• Journal of the Korean Wood Science and Technology
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• 제1권2호
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• pp.3-10
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• 1973

This study was carried out to examine the characeristics of waste sanders(S)from. plywood and pre-finishing plywood surface sanding and double saw finishing, as a new extander in urea-formaldehyde resin(UFR) in plywood adhesive, and to focus, adhesive strength using the glue extended with milled sanders(MS) as extender, leveling the optimum amount of MS to be added, and examining the physical properties of glue extended MS & S. Also economical good feasibility of substitution for wheat flour(WF) with MS as a new extender is analyzed and presented in details. Selecting three standard samples of 80, 100 and 180 mesh, sorking them in distilled water at $20^{\circ}C$, 24 hours, redrying at $105^{\circ}C$ and rescreening the sample with standard screen, again, the 3 samples of 80, 100, and 180 mesh are passed 23 percent through 80 mesh sander standard sample 27 percent through on 100 mesh and only 10.9 percent through 180 mesh, respectively. The particle size of retained parts are greater in size of redried form. It seems undoubtly that particles to be extended in glue are got swollen and become greater in size and coarser in shape. The shape of fresh S particles are irregular thin needle with small scale, as shown in Figure 5. PFS are so finer than plywood S that only 9.8 percent of the S retained on 100 mest screen, 24. 30 percent on 100-160 mesh, and 65.9% on 160-180 mesh. But particle size of the fresh S is large enough to make the viscosity of glue direct extended with S too high to apply it glue spreader. The glue extended with milled sanders(MS). 3 hours milled PFS or 6 hours milled plywood S, having particle sizes shown in Tables 7 and 8, as ratio of Reain/MS/WF/water: 100/8/8/10, indicate good viscosity of 16 to 24 ps, as shown in Figure 5, for applying direct to glue spreader, have high tensile-shear strength (adhesive strength), 102.4 kp/$cm^2$, and 94 percent wood failure.

• 한국생산제조학회지
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• 제8권1호
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• pp.81-88
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• 1999

This paper was carried out to know the influence of advanced austempered ductile cast iron (ADI) on the tool life and mechanical properties of drilling machinability. For manufactured method of ADI, the spheroidal graphite cast iron were austenized at 90$0^{\circ}C$ for 1 hour and then austempered for 2 hour at 37$0^{\circ}C$ in the salt bath. And interrelationship has been investigated between tool life and mechanical characteristics of specimen material on drilling condition when the ordinary and step-feed drilling are carried out to drill holes of specimens. Tensile strength and hardness of ADI decrease and elongation of ADI increases with the increase austempered temperature. It is known that about 2 times of tool life in the case of step-feed decreases compared with ordinary feed due to the high hardness of ADI and hardness ascribed to the fact that retained austenite became to martensite state due to cutting heat in drilling. Under the constant feed rate 0.1mm/rev relation between hardness and length of end tip after drilling can be formularized to Hv=$788.46L^{-0.096}$ for the cutting speed 6.1m/min.

• 한국주조공학회지
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• 제16권2호
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• pp.109-115
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• 1996

Effect of various austempered structures on fracture characteristics of C/V graphite cast iron has studied. The tensile strength and hardness reached the maximum value of 971.4MPa and HB302 at the austempering temperature of $250^{\circ}C$, respectively. As the austempering temperature increased, the amount of retained austenite increased from 18% to 22, 29%, while $K_{IC}$ values ranged from the value of $65MPa{\cdot}m^{12} to 70MPa{\cdot}m^{1/2}, 66MPa{\cdot}m^{1/2}. This fact that $K_{IC}$ value was not sensitive to the increase of the amount of the retained austenite was that $K_{IC}$ was dependent on the matrix structure in lower bainitic matrix, while dependent on the notch effect from C/V graphite shape in upper bainitic matrix. Fractured surfaces showed a ductile fracture pattern at $300^{\circ}C$. Very large coalescence by C/V graphite and relatively small voids by spheroidal graphite were observed.

