• Biomaterials and Biomechanics in Bioengineering
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• 제5권1호
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• pp.37-50
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• 2020

Development of lightweight implant plates are important to reduce the stress shielding effect for a prosthesis of femur bone fractures. Stainless steel (SS-316L) is a widely used material for making implants. Stress shielding effect and other issues arise due to the difference in mechanical properties of stainless steel when compared with bone. To overcome these issues, composite materials seem to be a better alternative solution. The comparison is made between two biocompatible composite materials, namely Ti-hydroxyapatite and Ti-polypropylene. "Titanium (Ti)" is fiber material while "hydroxyapatite" and "polypropylene" are matrix materials. These two composites have Young's modulus closer to the bone than stainless steel. Besides the variety of bones, present paper constrained to femur bone analysis only. Being heaviest and longest, the femur is the most likely to fail among all bone failures in human. Modelling of the femur bone, screws, implant and assembly was carried out using CATIA and static analysis was carried out using ANSYS. The femur bone assembly was analyzed for forces during daily activities. Ti-hydroxyapatite and Ti-polypropylene composite implants induced more stress in composite implant plate, results less stress induced in bone leading to a reduction in shielding effect than stainless steel implant plate thus ensuring safety and quick healing for the patient.

• 대한의용생체공학회:학술대회논문집
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• 대한의용생체공학회 1997년도 추계학술대회
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• pp.263-266
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• 1997

Three dimensional numerical model based on the finite element method(FEM) were developed to predict the mechanical behavior of hip implants. The purpose of this study is to investigate the stress distribution of two types of cementless total hip replacement femoral component -a straight stem and a curved stem, and to compare their effect on the stress shielding between two types by three dimensional finite element method. The authors analyzed von Mises stress in the cortex & stem and compared the stress between the straight and the curved stem. In comparison of stresses between two different design of femoral stem, there was 25% more decrease of stress in straight stem than curved stem in the medial cortex at proximal region. The straight stem had consistently much lower stresses than the curved stem throughout the whole medial cortex with maximum 70% reduction of stress. However, there was little change in stress between nature and 2 implanted femur throughout the lateral cortex. Stress of femoral stem was much higher in the straight stem than the curved stem up to 60%. The straight stem had more chance of stress shielding and a risk of fatigue fracture of the stem compared with the curved stem in noncement hip arthroplasty. In design of femoral stem still we have to consider to develop design to distribute more even stress on the proximal medial cortex.

• 대한기계학회논문집A
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• 제24권11호
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• pp.2777-2785
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• 2000

In cementless total hip replacement(THR), an initial stability of the femoral component is important to long term fixation of femoral stem. The intial stability has close relationship with the relative displacement of prosthessis and sponge bone at the proximal of femur. After implantation of the proshesis, the surrounding bone is partially shielded from load carrying and starts to resorb. Stress shielding is the cause of the loss of proximal bone. Assessing stress distribution of femur is important to predict stress shielding. The initial stability and the stress shielding were investigated for two loading conditions approximating a single leg stance and a stair climbing. Three types of stems were studied by the finite element method to analyze the biomechanical effects of distal filling of cementless femoral stems. Three types of stems empolyed are a distal filling stem, a distal flexible stem, and a distal tapered stem.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집A
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• pp.387-392
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• 2000

In cementless total hip replacement(THR), an initial stability of the femoral component is important to long term fixation of femoral stem. The initial stability has close relationship with the relative displacement of prosthesis and spongy bone at the proximal of femur. After implantation of the prosthesis. the surrounding bone is partially shielded from load carrying and starts to resort. Stress shielding is the cause of the loss of proximal bone. Assessing stress distribution of femur is important to predict stress shielding. The initial stability and the stress shielding were investigated for two loading conditions approximating a single leg stance and a stair climbing. Three types of stems were studied by the finite element method to analyze the biomechanical effects of distal filling of cementless femoral stems, Three types of stems employed are a distal filling stem, a distal flexible stem, and a distal tapered stem.

• 한국CDE학회논문집
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• 제5권2호
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• pp.122-126
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• 2000

A major mechanical problem with total hip replacement is the loosening of the femoral component. The loss of proximal support, with firm fixation distally, has been thought to be a major caused of fatigue failure of femoral stems. While many causes have been proposed, the most frequently suggested cause of the calcar resorption is the disuse atrophy of the cortex of the calcar due to the stress shielding of the proximal bone by the metal femoral stem. In this research, the new-designed stem(modified collar stem) was considered which made a hole inside stem and had a 3 mm thickness. Using the 3-dimensional finite element methods, the common collar stem and the modified colla stem was modeled and analysed. Also, the two models was compared. The results showed that the modified collar stem decreased the stress-shielding and it made a effective load transfer at the entire femoral region.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2005년도 춘계학술발표대회 개요집
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• pp.209-211
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• 2005

Super duplex stainless steels have been used for offshore oil and gas piping systems which are subject to corrosion atmosphere, because they have excellent resistance to Stress Corrosion Cracking (SCC) and Pitting corrosion and high strength/weight ratio. Normally, the welding for duplex stainless steels has been peformed using GTAW with Ar shielding gas. However, in case of using Ar as shielding gas, the corrosion resistance at root weld metal will be deteriorated due to loss of nitrogen from weld deposit during welding. It is wellknown that the corrosion resistance of super duplex stainless can be restored by addition of nitrogen as shielding gas. In this study, we made super duplex welding with using several kinds of shielding and purging gases and investigated the relationship between shielding gas and corrosion resistance. Consequently, it was shown that corrosion resistance of weld deposit can be restored by addition of $N_{2}$ as shielding gas.

