• Elastomers and Composites
• /
• 제46권2호
• /
• pp.132-137
• /
• 2011

본 연구는 H-NBR 함량 변화에 따른 H-NBR/NBR 블렌드의 열노화 거동에 대하여 살펴보았다. 이 때 가교제로는 dicumyl peroxide와 황 혼합물을 사용하였으며, 열노화에 따른 H-NBR/NBR 블렌드의 인장강도, 파괴신율, 경도 그리고 내마모성의 변화를 살펴보았다. H-NBR을 첨가함에 따라 인장강도는 증가하였으나 내마모성은 감소하는 현상을 나타내었다. 파괴신율과 경도는 H-NBR의 영향을 받지 않았다. 노화가 진행된 모든 시편은 초기 시편보다 낮은 인장강도, 파괴신율, 경도를 나타내었다. 그러나 H-NBR의 함량이 증가함에 따라 이러한 물성저하 속도가 감소함을 알 수 있었다. 즉 H-NBR 첨가에의해 열노화 특성이 향상됨을 알 수 있었다. 모든 NBR/H-NBR 블렌드는 노화시간이 증가함에 따라 내마모성이 감소하였으며, H-NBR을 첨가한 경우 내마모성의 저하가 상대적으로 낮음을 알 수 있었다.

• 한국식품영양과학회지
• /
• 제30권3호
• /
• pp.494-499
• /
• 2001

어분으로부터 추출한 어분 단백질을 이용하여 가식성 및 생분해성 필름을 제조할 때, 어분 단백질의 추출 시간을 달리하여 제조된 필름의 수증기 투과도, 인장강도, 신장률 및 용해도의 변화를 측정한 결과는 다음과 같다. 어분단백칠 추출시간이 FMPI 필름의 수증기 투과도에 미치는 영향은 크지 않았다. 가소제로써 glycerol을 첨가한 필름의 수증기 투과도가 sorbitol을 첨가한 필름보다 높았다. 인장강도의 신장률은 어분 단백질의 추출시간이 증가함에 따라 증가하다가 1시간일 때 가장 높았으며 그 이상 추출시간이 증가함에 따라 감소 하였다. 총 용해물질의 함량과 수용성 단백질 함량은 어분 단백질의 추출시간이 증가함에 따라 감소하였다가 1시간일 때 가장 낮았으며, 추출시간이 1시간 이상 증가함에 따라 증가하였다. 필름의 수용성 단백질 함량과 인장강도와 신장률은 음의 상관 관계를 나타내었으며 신장률($r^{2}=0.62$)보다는 인장강도($r^{2}=0.83$)가 수용성 단백질의 함량과 밀접한 상관관계를 나타내었다.

• 대한치과교정학회지
• /
• 제20권2호
• /
• pp.381-390
• /
• 1990

The purpose of this study was to evaluate the effects of heat treatment on mechanical properties in $0.016^{{\prime}{\prime}}{\times}0.022^{{\prime}{\prime}}$ blue Elgiloy wires and to measure the amounts of nickel and chromium released from the wires in artificial saliva. Ultimate tensile strength, yield strength and elongation were measured with universal testing machine (Instron). and the amounts of nickel and chromium released from the sample were measured with atomic absorption spectrophotometer after one week immersion in the artificial saliva. Ultimate tensile strength and yield strength were progressively increased below $1000^{\circ}F$, but elongation was decreased. And the results were reversed above $1100^{\circ}F$. After heat treatment of the sample for 9 minutes at $1000^{\circ}F$, the maximum tensile strength and yield strength were $213.6kg/mm^2$, $140.1kg/mm^2$, respectively. Both tensile strength and yield strength were decreased progressively above $1100^{\circ}F$. Elongation was appeared the minimum value (8.6%) after heat treatment for 9 minutes and 12 minutes at $1000^{\circ}F$. There was a pronounced increase in nickel and chromium liberation with increasing time and temperature. The maximum amounts of nickel and chromium released form the sample were $4.947{\mu}m/cm^2$, $3.088{\mu}g/cm^2$, respectively after heat treatment for 12 minutes at $1300^{\circ}F$. Heat treatment is applied to orthodontic wires, especially cobalt-chromium alloys, for the purpose of stress-relievning and hardening. When the heat-treatment of orthodontic wires, the heating procedure should be well controlled in order to have no effect on corrosion resistance and mechanical properties.

