• Design & Manufacturing
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• 제14권4호
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• pp.52-57
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• 2020

In this study attempted to prevent defects due to blow holes among defects of sand casting products. It was intended to reduce the defect rate by reducing the blow hole of the inner surface. Currently, expectations and requirements for the quality level of non-ferrous aluminum casting in the casting industry are increasing. In addition, the shape is complex and the shrinkage precision is required. Among them, the test prototype is expensive to manufacture the mold, and the production time is also long, and the product is manufactured by sand casting. At this time, the highest defect rates are defects caused by shrinkage defects, surface defects, and blow holes.. At this study, the manufacturing time was shortened by using the shape of the fluid movement path in advance. Also, it is possible to reduce defects due to blow holes.

• 한국주조공학회지
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• 제41권6호
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• pp.521-527
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• 2021

본 연구는 고압 다이캐스팅 공정에서 제품 결함을 사전에 예측하기 위한 기계 학습 기반의 공정 관리 모델 개발에 관한 연구이다. 모델은 이전 사이클에서의 온도를 입력받고, 사이클에 걸쳐서 나타나는 특징을 인식하여 다음 사이클의 결함 발생 여부를 예측한다. 기어 박스 형상에 대하여 제안된 알고리즘을 적용하여, 3 사이클의 정보를 통해서 98 .9%의 정확도와 96.8 %의 재현율로 제품 수축 결함을 사전에 예측하였다.

• 한국세라믹학회지
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• 제50권2호
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• pp.142-148
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• 2013

Conventional cold isostatic pressing, slip casting, and filter pressing are not completely suitable for fabricating large plates because of disadvantages such as the high cost of equipment and formation of density gradient. These problems could be avoided by employing pressure-vacuum hybrid slip casting (PVHSC). In the PVHSC, the consolidation occurs not only by the compression of the slip in casting room, but also by vacuum sucking of the dispersion medium around the mold. We prepared the alumina bodies by the PVHSC in a static- or stepwise-pressure manner for loading up to 0.5 MPa using an aqueous slip. The green bodies were dried at $30^{\circ}C$ with 40 ~ 80% relative humidity. Under static pressure, casting induced a density gradient in the formed body, resulting in cracking and distortion after the firing. However, the stepwise pressure loading resulted in green bodies with homogeneous density, and the minimization of the appearance of those defects in final products. Desirable drying results were obtained from the cast bodies dried with 80% RH environment humidity. When sintered at $1650^{\circ}C$ for 4 h, the alumina plate made by stepwise-pressure casting reached full density (> 99.7% relative density).

• 한국안전학회지
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• 제27권4호
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• pp.7-12
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• 2012

In this study, the solidification characteristics inside the AC7A casting material was analyzed using the numerical analysis method and was verified using the experimental method by the pre-heated temperature conditions of metal casting device. For the numerical analysis, "COMSOL Multiphysics", the commercial code based on the finite element analysis(FEA), was used in order to predict the thermal deformation of the AC7A casting material including temperature, displacement and stress distribution. Also, in order to verify the results calculated by the numerical analysis, the experiment for temperature measurement inside the AC7A casting material was performed using the K-type thermocouple under the same condition of numerical analysis method. In the numerical results, thermal deformation inside AC7A casting material was well-suited for manufacturing products when the pre-heated temperatures of the metal casting device was $250^{\circ}C$. When the results of the temperature distribution were experimentally measured and were compared with those of the numerical result, it appeared that there was some temperature difference because of the latent heat by phase change heat transfer. However, the result of cooling temperature and patterns were almost similar except for the latent heat interval. The solidification characteristics was closely related to the temperature difference between the surface and inside of the casting.

• Advances in concrete construction
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• 제10권5호
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• pp.455-462
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• 2020

This study investigated the effect of horizontal casting joints on the mechanical properties and structural behavior of sustainable self-compacting reinforced concrete beams (SCRCB). The experimental research consisted of two stages. The first stage used four types of concrete mixtures which were produced to indicate the effects of cement replaced with cement waste at 0%, 5%, 10%, and 15% by weight of cement content on fresh concrete properties of self-compacting concrete (SCC) such as, passing ability, filling ability, and segregation resistance. In addition, mechanical properties such as compressive, tensile, and flexural strength were also studied. The second stage selected the best mixture from the first stage and studied the effect of horizontal casting joints on the structural behavior of sustainable SCRCBs. The effect of horizontal casting joints on the mechanical properties and structural behavior were at the 25%, 50%, 75%, and 100% of sample height. Load deflection, failure mode, and theoretical analysis were studied. Results indicated that the incorporation of replacement with cement waste by 5% to 10% led to economic and environmental advantages, and the results were acceptable for fresh and mechanical properties. The results indicated that delaying the time for casting the second layer and increasing the cement waste in concrete mixtures had a great effect on the mechanical properties of SCC. The ultimate load capacity of horizontal casting joints reinforced concrete beams slightly decreased compared with the control beam. The maximum deflection of casting joint beams with 75% of samples height is similar with the control beam. The experimental results of reinforced concrete beams were substantially acceptable with the theoretical results. The failure modes obtained the best forced casting joint on the structural behavior at 50% height of casting in the beam.

