• Journal of Ocean Engineering and Technology
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• v.26 no.6
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• pp.19-26
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• 2012

Recently the world has been suffering from difficulties related to the demand and supply of energy due to the democratic movements sweeping across the Middle East. Consequently, many have turned their attention to never-developed extreme regions such as the polar lands or deep sea, which contain many underground resources. This research investigated the strength and initial elastic modulus values of eternally frozen ground through a uniaxial compression test and indirect tensile test using frozen artificial soil specimens. To ensure accurate test results, a sandymud mixture of standard Jumunjin sand and kaolinite (20% in weight) was used for the specimens in these laboratory tests. Specimen were prepared by varying the water content ratio (7%, 15%, and 20%). Then, the variation in the strength value, depending on the water content, was observed. This research also established three kinds of environments under freezing temperatures of $-5^{\circ}C$, $-10^{\circ}C$, and $-15^{\circ}C$. Then, the variation in the strength value was observed, depending on the freezing environment. In addition, the tests divided the loading rate into 6 phases and observed the variation in the stress-strain ratio, depending on the loading rate. The test data showed that a lower freezing temperature resulted in a larger strength value. An increase in the ice content in the specimen with the increase in the water content ratio influenced the strength value of the specimen. A faster load rate had a greater influence on the uniaxial compression and indirect tensile strengths of a frozen specimen and produced a different strength engineering property through the initial tangential modulus of elasticity. Finally, the long-term strength under a constant water content ratio and freezing temperature was checked by producing stress-strain ratio curves depending on the loading rate.

• Steel and Composite Structures
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• v.15 no.6
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• pp.659-677
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• 2013

This paper introduces new specimens of Steel-Carbon Fibre Reinforced Polymer composite developed in accordance with standard test method and definition for mechanical testing of steel (ASTM-A370). The main purpose of this research is to study the behaviour of steel-CFRP composite specimen under uniaxial tension to use it in beams in lieu of traditional steel bar reinforcement. Eighteen specimens were prepared and divided into six groups, depending upon the number of the layers of CFRP. Uniaxial tensile tests were conducted to determine yield strength and ultimate strength of specimens. Test results showed that the stress-strain curve of the composite specimen was bilinear prior to the fracture of CFRP laminate. The tested composite specimens displayed a large difference in strength with remarkable ductility. The ultimate load for Steel-Carbon Fibre Reinforced Polymer composite specimens was found using the model proposed by Wu et al. (2010) and nonlinear FE analysis. The ultimate loads obtained from FE analysis are found to be in good agreement with experimental ones. However, ultimate loads obtained applying Wu model are significantly different from experimental/FE ones. This suggested modification of Wu model. Modified Wu's model which gives a better estimate for the ultimate load of Steel-Carbon Fibre Reinforced Polymer (SCFRP) composite specimen is presented in this paper.

• Journal of Korea Foundry Society
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• v.17 no.5
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• pp.450-457
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• 1997

Effects of Ti addition and homogenizing heat treatment on the mechanical properties in Cu-Zn-Al alloy (high strength yellow brass) were investigated. Grain refinement was successfully achieved by Ti addition. The microstructure, which was composed of island or fine feather-like branched Ti compounds was changed to feather-like eutectic microstructure as the content of Ti increased. The highest hardness value was obtained for 0.5 wt.% Ti specimen and the second was Ti non-added specimen in as-cast condition. The highest tensile strength was obtained for 0.5 wt.% Ti specimen. Because of the presence of cast defects and worse castability, tensile strength decreased as the content of Ti increased. Elongation increased with increasing homogenizing time and temperature; remarkable increase was obtained for $400^{\circ}C$ homogenizing temperature in the 0.5 wt.% Ti specimen. For $500^{\circ}C$ and $600^{\circ}C$ homhgenizing, temperature, high elongation was obtained in 2 and 4 wt.% Ti specimen.

• Journal of the Korean Society for Precision Engineering
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• v.20 no.2
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• pp.154-161
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• 2003

The effects of specimen geometry, and loading conditions on the J-integral fur CCT (center cracked tension) specimens are investigated by using FEM. It is found that the J-integral tends to decrease according to the parallel tensile loading to crack line. Furthermore, it is verified that the compressive parallel loading to crack line is likely to increase the J-integral. A stress ratio of length to width of the center CCT specimen is confirmed to affect the J-integral significantly.

• Journal of the Korean Society of Industry Convergence
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• v.23 no.3
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• pp.375-380
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• 2020

In this study, we tried to evaluate the mechanical properties of Polycarbonate(PC) and acrylonitrile-butadiene-styrene(ABS) plastic materials, which are frequently used as parts of home appliances and machinery, when repeated impacts were applied. A repeating impact tester for this research was designed and manufactured to apply repetitive impacts. Two types of plastic were repeatedly impacted under a constant load, and a tensile test was performed on the plastic material that was impacted. The tensile strength of PC plastic materials that received impact more than 2000 times was reduced by about 45 % and elongation was reduced by about 10 % when compared to impact free specimens. On the other hand, in ABS plastic, a reduction of tensile strength of about 20 % was observed at about 2,000 impacted specimen, but at about 20,000 repetitive impacted specimen, a tensile strength decrease of about 65 % was observed. And the elongation was reduced by 10 % due to the cyclic harding behavior of the material.