• 한국주조공학회지
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• 제12권6호
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• pp.442-449
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• 1992

Grey cast iron containing a small amount of Cu and Mo to improve the effect of heat treatment and microstructure were cast and them austenitized. After austenitizing the specimens of castings were austempered at 250$^{\circ}C$, 300$^{\circ}C$ and 350$^{\circ}C$. The effects of matrix structures on mechanical properties and fracture characteristics at the different austempering temperature were investigated. Tensile strength, hardness and impact toughness of austempered grey cast iron showed maximum valve 359 MPa, 321 HB, 3.9 CVN respectively at the lowest austempering temperature, 250$^{\circ}C$. $K_{IC}$ of gref cast iron at a austempering temperature, 250$^{\circ}C$, showed maximum 44 MPa.$m^{1/2}$ even though the amount of retained austenite in it is only 16%. This mainly comes from the refinement of the retained austenite. Quasi-cleavage pattern with a little fit of fibrous pattern was shown on the fractured surface of austempered grey cast iron at all of the temperatures tested.

• 한국염색가공학회지
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• 제29권2호
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• pp.97-103
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• 2017

Polyketone fiber, a newly developed high strength fiber, has a tenacity and modulus similar to the p-aramid fiber, and can be used for reinforcing mechanical rubber goods(MRG), such as tires, hoses, and technical textiles. It will be expected for replacement of super fiber such as aramids and increasing the technical textile market share. This paper surveys the mechanical properties of polyketone fiber for technical textiles. For this purpose, dyed polyketone fabric is prepared, mechanical properties of coated and uncoated polyketone fabrics such as tensile strength, elongation and tear strength were examined before and after weather resistance test(temperature $63{\pm}3^{\circ}C$, humidity 60%, amount of power $0.35w/m^2$). The differences of mechanical properties between uncoated and coated fabrics for high functional technical textiles and composite materials are estimated through this study. The UV-stability of polyketone fabric showed obvious improvement after coating. After 168h(7day) of UV exposure, the coated fabric showed less deterioration in mechanical properties with the retained tensile strength and elongation at break greater than 22 and 17% of the uncoated polyketone fabrics values, respectively.

• 한국염색가공학회지
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• 제25권3호
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• pp.172-180
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• 2013

Aramid fibers are being used increasingly in a wide range of application due to low density, high specific strength, high modulus, and high thermal resistance. But owing to its special physical and chemical structures, it is sensitive to absorb the ultraviolet light which will degrade the fiber's useful mechanical properties and structure. In this paper, the sol-gel technique was used to improve the photo-stability of p-aramid fibers. $TiO_2$, modified $SiO_2$/$TiO_2$ sol were used as coating solutions. The influence of the such coatings on the photo-stability of p-aramid fiber was investigated by an accelerated photo-ageing method using xenon lamp. The photo-stability of p-aramid fiber showed obvious improvement after the modified silica binding coating. But the amorphous $TiO_2$ sol coatings showed a negative effect. After 144h light exposure, the modified silane binder-coated fibers showed less degradation in mechanical properties with the retained tensile strength greater than about 70% of the original value.

• Journal of Advanced Marine Engineering and Technology
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• 제19권4호
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• pp.42-50
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• 1995

To study the effect of welding methods on the Stress Corrosion Cracking (SCC) behavior of welded AISI type 316L and 304 austenitic stainless steel, the Slow Strain Rate Technique(SSRT) has been adopted in the boiling 45 wt% $MgCl_2$ solution. The results are as follows. 1) Welded sections are more susceptible than base metal in SCC, and the rank of SCC, and the rasistance in welding method is TIG, MIG, $CO_2$ and ARC. 2) The Ultimate tensile strength(UTS) and the strain of both base metal and welded joint are reduced as decreasing extension rate. 3) The SCC resistance of 316L base metal and welded sections are superior than that of 304. 4) The tendency of pitting and the SCC suseptibility are agreed well, and the SCC site is welded deposit section in 316L whereas HAZ in 304.

