• Composites Research
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• 제24권2호
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• pp.46-50
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• 2011

이 논문은 전투차량의 주 장갑재료로 사용되는 금속장갑재료의 개발현황 및 방탄성능에 영향을 미치는 조직학적 요인들을 중심으로 방탄성 향상을 위한 요소기술을 살펴보고, 향후 금속장갑재의 발전전망에 대하여 서술하였다. 금속장갑재는 요구되는 방호특성에 따라 사용되는 합금계가 다르지만 강도와 인성을 최적화하여 위협 탄에 대한 관통저항성 및 취성파단에 대한 저항성을 극대화하는 것이 필요하며, 이를 위해서는 금속재료의 방탄조건에서 특정적으로 나타나는 단열전단현상을 이해하고 적절히 제어하는 기술이 요구된다.

• 한국염색가공학회지
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• 제17권3호
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• pp.8-15
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• 2005

Cationic dyeable polyester(CDP) fabric was annealed at varying temperatures range from $120^{\circ}C$ to $220^{\circ}C$ for 1, 3, and 5 min under tension. Dyeing rates of CDP fabrics were measured with cationic and disperse dyes at $100^{\circ}C$ and $120^{\circ}C$ in water system. Also X-ray diffraction pattern, DSC thermograms and dyeability of fabric with cationic and disperse dyes were investigated. The intensities of X-ray diffraction peaks of annealed fabric were increased with increasing in annealed temperature, and peak became sharp with heat setting temperature. The apparent color depth (K/S) of CDP fabric initially decreased with increase of heat-setting temperature up to $160\~180^{\circ}C$ and then increased at higher temperature. The shearing modulus(G) and surface roughness were increased with annealing temperature.

• 한국농공학회지
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• 제39권6호
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• pp.99-110
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• 1997

The study was conducted in order to investigate the basic geotechnical properties of sand-bentonite mixtures with the various bentonite contents. The results obtained are as follows : 1. Optimum moisture content of sand-bentonite mixtures was approximately 17.10~18.52% corresponding to the maximum dry density of 1.58~1 .64gf/$cm^3$. As the bentonite contents and curing peroid increased, both the maximum dry density and optimum moisture content of sand-bentonite mixtures increased. 2. The unconfined compressive strength of sand-bentonite mixtures increased as the increase of bentonite content, but it did not change along the curing period. 3. The sand-bentonite mixtures ruptured at 8~15% of the axial strain and the maxi-mum shearing stress was about O.7Okgf/$cm^2$. 4. According to the increase of bentonite content, the cohesion intercept and internal friction of the sand-bentonite mixtures increased slightly in the shear test, while the cohesion intercept increased largely, and the internal friction angle decreased largely in the triaxial test. 5. Both the initial void ratio and swelling of the sand-bentonite mixtures were very low with respect to the consolidation pressure increase. 6. The swelling and shrinkage of sand-bentonite mixtures increased slightly according to the increment of bentonite content.

• 터널과지하공간
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• 제24권1호
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• pp.89-96
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• 2014

절리면의 전단강도를 결정하는 중요한 인자로 알려진 암반 절리면의 거칠기는 여러 가지 방법에 의해 연구되어 왔다. 하지만, 거칠기를 구성하는 요소인 1차 거칠기와 2차 거칠기를 분리하여 거칠기를 평가하려는 시도는 매우 제한적으로 수행되고 있다. 본 연구에서는 인장절리 시험편을 이용하여 직접전단시험을 통해 2차 거칠기 요소를 파괴하고 이를 거칠기 파라미터를 이용하여 정량화 하였다. 거칠기 파라미터는 수직응력과 측정 간격이 증가할수록 감소하였으나, 1.5 MPa 이상의 수직응력에서는 일정한 경향을 나타내지 않았다. 또한 전단 반대방향의 거칠기 면적 감소율은 거칠기 파라미터가 증가할수록 감소하였다.

• Tribology and Lubricants
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• 제4권1호
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• pp.43-55
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• 1988

A Study on the effect of the additives in lubricating oil was investigated on the basis of the thermal activated wear theory in terms of their wear behaviours, using four ballwear machine. The sample oils, which included diethyl-3, 5-di-t-butyi-4-hydroxy-benzyl phosphonate (DEP), ZDDP and TCP additives respectively, showed distinct wear characteristics depending upon the bulk oil temperature and the sliding velocity. The newly synthesized additive, viz., DEP showed excellent antiwear performance cornpared with the conventional additives, ZDDP and TCP. On the basis of the experimental results, it is reduced that the wear mechanism of the conventional additives, viz., ZDDP and TCP is the protective film formation and their antiwear capability is depending upon the shearing strength of the film formed. On the other hand, the new additive, DEP showed that the secondary activation energy was much eliminated and so, the thermal instability was reduced by the hydrogen scavenging reaction of the new additive, which was virtually an endothermic reaction process.In conclusion, a new concept of antiwear mechanism is estabilished and testified. And new chemical, which showed the function of hydrogen and free radical scavenging role, is synthesized and introduced as the new, highly antiwear effective lubricating oil additive.

