• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.45 no.4
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• pp.1-8
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• 2013

High loading of printing and writing grades with fillers has many advantageous aspects in papermaking because it allows decreasing fiber use and reducing manufacturing cost. High loading technology, however, has some disadvantageous aspects as well. It decreases physical properties of papers, especially strength properties. The problem associated with high loading can be reduced by applying surface sizing starch solution onto paper surface. It is important to control the penetration of the surface sizing starch solution into paper web to obtain the desired property improvement. In this study, the effect of the addition of two polymers into starch solution on paper properties has been examined. PVOH and polyDADMAC were used as polymeric additives for surface sizing with oxidized starch. Viscosity of starch solutions and surface roughness of dried starch films on glass slides showed that some interactions between polymeric additives and oxidized starch have been occurred and the most extensive interaction with starch solution was obtained with high molecular weight polyDADMAC. Low molecular weight PVOH was most effective in improving folding endurance and internal bond strength. On the other hand, polymer addition showed no effect on surface strength of paper. This indicates that not the level of starch holdout but the bonding strength of starch itself has predominant influence on surface strength of paper.

• International Journal of Highway Engineering
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• v.11 no.4
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• pp.95-105
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• 2009

This study was conducted to investigate the effects of concrete flexural strength and surface smoothness, which were pay factors of concrete pavements, on pavement performance, and to develop the methodologies to determine the proper allowable ranges according to the magnitudes of those pay factors. The concrete flexural strength was analyzed using the AASHTO, power, and linear fatigue failure models, and the surface smoothness was analyzed for the roughness indices of PSI, IRI, and PrI using the AASHTO model. The analysis results showed that the allowable range of the flexural strength should be determined using the rate between the deficiency and strength, and the penalty should be linearly proportional to the strength deficiency rate because the linear relationship between the strength deficiency rate and the reduction in pavement life was observed. As the initial surface smoothness became better, the smoothness deficiency rate should be larger. The penalty due to the surface smoothness deficiency should also be linearly proportional to the smoothness deficiency rate.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2002.05a
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• pp.5-8
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• 2002

The use of the co-cured joining method for composite structures is attractive due to several benefits. However, since the design stress level in cyclic loads is often smaller than the joint strength obtained from the static tensile load test, it is important to establish proper fatigue design criteria. Although some researchers have reported on co-cured joints, there are only a few papers published on the fatigue characteristics of co-cured joints. In this paper, the effect of bond parameters on the fatigue characteristics of a steel-composite co-cured double lap joint under cyclic tensile loads was experimentally investigated. We considered the surface roughness of the steel adherend and the stacking sequence of the composite adherend as bond parameters. A fatigue failure mechanism of the co-cured double lap joint was explained systematically by investigating the surfaces of failed specimens.

• Transactions of the Korean Society of Mechanical Engineers
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• v.14 no.1
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• pp.37-42
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• 1990

Carbon fiber epoxy composite materials are widely used in the structures of aircrafts, robots and other machines because of their high specific stiffness, high specific strength and damping. In order for the composite materials to be used in the robot structure or machine element, bearing mounting and joining surfaces must be provided, which require accurate machining. In this paper, the machinability and tool wear characteristics of the milling operation of the carbon fiber epoxy composite materials were experimentally measured. The tool wear mechanism and the Taylor tool wear constants were determined. Also, the surface roughness of milling operation was measured w.r.t. cutting speed and feed.

• Journal of the Korean Society for Precision Engineering
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• v.23 no.6 s.183
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• pp.187-195
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• 2006

FDM, SLS, and EOS processes are the layered manufacturing processes far functional prototypes. In this paper, bench mark tests of those processes were carried out using various materials. The test includes mechanical properties, such as tensile and compressive strengths, hardness, impact strength, and heat resistance, and surface roughness, shape and dimensional accuracy, manufacturing time, and manufacturing costs. It is verified that SLS method is advantageous in surface roughness and manufacturing time, EOS method in shape accuracy, and FDM method is great in manufacturing costs.

• Journal of the Korean Ceramic Society
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• v.34 no.4
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• pp.380-386
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• 1997

The tribological properties of ceramics are very important in the application to engineering ceramic parts such as seal rings, pump parts, thread guides, and so on. In this study, the effects of graphite addition on the mechanical and tribological properties of alumina/graphite composites were investigated. The composites were prepared by the adding of graphite powder to the mixture of Al2O3, talc and calcium carbonate. Bending strength, water absorption, friction coefficient, the amount of worn out material at a certain time, and maximum surface roughness(Rmax) of the prepared composites were measured. Crystalline phases and microstructure were examined with XRD and SEM. The melt of Al2O3-CaO-MgO-SiO2 system was shown over 10 vol% graphite composition. As the amount of the graphite is increased, needle like crystals of mullite were formed and grown. We obtained the good properties of friction coefficients and wear resistance at the powder composition containing 15 vol% of graphite.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.12 no.6
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• pp.36-43
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• 2003

In machining of ceramic materials, they are very difficult-to cut materials because of there high strength and hardness. Machining of ceramics are characterized by cracking and brittle fracture. Generally, ceramics are machined using conventional method such as finding and polishing. However these processes are generally costly and have low MRR(material removal rate). This paper focuses on determining the optimal levels of process parameters for products with CNC machining center. For this purpose, the optimization of cutting parameters is performed based on experimental design method. A design and analysis of experiments is conducted to study the effects of these parameters on the surface roughness by using the S/N ratio, analysis of ANOVA and F-test. Cutting parameters, namely, cutting speed, feed and depth of cut are optimized with consideration of the surface roughness.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.10a
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• pp.879-882
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• 1997

This paper aims to clarify the effect of the sol-gel sintered alumina grain and the PbO content of binder on the performance of the vitrified alumina stone for superfinishing the ball bearing race with the vitrified alumina superfinishing stone. The main conclusions obtained were as follows. The stone that contain 8- 11% PbO in binder shows the highest grinding ratio, and increasing or decreasing the PbO contents causes lower grinding ratio. When superfinishing with the stone using the 45% fused alumina and 55% sol-gel sintered alumina grain, the grinding ratio becomes the best, the other ratio of grain contents shows lower performance. With increasing the bending strength of stone, the grinding ratio becomes larger. The roughness of the finished surface is the lowest in case of using the stone of the above mentioned conditions.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.10a
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• pp.291-295
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• 2002

Ceramics are very difficult-to-cut materials because of its high strength and hardness. Their machining process can be characterized by cracking and brittle fracture. Generally, ceramics are machined using traditional method such as grinding and polishing. However, such processes are generally costly and have low material removal rate. In this paper, to develop machinable ceramics those have good machinability without losing their material properties, machinability evaluations are performed by applying the experimental design method. In this paper, to evaluate the machinability of the developed ceramics, various workpieces are machined on the CNC machining center, and surface roughness are measured under predefined process parameters obtained using Taguchi method. And the experimental results are investigated to derive optimum cutting parameters for the given materials.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.12
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• pp.2279-2286
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• 1992

A hypereutectic Aluminum-Silicon Alloy is widely used in the parts of autombile because of high-resistance and good strength. In this study, the cutting of a hypereutectic Al-Si alloy (A390) for extraction of Si particle was experimentally investigated. By proper selection of cutting tool materials and optimization of cutting conditions, economical machining of this alloy is achieved. The surface roughness relates closely with the feed rate and cutting speed.