• 소성∙가공
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• 제11권6호
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• pp.503-512
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• 2002

The drawbead is used to control material flow into the die during the binder wrap process and the stamping process in the sheet metal forming process. Since the dimension of drawbead is relatively small in comparison with the typical dimensions, it is difficult to include drawbeads in finite element analysis of the sheet metal forming process. It is because the mesh system has to be fine enough to describe the drawbead and the computation time is drastically increased. In this paper, simulation of drawbead forming has been carried out to obtain the equivalent boundary conditions in the binder wrap process and the stamping process. In order to investigate the effect of various die geometries, parameter studies are performed with the variation of parameters such as the blank length, the drawbead depth, the drawbead radius, the inclination of die and the friction coefficient.

• 소성∙가공
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• 제23권3호
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• pp.145-150
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• 2014

Precision control of the slab is crucial for product quality and production economy in hot strip mills. The current study presents a new model for predicting width spread of a slab with a rectangular cross section during roughing. The model is developed on the basis of the extremum principle for a rigid plastic material and a three dimensional admissible velocity field. This model incorporates the effect of process variables such as the shape factor and the ratio of width to thickness. We compare the results of this model to 3-D finite element (FE) process simulations and also to results from a previous study.

• 품질경영학회지
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• 제41권3호
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• pp.457-463
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• 2013

Purpose: For effective quality assurance activities, BOM-based quality assurance method is presented. This study introduces various BOM conversions such as Q-BOM, T-BOM, and S-BOM based on M-BOM structure. Methods: Product quality control via Q-BOM manages inspection/audit information, overall supply-chain of product, part requirements, and inventory status. T-BOM manages part traceability, and S-BOM enables statistical control over key process and parts at various hierarchy levels. Results: Quality plan template was developed based on the study results of BOM system including Q-BOM, T-BOM, and S-BOM. Conclusion: Through BOM(Q-BOM, T-BOM, and S-BOM) study and development of quality plan template, more systematic and comprehensive quality management plan is achieved.

• Advances in concrete construction
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• 제3권1호
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• pp.55-69
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• 2015

Tailing Material (TM) and Fly Ash (FA) are obtained as waste products from the mining and thermal industries. Studies were carried out to explore the possibility of utilizing TM as a part replacement to fine aggregate and FA as a part replacement to cement, in concrete mixes. The effect of replacing fine aggregate by TM and cement by FA on the standard sized specimen for compressive strength, split tensile strength, and flexural strengths are evaluated in this study. The concrete mix of M40 grade was adopted with water cement ratio equal to 0.40. Concrete mix with 35% TM and 65% natural sand (TM35/S65) has shown superior performance in strength as against (TM0/S100, TM30/S70, TM40/S60, TM50/S50, and TM60/S40). For this composition, studies were performed to propose the optimal replacement of Ordinary Portland Cement (OPC) by FA (Replacement levels studied were 20%, 30%, 40% and 50%). Replacement level of 20% OPC by FA, has shown about 0-5% more compressive strength as against the control mix, for both 28 day and 56 days of water curing. Interestingly results of split tensile and flexural strengths for 20% OPC replaced by FA, have shown strengths equal to that of no replacement (control mix).

• 폴리머
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• 제36권6호
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• pp.677-684
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• 2012

사출성형공정은 고온으로 수지를 가소화시키고 고압으로 금형에 흘려 보내어 제품을 성형하는 방법이다. 이 과정에서 고분자 수지는 온도의 변화에 따라 수축을 하게 되는 성형수축이 발생된다. 그리고 시간이 흐른 뒤에도 제품에 변형이나 휨이 발생하게 되는데 이는 제품에 포함되어 있는 잔류응력의 이완 때문이다. 이러한 휨을 막기 위해 수지에 무기물을 첨가하여 수축을 줄이거나, 수지에 유리섬유나 카본섬유 등 섬유를 사용하여 휨의 저항성을 높인다. 그리고 성형품을 강건하게 설계하여 응력에 따른 휨의 저항을 향상시킨다. 본 연구에서는 강건설계를 위해 리브를 설치한 성형품에 나타나는 휨을 실험을 통하여 조사하였다. 성형조건에 따라서, 그리고 금형설계에 따라서 즉, 게이트의 위치에 따라서 휨의 변화를 조사하였다. 수지의 흐름방향과 흐름의 직각방형의 휨도 조사하였다. 게이트 근처와 게이트에서 먼 부분의 휨도 비교분석 하였다. 수지는 유리섬유로 보강된 결정성 수지인 PP와 PA66를 사용하였다. 유리섬유가 포함된 결정성 수지는 유리섬유가 포함된 비결정성 수지보다 휨이 컸다. 결정성 수지는 비결정성 수지에 비해 휨이 성형조건에 다소 적게 영향을 받았지만 제품의 설계에 따라서는 크게 변하였다.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2003년도 The 8th Asian Symposium on Precision Forging ASPF
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• pp.59-62
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• 2003

