• Journal of Korea Technical Association of The Pulp and Paper Industry
• /
• v.42 no.1
• /
• pp.48-53
• /
• 2010

Commercial micro pulps(Arbocel) were coated with three kinds of polymers using spray method. These coated micro pulps were used to papermaking additives to evaluate retention, drainage and physical properties of paper. The retention and drainage were improved with addition of polymer coated micro pulp. The bulk index of paper was also increased, but tensile and tear strength were decreased slightly, probably due to weakening of internal bonding. These results showed that the use of polymer coated micro pulp was an effective method to improve retention, drainage and bulk index of paper.

• Journal of Ocean Engineering and Technology
• /
• v.10 no.4
• /
• pp.58-66
• /
• 1996

The purpose of this investigation is to estimate the strength with the variations of the notch shape and the adgesive condition at the fiber/matrix micro interface of E-glass/PP laminates. To promote the degradation of the adhesive condition at the fiber/matrix micro interface without matrix dissolution loss, low-, hot-wet and spiking tests were carried out. The absorpotion properties and the tensile properties were compared accrding to the fiber orientation and the content. The results show that, firstly, saturated moisture absorption was reached at 5cycles and their absorptions of RD-40, UD-42 and UD-50 are 0.68%, 0.63%, 0.60%, respectively. Secondly, all the specimens investigated were mostly degraded at 5cycle, whereas UD-50 having ellipse shaped notch the least decrement of strength.

• Proceedings of the KACD Conference
• /
• 2002.11a
• /
• pp.706-706
• /
• 2002

No Abstract, See Full Text

• Korean Journal of Materials Research
• /
• v.22 no.10
• /
• pp.513-518
• /
• 2012

Recently, automobile parts have been required to have high strength and toughness to allow for weight lightening or improved stability. But, traditional micro-alloyed steel cannot be applied in automobile parts. In this study, we considered the influence of quenching temperature and cooling rate for specimens fabricated by vacuum induction furnace. Directly quenched micro-alloyed steel for hot forging can be controlled according to its micro structure and the heat-treatment process. Low carbon steel, as well as alloying elements for improvement of strength and toughness, was used to obtain optimized conditions. After hot forging at $1,200^{\circ}C$, the ideal mechanical properties (tensile strength ${\geq}$ 1,000 MPa, Charpy impact value ${\geq}\;100\;J/cm^2$) can be achieved by using optimized conditions (quenching temperature : 925 to $1,050^{\circ}C$, cooling rate : ${\geq}\;5^{\circ}C/sec$). The difference of impact value according to cooling rate can be influenced by the microstructure. A fine lath martensite micro structure is formed at a cooling rate of over $5^{\circ}C/sec$. On the other hand, the second phase of the M-A constituent microstructure is the cause of crack initiation under the cooling rate of $5^{\circ}C/sec$.

• Composites Research
• /
• v.31 no.5
• /
• pp.209-214
• /
• 2018

This paper explain about the development of environmental friendly, low cost and stable supply material i.e., rice husk and shell were used as micro incorporating bio waste filler. Those were processed by ball mill and analyzed through micro observation by FE-SEM, EDS and particle size distribution. The obtained filler was mixed with epoxy resin for the manufacturing of CFRP composite and study tensile properties. In EDS analysis main contents of rice husk and rice husk ash are C, O and Si. When rice husk was burned C and Si ration were increased. Shell powder has C, O and Ca. It caused $CaCO_3$ from shell. Surface weighted mean of rice husk powder is $6.19{\mu}m$ and volume weighted mean is $14.77{\mu}m$. And it has rod type particles which caused hair and husk structure parts. Surface weighted mean of rice husk ash powder is $1.55{\mu}m$ and volume weighted means is $8.20{\mu}m$. Surface weighted mean of shell powder is $2.53{\mu}m$ and volume weighted mean is $5.79{\mu}m$. The tensile decreased with increasing the content of micro filler in CFRP composites. In case of rice husk, the significant decrement of tensile strength was observed. and in case of shell powder, there is no effect of changes take place in tensile strength.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.14 no.2
• /
• pp.25-30
• /
• 2015

This study involved the fabrication of precision machine tools using a polycrystalline diamond tip [sintered PCD and cemented carbide (WC-Co) tip] and WC-Co shanks via diffusion bonding with a paste-type nickel alloy filler metal. Diffusion bonding is a process whereby two materials are pressed together at high temperature and high pressure for a sufficient period of time to allow significant atomic diffusion to occur. For smooth progress, a filler metal of nickel alloy was used at the interface. Optical microscopy images were used to observe the copula of the bonded layer. It was confirmed that cracks occurred near the junction in all cases. The tensile strength of the bond was measured using a universal testing machine (UTM) with WC-Co proportional test specimens.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.25 no.1
• /
• pp.54-60
• /
• 2001