• 한국재료학회지
• /
• 제27권4호
• /
• pp.184-191
• /
• 2017

This present study deals with the effect of micro-alloying elements and transformation temperature on the correlation of microstructure and tensile properties of low-carbon steels with ferrite-pearlite microstructure. Six kinds of low-carbon steel specimens were fabricated by adding micro-alloying elements of Nb, Ti and V, and by varying isothermal transformation temperature. Ferrite grain size of the specimens containing mirco-alloying elements was smaller than that of the Base specimens because of pinning effect by the precipitates of carbonitrides at austenite grain boundaries. The pearlite interlamellar spacing and cementite thickness decreased with decreasing transformation temperature, while the pearlite volume fraction was hardly affected by micro-alloying elements and transformation temperature. The room-temperature tensile test results showed that the yield strength increased mostly with decreasing ferrite grain size and elongation was slightly improved as the ferrite grain size and pearlite interlamellar spacing decreased. All the specimens exhibited a discontinuous yielding behavior and the yield point elongation of the Nb4 and TiNbV specimens containing micro-alloying elements was larger than that of the Base specimens, presumably due to repetitive pinning and release of dislocation by the fine precipitates of carbonitrides.

• Corrosion Science and Technology
• /
• 제5권5호
• /
• pp.168-172
• /
• 2006

Alloy 600 having a superior resistance to a corrosion is used as a steam generator tubing in nuclear power plants. In spite of its high corrosion resistance, there are many tubings which experience corrosion problems such as a SCC under the high temperature and high pressure environments of nuclear power plants. The Alloy 600 tubing can be repaired by using a Ni electroplating having an excellent SCC resistance. In order to carry out a successful Ni electrodeposition inside a steam generator tubing, the effects of various parameters on the material properties of the electrodeposit should be elucidated. Hence this work deals with the effects of an applied current density, duty cycle($T_{on}/(T_{on}+T_{off})$) of a pulse current, bath temperature and solution pH on the material properties of Ni electrodeposit obtained from a Ni sulphamate bath by analyzing the current efficiency, potentiodynamic curve, hardness and stress-strain curve. Hardness, YS(yield strength) and TS(tensile strength) decreased whereas the elongation increased as the applied current density increased. This was thought to be by a concentration depletion at the interface of the electrodeposit/solution, and a fractional decrease of the hydrogen reduction reaction. As the duty cycle increased, the hardness, YS and TS decreased while the elongation increased. During an off time at a high duty cycle, the concentration depletion could not be recovered sufficiently enough to induce a coarse grain sized electrodeposit. With an increase of the solution temperature and pH, the YS and TS increased while the elongation decreased. The experimental results of the hardness and the stress-strain curves can be supplemented by the results of the potentiodynamic curve.

• 한국주조공학회지
• /
• 제29권3호
• /
• pp.128-137
• /
• 2009

The effects of alloying elements on the mechanical properties of 3.6wt%C-2.6wt%C ductile cast iron poured into shell stack molds were investigated. The strength and hardness of the specimens obtained from the center layer in the 5-story stack mold were the lowest and those for other specimens were increased with increased distance from the center. The strength and hardness of the specimens obtained from the center layer were decreased with increased number of layers of the shell stack mold. The strength and hardness of the smaller specimens with the diameter of 9.5 mm were higher than those of 17.5 mm. On the other hand, the elongation of the former was lower than that of the latter. The strength and hardness were increased and the elongation was decreased roughly with the increased amounts of manganese and copper added, respectively. The strength and hardness were increased with the incrcased amount of molybdenum added to 0.40wt% and rather decreased with that to 0.80wt%. Those were greatly increased with the increased amount of tin added and the elongation was roughly decreased with it.

• 한국의류산업학회지
• /
• 제21권2호
• /
• pp.203-208
• /
• 2019

This paper considers the moisture permeability and fashion in the upper fabrics of cotton fabric shoes woven into various tissues and properties measured to examine the use as upper fabrics. We measured the tissues of the manufactured upper fabric are 1/3 twill, $4{\times}4$ weft rib, Maya, Triple, Deformed twill design (DTD), Diamond tissues and tear strength, tensile strength, breaking elongation, stretching under load at 100N, stitch tear resistance, and fastness. In the case of $4{\times}4$ weft rib, the tear strength and tensile strength were excellent; however, the elongation and stitch tear resistance at 100N load were less than the standard value. DTD fabrics are characterized by physical properties in the warp direction that are superior to those in the weft direction; however, the tear strength and tensile strength in the weft direction are less than the standard value. The 1/3 twill fabrics showed high tensile strength value and stitch tear resistance value in the warp direction; however, toughness, the main property of the shoe upper, was below the standard value. Triple and diamond fabrics, which have a significant effect on the performance of the shoe upper fabric, also had less than the standard value of tear strength. Maya upper fabric for shoes has better properties than other upper fabrics except for the elongation at break, and the stitch tear resistance has a value of 178% in the warp direction and 214% in the weft direction compared to the standard value. Therefore, the Maya fabric showed the possibility of being used as an upper textile for shoes.

