In order to develop a new commercial Al-12%Si casting alloy with improved physical properties, we investigated the effect of adding Sr and TiB to the alloy. Al-12%Si alloys were prepared by die casting at 660 oC. The eutectic temperature of the Sr-modified Al-12%Si alloy decreased to 9 oC and the mushy zone region increased. The shape of the Si phase changed from coarse acicula to fine fiber with the addition of Sr. The addition of TiB in the Al-12%Si alloy reduced the size of the primary α-Al and eutectic Si phases. When Sr and TiB were added together, it worked more effectively in refinement and modification. The density of twins in the Si phase-doped Sr increased and the width of the twins was refined to 5 nm. These results are related to the impurity induced twinning(IIT) growth.

본 연구의 목표는 분변토로부터 분리한 Bacillus subtilis외 2종의 복합 생균제를 이용하여 제 조한 발효사료가 산란계 생산성, 계란품질 및 양계장 악취저감에 미치는 효과를 조사하는 것이었다. 산 란계 240마리를 4개의 처리구로 구분하여 완전임의 배치하였다. 실험 처리구는 대조구, 분변토발효사료 0.3, 0.5% (FECF3, FECF5), 일반생균제 0.2% (CP)로 구분하였다. 산란율은 일반사료를 섭취한 대조구 와 비교할 때 FECF 처리구는 유의하게 높았으나 CP 처리구는 차이가 없었다. 호우유닛, 난각두께, 파 란강도, 난황색 지수 및 농후난백 높이는 대조구와 비교할 때 FECF 처리구가 증가하였으나 CP 처리구 와 차이는 없었다. 계란의 n-3 함량은 대조구와 비교할 때 FECF 처리구가 높았으나 n-6/n-3 비율은 낮았으며 CP 처리구와의 차이는 없었다. 계분을 실온에서 5일간 방치 후 암모니아 발생량은 대조구와 비교할 때 CP와 FECF 처리구가 낮았다.

In case of underground construction affected by groundwater, CIP (Cast-In-Place Pile) method is generally used to resolve the geo-hydraulic problem. However, as this method has poor connectivity between piles, an auxiliary method for cut-off is needed in many cases. In this study, a new concept earth retaining wall method (H-CIP) with no auxiliary method, by using surfactant grout (Hi-FA) which improves antiwashout and infiltration ability, is introduced, and its field applicability is evaluated. CIP and H-CIP piles were installed with same ground conditions, and field permeability tests were conducted to verify the performance. As results, newly contrived H-CIP method shows higher antiwashout performance for cut-off than conventional CIP method.

The effect of heat treatment on the microstructure and mechanical properties of cast Ti-6%Al-4%V alloy was investigated. Heat treatment of cast Ti-6Al-4V alloy was conducted by solution treatment at 950 oC for 30 min; this was followed by water quenching and then aging at 550 oC for 1 to 1440 min. The highest hardness of the heat-treated specimens was obtained by solution treatment and subsequent aging for 5 min due to precipitates of fine α that formed from retained β phase. The tensile strength of this alloy increased without dramatic decrease of the ductility due to microstructural refinement resulting from the decomposition of α' martensite into fine α and β phases, and also due to the fine α phase formed from the retained β phase by aging treatment for 5 min. In addition, this strengthening might be caused by the transformation induced plasticity (TRIP) effect, which is a strain-induced martensite transformation from the retained β phase during deformation, and which occurs even after aging treatment at 550 oC for 5 min.

Bond stress between cast-in-place ductile fiber reinforced cementitious composites and CFRP plank were experimentally analyzed. As failure shape, the mixture of failure between CFRP plank and epoxy, and failure between concrete and epoxy was shown. In case of RFCON from the suggested simple bond slip relationship, the maximum average bond stress was 5.39MPa, the initial slope was 104.09MPa/mm, and the total slip length was 0.19mm. PPCON showed the maximum average bond stress of 4.31MPa, the initial slope of 126.67MPa/mm, and the total slip length of 0.26mm, while RFCON+ appeared to have 8.71MPa, 137.69MPa/mm, 0.16mm. PPCON+ had 6.19MPa maximum average bond stress, 121.56MPa/mm initial slope, and 0.34mm total slip length. To comprehend the behavior of composite structure of FRP and concrete, local bond slip relation is necessary, and thus a simple relation is suggested to be easily applied on hybrid composite system

In order to fabricate porous mullite ceramics with controlled pore structure and improved mechanical strength, a freeze casting route has been processed using camphene mixed with tertiary-butyl alcohol (TBA) and coal fly ash/alumina as the solvent and the ceramic material, respectively. After sintering, the solidification characteristics of camphene and TBA solvent were evident in the pore morphology, i.e., dendritic and straight pore channels formed along the solidification directions of camphene and TBA ice, respectively, after sublimation. Also, the presence of microcracks was observed in the bodies sintered at 1500 oC, mainly due to the difference in solidification volume change between camphene and TBA. The compressive strength of the sintered bodies was found generally to be dependent, in an inverse manner, on the porosity, which was mainly determined by the processing conditions. After sintering at 1300~1500 oC with 30~50 wt% solid loading, the resulting mullite ceramics showed porosity and compressive strength values in ranges of 83.8~43.1% and 3.7~206.8 MPa, respectively.

