• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2002년도 제5회 압출 및 인발가공 심포지엄
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• pp.43-49
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• 2002

A7003 alloy has characteristics of their excellent weldability, high corrosion resistance and superior plastic working however the broadening of application for the alloy has been hampered by the lower extrudability associated by Mg content. For improvement of extrudability and enhanced recovery efficiency during Al scrap recyeling, it has been generally practiced to reduce Mg content in A7003 alloy. Therefore, it is necessary to investigate the influence of Mg content on mechanical strength and extrudability of A7003 alloy. For efficient material processing which has small amounts, life cycle assessment in material processing(MLCA) is evaluated. The quantitative analysis of energy requirements and $CO_2$ emission for production of A7003 extruded bar are estimated with different Mg content and billet pre-heating process (heating source by light oil or LPG). In particular, the estimation of energy requirements was performed within shipping and gating range (except the mining and extraction stages)to investigate the influence of the variables on energy requirements and $CO_2$ emission in detail. As Mg content increased, the flow stress and the extrusion pressure for A7003 alloy increased. It has been thought that an increment in extrusion pressure with increasing Mg content is caused by the solid solution hardening of Mg atoms in the matrix and increment in volume fraction of intermetallic compound, $Mg_2Si$. The extrudability and the tensile strength are equal to, or above that of conventional A 7003 alloy even the content of Mg varied from $1.1wt.\%\;to\;0.5wt.\%$ alloy. This means that minimizing the content of Mg in A7003 alloy can enhance recovery efficiency during Al scrap recycling. It can be quoted that rather than Mg content energy source for billet heating is a prime factor to determine the atmospheric $CO_2$ emission.

• 소성∙가공
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• 제15권4호
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• pp.274-280
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• 2006

• 한국작물학회:학술대회논문집
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• 한국작물학회 2006년도 한국약용작물학회 공동춘계학술발표회
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• pp.640-641
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• 2006

• Journal of Pharmaceutical Investigation
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• 제5권1호
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• pp.41-48
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• 1975

Extrusion-Spheronization Processing (ESP) was applied to preparate sustained release spherical particles as a form of matrix spherical particle (MSP). dl-methylephedrine HCI (ME) was the drug chosen and several dissolution retardants and binders were selected to estimate a relatively good formulation on this purpose. The effect of physicochemical nature, concentration, and solvents of these dissolution retardants and binders on regularity in shape of MSP and in vitro release rate was investigated. The effect of Particle size of matrix particles was also evaluated. It is, therefore, concluded that this ESP would be a relatively good preparation method of sustained release MSP of ME which has the sustained action of about 5 and 8 hours by formulating of ethylcellulose and ethylcellulose-paraffin as a dissolution retardant, respectively, and then ethylcellulose solution of 80% EtOH is recommended as a binder.

• 소성∙가공
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• 제23권3호
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• pp.178-183
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• 2014

Continuous casting is a process where molten metal is solidified into a semi-finished billet on a large scale with either a rectangular or round cross section for subsequent processing. The use of continuous casting provides an opportunity for producing material on a practical industrial scale with lower cost than conventional casting. In the current study, the material was fabricated by continuous casting and subsequent extrusion. Tensile tests were conducted on continuous cast ZK60A after extrusion over a range of strain rates at temperatures from 473K to 623K. The alloy exhibits a quasi-superplastic behavior with a maximum recorded elongation of ~250% at 523K when tested with an initial strain rate of $10^{-5}/s$. The experiments give a strain rate sensitivity exponent of 0.3~0.4 and an activation energy of 108 kJ/mol. From the current investigation, it was found that the high-temperature plastic flow of the ZK60A is controlled by a dislocation viscous glide mechanism.

• Journal of Periodontal and Implant Science
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• 제45권2호
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• pp.46-55
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• 2015

Purpose: This study evaluated the mechanical and structural properties of biphasic calcium phosphate (BCP) blocks processed using a modified extrusion method, and assessed their in vivo effectiveness using a rabbit calvarial defect model. Methods: BCP blocks with three distinct ratios of hydroxyapatite (HA):tricalcium phosphate (TCP) were produced using a modified extrusion method:HA8 (8%:92%), HA48 (48%:52%), and HA80 (80%:20%). The blocks were examined using scanning electron microscopy, X-ray diffractometry, and a universal test machine. Four circular defects 8 mm in diameter were made in 12 rabbits. One defect in each animal served as a control, and the other three defects received the BCP blocks. The rabbits were sacrificed at either two weeks (n=6) or eight weeks (n=6) postoperatively. Results: The pore size, porosity, and compressive strength of the three types of bone block were $140-170{\mu}m$, >70%, and 4-9 MPa, respectively. Histologic and histomorphometric observations revealed that the augmented space was well maintained, but limited bone formation was observed around the defect base and defect margins. No significant differences were found in the amount of new bone formation, graft material resorption, or bone infiltration among the three types of BCP block at either of the postoperative healing points. Conclusions: Block bone substitutes with three distinct compositions (i.e., HA:TCP ratios) processed by a modified extrusion method exhibited limited osteoconductive potency, but excellent space-maintaining capability. Further investigations are required to improve the processing method.

