• Advances in materials Research
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• v.1 no.3
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• pp.169-182
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• 2012

In this paper the intrinsic influence of micron-sized nickel particle reinforcements on microstructure, micro-hardness tensile properties and tensile fracture behavior of nano-alumina particle reinforced magnesium alloy AZ31 composite is presented and discussed. The unreinforced magnesium alloy (AZ31) and the reinforced nanocomposite counterpart (AZ31/1.5 vol.% $Al_2O_3$/1.5 vol.% Ni] were manufactured by solidification processing followed by hot extrusion. The elastic modulus and yield strength of the nickel particle-reinforced magnesium alloy nano-composite was higher than both the unreinforced magnesium alloy and the unreinforced magnesium alloy nanocomposite (AZ31/1.5 vol.% $Al_2O_3$). The ultimate tensile strength of the nickel particle reinforced composite was noticeably lower than both the unreinforced nano-composite and the monolithic alloy (AZ31). The ductility, quantified by elongation-to-failure, of the reinforced nanocomposite was noticeably higher than both the unreinforced nano-composite and the monolithic alloy. Tensile fracture behavior of this novel material was essentially normal to the far-field stress axis and revealed microscopic features reminiscent of the occurrence of locally ductile failure mechanisms at the fine microscopic level.

• The Journal of Advanced Prosthodontics
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• v.2 no.4
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• pp.117-121
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• 2010

PURPOSE. The present study was intended to evaluate the effect of soldering techniques with infrared ray and gas torch under different gap distances (0.3 mm and 0.5 mm) on the tensile strength and surface porosity formation in Ni-Cr base metal alloy. MATERIALS AND METHODS. Thirty five dumbbell shaped Ni-Cr alloy specimens were prepared and assigned to 5 groups according to the soldering method and the gap distance. For the soldering methods, gas torch (G group) and infrared ray (IR group) were compared and each group was subdivided by corresponding gap distance (0.3 mm: G3 and IR3, 0.5 mm: G5, IR5). Specimens of the experimental groups were sectioned in the middle with a diamond disk and embedded in solder blocks according to the predetermined distance. As a control group, 7 specimens were prepared without sectioning or soldering. After the soldering procedure, a tensile strength test was performed using universal testing machine at a crosshead speed 1 mm/min. The proportions of porosity on the fractured surface were calculated on the images acquired through the scanning electronic microscope. RESULTS. Every specimen of G3, G5, IR3 and IR5 was fractured on the solder joint area. However, there was no significant difference between the test groups (P > .05). There was a negative correlation between porosity formation and tensile strength in all the specimens in the test groups (P < .05). CONCLUSION. There was no significant difference in ultimate tensile strength of joints and porosity formations between the gas-oxygen torch soldering and infrared ray soldering technique or between the gap distance of 0.3 mm and 0.5 mm.

• Journal of Welding and Joining
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• v.27 no.3
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• pp.73-79
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• 2009

This present paper investigated the mechanical properties and the microstructures of each penetration shapes classifying the conduction shape area and the keyhole shape area about electron beam welded 120(T)mm thick plated aluminum 5052 112H. As a result the penetration depth is increased linearly according to the output power, but the aspect ratio is decreased after the regular output power. In the conduction shape area, the Heat affected zone is observed relatively wider than the keyhole shape area. In the material front surface of the welded specimen, the width is decreased but the width in the material rear surface is increased. After the measuring the Micro Vikers Hardness, it showed almost similar hardness range in all parts, and after testing the tensile strength, the ultimate tensile strength is similar to the ultimate tensile strength of the base material in all the specimens, also the fracture point was generated in the base materials of all the samples. In the result of the impact test, impact absorbed energy of the Keyhole shape area is turned up very high, and also shown up the effect about four times of fracture toughness comparing the base material. In the last result of observing the fractographs, typical ductile fraction is shown in each weld metal, and in the basic material, the dimple fraction is shown. The weld metals are shown that there are no other developments of any new chemical compound during the fastness melting and solidification.

• Advances in nano research
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• v.15 no.1
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• pp.59-65
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• 2023

In this present article, the mechanical behavior of single-walled black phosphorene nanotubes (SW-αPNTs) is simulated using molecular dynamics (MD). The proposed model is subjected to the axial loading and the effects of morphological parameters, such as the mono-vacancy defect and strain rate on the tensile behavior of the zigzag and armchair SW-αPNTs are studied as a pioneering work. In order to assess the accuracy of the MD simulations, the stress-strain response of the current MD model is successfully verified with the efficient quantum mechanical approach of the density functional theory (DFT). Along with reproducing the DFT results, the accurate MD simulations successfully anticipate a significant variation in the stress-strain curve of the zigzag SW-αPNTs, namely the knick point. Predicting such mechanical behavior of SW-αPNTs may be an important design factor for lithium-ion batteries, supercapacitors, and energy storage devices. The simulations show that the ultimate stress is increased by increasing the diameter of the pristine SW-αPNTs. The trend is identical for the ultimate strain and stress-strain slope as the diameter of the pristine zigzag SW-αPNTs enlarges. The obtained results denote that by increasing the strain rate, the ultimate stress/ultimate strain are respectively increased/declined. The stress-strain slope keeps increasing as the strain rate grows. It is worth noting that the existence of mono-atomic vacancy defects in the (12,0) zigzag and (0,10) armchair SW-αPNT structures leads to a drop in the tensile strength by amounts of 11.1% and 12.5%, respectively. Also, the ultimate strain is considerably altered by mono-atomic vacancy defects.

