• Journal of Adhesion and Interface
• /
• v.12 no.3
• /
• pp.94-98
• /
• 2011

Ballistic property of Heracron/phenol composites was evaluated as a function of polyurethane (PU) type and their loadings. First, prepregs of phenol and polyurethane were prepared by spray coating on Heracron fabric and then they were utilized to prepare composite by varying their ratio. Next, they were consolidated at $150^{\circ}C$ for 25 min at $150kg/cm^2$ pressure and then ballistic property was measured with 1.1 g FSP (22 cal). V50 was evaluated interms of polyurethane type and ratio of phenol/PU prepreg.

• Proceedings of the KSME Conference
• /
• 2007.05a
• /
• pp.279-284
• /
• 2007

Elasto-forming has been dedicated to specific and limited production. Today, using enhanced pad materials, it has become an efficient and economical process alternative for low and medium volume metal-forming production. The non-linear properties of elastomer which are described as strain energy function are important parameter to design and evaluate of elastomer component. These are determined by material tests which are uni-axial tension and bi-axial tension. In order to investigate the design paramerer, Finite element analysis was carried out for elasto-forming process.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.34 no.5
• /
• pp.549-556
• /
• 2010

In general, materials that can be used to form elastic pads, such as urethane and rubber, are often used in flexible forming processes by inserting the pads between a blank and flexible die for smoothing the forming surface that is formed by a reconfigurable die. In this study, the effects of the elastic pad on formability in the flexible forming process for sheet metals are investigated by performing numerical simulations. In the simulation, the hyperelastic material model is used, where the urethane elastic pads serve as elastic cushions. Case studies are carried out for elastic materials with different hardness values and thicknesses. The results are used to evaluate formability by comparing the configuration of the deformed blank and its major cross-sectional profiles. It is verified that the elastic pad used in the flexible forming process for sheet materials should be hard and that its thickness should be chosen appropriately.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.31 no.3D
• /
• pp.413-420
• /
• 2011

An experiment was conducted to suggest the road pavement material combining wooden chip crushed from little useful roots and branches from logging sites or wood waste from construction sites with urethane resin. For the specimen, the mass ratio of urethane resin to construction wood waste chip/lumber waster chip was set to three different levels of 0.5, 0.75, and 1.0, which was measured, mixed with mixer, and molded; 7 days after, tensile strength test, elasticity test using golf balls and steel balls, permeability coefficient measurement, and flammability test were executed. As the result, the tensile strength of the specimen at the dry state in the air exhibited the range of 0.2-1.1MPa, and there was no change after 7 days of aging. When submerged in water, however, the strength was partially diminished; the diminishing rate was greater for less urethane resin usage, and therefore it appears desirable to set the mass ratio of resin to the wood waste chip over 0.75 to consider the moisture intrusion by precipitation and such. As the result of elasticity test, the GB and SB coefficients of the specimen using wood waste chips and urethane resin were measured to be low at below 20%, exhibiting excellent elasticity as road pavement material. Also, the permeability coefficient was over 0.5mm/sec for specimens of all combinations, exceeding the standard value required after construction for permeable pavement material, and the flammability of wood-type pavement material was evaluated to have no practical issues.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.15 no.6
• /
• pp.50-57
• /
• 2016

Refrigerator glass shelves are manufactured by Insert Injection Molding. The current process of injection of glass into the mold induces movement of the core, on urethane springs. Defects in the product can result from too low a force being transmitted from the springs. To solve this problem, the force on the moving core and the injection molding pressure were subjected to numerical analysis. Based on this, the number of urethane springs as well as their hardness was changed to improve the situation. The number of springs was changed from 6 to 4. The diameter of the springs was increased from ${\emptyset}75$ to ${\emptyset}100$, and the hardness was increased from 70 (shore A) to 90 (shore A). These improvements caused the force on the molding core to increase by approximately 65,442 N. The proportion of defects decreased by 66%.

• Proceedings of the Korean Powder Metallurgy Institute Conference
• /
• 2003.04a
• /
• pp.59-59
• /
• 2003

