 얻기 위해서는 Exo-type 감쇠시스템과 대상 건물의 강성비는 7.0 이상 확보를 하여야 하며, 감쇠시스템에 적용된 감쇠장치의 항복비는 대상 건물의 층전단력의 약 8.0% 이상 확보할 필요가 있는 것으로 나타났다. 또한, Exo-type 감쇠시스템을 5개층 적용 시에는 대상 건물 15층과 20층 모두 Exo-type 감쇠시스템과 대상 건물의 강성비는 2.5 이상 확보 하여야 하며, 감쇠시스템에 적용된 감쇠장치의 대상 건물의 층전단력의 약 3.5%이상 확보할 필요가 있는 것으로 나타났다.

We have experienced cracking around column bottom and safety check places on a bridge due to lamp post shaken by traffic and wind. So we need to take a measure to decrease stress on lamp post by suppressing vibration. In this study, We have tested how much we can reduce the stress by using an anti vibration damper.

In this paper, the seismic response characteristics of the structures connected through the expansion joint and the possibility of collision and separation between those structures were examined through nonlinear time history analysis. Through this experiment, the usefulness of the interaction vibration control using a steel body and a damper as connection members was verified as the seismic response behavior of the structures was reduced and the collision and separation between those structures were prevented.

컨테이너 크레인 스프레더는 체결시 발생하는 충격으로 인해 많은 고장이 발생한다. 이러한 충격력을 줄이기 위해 2자유도계 유압충격흡수장치를 설계하여 실린더 벽면의 치수변화가 감쇠계수에 미치는 영향에 대해 연구하였다. 내부압력이 작용할 때 벽면 치수를 2～3Omm로 변화시켜 이때 발생하는 실린더 벽면과 피스톤 사이의 틈새는 측정한 결과 Sun이하의 치수에는 벽면형상 굴곡 되며 l0mm이상의 치수에서 감쇠계수에 영향을 미치지 않는 것을 알 수 있다.