• 대한금속재료학회지
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• 제48권3호
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• pp.248-255
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• 2010

The effect of various alloying elements and melt treatment on the microstructural control of Al-Sn metallic bearing alloy was investigated. The thickness of tin film crystallized around primary aluminum decreased with the addition of 5% Cu in Al-Sn alloy, with tin particles being reduced in size by intervening the Ostwald ripening. With the addition of Si in Al-10%Sn alloy, the tin particles were crystallized with eutectic silicon, resulting in uniform distribution of tin particles. With the addition of Cu and Si in Al-Sn alloy, both the tensile strength and yield strength increased, with the increasing rate of yield strength being less than that of tensile strength. Although the Al-10%Sn-7%Si alloy has similar tensile strength compared with Al-10%Sn-5%Cu, the former showed superior abrasion resistance, resulting from preventing the tin particles from movement to the abrasion surface.

• 소성∙가공
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• 제31권3호
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• pp.117-123
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• 2022

In this study, a commercial AZ61 magnesium alloy is extruded at 300 ℃ and 400 ℃ and the microstructures, mechanical properties, and high-cycle fatigue properties of the extruded materials are investigated. Both extruded materials have a fully recrystallized microstructure with no Mg₁₇Al₁₂ precipitates. The average grain size and maximum basal texture intensity of the extruded material increase with increasing extrusion temperature. The material extruded at 400 ℃ (AZ61-400) has higher tensile yield strength and lower compressive yield strength than the material extruded at 300 ℃ (AZ61-300) because of the stronger basal texture of the former. Because of coarser grain size, the tensile elongation of AZ61-400 is lower than that of AZ61-300. Despite the differences in microstructures and tensile/compressive properties, the two extruded materials have the same fatigue strength of 110 MPa. This is because the finer grain size of AZ61-300 causes an increase in fatigue strength, but its weaker texture causes a decrease in fatigue strength. In both extruded materials, fatigue cracks initiate at the surface of fatigue specimens at all stress amplitudes tested.

• 소성∙가공
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• 제30권6호
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• pp.284-290
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• 2021

Manufacturing using a 3D printer has recently increased in many fields and the material extrusion method, which is a lamination method, is commonly used. Since it uses a plastic material, the strength of the output of 3D printing is lower than that of steel material. For this reason, research on improving the mechanical properties of the output of 3D printing is continuously being conducted. In this study, tensile strength was compared with changes in the material type (PLA+, ABS) and density (60, 80, and 100%), layer height (0.1, 0.2, and 0.3 mm), layer direction (transverse and lengthwise), and fill pattern (zigzag, honeycomb, and concentric) among 3D printing output conditions. Tensile tests according to 3D printing output conditions were performed using a Universal Testing Machine. The results showed that tensile strength ranged from 21.10 MPa to 43.65 MPa according to the 3D printing output conditions.

• 구강회복응용과학지
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• 제19권4호
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• pp.269-279
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• 2003

This study investigated the mechanical properties of precious metal-ceramic alloy joined by the laser-welding and the soldering compared with the parent metal. Twenty-four tensile specimens were cast in precious metal-ceramic alloy and divided into three groups of eight. All specimens in the control group(group 1) were left in the as-cast condition. Group 2 and 3 were the test specimens, which were sectioned at the center. Eight of sectioned specimens were joined by soldering with a propane-oxygen torch, and the remaining specimens were joined by laser-welding. After joining, each joint diameter was measured, and then tested to tensile failure on an Instron machine. Failure loads were recorded, and then fracture stress(ultimate tensile strength), 0.2% yield strength and % elongation calculated. These data for three groups were subjected to a one-way analysis of variance(ANOVA). Neuman-Keuls post hoc test was then used to determine any significant differences between groups. The fracture locations, fracture surfaces were examined by SEM(scanning electron microscope). The results were as follows: 1) The tensile strength and 0.2% yield strength of the soldered group($280.28{\pm}49.35MPa$, $160.24{\pm}26.67MPa$) were significantly less than both the as-cast group($410.99{\pm}13.07MPa$, $217.82{\pm}17.99MPa$) and the laser-welded group($383.56{\pm}59.08MPa$, $217.18{\pm}12.96MPa$). 2) The tensile strength and 0.2% yield strength of the laser-welded group were about each 98%, 99.7% of the as-cast group. There were no statistically significant differences in these two groups(p<0.05). 3) The percentage elongations of the soldered group($3.94{\pm}2.32%$) and the laser-welded group($5.06{\pm}1.08%$) were significantly less than the as-cast group($14.25{\pm}4.05%$) (p<0.05). 4) The fracture of the soldered specimens occurred in the solder material and many porosities were showed at the fracture site. 5) The fracture of the laser-welded specimens occurred also in the welding area, and lack of fusion and a large void was observed at the center of the fracture surface. However, the laser-welded specimens showed a ductile failure mode like the as- cast specimens. The results of this study indicated that the tensile strengths of the laser-welded joints were comparable to those of the as-cast joints and superior to those of the soldered joints.