• 소성∙가공
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• 제16권7호
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• pp.521-529
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• 2007

This paper is concerned with the analysis on the surface expansion of AA 2024 and AA 1100 aluminum alloys in backward extrusion process. Due to heavy surface expansion appeared usually in the backward can extrusion process, the tribological conditions along the interface between the material and the punch land are very severe. In the present study, the surface expansion is analyzed especially under various process conditions. The main goal of this study is to investigate the influence of degree of reduction in height, geometries of punch nose, friction and hardening characteristics of different aluminum alloys on the material flow and thus on the surface expansion on the working material. Two different materials are selected for investigation as model materials and they are AA 2024 and AA 1100 aluminum alloys. The geometrical parameters employed in analysis include punch corner radius and punch nose angle. The geometry of punch follows basically the recommendation of ICFG and some variations of punch geometry are adopted to obtain quantitative information on the effect of geometrical parameters on material flow. Extensive simulation has been conducted by applying the rigid-plastic finite element method to the backward can extrusion process under different geometrical, material, and interface conditions. The simulation results are summarized in terms of surface expansion at different reduction in height, deformation patterns including pressure distributions along the interface between workpiece and punch, comparison of surface expansion between two model materials, geometrical and interfacial parametric effects on surface expansion, and load-stroke relationships.

• 한국식품과학회지
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• 제27권6호
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• pp.934-938
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• 1995

Autoclaving, microwaving, 압출성형 등의 열 및 기계적 에너지에 대한 밀기울 세포벽의 반응성을 구명하기 위하여 수용성 분획의 특정을 연구하였다. 수용성 분획의 화학적 분석과 겔여과 크로마토그래피 결과에 의하면 밀기울에 포함되어 있는 전분의 호화가 가장 중요한 수용화 기작으로 작용하며, 이 과정에서 비전분성 세포벽 구성물질의 수용화도 일어냐는 것으로 밝혀졌다. 수용성의 비전분 다당류의 GC 분석결과 적용된 열처리 과정에서 세포벽의 arabinoxylan 부위가 많이 수용화되는 현상을 보였다. 특히, 고온파 고전단력을 동시에 제공하는 압출성형은 밀기울의 수용화에 가장 효율적이었으며, 또한 상대적으로 고분자량의 비전분성 구성성분을 수용 화시켰다.

• 한국식품영양과학회지
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• 제32권8호
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• pp.1270-1277
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• 2003

두유박과 옥분 혼합물의 압출성형물을 제조하기 위한 공정 조건의 위하여 스크류 속도 150∼250 rpm, 혼합물의 수분함량 20∼30%, 온도 100∼15$0^{\circ}C$의 조건에서 압출 성형하고, 반응표면분석법 (RSM)을 이용하여 최적 조건을 분석하였다. 공정 조건에 따른 팽화율에서는 스크류 속도가 높고 수분함량이 낮을수록 팽화가 크게 일어났고, 수분함량이 많을수록 용적 밀도를 높이는 것으로 나타났다. 절단강도의 경우 수분 함량에 따라 감소하다 증가하는 추세를 보여주었고, WSI는 스크류 속도와 수분함량에 WAI는 수분함량과 온도에 많은 영향을 받았다. 색도에서는 b＊ 값을 제외하고는 유의적인 차이를 보이지 않았다. 각 조건별 실험결과를 반응표면분석을 한 결과 팽화율과 용적 밀도, WSI, b＊ 값은 linear모델로 결정되었고, 절단강도와 WAI는 quadratic 모델이 유의성을 나타내었다. 압출 성형 공정의 최적화는 결정된 반응식과 반응표면 그래프를 이용한 결과 수치 최적화에서는 스크류 속도 250 rpm, 수분함량 22.43%, 온도 128.16$^{\circ}C$이었고, 모형적 최적화에서는 desirability가 0.727인 스크류 속도 250 rpm, 수분함량 22.43%, 온도 128.02$^{\circ}C$로 결정되었다.

• 소성∙가공
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• 제4권2호
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• pp.131-140
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• 1995

In this paper damage propagation of a material during forming is investigated with the concept of continuum damage mechanics. An isotropic damage model based on the theory of materials of type N is adopted to describe the damage process of a ductile material with large elasto-viscoplastic deformation. The stiffness degradation of the loaded material is chosen as a damage measure. The highly nonlinear equilibrium equations are reduced to the incremental weak form and approximated by the total Lagrangian finite element method. To simulate contact condition, extended interior penalty method with modified coulomb friction law is adopted. The displacement control method along with the modified Riks' continuation technique is used to solve the incremental iterative equations. As numerical examples, upsetting problem and backward extrusion problem are simulated and the results of damage propagation and $J_2$ stress contours with and without friction are presented.