• 한국토양비료학회지
• /
• 제38권5호
• /
• pp.238-246
• /
• 2005

두 가지 이상의 중금속이온이 토양에 존재할 때 토양입자표면에 흡착되는 중금속 이온은 복합적인 경쟁이온치환과 특정결합기작에 따라 흡착량이 결정된다. 본 연구는 충남 논산과 대전시 유성에 소재하는 밭토양에서 채취한 사질식양토와 식토를 공시토양으로 하여 중금속의 다중경쟁흡착특성을 조사하였다. 경쟁흡착은 조사 대상 중금속인 Cr, Cd, 및 Pb를 토양용액에 처리 농도를 달리하여 단일, 이중, 삼중체계로 처리하였다. 등온흡착은 평형농도가 증가함에 따라 흡착이 증가하는 경향을 보여주었으며 이중과 삼중체계에서는 동일 평형농도에서 흡착량은 각각의 중금속이온의 농도와 중금속 전하에 의해 영향을 받는 것으로 조사되었다. 3가지 중금속이온의 이중경쟁 흡착특성은 전기음성도는 낮으나 이온포텐셜이 높은 Cr 이온이 경쟁이온 보다 선택적 흡착특성을 보여주고 있으며 Cd와 Pb가 Cr 흡착에 미치는 영향은 유사한 것으로 조사되었다. 따라서 본 연구 결과 3중 경쟁 흡착 시 중금속 이온의 흡착량이 단일과 이중 경쟁흡착보다 증가하는 특성을 구명하기 위해서는 다중 형태로 존재하는 중금속이온의 흡착기작과 다중 형태상의 중금속이온의 반응식, 그리고 반응식에 따른 가수분해상수를 구하여 흡착정도와 경쟁 상태에 대한 추가 연구가 필요하다. 결론적으로 다중 중금속이온이 존재하는 상태 하에서 흡착친화도는 토양 내 중금속이온의 이동성과 불용화 및 가용화 사이의 분배특성에 영향을 주는 것으로 판단되었다.

• Journal of Welding and Joining
• /
• 제34권2호
• /
• pp.11-15
• /
• 2016

FE analyses for weldment of ship structure are required for various reasons such as stress concentration for bead tow, residual stress and distortion after welding, and hydrogen diffusion for prediction of low temperature crack. These analyses should be done by solid element modeling, but most of ship structures are modeled by shell element. If we are able to make solid element in the shell element FE modeling it is easily to solve the requirement for solid elements in weld analysis of large ship structures. As the nodes of solid element cannot take moments from nodes of shell element, these two kinds of element cannot be used in one model by conventional modeling. The PSCM (Perpendicular shell coupling method) can connect shell to solid. This method uses dummy perpendicular shell element for transferring moment from shell to solid. The target of this study is to develop a FE pre-processing system applicable at welding at ship structure by using PSCM. We also suggested glue-contact technique for controlling element numbers and element qualities and applied it between PSCM and solid element in automatic pre-processing system. The FE weldment modeling through developed pre-processing system will have rational stiffness of adjacent regions. Then FE results can be more reliable when turn-over of ship-block with semi-welded state or ECA (Engineering critical assessment) of weldment in a ship-block are analyzed.

• 대한기계학회논문집A
• /
• 제29권2호
• /
• pp.270-276
• /
• 2005

This paper develops the flexible computational model of a heavy truck by interfacing the frame modeled as a flexible body to the heavy truck's computational model composed of rigid bodies. The frame is modeled by the finite element method. Three torsional modes and three bending modes of the frame are considered for the interface of the heavy truck's computational model. The actual vehicle test is conducted off road with a velocity of 20km/h. The vertical accelerations at the cab and front axle are measured in the test. For the verification of the developed computational model, the measured vertical acceleration profiles are compared with the simulation results of the heavy truck's flexible computational model. E grade irregular road profile of ISO is used as an excitation input in the simulation. The verified flexible computational model is used to compare the vibration characteristics of a front suspension system having a multi-leaf spring and that having a tapered leaf spring. The comparison results show that the front suspension having a tapered leaf spring has a higher vertical acceleration at the front axle but a lower vertical acceleration at the cab than the suspension system having a multi-leaf spring.

• 대한조선학회논문집
• /
• 제58권5호
• /
• pp.314-321
• /
• 2021

In the existing whole ship analysis, topside was modeled as mass element. However recently, the topside is modeled as beam element due to the owner's requirement to improve the maturity of the whole ship FE model. To follow the owner'srequirement, detailed information for topside drawing and modeling, which may delay analysis schedule, is needed. However, it is hard to respond effectively to this matter due to the lack of study on the topside from the hull perspective. Therefore in this study, the effect of the topside on the hull is investigated when the topside is modeled as a mass element or beam element respectively. In addition, the interface modeling method is analyzed to verify modeling method used in the existing whole ship analysis. The results indicate that the interface and topside modeling method used in existing whole ship analysis are appropriate. This conclusion will be the technical basis for responding to owner's requirement about the topside modeling method.