• 한국의류학회지
• /
• 제34권11호
• /
• pp.1889-1899
• /
• 2010

This study examines the preparation and characterization of Kenaf/Starch bio-composites used as filler and a matrix. Kenaf was cultivated in Chung-ju in Korea, and the Kenaf/Starch bio-composites were prepared under various conditions of kenaf fiber length (1-5 centimeters); the content of Kenaf fiber was 10%, 20%, 30%, and 40%, and the number of composite layers (one-four). Depending on the formation conditions of Kenaf/Starch composites, the physical properties such as tensile strength, elongation, and the young modulus of the Kenaf/Starch composites were measured. In addition, we measured the SEM cross-section images in order to investigate the interfacial adhesion properties of fractured surfaces. As a result, the tensile strength and elongation of the Kenaf/Starch composites were highest in the molding conditions of a hot press at $120^{\circ}C$, 3000PSI of pressure, and for 30 minute periods. The result of measuring the physical properties of the composites manufactured by varying the content of Kenaf fiber when the content of Kenaf fiber was 30% as well the physical properties of the Kenaf/Starch composite was found desirable. It was found that the physical properties improved with more overlapped layers in the composites manufactured by varying the number of overlapped layers. Through the measuring of the SEM cross-section images, we found that the interfacial adhesion state between the filler and matrix of Kenaf/Starch composite greatly affects the physical properties.

• 한국소성가공학회:학술대회논문집
• /
• 한국소성가공학회 2007년도 춘계학술대회 논문집
• /
• pp.254-257
• /
• 2007

In this study, hydroformability and mechanical properties of pre- and post- heat treated Al6061 tubes at different extrusion type were investigated. For the investigation, as-extruded, full annealed and T6-treated Al 6061 tubes at different extrusion type were prepared. To evaluate the hydroformability, uni-axial tensile test and free bulge test were performed at room temperature and $200^{\circ}C$. Also mechanical properties of hydroformed part at various pre- and post-heat treatments were estimated by tensile test. And the tensile test specimens were obtained from hexagonal prototype hydroformed tube at $200^{\circ}C$. As for the heat treatment, hydroformability of full annealed tube is 25% higher than that of extruded tube. The tensile strength and elongation were more than 330MPa and 12%, respectively, when hydroformed part was post-T6 treated after hydroforming of pre- full annealed tube. However, hydroformed part using T6 pre treated tube represents high strength and low elongation, 8%. Therefore, the T6 treatment after hydroforming for as-extruded tube is cost-effective. Hydroformability of Al6061 tube showed similar value for both extrusion types. But flow stress of seam tube showed $20{\sim}50MPa$ lower value.

• 한국주조공학회지
• /
• 제20권5호
• /
• pp.316-322
• /
• 2000

Effect of surface roughness and microstructure of the specimen on tensile properties of Ni-Al bronze casting has been investigated. surface roughnesses of the tensile test specimen of interest are in range of 0.1 to 2.0 ${\mu}m$ in Ra obtained by changing machining conditions. Fracture of the Ni-Al bronze casting initiated at the surface and propagated in a brittle manner during tensile tests. Tensile elongation value of the casting was strongly dependent on the surface roughness range studied, while tensile and yield strengths were almost independent on it. The elongation value was almost constant up to the surface roughness of 1.0 ${\mu}m$ in Ra, and then decreased in a linear manner with an increase in Ra value up to 2.0 ${\mu}m$. However, tensile strength and hardness were strongly dependent on the microstructure, especially ${\alpha}$ phase fraction, and were decreased with increasing ${\alpha}$ phase fraction in microstructure. It is, therefore, recommended that decrease of surface roughness up to 1.0 ${\mu}m$ in Ra, shrinkage porosity and ${\alpha}$ phase are required in order to obtain good tensile properties for Ni-Al bronze casting.