The precision cold forging of helical gear for steering pinion has been studied. Because of the large helix angle, there are many difficult problems to control the material flow and part dimension. The die shape was proposed to improve the flow of workpiece. In order to improve the dimensional accuracy of forged part, a FE analysis was performed. The proposed die shape drives to flow amicably workpiece. The applied load was reduced up to 10 percent, compared to the conventional-shaped-die. The elastic deformation of die has been investigated quantitatively by the 3-dimensional FE analysis. The die-land has been expanded up to $10{\mu}m$ on loading stage, based on the FEM results. Therefore, the elastic deformation amounts should be taken into consideration to improve the dimensional accuracy of forged helical gear.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2004년도 추계학술대회논문집
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• pp.99-102
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• 2004

In rheo forming process, slurry making is very important factor because the microstructure of slurry affects the quality of final products. To control the microstructure of slurry, slurry making by new rheo die casting was studied. In new rheocasting method, processes parameters are degree of overheat in molten metal, cooling condition, high frequency induction heating condition and cup temperature. Microstructures according to these parameters were observed. By image analysis, equivalent diameter and roundness of grain were investigated and discussed. To find out mechanical properties of grain controlled aluminum part by rheo die casting, tensile tests were carried out to the T6 heat treatment.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 하계학술대회 논문집 D
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• pp.2535-2537
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• 2000

In order to detect and monitor the broken cords of steel-cord belt from being damaged by impact of large lump of materials and the corrosion of steel cord, we developed a non-contact magnetic coil detection system. This measures the deterioration of reinforcing cables in steel cord conveyor belt which transport the ores in raw material plant. In this research, magnetic coil sensor of broken-cord detection system has exciting part and sensing part. The broken-cord detection system is operated by supplying a transmitter coil with electric power to generate magnetic field, and then the change of induced voltage is detected in each receiver coils due to resultant magnetic flux effected by the broken steel cords at the inside of the conveyor belt. By the informations such as the position and size of the broken steel cords obtained by SCBMS(Steel Cord Belt Monitoring System), it is expected that not only the span of belt life will be lengthened, but also this system can enable operators to plan scheduled maintenance and prevent the enlargement of damaged parts in steel cord belt at an early stage

• 콘크리트학회논문집
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• 제23권1호
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• pp.87-98
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• 2011

철근콘크리트 부재의 균열은 필수불가결한 현상이다. 따라서 효과적으로 균열폭을 측정하기 위한 많은 경험식이 제시되었고, 또한 간편한 적용성 때문에 철근 간격과 직경의 제어를 통한 간접균열제어법이 제시되고 널리 사용되고 있다. EC2에서는 최대균열간격과 평균변형률의 곱으로 설계 균열폭을 산정한다. 이 연구에서는 재료 특성에 따른 최대철근간격과 최대철근직경을 산정하였다. 특히 인장증강효과 모델과 최대균열간격에 따른 영향을 분석하였고, 이를 콘크리트구조설계기준에서 제시한 값과 비교하였다. 해석 결과 인장증강효과 모델에 따라 큰 차이가 발생하였고, 2차식 형태의 인장증강효과 모델과 Part II의 최대균열간격을 사용함으로써 과소평가되었다. 따라서 2차식 형태의 인장증강효과 모델을 사용함으로써 합리적인 간접균열제어가 가능하다. 또한 이를 통해 휨부재의 사용성 검증에 일관성을 확보할 수 있을 것으로 판단된다. 이와 함께 균열제어를 위한 두 가지 모델을 제안하였다.

• Structural Engineering and Mechanics
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• 제5권3호
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• pp.221-237
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• 1997

This paper presents a new uniaxial material model for rate-sensitive analysis addressing both the transient and steady-state responses. The new model adopts visco-plastic theory for the rate-sensitive response, and employs a three-parameter representation of the overstress as a function of the strain-rate. The third parameter is introduced in the new model to control its transient response characteristics, and to provide flexibility in fitting test data on the variation of overstress with strain-rate. Since the governing visco-plastic differential equation cannot be integrated analytically due to its inherent nonlinearity, a new single-step numerical integration procedure is proposed, which leads to high levels of accuracy almost independent of the size of the integration time-step. The new model is implemented within the nonlinear analysis program ADAPTIC, which is used to provide several verification examples and comparison with other experimental and numerical results. The companion paper extends the three-parameter model to trilinear static stress-strain relationships for steel and concrete, and presents application examples of the proposed models.