• 한국CDE학회논문집
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• 제21권4호
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• pp.426-432
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• 2016

Designing a morphologically well-fitted hip implant to a patient anatomy is desirable to improve surgical outcomes since a commercial ready-made hip implant may not well conform to the patient joint. In this study, biomechanical stability of patient-specific hip implants with two different stem lengths was compared and discussed using a 3D finite element analysis (FEA). The FEA results in this study showed that an increase in stem length brings about more the peaked von-Mises stress (PVMS) in the prosthesis and less in the femur. However the decrease in von-Mises stress in the femur causes stress shielding phenomenon that usually leads to considerable bone resorption. Although, in biomechanical stability point of view, this work recommends the use of smaller stems, the length of stem must be determined by considering both the von-Mises stress and the stress-shielding phenomenon.

• 연구논문집
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• 통권33호
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• pp.183-190
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• 2003

Today, We have used many electronic equipment such as computer, TV, cellular phone and so on. These equipment radiate a large amount of EMI(Electromagnetic interference) which is occurred trouble of airplane, medical equipment, communicate equipment, and especially, human health. So, Ni mesh fabrication for EMI shielding by continuous electroforming process was investigated. Continuous electroforming apparatus was made by means of rotating cathode drum. And We investigated the characteristics of two types of Ni electroforming solution. One was made by laboratory and the other was produced by M cooperation. The grain size increased with increasing current density and bath temperature, and decreasing rotating speed of cathode drum. EDX results indicate that the Ni mesh electroformed by the KIMM solution is composed of pure Ni. But the Ni mesh electroformed by the M cooperation solution has Ni and S element. The incorporation of S element in the Ni mesh has a profoundly effect on mechanical properties such as hardness, internal stress and so on.

• Carbon letters
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• 제22권
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• pp.36-41
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• 2017

Biodegradable epoxy (B-epoxy) was prepared from diglycidyl ether of bisphenol A and epoxidized linseed oil. The mechanical properties of B-epoxy composites reinforced with multi-walled carbon nanotubes (MWCNTs/B-epoxy) were examined by employing dynamic mechanical analysis, critical stress intensity factor ($K_{IC}$) tests, and impact strength tests. The electromagnetic interference shielding effectiveness (EMI-SE) of the composites was evaluated using reflection and absorption methods. Mechanical properties of MWCNTs/B-epoxy were enhanced with an increase in the MWCNT content, whereas they deteriorated when the MWCNT content was >5 parts per hundred resin (phr). This can likely be attributed to the entanglement of MWCNTs with each other in the B-epoxy due to the presence of an excess amount of MWCNTs. The highest EMI-SE obtained was ~16 dB for the MWCNTs/B-epoxy composites with a MWCNT content of 13 phr at 1.4 GHz. The composites (13 phr) exhibited the minimum EMI-SE (90%) when used as shielding materials at 1.4 GHz. The EMI-SE of the MWCNTs/B-epoxy also increased with an increase in the MWCNT content, which is a key factor affecting the EMI-SE.

• 방사성폐기물학회지
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• 제5권3호
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• pp.199-212
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• 2007

IP-2형 운반용기는 정상운반조건에서의 자유낙하시험 및 적층시험을 수행한 후에 운반내용물의 분산 및 유실이 없어야 하며 외부표면에서의 방사선량률이 20%이상 증가할 수 있는 차폐능력의 상실이 없어야 한다. 본 연구에서는 두꺼운 철판을 구조재로 사용하며 볼트체결방식의 뚜껑을 가진 IP-2형 운반용기에 대한 구조 안전성을 평가하기 위한 해석적인 방안을 제안하였다. 해석적인 방법을 통하여 원자력발전소에서 발생된 방사성폐기물 드럼을 폐기물 처리시설에서 임시저장고까지 운반하기 위한 두 종류의 IP-2형 방사성폐기물 운반용기에 대하여 자유낙하조건에서 운반내용물의 분산 및 유실과 차폐손실이 없음을 확인하였다. 자유낙하조건에서 운반내용물의 분산 및 유실을 평가하기 위하여 최대 볼트단면 평균응력값과 최대 뚜껑열림량을 볼트의 인장강도와 뚜껑부에 존재하는 단차와 비교 평가하였다. 또한 최대 차폐두께 감소량을 이용하여 차폐손실을 평가하였다. 자유낙하조건에 대한 동적충돌해석을 검증하고 구조 안전성을 시험적으로 평가하기 위하여 자유낙하시험을 다양한 방향으로 실시하였다. 자유낙하시험에서는 운반내용물의 분산 및 유실은 볼트체결방식의 뚜껑에서 볼트의 파손 및 플랜지의 변형 등을 검사하여 평가하였으며, 차폐손실은 초음파 두께 측정기를 이용한 차폐두께를 측정하여 평가하였다. 해석에 대한 검증을 위하여 시험에서 취득한 변형률과 가속도를 동일한 위치에서 얻어진 해석결과와 비교하였다. 해석결과는 시험결과에 비하여 보수적인 결과를 보여주므로 해석에서 입증한 IP-2형 방사성폐기물 운반용기의 안전성은 보수적인 결과이다. 마지막으로 유한요소해석을 통하여 적층조건에 대한 IP-2형 방사성폐기물 운반용기는 안전함을 입증하였다.