• 소성∙가공
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• 제14권6호
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• pp.520-526
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• 2005

In recent years, there has been a growth of the manufacture and application of magnesium products because of its small specific gravity as well as its relatively high strength. However, there are so many studies to assure good formability because magnesium sheet alloy is difficult to form. In this study, uniaxial tensile and biaxial tensile tests of AZ31 magnesium sheet alloy with thickness of 1.2mm were performed at room temperature. Uniaxial tensile tests were performed until $7{\%}$ of engineering strain. Lankford values and stress-strain curve were obtained. Biaxial tensile tests with cruciform specimen were performed until the breakdown of the specimen occurs. The yield loci were calculated by application of plastic work theory. The results are compared with the theoretical predictions based on the Hill and Logan-Hosford model. In this study, Hill's 1979 yield function for the case of m=2.8 and Logan-Hosford yield function for the case of M=8 give good agreements with experimental results. However, next study will be performed at warm-temperature because the specimens are broken under the $0.5{\%}$ of equivalent strain at biaxial tensile test.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2001년도 춘계학술대회 논문집
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• pp.250-253
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• 2001

Mechanical properties of gold bonding wire for VLSI packaging have been studied. The diameters of gold wires are about 20-30 micrometer and fracture loads are 8-20 gram force. The elastic modulus, yield strength, fracture strength and elongation properties have been evaluated by micro-tensile test method. This work discusses for an appropriate selection of micro-force testing system and grip design in mim testing. The best method to determine gauge length of wire and to measure tensile properties has been proposed. The mechanical properties such as strength and elastic modulus of current gold bonding wire are higher than pure those of gold wire.

• 한국주조공학회지
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• 제11권1호
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• pp.63-70
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• 1991

Aluminium alloy castings, which can be not only manufactured in larger geometrically complex shapes, but also show good mechanical properties in addition to light weight, have kept their potential use as structures in the field of automotives, industrial machines and aircrafts. The variations of eutectic Si size a great effect on the elongation, impact value, fracture toughness and fatigue crack propagation rate without changes in the tensile strength or yield strength. The cooling curves with the solidification rate between $1.4^{\circ}C\;/min$ and $19.1^{\circ}C\;/min$ were obtained. With the increase of solidification rate, DAS, eutectic Si size and grain size were all decreased, which enhanced the mechanical properties. The tensile strength and yield strength were the most greatly influenced by DAS, and the elongation and impact value by eutectic Si size.

• 대한기계학회논문집A
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• 제24권3호
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• pp.625-633
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• 2000

The mechanical and curing properties of short nylon66 fiber reinforced Chloroprene rubber have been investigated as functions of interphase conditions and fiber content. The tensile strength exhibits a dilution effect at a low fiber content in each interphase. It is found that the interphase conditions have an important affect on the dilution ratio and critical fiber content. Double coatings of bonding agent 402 and rubber solution become the best interphase model in this study. The yield strength, tensile modulus, tear strength and fracture toughness at rupture, Jr are significantly improved due to fiber concentration.

• 한국주조공학회지
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• 제12권5호
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• pp.397-402
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• 1992

The effect of the solution & aging treatment on the tensile strength, yield strength, elongation, reduction of area, hardness was studied in the 17-4 PH stainless steel. SEM pictures were also taken in order to examine the fracture surfaces and precipitated particles. X-ray diffraction patterns for the heat treated samples were also observed. Mechanical properties of the heat treated samples were superior to those of as cast samples. Tensile strength, yield strength, hardeness decreased with the increase of aging temperature. On the other hand, elongation and reduction of area increased as the aging temperature increased.

• 자동차안전학회지
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• 제7권3호
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• pp.19-24
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• 2015

Brake pads are a component of disc brake system of automobile and consist of steel backing plates and friction material facing the disk brake rotor. Due to the repeated sliding forces and torque in vehicle braking, friction performance of brake pads are ensured. Futhermore, the brake pad is one of major tuning components in aftermarket, mechanical characteristics of the brake pad are necessary to evaluate for establishing the certification standards of tuning components. This study had performed the five specimen tests for friction coefficients and wear loss rates according to the SAE test specification. Using the instrumented indentation method, yield strength and tensile strength were measured. Friction coefficients, 0.386 - 0.489, and wear loss rates, 1.0% - 3.7% are obtained. The range of yield strength and tensile strength are 21.4 MPa - 105.3 MPa and 39.5 MPa - 176.4 MPa respectively.