경사기능 재료는 위치에 따른 특성 변화를 갖고 있어 변화하는 주변 환경에서 사용되는 재료의 응용성을 높일 수 있는 장점이 있다. 적합한 경사기능 재료의 제조를 위해서는 탄성률, 강도, 인성 등의 위치에 따른 변화를 예측하는 것이 필요하다. 그러나 재료 내에서의 탄성률 변화 등으로 인해 경사기능 재료에서 인성을 정량적으로 표현하는데는 어려움이 있으므로 이를 정량적으로 측정하고, R-curve를 결정하는 것은 재료의 응용성에 중요한 인자가 된다. 본 연구에서는 폴리우레탄 스폰지를 이용하여 밀도의 분포가 연속적으로 다른 폴리 우레탄 스폰지를 제조하고 이에 알루미나 분말 슬러리를 이용하여 slip casting을 행하였다. 그 후 폴리 우레탄 스폰지를 탈지한 후 알루미나 성형체를 소결하여 연속적인 기공률 분포가 다른 다공성 알루미나를 제조하였으며, 이에 Al을 용침하여 $Al_2O_3-Al$ 경사기능 재료를 제조하였다. 이러한 $Al_2O_3-Al$ 경사기능 재료에 대해 파괴인성 및 R-curve 특성을 CT(conpact tension)시편으로 측정하였으며, 이를 균일한 복합체의 파괴인성과 비교하였다. 또한 잔류 응력 특성을 파악하기 위해 실험적이 응력 데이터를 Moire interferometry를 이용하여 결정하였다. 또한 이를 유한요서 해석법(FEM)에 의한 계산치와 비교하였다. 서로 다른 조성 분포를 갖는 $Al_2O_3-Al$ 경사기능 재료와 균일한 복합체의 파괴인성을 비교한 결과 동일한 Al조성에서도 서로 다른 파괴 인성치가 나타났다. $Al_2O_3-Al$ 경사기능 재료에서 파괴인성에 영향을 줄 수 있는 인자로는 술수한 $Al_2O_3$의 파괴인성에 Al금속의 소성변형에 의한 인성증진 효과, 그리고 경사기능 재료에서 상호 조성차이에 따른 잔류응력을 고려할 수 있을 것이다. 이중 $Al_2O_3-Al$ 경사기능 재료의 파괴인성에 미치는 잔류응력의 영향을 고려하기 위해 이의 잔류응력에 대해 실험에 의한 유추된 잔류응력과 FEM계산에 의해 유추된 잔류 응력을 비교, 분석하였다.

• Polymer(Korea)
• /
• v.36 no.4
• /
• pp.413-419
• /
• 2012

Multi-functional urethane acrylate monomers as the curing agent of poly(phenylene ether) (PPE) were synthesized and then the urethane bond formation was checked by FTIR spectrometry and NMR analysis. The synthesized monomers were mixed with PPE and fabricated to dielectric substrates. After forming PPE/monomer composite sheets by a film coater, several sheets were laminated to a test substrate in a vacuum laminator and then its properties depending on the type and the amount of monomers, such as dielectric constant, dielectric loss, and peel strength, were measured. Between the two different hydroxyl acrylates, when the monomer synthesized with 2-hydroxy-3-phenoxypropyl acrylate containing a phenyl group was used as a curing agent, a smaller dielectric loss was obtained and the dielectric constant and loss decreased with a decrease in the amount of the monomer. The peel strength values of the test substrates, however, did not show any specific difference between the cases of two synthesized monomers. As a result, it was obtained the polymer substrate for high frequency application having peel strength of about 10 N, low dielectric constant of 2.54, and low dielectric loss of 0.0027 at 1 GHz.

• Journal of the Korean Society of Manufacturing Technology Engineers
• /
• v.18 no.4
• /
• pp.436-441
• /
• 2009

An air filter is a device to remove dust from the air supplied to the automotive engine. A requirement for the optimum air filter is to improve the capability to remove particles from the air it takes in, that is the efficiency and amount of dust collection. By removing dust from the air, the air filter prevents the engine cylinder from wear, reduces ventilation resistance, and thus improves engine output and guarantees intake performance. In order to guarantee such air filter performance, it is very important to properly seal the air filter. For passenger cars made in Korea, the air filters are fabricated with steel caps as their frames are large and their engine capacity is big. Recently however, European countries and Japan started using urethane for manufacturing the air filter, so that all foreign-made cars now have urethane filters. The urethanes used for air filters are applied in two ways: One is to use soft urethane for both top and bottom of the air filter and the other is to use soft urethane for the top and hard urethane for the bottom. Each of these method has unique problems. In this study, hard urethane is used for both top and bottom of the filter in order to improve those problems and increase the sealing efficiency. Especially for the top, NBR (rubber mold) is pre-settled in tough urethane and then the urethane is solidified through foaming, which makes it possible to develop a solid and double-sealed filter.

• Journal of the Korean Chemical Society
• /
• v.25 no.4
• /
• pp.214-218
• /
• 1981

Kinetic studies were carried out on urethane polymerization reaction of hydroxyl-terminated polybutadiene with isophorone diisocyanate under presence of Hexogen as solid additive. The rate was found to increase with the amount of Hexogen added. However the rate acceleration was not a catalytic effect but solely due to an increase of activation entropy. The reaction was a good 2nd order process with nearly constant activation energy of 8.4 kcal/mole.

• Elastomers and Composites
• /
• v.43 no.3
• /
• pp.173-182
• /
• 2008

Rubber-pad forming process for materials such as metal in which portions of the die which act upon the material is composed of a natural or synthetic rubber or elastomer material. This makes the rubber pad forming process relatively cheap and flexible, high accuracy for small product series in particular. In this study, we carried out the physical test and finite element analysis of elastomer such as natural rubber and urethane for steel rack rube forming. The non-linear property of elastomer which are described as strain energy function are important parameter to design and evaluate of elastomer component. These are determined by material tests which are uni-axial tension and bi-axial tension. This study is concerned with simulation and investigation of the significant parameters associated with this process.