This study is to investigate the mechanical properties and the fatigue crack propagation of fire resistance steel for frame structure as the chemical composition was changed by addition of N, B and rolled end temperature was varied. We used two kinds of specimen, the one is parallel and the other is perpendicular to the rolling directions. As rolled end temperature increased, volume fraction of ferrite and pearlite decreased, but volume fraction of baintie and grain size increased. Micro-hardness decreased as rolled end temperature increased, but tensile and yield strength increased. Volume fraction of ferrite and pearlite decreased by addition of N. But volume fraction of bainite, tensile and yield strength increased. Microstructure was changed to martensite by addition of B, and tensile and yield strength increased. Fatigue life of TL direction specimen was shorter than that of LT direction specimen. There was no significant effect to fatigue crack propagation rate by addition of N and changing rolling condition, but fatigue life was increased by addition of B.

• International Journal of Highway Engineering
• /
• v.20 no.4
• /
• pp.27-34
• /
• 2018

PURPOSES : The objective of this study is to evaluate the physical properties of recycled asphalt mixtures reinforced with glass fiber. METHODS : Firstly, mixing design was conducted on recycled asphalt mixture for use of 50% recycled aggregate. Various laboratory tests were performed on four types of recycled asphalt mixtures with different glass fiber content to evaluate the physical properties. The laboratory tests include indirect tensile strength test, dynamic modulus test, Hamburg wheel tracking test and tensile-strength ratio to evaluate cracks, rutting and moisture resistance of mixtures. RESULTS : The indirect tensile strength of fiber reinforced glass increased about 139.4%. As a result of comparing the master curves obtained by the dynamic modulus test, the elasticity was low in the low temperature region and high in the high temperature region when the glass fiber was reinforced. The glass fiber contents of PEGS 0.3%, Micro PPGF 0.1% and Macro PPGF 0.3% showed the highest moisture resistance and rutting resistance. CONCLUSIONS : The test results show that use of glass fiber reinforcement can increase the resistance to cracking, rutting, and moisture damage of asphalt mixtures. It is also necessary to validate the long-term performance of recycled asphalt mixtures with glass fiber using full scale pavement testing and field trial construction.

• Advances in concrete construction
• /
• v.15 no.6
• /
• pp.405-417
• /
• 2023

While ultra-high performance concrete (UHPC) is commonly reinforced with micro straight steel fibers in existing applications, studies have indicated that the use of deformed steel macro-fibers leads to enhanced ductility and post-peak responses for UHPC structural elements, which is of particular importance for earthquake-resistant structures. However, there are potential concerns regarding the use of UHPC reinforced with macro-fibers due to the issues of workability and fiber distribution. The objective of this study was to address these issues by extensively investigating the restricted and non-restricted deformability, filling ability, horizontal and vertical velocities, and passing ability of UHPC containing macro hooked-end steel fibers. A new approach is suggested to examine the homogeneity of fiber distribution in UHPC. The influences of ultra-fine fillers and steel macro-fibers on the workability of fresh UHPC and the mechanics of hardened UHPC were examined. It was found that although increasing the ratio of quartz powder to cement led to an improvement in the workability and tensile strain hardening behavior of UHPC, it reduced the fiber distribution homogeneity. The addition of 1% volume fraction of macro-fibers in UHPC improved workability, but reduced its compressive strength, which is contrary to the effect of micro-fiber inclusion in UHPC.

• Advances in concrete construction
• /
• v.6 no.2
• /
• pp.145-157
• /
• 2018

This paper presents a review on the use of Silica Fume (SF) as a mineral admixture in the concrete. Distinctive outcome from several researches have been demonstrated here, particularly emphasizing on the fresh and hardened properties of concrete when blended with Silica Fume (Micro-silica or Nano-silica). The results showed a substantial enhancement in the mechanical properties of concrete when replaced with SF. The review also presented a brief idea of percentage replacement of SF in case of normal and high-strength concrete. A decreasing trend in workability (slump value) has been identified when there is a increase in percentage replacement of SF. It can be concluded that the optimize percentage of replacement with SF lies in the range of 8-10% particularly for compressive strength. However the variation of blending goes up to 12-15% in case of split tensile and flexure strength of concrete. The study also demonstrates the effect of silica fume on durability parameters like water absorption, permeability, sulphate attack and chloride attack.