• 한국철도학회:학술대회논문집
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• 한국철도학회 2007년도 춘계학술대회 논문집
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• pp.1626-1630
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• 2007

This dissertation finds out trouble types and occurrence regions using the faulty statistics of nondestructive test items in rolling stock parts of the Seoul Metro and using mechanical test about defective and broken parts with broken surface observation, cutting examination about trouble region, hardness experiment and tensile test. Also this dissertation finds out cause of trouble and damage through observation of microscopic formation using metallurgical microscope and scanning electron microscope, residual stress measurement about welding parts and damage diagnosis about defective and broken parts. Moreover it will present the improved plan of nondestructive method about trouble and the removal method of defect and repair welding and find solutions of reliability in parts and preventive maintenance.

• 한국해양공학회지
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• 제10권4호
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• pp.58-66
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• 1996

The purpose of this investigation is to estimate the strength with the variations of the notch shape and the adgesive condition at the fiber/matrix micro interface of E-glass/PP laminates. To promote the degradation of the adhesive condition at the fiber/matrix micro interface without matrix dissolution loss, low-, hot-wet and spiking tests were carried out. The absorpotion properties and the tensile properties were compared accrding to the fiber orientation and the content. The results show that, firstly, saturated moisture absorption was reached at 5cycles and their absorptions of RD-40, UD-42 and UD-50 are 0.68%, 0.63%, 0.60%, respectively. Secondly, all the specimens investigated were mostly degraded at 5cycle, whereas UD-50 having ellipse shaped notch the least decrement of strength.

• 한국전기전자재료학회논문지
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• 제26권5호
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• pp.415-420
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• 2013

The new recycling technology for aged Aluminum wires in overhead conductor have been carried out. We are attempting to develop remanufacturing method for them for more effective way of recycling in stead of its conventional remelting process. The weld of aged aluminum wires play a vital role in remanufacture process. The paper investigates the mechanical properties during cold welding process of aged Aluminum wire. The tensile tests and microscopic analysis results are discussed to underscore the hardening features of welded aluminum wire. Various graphs are presented accompanied by discussion about their relevance on the process.

• Journal of Mechanical Science and Technology
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• 제18권3호
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• pp.453-459
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• 2004

TiNi/ Al6061 shape memory alloy (SMA) composite was fabricated by hot press method to investigate the microstructure and mechanical properties. Interface bonding between TiNi reinforcement and A1 matrix was observed by using SEM and EDS. Pre-strain was imposed to generate compressive residual stress inside composite. A tensile test for specimen, which under-went pre-strain, was performed at high temperature to evaluate the variation of strength and the effect of pre-strain. It was shown that interfacial reactions occurred at the bonding between matrix and fiber, creating two inter-metallic layers. And yield stress increased with the amount of pre-strain. Acoustic Emission technique was also used to nondestructively clarify the microscopic damage behavior at high temperature and the effect of pre-strain of TiNi/ Al6061 SMA composite.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2007년 추계학술발표대회 개요집
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• pp.155-157
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• 2007

The Friction spot dissimilar welding of galvanized steel/Al6061-T6 was performed to investigate the mechanical characteristics of the joints. The presence of thin film of aluminum oxide on the surface and melting of zinc in the coating, made substandard joint characteristics for dissimilar Friction spot joining(FSJ) performed with out removing the coating. Where as, for dissimilar FSJ of galvanized steel/Al6061-T6 after removing the coating, superior agitation and welding quality has been obtained for a configuration of galvanized steel as the upper plate and Al6061-T6 as lower plate. The results from tensile tests and microscopic examination for various combinations of the welding parameters have been presented.

• 한국분말재료학회지
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• 제9권4호
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• pp.203-210
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• 2002

A new PIM in-process joining technique has been developed for more complicated and functional PIM components by application of the exuded wax from the green compacts during solvent debinding step. At first, various stainless steels and iron compacts with rectangular shape were combined, and the joining behaviors and properties were investigated by shear and tensile test, and microscopic observation. Subsequently, perfect joined three pieces of thin and hollow compacts were obtained for the combination of same and different stainless steels, and it was difficult to join the iron and stainless steel compacts in hydrogen atmosphere because of the different starting temperature of shrinkage. However, pretty good joined iron and stainless steel compacts were obtained by consideration of particle size and vacuum atmosphere. Finally, for the combination of ferro-silicon and austenitic stainless steel compacts, high functionality (magnetic (1.60Tes1a) & non-magnetic) and perfect joint were obtained.

• International Journal of Korean Welding Society
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• 제2권1호
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• pp.57-61
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• 2002

This paper presents development of a SEC(Solar Energy Concentration) utilizing the concentrated solar beam radiation for joining engineering thermoplastics such as Acrylonitrile/Butadiene/Styrene(ABS), Polycarbonate(PC) and Polymethylmethacrylate (PMMA). In addition, to study the joining of the materials, necessary experimentation with applying primer was performed. Tensile tests were conducted to determine the bond strength achieved at the specimen Joint interface. Microscopic examinations of the fractured joints were performed in order to analyze the overall bond quality. Finally, the results in terms of bond strength achieved at the joint interface and energy consumed in the process was compared with those obtained with similar thermoplastic joining technique utilizing microwave energy.