• Journal of the Korean Wood Science and Technology
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• 제24권3호
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• pp.45-50
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• 1996

Wood chips of oak(Quercus mongolica) and larch(Larix leptolepis) were treated with low pressure steaming explosion. Main components of exploded wood were separated with hot water and methanol extraction. Crude lignin separated from those extractives were purified and those chemical characteristics were investigated. And also, lignin adhesive was prepared from crude lignin and studied those chemical characteristics. The results can be summarized as follows ; 1. The purified lignin by Bj$\ddot{o}$kman's method from crude lignin is about 30% in exploded oak wood and is about 11% in exploded larch wood as a low amount. 2. The phenolic hydroxyl groups in the purified lignins are little higher than those of MWL and molecular weight distributions of the purified lignins are some lower than that of MWL. 3. Alkaline nitrobenzene oxidation products are very low in the clude lignin but those are increased in the purified lignin 4. The gravity of lignin resins(1.15 and 1.13) are a little lower than that of phenol resin(1.16) and the compressive shearing strength of lignin resins are higher than those of phenol resin.

• 패션비즈니스
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• 제14권5호
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• pp.102-111
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• 2010

The pegging board planning for jacquard weaves was carried out to express a big enough design in 60 inch width. 20 Kinds of fabrics were fabricated by a jacquard loom with a warp density of 168 yarns/inch, a weft density of 100T, and a weight of 180-220g/$m^2$ or 250-300g/$m^2$. The result of sanitary test about Escherichia coli, Staphilococcus aureus, Klebsiella pneumoniae and Salmonella typhimurium showed a sterilizing power of over 90% after cultivating for 30, 60, 120 minutes. And also its property was sustained after laundrying 20 times. The flame retardant properties showed a good result and complied with the flame retardant criteria of KOFEI 1001. Abrasion, laundry and light fastnesses of flame retardant fabrics showed 4-5 grades. The fabrics manufactured from 30's fiber appeared a little fluff and pill on the fabric. Therefore, they need a shearing process after finishing all processes to decrease the fluff or pill on the fabric. The flame retardant fabric manufactured from 30's and 40's fiber showed increased strength and elongation after soaping and dyeing finishing because the fabrics were shrunk.

• 한국지반공학회논문집
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• 제21권7호
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• pp.81-89
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• 2005

지오텍스타일을 포함하지 않은 토목섬유 경계면의 동적마찰저항과 전단변위속도, 그리고 여타 마찰특성의 상관성에 대한 실험적 연구를 수행하였다 변위속도 조절이 가능한, 진동대를 이용한 진동식 실험장치를 제작하여 사용하였다. 다양한 변위속도를 포함한 실험을 수행한 결과, 지오텍스타일을 포함하지 않은 토목섬유 경계면은 지오텍스타일을 포함한 토목섬유 경계면의 전단특성과 확연히 구별되는 거동을 보였다. 지오텍스타일을 포함한 토목섬유 경계면과 달리 지오텍스타일을 포함하지 않은 토목섬유 경계면의 전단 거동은 전단 변위 속도에 민감하지 않으며 강-완전소성에 근사하다는 결론을 얻었다.

• Geomechanics and Engineering
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• 제5권6호
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• pp.499-517
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• 2013

In order to investigate shear behavior of granular materials due to excavation and associated unloading actions, load-controlled plane strain compression tests under decreasing confining pressure were performed under drained conditions and the results were compared with the conventional plane strain compression tests. Four types of granular material consisting of two quartz sands and two glass beads were used to investigate particle shape effects. It is clarified that macro stress-strain behavior is more easily influenced by stress level and stress path in sands than in glass beads. Development of localized deformation was analyzed using photogrammetry method. It was found that shear bands are generated before peak strength and shear band patterns vary during the whole shearing process. Under the same test condition, shear band thickness in the two sands was smaller than that in one type of glass beads even if the materials have almost the same mean particle size. Shear band thickness also decreased with increase of confining pressure regardless of particle shape or size. Local maximum shear strain inside shear band grew approximately linearly with global axial strain from onset of shear band to the end of softening. The growth rate is found related to shear band thickness. The wider shear band, the relatively lower the growth rate. Finally, observed shear band inclination angles were compared with classical Coulomb and Roscoe solutions and different results were found for sands and glass beads.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 추계학술대회 논문집
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• pp.627-631
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• 2005

In this study, low fatigue behavior of laser welded sheet metal were investigated. Before welding, the cross section of butt joint was prepared only by fine shearing without milling process. Specimens were same sheet metal and welding condition that using automobile manufacturing company at present. Butt joint of cold rolled sheet metal was welded by $CO_2$ laser. It is used that welding condition such as laser welding speed was 5.5m/sec and laser output power was 5kW for 0.8mm and 1.2mm sheet metal. The laser weldments were machined same or different thickness and same or different material. In order to mechanical properties of around welding zone, hardness test was performed. Hardness of welding bead is about 2 times greater than base material. We performed the low cycle fatigue tests for obtaining fatigue properties about thickness and the weld line direction of specimen. The results of strain controlled low cycle fatigue test indicate that all specimens occur cyclic softening, as indicated by the decrease in stress to reach a prescribed strain.