In this study, we designed the 3-dimensional tire mold according to the A automobile company’s tire model, and analysed the distribution of temperature of mold using the numerical method when the heat flux and heat transfer time at the surface of tire mold were changed. A analysis region of mold was the 1/16 of entire mold, and the grid number was about more than 880 thousand. In order to analyze the temperature change of mold, the thinnest part of the mold was chosen as the research object, and then the temperature of 6 points on the vertical downward direction of the thinnest part was analyzed with the time change. While the numerical condition was that heat flux was 321,200 W/m2, 440,000 W/m2 and 880,000 W/m2, and measuring time was 0.1 second, 0.2 second, 0.5 second and 1 second, respectively. As a result, the temperature difference between the surface temperature and the lowest temperature of mold was 7.3℃ when the heat transfer time was 0.1 second. Also, the minimum temperature difference was almost 0.11℃ when the heat transfer increased to 1 second. It can be explained that the main material of tire mold was aluminum and its thermal conductivity was high (k=140 W/m·K). In addition, when the heat transfer time was more than 1 second, the heat flux of mold surface will be transmitted at the inside of the thinnest part, and the heat transfer will be a marked difference according to the shape of the thinnest part.

In recent years, demands for sintered ferrous material with higher strength are increasing. To satisfy these demands, studies and commercial use of the die wall lubrication method, the warm compaction method and the combination of both methods are widely carried out to achieve high density. The die wall lubrication warm compaction method makes it possible to achieve high density by reducing internal lubricant through die wall lubrication, although the method involves several issues such as prolonged cycle time due to lubricant spraying and difficulty in spraying lubricant in the case of compacting with complicated geometry. Meanwhile, the conventional warm compaction method requiring no die wall lubricant application cannot achieve such a high density as in the case of die wall lubrication warm compaction due to higher volume of internal lubricant. However, this report discloses our study result in which the possibility of improving density is exhibited by using a lubricant type with superior dynamic ejection property that can reduce volume of lubricant additive.

In the present study, the focus is on the analysis of the effect of the mold dimensions on the temperature distribution of a die during plasma activated sintering. The temperature distribution of a cylindrical mold with various dimensions was measured using K-type thermocouples. The temperature homogeneity of the die was studied based on the direction and dimensions of the die. A temperature gradient existed in the radial direction of the die during the plasma activated sintering. Also, the magnitude of the temperature gradient was increased with increasing sintering temperature. In the longitudinal direction, however, there was no temperature gradient. The temperature gradient of the die in the radial direction strongly depended on a ratio of die volume to punch area

초합금의 진공정밀주조시에 진공하에서 용해한 합금을 1000~1700˚C로 가열한 세라믹 주형에 주입하고 난 후, 용탕이 장시간 주형안에 노출됨으로써, 주형의 고온강도가 높아야 하므로 고품위의 주형재를 사용하여 왔으나, 저품위의 값싼 소재를 사용하여 고품위의 주형과 동등한 효과를 갖게 하고자 주형내의 Silica 함량을 조절하였다. 그 결과 SiO2 첨가량이 7.7wt.%일 때, 다른 시험편에 비해 소성강도와 고온강도가 10-55%가량 증가 하였다. 따라서 일반적으로 정밀주조 주형으로 사용하는 용융알루미나와 colloidal silica의 혼합비를 제어하여 단결절 주조용 주형을 개발하였다.

본 연구는 타설 콘크리트의 온도를 무선센서 방식으로 현장에서 직접 간편하게 계측할 수 있는 장치를 개발하고, 무선 전송네트워크시스템을 통하여 현장사무실 및 본사 등에서 실시간 효율적 온도이력관리를 할 수 있는 시스템을 구축하는데 목적이 있다. 실험결과, 우선 무선센서네트워크시스템의 기본이 되는 온도센서는 콘크리트 타설시 안정적으로 측정될 수 있도록 무선방식의 막대타입의 스텐레스 프로브형으로 제작하였으며, 거푸집에서의 탈부착이 간편하고 장기간의 내장전력공급이 가능한 거푸집일체형의 무선센서네트워크 장치를 개발하였다. 또한 무선센서네트워크시스템의 구성은 센서노드와 라우터, 게이트웨이 및 CDMA 통신방식으로 구성하였으며, 콘크리트의 동일한 양생조건 및 상이한 양생조건에서 온도를 측정한 결과, 기존의 유선방식과 동일한 온도분포를 보였다. 향후, 개발된 무선센서네트워크 장치를 현장에서 사용할 경우, 현장 사무실에서의 정량적인 콘크리트 온도관리가 효율적으로 이루어 질 것으로 판단되며, 감리 감독업무의 생산성 향상과 더불어 전반적인 콘크리트 구조체의 품질에 크게 기여할 것으로 판단된다.