본 연구는 수용자의 인지욕구에 따라 제품유형과 매체유형의 설득효과를 검증하는데 목적을 두었다. 연구결과, 인지욕구 수준이 높은 집단의 경우 하이테크 제품과 비하이테크 제품 모두 팟캐스트 매체에 대 한 광고태도가 높은 것으로 나타났으나, 인지욕구 수준이 낮은 집단은 하이테크와 비하이테크 제품 모두 인쇄매체에 대한 광고태도가 더 높은 것으로 나타났다. 브랜드태도의 경우에는 삼원상호작용 효과가 나 타나지 않았다. 광고주 공신력의 경우 인지욕구가 높은 집단과 낮은 집단 모두 팟캐스트 매체가 효과적인 것으로 나타났으나, 제품 유형에 따라서는 인지욕구 수준에 따라 서로 다른 효과가 있는 것으로 나타났다. 즉 인지욕구가 높은 집단의 경우 팟캐스트와 인쇄매체 모두 하이테크 제품에 광고주 공신력을 높게 평가 하는 것으로 나타났고, 인지욕구가 낮은 집단은 팟캐스트와 인쇄매체 모두 비하이테크 제품에 광고주 공 신력을 높게 평가하는 것으로 나타났다. 구매의도에 대해 매체별로는 인지욕구가 높은 집단과 낮은 집단 모두 팟캐스트 매체가 더욱 효과적인 것으로 나타났으며, 인지욕구가 높은 집단은 두 가지 매체 모두 하이 테크 제품에 구매의도가 높으며, 인지욕구가 낮은 집단은 비하이테크 제품에 더 높은 구매의도를 보이는 것으로 나타났다. 특히 인지욕구가 높은 집단의 경우에는 팟캐스트를 활용한 비하이테크 제품보다 인쇄 매체를 활용한 하이테크 제품에 대한 구매의도가 높았으며, 인지욕구가 낮은 집단의 경우 팟캐스트를 활 용한 비하이테크 제품에 구매의도가 가장 높은 것으로 나타났다.

This research developed ultra-pressure pump main body by using ductile cast iron FCD500, conducted quantitative analysis on following phenomenon of flow or solidification processing in cast processing for improvement of cast device, after extracting model from cast concluded as follows by brinel hardness test. after selecting the ideal condition of cast and it applied to cast of real product shape, discovered the ideal filling processing under the condition that temperature of molten metal was between 1300℃ and 1280℃. and after finishing filling, solidification was commenced rapidly when percentage of solidification completion was between 40%~50%, at that moment, the termperature was measured 1100℃. moreover under the condition of temperature below 900℃, keeping temperature on the center of parts for a certain period of time brings stability of stabilization of heat in parts and organizational stabilization of ductile cast iron. As the results of the casting method design, it was that the ductile cast parts of pump main body was obtained as the maximum HB of 220 was recorded and good test results were achieved

An attempt was made to evaluate creep reliability of two commercial Ni-based superalloys by using ultrasonic wave. The materials include fine-grained PM alloy fabricated by mechanical alloying and subsequent hot isostatic pressing, and IN738LC cast alloy with a grain size of a few cm. Microstructural parameters (fraction of creep cavity and size of precipitates) and ultrasonic parameters (velocity, attenuation) were measured to try to find relationships between them. Ultrasonic velocity decreased with creep cavity formation in PM alloy. On the other hand, no distinct changing trend of ultrasonic velocity was observed for IN738LC alloy. Ultrasonic attenuation was found to have a linear correlation with the size of precipitates and was suggested as a potential parameter for monitoring creep reliability of IN738LC alloy.

Currently, there are two main issues regarding the development of core technologies in the automotive industry: the development of environmentally friendly vehicles and securing a high level of safety in the event of an accident. As part of the efforts to address these issues, research into alternative materials and new car body manufacturing and assembly technologies is necessary, and this has been carried out mainly by the automotive industries. Large press molds for producing car body parts are made of cast iron. With the increase of automobile production and various changes of design, the press forming process of car body parts has become more difficult. In the case of large press molds, high hardness and abrasive resistance are needed. To overcome these problems, we attempted to develop a combined heat treatment process consisting of local laser heat treatment followed by plasma nitriding, and evaluated the characteristics of the proposed heat treatment method. From the results of the experiments, it has been shown that the maximum surface hardness is 864 Hv by the laser heat treatment, 953 Hv by the plasma nitriding, and 1,094 Hv by the combined heat treatment. It is anticipated that the suggested combined heat treatment can be used to evaluate the durability of press mold.