• Journal of Korean Society of Steel Construction
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• v.23 no.6
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• pp.715-724
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• 2011

A turn buckle inserted between tension members that sustain the structural loads in a suspension structure system is a device that is capable of adjusting the tensile force. The tension member is an important element of a tension structure, but no simple and economical method of measuring a tensile force applied to members has been proposed yet. Thus, a turn buckle for measuring the tensile force in a tension member was developed in this study. The turn buckles of the measurement limit loads of 100kN, 200kN, and 300kN were tested through a theoretical analysis and a finite element analysis. There was no significant difference in the results of the theoretical analysis, FEA, and the test. In addition, the ultimate strength of the turn buckle using FEA showed that a new turn buckle is sufficiently safe to use even when there is a five-times overload in the measurement limit load.

• Proceedings of the KSR Conference
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• 2011.10a
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• pp.621-629
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• 2011

Uniaxial and biaxial torsional fatigue tests were conducted on the samples extracted from urban railway wheel steel. Ultimate and yield strengths of the steel were 1027.7 MPa and 626 MPa, respectively. The uniaxial fatigue limit was 422.5 MPa, corresponding 67% of the ultimate tensile strength. The ratio of ${\tau}_e/{\sigma}_e$ was 0.63. Fatigue strength coefficient and exponent were 1319.5 MPa and 0.339, respectively. Maximum principal and equivalent strain were found to be adequate parameter to predict fatigue lifetime of the steel under multiaixal fatigue condition.

• Structural Engineering and Mechanics
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• v.40 no.2
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• pp.215-231
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• 2011

The axial compressive strength of unidirectional FRP is generally quite lower than its axial tensile strength. This fact decreases the advantages of FRP as main load bearing member in engineering structure. In order to restrain the lateral expansion and splitting of GFRP, and accordingly heighten its axial compressive bearing capacity, a project that to confine GFRP pole with surrounding CFRP sheet is suggested in the present study. The Experiment on the CFRP sheet confined GFRP poles showed that a combined structure of high bearing capacity was attained. Basing on the experiment research a theoretical iterative calculation approach is suggested to predict the ultimate axial compressive stress of the combined structure, and the predicted results agree well with the experimental results. Then the influences of geometrical parameters on the ultimate axial compressive stress of the combined structure are also analyzed basing on this approach.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.1321-1325
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• 2003

Nickel thin film is one of the most important materials used in micromachined structure. To measure the mechanical properties of electroplated nickel thin film, two techniques are adopted and compared quantitatively with. One is nano-indentation test to measure the elastic modulus. The other is tensile test to measure not only elastic modulus but also yield strength and plastic deformation, ultimate strength. To perform the tensile test, the test apparatus was constructed with linear guided servo motor for actuation, load cell for force measurement and dual microscope for strain measurement.

• Journal of Powder Materials
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• v.15 no.2
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• pp.142-147
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• 2008

The hypereutectic Al-20 wt%Si powders including some amount of Cu, Fe, Mg, Mn were prepared by a gas atomization process. In order to get highly densified Al-Si bulk specimens, the as-atomized and sieved powders were extruded at $500^{\circ}C$, Microstructure and tensile properties of the extruded Al-Si alloys were investigated in this study. Relative density of the extruded samples was over 98%. Ultimate tensile strength (UTS) in stress-strain curves of the extruded powders increased after T6 heat treatments. Elongation of the samples was also increased from 1.4% to 3.2%. The fracture surfaces of the tested pieces showed a fine microstructure and the average grain size was about $1{\mu}m$.

• Journal of the Korea Concrete Institute
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• v.18 no.5 s.95
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• pp.621-630
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• 2006

Twelve beams made of lightweight high-strength concrete were tested to determine their diagonal cracking and ultimate shear capacities. A total of 12 beams without(4 beams) and with lightweight(8 beams) were tested in a stiff testing facility, and complete load-midspan deflection curves, including the maximum capacities portion, were obtained. The variables in the test program were concrete strength, which varied 35.4 MPa, 65.3 MPa; shear span-depth ratios a/d=1.5, 2.5, 3.5, 4.5; and tensile steel ratio between 0.57 and 2.3 percent. Also, we divided beam by diagonal tension crack and ultimate shearing strength to propose an equation. In addition, it analyzed comparison mutually applying existing proposal and guide. $V_{cr}$ was as result that AIK recommendations and Zsutty proposal decrease more than a/d=2.5, increased some in Mathey's proposal equation. $V_{cr,\exp}/V_{cr,cal}$ showed tendency of overestimation according to increase of tensile steel ratio and compressive strength of concrete. On the other hand, $V_{cr,\exp}/V_{cr,cal}$ is superior in conformability with an experiment result Zsutty's proposal among other equations. The proposal equation hew that expect $V_{cr}/V_u$, rationally about shearing strength. Therefore, shear strength an equation is considered to be utilized usefully evaluating capacity by change of the shear span depth ratio of lightweight concrete, tensile steel ratio, and compressive strength of the concrete in this research.