• Journal of Ocean Engineering and Technology
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• v.20 no.2 s.69
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• pp.52-58
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• 2006

The effect of various environmental conditions on the durability of E-glass fiber/vinylester resin composites have been investigated using the tensile test specimen of strand type. It was found that the durability test method performed by the stand type specimen was more convenient and reliable than other conventional test method. The weight gains increased with the immersion time in both water and alkaline solution, and the Weight gains at $50^{\circ}C$. were much bigger than those at $20^{\circ}C$ in both conditions. The tensile strength decreased with the pass of immersion time in all aqueous solution, and the tensile strength at $80^{\circ}C$ in alkaline solution decreased very steeply at beginning of immersion time. The decrement of tensile strength according to the immersion time in various environmental conditions was mainly caused by the degradation of interface and the damage of glass fiber surface.

• Structural Engineering and Mechanics
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• v.68 no.5
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• pp.537-547
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• 2018

This research presents the effect of anisotropy of the hollow disc mode under Brazilian test using PFC3D. The Brazilian tensile strength test was performed on the hollow disc specimens containing the bedding layers and then these specimens were numerically modeled by using the two dimensional discrete element code (PFC3D) to calibrate this computer code for the simulation of the cracks propagation and cracks coalescence in the anisotropic bedded rocks. The thickness of each layer within the specimens varied as 5 mm, 10 mm and 20 mm and the layers angles were changed as $0^{\circ}$, $25^{\circ}$, $50^{\circ}$, $75^{\circ}$ and $90^{\circ}$. The diameter of internal hole was taken as 15 mm and the loading rate during the testing process kept as 0.016 mm/s. It has been shown that for layers angles below $25^{\circ}$ the tensile cracks produce in between the layers and extend toward the model boundary till interact and break the specimen. The failure process of the specimen may enhance as the layer angle increases so that the Brazilian tensile strength reaches to its minimum value when the bedding layers is between $50^{\circ}$ and $75^{\circ}$ but its value reaches to maximum at a layer angle of $90^{\circ}$. The number of tensile cracks decreases as the layers thickness increases and with increasing the layers angle, less layer mobilize in the failure process.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.1818-1823
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• 2007

In this paper, notched bar tensile tests of Inconel 617 were performed at room ($20^{\circ}C$) and elevated ($800^{\circ}C$) temperature. Finite element analyses are also performed. It is found that, at the room temperature, smooth bar tensile test results could be used to simulate notched bar tensile tests. However, at the elevated temperature, notched bar tensile test results can not be simulated from smooth bar tensile test results. Metallurgical examination reveals that strength weakening results from many cavities over the specimens for smooth bar test at the elevated temperature. "True" tensile properties at the elevated temperature is found using FE simulations. It also suggests that cautious should be taken to determine tensile properties of Inconel 617 at elevated temperatures using smooth bar tests.

• Transactions of Materials Processing
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• v.31 no.2
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• pp.89-95
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• 2022

3D printing products manufactured by material extrusion are used in many industrial fields recently. However, these products are difficult to use in the field due to their low tensile strengths. In order to solve this problem, research on improving the tensile strength of the output using a 3D printer has been continuously conducted. In this study, we performed a tensile test using Universal Testing Machine according to infill pattern, nozzle temperature, bed temperature, and printing speed conditions. Results revealed that tensile specimen of concentric shape had the highest tensile strength in infill pattern condition and that the tensile strength increased linearly with increasing nozzle and bed temperatures. However, the tensile strength decreased with increasing printing speed. Consequently, we confirmed that tensile strength could be increased and decreased depending on output conditions of 3D printing.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.1
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• pp.54-60
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• 2001

This study is to investigate the mechanical properties and the fatigue crack propagation of fire resistance steel for frame structure as the chemical composition was changed by addition of N, B and rolled end temperature was varied. We used two kinds of specimen, the one is parallel and the other is perpendicular to the rolling directions. As rolled end temperature increased, volume fraction of ferrite and pearlite decreased, but volume fraction of baintie and grain size increased. Micro-hardness decreased as rolled end temperature increased, but tensile and yield strength increased. Volume fraction of ferrite and pearlite decreased by addition of N. But volume fraction of bainite, tensile and yield strength increased. Microstructure was changed to martensite by addition of B, and tensile and yield strength increased. Fatigue life of TL direction specimen was shorter than that of LT direction specimen. There was no significant effect to fatigue crack propagation rate by addition of N and changing rolling condition, but fatigue life was increased by addition of B.