• 한국구조물진단유지관리공학회 논문집
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• 제23권2호
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• pp.51-59
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• 2019

철근의 대체보강재로서 섬유보강근에 대한 적용연구가 증가하고 있으며, 단기거동에 대한 많은 연구가 진행되어 왔다. 본 연구에서는 동결융해와 알칼리 환경하에서의 바살트와 유리섬유보강근의 미세구조와 인장거동 변화를 실험적으로 평가하였다. 100회까지의 동결융해에서 5% 내외의 강도와 탄성계수 저하가 발생하였다. 20일까지의 초기 미세구조변화의 경우 알칼리용액의 온도가 낮은 경우에는 손상이 거의 발생하지 않았으나, $60^{\circ}C$에서는 20일 경과시에도 수지 용해와 섬유 손상이 관찰되었으며, 수지계면의 섬유분리가 발견되었다. 알칼리 환경에서는 $20^{\circ}C$환경에서 100일까지는 10% 내외의 강도저하 현상이 발생하였으며, 500일 노출시 최대50%의 강도 저하가 발생하는 것으로 관찰되었다. $40^{\circ}C$와 $60^{\circ}C$ 환경에서는 50일과 100일에서 급격한 강도저하가 관찰되었으며, 바살트섬유보강근의 경우에는 알칼리에서 섬유부풀음에 의한 손상으로 강도저하가 더 크게 나타났다. 따라서 블레이디드된 섬유보강근의 장기성능을 향상시키기 위해서는 내알칼리성 확보를 위한 표면처리가 필요한 것으로 분석되었다.

• Composites Research
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• 제35권1호
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• pp.42-46
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• 2022

탄소섬유 복합재를 제작하였을 때, 함께 적층되는 유리섬유 부직포 개수 및 적층 순서에 따른 기공률과 기계적 물성 간의 상관관계를 확인하였다. 탄소섬유 복합재는 고 투과성 물질인 유리섬유 부직포를 함께 적층 하여 진공 수지 이송 성형 법(vacuum assisted resin transfer molding, VARTM)을 통해 제작하였다. 기공률은 시편의 단면을 광학현미경으로 촬영 후 MATLAB의 기공률 계산 코드를 통해 측정하였고, 기계적 물성은 인장시험을 통해 인장 강도 및 인장 강성, 굽힘 강도, 굽힘 강성을 측정하였다. 또한, 기공률과 기계적 물성 간의 상관관계를 확인하기 위해 두 변수간 피어슨 상관계수를 계산하였다. 결과적으로 유리섬유 부직포의 개수가 증가할수록, 적층 시 중심에서 멀어질수록 기공률이 증가하는 것을 확인할 수 있었다. 또한, 인장 강도 및 인장 강성은 기공률과 약한 양의 상관관계를 보였다. 또한, 인장 강도 및 강성에 기공률만이 미치는 영향을 확인하기 위해 고전 적층 판 이론으로 계산한 기계적 물성과 실험값을 비교하였으며, 인장 강도의 차이는 기공률에 강한 양의 상관관계를 인장 강성은 약한 양의 상관관계를 보였다.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• 제27권6호
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• pp.491-497
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• 2001

Polymethylmethacrylate(PMMA) is currently commonly used material for the reconstruction of bone defects and fixation of joint prosthetics following congenital and acquired causes. Although PMMA has widespread use, it does not possess the ideal mechanical characteristics with osteoconductivity and osteoinductivity required. In order to overcome these problem, addition of bovine bone drived defatting demineralized bone(BDB) powders to a PMMA bone cement was done for improvement of physical property and bone forming characteristics of composite. In order to investigate the influence of BDB reinforcement on the PMMA, we measured physical property of compressive, tensile, flexural strength, and scanning electron microscopic examinations. The results were obtained as follows: 1. The PMMA forms a solid cellular matrix with open cells about $100{\mu}m$ in variable size and incorporating BDB. BDB aggregates inside the cells form a porous network that is accessible from the outer surface. 2. The physical properties were compressive strength of mean $22.74{\pm}1.69MPa$, tensile strength of mean $22.74{\pm}1.69MPa$, flexural strength of mean $77.53{\pm}6.93MPa$. Scanning electron microscopic examinations were revealed that there was DBD particles form a highly porous agglomerates. BDB can be added PMMA in the form of dried powders, the composites are applicable as bone substitutes. BDB and PMMA mixture is shown to produce a class of composites that due to their microstructure and improved mechanical properties may be suitable for application as bone subsitutes. The mechanical and material properties of the BDB-PMMA bone substitute composites are competitive with those properties of a porous ceramic matrix of other hydroxyapatite and with those of natural bones.