• 산업경영시스템학회지
• /
• 제46권spc호
• /
• pp.61-67
• /
• 2023

Special equipment used for snow removal is only used in the winter and must be moved into storage during non-winter seasons. However, when moving heavy equipment using a forklift within a limited space, safety accidents may occur due to deformation and damage due to the worker's limited visibility and excessive loading of heavy objects. In this study, the scissors boom of the developed heavy load transporter was conducted in two cases: link structural analysis and position-based structural analysis. In detail, the link structural analysis covers four cases of stress and safety factor according to material and thickness to optimize the specifications of the material selected during development, and the structural analysis according to position covers two cases before and after the lift, when maximum stress concentration is achieved. Safety was evaluated through finite element analysis. As a result of the study, when manufacturing a scissors boom type heavy load transporter that can withstand a load of 10 tons, the link showed safety at SS400 4.5mm or higher, and reinforcement is needed in the upper and lower structures, so it is judged to be useful in applying materials according to the load.

• 한국원자력학회:학술대회논문집
• /
• 한국원자력학회 2005년도 춘계학술발표회
• /
• pp.857-858
• /
• 2005

• Journal of Welding and Joining
• /
• 제32권1호
• /
• pp.61-65
• /
• 2014

The purpose of this study is to evaluate the applicability of the element stress to establish S-N design curve for the welded lap joint with thin plates below 2mm thickness. In order to do it, the extensive fatigue tests of the welded lap joints with INVAR alloy were performed. With the results, the deign S-N curves for the lap-weld were established by using the reference stresses such as the nominal stress range at the weld throat area, hot spot stress range and element stress range, and compared with regard to the standard deviation. The standard deviation of S-N curves with element stress range was less than that of S-N curves with other reference stresses. In addition, FEA results show the amount of the element stress is less sensitive to mesh size. Based on the results, it can be concluded that the element stress is to be used as the reference stress for the design S-N curves of the welded lap joint.

• 한국소음진동공학회논문집
• /
• 제14권2호
• /
• pp.128-135
• /
• 2004

Generally, heavy electronic products undergo many different types of shocks in transportation from a manufacturer to customers. Cushioning package is used to protect electronic products from severe shock environments. Since the mass distribution of heavy electronic products is usually unbalanced and complex. it is very difficult to design a cushioning package with having high performance by considering only the equivalent stiffness of that. Therefore, when designing the cushioning package for a heavy electronic product, it is necessary to optimize its shape in order to maximize the cushioning performance. In this study, it is focused on designing an optimal shape of cushioning package for a large refrigerator and an efficient design method is suggested by using a dynamic finite element analysis. As the results of this study the optimal shape of cushioning package, which has high cushioning performance and minimized volume, was obtained through the mechanical drop analysis and a optimization process. Through free drop tests of refrigerators, it was identified that the cushioning performance of the cushioning package was improved up by 25% and the its own volume was reduced by 22 ％.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2003년도 추계학술대회논문집
• /
• pp.677-683
• /
• 2003

Generally, heavy electronic products undergo many different types of shocks in transporting from a manufacturer to customers. Cushioning package materials are used to protect electronic products from severe shock environments. Since the mass distributions of heavy electronic products are usually unbalanced and complex, it is very difficult to design a cushioning package with haying high performance by considering only the equivalent stiffness of that. Therefore, when designing the cushioning material for a heavy electronic product, it is necessary to optimize its shape in order to maximize the cushioning performance. In this study, it is focused on designing an optimal shape of cushioning material for a large-sized refrigerator and an efficient design method is suggested by using a dynamic finite element analysis. As the results of this study, the optimal shape of cushioning material, which has high cushioning performance and minimized volume, was obtained from the drop analysis and a optimization process. From free drop tests of a refrigerator, it was identified that the cushioning performance of the optimal package were improved up to 16 % and the volume of it was reduced in a range of 22 %.

• 한국정밀공학회지
• /
• 제33권8호
• /
• pp.623-628
• /
• 2016

This article describes the determination of the dynamic stability for a heavy press, particularly considering rotational speed. A finite element model of the driving parts for the heavy press was generated. We also applied boundary conditions and dynamic loads considering the driving conditions. Modal analysis was conducted using the finite element construction model. Therefore, no resonance was identified with the comparison between the results of the modal analysis and vibration excitation frequency by the gear tooth. In addition, the stress distribution of the driving parts for press was determined using transient analysis. As compared to the yield strength of the material, the dynamic stability the heavy press was confirmed.