• 열처리공학회지
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• 제27권6호
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• pp.281-287
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• 2014

Microstructural and mechanical characteristics of Al-6Si-2Cu alloy for engine mount bracket prepared by gravity casting (as-cast) and die-casting (as-diecast) process have been investigated. For the microstructural characterization, the inductively coupled plasma mass spectrometry (ICP-MS), optical microscope (OM), scanning electron microscope (SEM) and electron probe microanalysis (EPMA) analyses are conducted. For the intermetallic phases, the X-ray diffraction (XRD) and energy dispersive spectroscopy (EDS) are also conducted with quantitative and qualitative analysis. Micro Vickers hardness and static tensile test are achieved in order to measure mechanical properties of alloys. Secondary dendrite arm spacing (SDAS) of as-cast and as-diecast show 37um and 18um, respectively. A large amount of coarsen eutectic Si, $Al_2Cu$ intermetallic phase and Fe-rich phases are identified in the Al-6Si-2Cu alloy. Mechanical properties of gravity casting alloy are much higher than those of die-casting alloy. Especially, yield strength and elongation of gravity casting alloy show 2 times higher than die-casting alloy. After shot peening, shot peening refined the surface grains and Si particles of the alloys by plastic deformation. The surface hardness value shows that shot peening alloy has higher value than unpeening alloy.

• Design & Manufacturing
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• 제15권2호
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• pp.30-35
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• 2021

The casting method uses a mold to solidify a liquid metal to make a solid metal. Since it uses a liquid metal with the least deformation resistance, it has the characteristic that it can easily manufacture even a complex shape. However, the process of solidifying a liquid metal into a solid metal inevitably involves a volume change and contains internal defects such as shrinkage holes. Therefore, in the design of the casting plan, an excess volume called a pressurization compensates for the volume shrinkage. in the product, and it induces the shrinkage hole defects to occur in parts other than the product1). In this study, casting analysis was performed using casting analysis software (anycasting) in order to optimize the design of the tilting gravity casting method for automobile brackets. In particular, the filling and solidification analysis according to the shape and volume of the pressurized metal was conducted, and applied to the actual product to study the effect of the pressurized metal on the shrinkage defect. Through this study, it is possible to understand the effect of the pressure metal on shrinkage defects in the actual product and propose a design of the pressure metal that improves reliability and productivity.

• 한국결정성장학회지
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• 제32권1호
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• pp.25-32
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• 2022

인베스트먼트 주조는 정밀기기, 의료분야, 액세서리 등의 제조에 일반적으로 사용되는 생산방식으로 장비의 현대화와 고품질의 재료를 통해 발전을 거듭해 왔으며 그 활용 범위가 확대되고 있다. 본 연구의 목적은 인베스트먼트 주조 공정의 핵심 요소인 금형 온도의 구조적 개선 및 표준화를 도출하여 불량률을 최소화하여 경제성과 생산성을 향상시키는 것이다. 연구의 범위는 소형탕도의 구조와 원리를 이해하기에 적합한 Jewelry 제조 주조 공정에 국한되어 있으며 연구 재료로 soft Wax, 석고 분말 및 14 K Gold를 사용하여 실험적 연구를 수행했다. 그 결과 Alloy 14 k의 주물 패턴에 가장 적합한 주물 표준 온도는 980℃ 플라스크 온도 550℃에서 가장 낮은 난류로 좋은 제품을 생산할 수 있었다. 본 연구의 향후 과제로 소형탕도의 구조 및 표준온도를 데이터를 분석하고, 현장의 생산 불량을 감소시키고 우수한 인베스트먼트 주조 공법의 경쟁력 확보를 위한 데이터를 제공하기 위한 세부 연구가 필요하다.

• 한국주조공학회지
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• 제37권6호
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• pp.173-180
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• 2017

In this paper, the casting design of the integrated twin-scroll turbine housing with exhaust manifold using stainless steel is investigated. Due to the complexity in its geometry and the poor castability of stainless steel, it is more crucial to set up the appropriate casting design to avoid casting defects. Gas porosity and shrinkage formation with the changes of gating systems (one-/two-side), riser conditions and pouring temperatures are examined via casting simulation and virtual castings. Simulation results show that two-side gating system produced better quality casting than that of one-side gating system, minimizing the gas content of the castings and it is also verified by X-ray analysis for the virtual castings. For the changes of riser conditions and pouring temperatures in the two-side gating system, it is found that the change of the height of two risers plays an important role in obtaining the best quality by reducing shrinkage defects.

• 한국정밀공학회지
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• 제28권11호
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• pp.1309-1315
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• 2011

The design process for obtaining the reliable steeraxle casting beam of fork lift truck is studied in this paper, as the casting beam is major component of steeraxle which has a steering function at driving. In this study, the driving mode and damage pattern of casting beam which could be occurred from the customer site were analyzed and it established the design process to predict the fatigue life by FEA(Finite Element Analysis) so that the reliability of steeraxle casting beam could be verified at DVT(Design Validation Test) mode. This paper provides guidance on the process of designing the reliable steeraxle casting beam at the initial design stage and also, provides guidance on the process of solving the problem when the failure is occurred in the field.