• 한국방재학회 논문집
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• 제2권2호
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• pp.61-72
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• 2002

본 연구에서는 마샬 배합설계법을 이용하여 섬유와 아스팔트 바인더의 적정한 양을 결정한 후 마샬 공시체를 제작하였다. 제작된 공시체를 이용하여 3단계의 온도(5, 20, 60$^{\circ}C$)하에서 간접인장강도 시험을 수행한 후 물성을 측정하여 기존의 아스팔트 혼합물(밀입도 20)과 섬유보강 아스팔트 혼합물 사이의 기계적 특성을 비교 분석하였다. 특히 혼합물의 소성 변형에 대한 저항성을 평가하기 위하여 휠트랙킹 시험을 실시하였다. 시험결과 전체적으로 재래식 밀입도 20 아스팔트 혼합물보다 섬유보강 아스팔트 혼합물의 간접인장강도가 높은 것으로 나타났으며, 특히 인성 (Toughness)값은 시험온도에 따라 $1.27{\sim}1.97$배 높게 나타났다. 또한 본 연구에서 수행되어진 $60^{\circ}C$에서 휠트랙킹 시험과 잔류 간접인장강도 시험에 대한 특성은 하절기의 고온 다습한 기후하에서 재래식 밀입도 20 혼합물보다 섬유보강 아스팔트 혼합물의 소성변형에 대한 저항성이 우수할 것으로 판단된다.

• 대한치과보철학회지
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• 제37권4호
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• pp.465-473
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• 1999

Bond strength of luting cements to dentin is a critical consideration for success of complete cast crowns. This study was performed to evaluate the relationship between surface characteristics of teeth prepared for complete cast crowns and retention of cemented restorations. Eighty artificial crowns were cast for standardized complete crown tooth preparations accomplished with the use of a special device on recently extracted human teeth. Coarse diamond(#102R, Shofu) and superfine finishing diamond(#SF102R, Shofu) burs of similar shape were used. Crowns in each group were randomly subdivided into few subgroups of 10 for luting cements selected for this study: zinc phosphate cement (FLECK' S), polycarboxylate cement (Poly-F), rein-forced glass ionomer cement (Fuji PLUS). and adhesive resin cement (Panavia 21). Retention was evaluated by measuring the tensile load required to dislodge the artificial crown from tooth preparations with an Instron testing machine, and analysed by one-way ANOVA and Student's t-test. The obtained results were as follows ; 1. When tooth preparation was done with coarse diamond bur, retentive force was diminished in order of Panavia 21 Fuji PLUS, FLECK'S, and Poly-F. Retentive forces showed the significant difference between Fuji PLUS group and FLECK'S group(p<0.001). 2. When tooth preparation was done with superfine diamond bur, retentive force was diminished in order of Fuji PLUS, Panavia 21, FLECK'S, and Poly-F. Retentive forces showed the significant difference between Panavia 21 group and FLECK'S group(p<0.001). 3. Retentive force in coarse tooth surfaces was significantly higher than that in superfine tooth surface with all luting cements(p<0.001), and cement residues were almost retained with-in the cast crown in all groups.

• 한국재료학회지
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• 제33권11호
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• pp.439-446
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• 2023

Changes in the microstructure and mechanical properties of as-roll-bonded AA6061/AA5052/AA1050 three-layered sheet with increasing annealing temperature were investigated in detail. The commercial AA6061, AA5052 and AA1050 sheets with 2 mm thickness were roll-bonded by multi-pass rolling at ambient temperature. The roll-bonded Al sheets were then annealed for 1 h at various temperatures from 200 to 400 ℃. The specimens annealed up to 250 ℃ showed a typical deformation structure where the grains are elongated in the rolling direction in all regions. However, after annealing at 300 ℃, while AA6061 and AA1050 regions still retained the deformation structure, but AA5052 region changed into complete recrystallization. For all the annealed materials, the fraction of high angle grain boundaries was lower than that of low angle grain boundaries. In addition, while the rolling texture of the {110}<112> and {123}<634> components strongly developed in the AA6061 and AA1050 regions, in the AA5052 region the recrystallization texture of the {100}<001> component developed. After annealing at 350 ℃ the recrystallization texture developed in all regions. The as-rolled material exhibited a relatively high tensile strength of 282 MPa and elongation of 18 %. However, the tensile strength decreased and the elongation increased gradually with the increase in annealing temperature. The changes in mechanical properties with increasing annealing temperature were compared with those of other three-layered Al sheets fabricated in previous studies.