Effect of Cu content on microstructural and magnetic properties of a (wt.%), (x = 0.2, 0.3, 0.4, 0.5) strip-cast was studied. The average inter-lamellar spacing in the free surface and wheel side of the strip cast increased as the Cu content increases. The grain uniformity, the grain alignment, and (00L) texture of the strip cast increased with Cu contents up to 0.4 wt.%. These microstructural changes were attributed to the decrease of the effective cooling rate of the melted alloy caused by the decrease of the melting temperature of resulting from Cu addition. Coercivity and remanence were increased because of the grain alignment and (00L) texture improvement with Cu contents up to 0.4 wt.%.

In this study, Cu-10Sn and Cu-10Sn-2Ni-0.2Si alloys have been manufactured by spray casting in order to achieve a fine scale microstructure and high tensile strength, and investigated in terms of microstructural evolution, aging characteristics and tensile properties. Spray cast alloys had a much lower microhardness than continuous cast billet because of an improved homogenization and an extended Sn solid solubility. Spray cast Cu-Sn-Ni-Si alloy was characterized by an equiaxed grain microstructure with a small-sized (Ni, Si)-rich precipitates. Cold rolling of Cu-Sn-Ni-Si alloy increased a tensile strength to 1220 MPa, but subsequent ageing treatment reduced a ultimate tensile strength to 780 MPa with an elongation of 18%.

Recently, metal molding has become essential not only for automobile parts, but also mass production, and has greatly influenced production costs as well as the quality of products. Its surface has been treated by carburizing, nitriding and induction hardening, but these existing treatments cause considerable deformation and increase the expense of postprocessing after treatment; furthermore, these treatments cannot be easily applied to parts that requiring the hardening of only a certain section. This is because the treatment cannot heat the material homogeneously, nor can it heat all of it. Laser surface treatment was developed to overcome these disadvantages, and, when the laser beam is irradiated on the surface and laser speed is appropriate, the laser focal position is rapidly heated and the thermal energy of surface penetrates the material after irradiation, finally imbuing it with a new mechanical characteristic by the process of self-quenching. This research estimates the material characteristic after efficient and functional surface treatment using HPDL, which is more efficient than the existing CW Nd:YAG laser heat source. To estimate this, microstructural changes and hardness characteristics of three parts (the surface treatment part, heat affect zone, and parental material) are observed with the change of laser beam speed and surface temperature. Moreover, the depth of the hardened area is observed with the change of the laser beam speed and temperature.

Austenite precipitation behavior was studied with solidification rates and alloying contents, N and Cr, in duplex stainless steels by directional solidification. Directional solidification experiments were carried out with solidification rates, 1~100mm/s, and N and Cr contents, 0~0.27wt.%, 25~28wt.% respectively, in a duplex stainless steel, CD4MCU. As the solidification rate increases, the dendrite spacing reduced and the austenite phase in the ferrite matrix became finer. The volume fraction of austenite phase increased and its shape went to be round with increasing nitrogen contents in duplex stainless alloys. The Cr alloying element, even though it is a ferrite former, showed to enhance the nitrogen solubility in the alloy and caused the austenite round and finer. Also, Cr was supposed to decrease the austenite volume fraction, but it increased the austenite slightly due to increasing nitrogen solubility during solidification.

폭주부족은 원방에서 근방을 주시할 때 양안을 정렬할 수 없는 현상이다. 일반적으로 근거 .리에서 외사위나 간헐성 외사시, 폭주근점 저하, 양성 융합 폭주력 저하, 낮은 AC/A 비에서 나타난다. 증상으로는 안정피로, 두통, 복시, 흐림 등이 나타난다. 폭주부족의 원인은 명확하지 않지만 조절부족과 관련이 있다. 근본적인 문제는 근거리에서 융합성 폭주가 부족하고 강한 외사위가 있는 경우이다. 시기능 훈련은 6주간 실시하였다. 훈련 실시 후에 자각증상들이 감소하였고 폭주근점이 증가하였으며 양성 융합 폭주력도 증가하였다.

In this work, the dispersion behavior of particles in binary aluminum (Al)-copper (Cu) cast alloy was investigated with respect to Cu contents of 20 (hypoeutertic), 33 (eutectic) and 40 (hypereutectic) wt.%. In cases of hypo and hypereutectic compositions, SEM images revealed that the primary Al and phases were grown up at the beginning, respectively, and thereafter the eutectic phase was solidified. In addition, it was found that some of particles can be dispersed into the primary Al phase, but none of them are is observed inside the primary 6 phase. This different dispersion behavior of particles is probably due to the difference in the val- ues of specific gravity between particles and primary phases. At eutectic composition, particles were well dispersed in the matrix since there is few primary phases acting as an impediment site for particle dispersion during solidification. Based on the experimental results, it is concluded that particles are mostly dispersed into the eutectic phase in binary Al-Cu alloy system.

This paper introduces a special spheroidizing technology at ultra-high temperature. The conventional cast tungsten carbide (YZ) is melted at high temperature, rapidly cooled and spheroidized on a new ultra-high temperature spheroidizing equipment to prepare various grades WSC powders.