• Carbon letters
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• v.27
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• pp.72-80
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• 2018

In the present work, a comparative study of the mechanical behavior of two series of elastomeric composites, based on carboxylated styrene butadiene rubber (X-SBR) and reinforced with rice bran carbon (RBC) and graphite, is reported. Hybrid composites of X-SBR filled with RBC-graphite were also investigated in terms of the cure characteristics, hardness, tensile properties, abrasion resistance, and swelling. It was observed that the cure times decreased with the incorporation of a carbon filler whereas the torque difference, tensile strength, tensile modulus, hardness, and swelling resistance increased compared to the neat X-SBR revealing a favorable characteristic of crosslinking. Dynamic rheological analysis showed that the G' values of the composites, upon the addition of RBC-graphite, were changed to some extent. This demonstrates that the presence of a strongly developed network of fillers will ensure a reinforcing characteristic in a polymer matrix.

• Korean Journal of Metals and Materials
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• v.48 no.8
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• pp.717-723
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• 2010

The degradation behavior of fuel cladding is a very import concern in nuclear power generation, because the operation of nuclear plants can be limited by fuel cladding degradation. In order to evaluate the hydride effect on failure of zirconium fuel claddings, a ring tensile test for the circumferential direction was carried out at room temperature for claddings having different hydride characteristics such as density and orientation; microstructural evaluation was also performed for those claddings. The circumferential failure of the claddings was promoted by increasing the hydride concentration in the matrix; however, the failure of the claddings was affected by the hydride orientation rather than by the hydride concentration in the matrix. From fracture surface observation, the cladding failure during the ring tensile test was matched with the hydride orientation.

• Journal of the Korea Concrete Institute
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• v.28 no.2
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• pp.223-234
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• 2016

In this study, direct tension test for hybrid steel fiber reinforced ultra-high performance concrete (UHPC) containing two different steel fibers with a length of 16 and 19 mm was performed to investigate the fracture behavior of UHPC. Test results showed that crack strength and tensile strength, and fracture energy increased with increasing the fiber volume ratio. Based on the test results, the peak cohesive stress at the crack tip, tensile strength, and fracture energy depending on the fiber volume ratio were proposed. The proposed tensile strength of UHPC was suggested as a function of the fiber volume ratio and compressive strength. The peak cohesive stress at the crack tip and fracture energy were also proposed as a function of the tensile strength. The predicted values were relatively agree well with the test results. Thus, the proposed equations is expected to be applicable to UHPC with a compressive strength of 140~170 MPa and a fiber volume ratio of less than 2%.

• Journal of the Korean Society for Heat Treatment
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• v.11 no.4
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• pp.333-341
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• 1998

The study was investigated on the effect of austenitizing and austempering conditions on retained austenite amount and carbon contents in retained austenite and simultaneously the effect of these variation on hardness, tensile and impact properties. A material of as-cast condition is composed of bull's eye structure with ferrite surrounding spheroidized graphite having about $5-10{\mu}m$ size and matrix structure of pearlite. Then, the contents of spheroidized graphite was about 5%. The retained austenite and carbon contents in the retained austenite were increased with the increasing of austenitizing and austempering temperatures, while the retained austenite showed the peak value and is decreased with increasing of austempering time. With increasing of austenitizing temperature, tensile strength, elongation and impact absorb energy increased and hardness was almost not changed, while with increasing of austempering temperature, tensile strength and hardness decreased, whereas elongation and impact absorb energy was increased. With increasing of retained austenite amount, the tensile strength is slowly decreased but elongation was increased with direct proportion. Also, Impact absorb energy is shown identity value untile about 18%, but rapidly increased above it. Elongation and Impact absorb energy are strongly controlled by the amount of retained austenite, but tensile strength is affected with various factors such as retained austenite amount and bainitic morphology.

• Structural Engineering and Mechanics
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• v.52 no.1
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• pp.75-87
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• 2014

To analyze the tension performance of laminated rubber bearings under tensile loading, a theoretical tension model for analyzing the rubber bearings is proposed based on the theory of elasticity. Applying the boundary restraint condition and the assumption of incompressibility of the rubber (Poisson's ratio of the rubber material is about 0.5 according the existing research results), the stress and deformation expressions for the tensile rubber layer are derived. Based on the derived expressions, the stress distribution and deformation pattern especially for the deformation shapers of the free edges of the rubber layer are analyzed and validated with the numerical results, and the theory of cracking energy is applied to analyze the distributions of prediction cracking energy density and gradient direction. The prediction of crack initiation and crack propagation direction of the rubber layers is investigated. The analysis results show that the stress and deformation expressions can be used to simulate the stress distribution and deformation pattern of the rubber layer for laminated rubber bearings in the elastic range, and the crack energy method of predicting failure mechanism are feasible according to the experimental phenomenon.

• Advances in concrete construction
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• v.1 no.4
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• pp.341-358
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• 2013

Due to fast growth in urbanisation, a highly developed infrastructure is essential for economic growth and prosperity. One of the major problems is to preserve, maintain, and retrofit these structures. To meet the requirements of construction industry, the basic information on all the mechanical properties of various concretes is essential. This paper presents the details of development of various concretes, namely, normal strength concrete (around 50 MPa), high strength concrete (around 85 MPa) and ultra high strength concrete (UHSC) (around 120 MPa) including their mechanical properties. The various mechanical properties such as compressive strength, split tensile strength, modulus of elasticity, fracture energy and tensile stress vs crack width have been obtained from the respective test results. It is observed from the studies that a higher value of compressive strength, split tensile strength and fracture energy is achieved in the case of UHSC, which can be attributed to the contribution at different scales viz., at the meso scale due to the fibers and at the micro scale due to the close packing of grains which is on account of good grading of the particles. Micro structure of UHSC mix has been examined for various magnifications to identify the pores if any present in the mix. Brief note on characteristic length and brittleness number has been given.

• Journal of Powder Materials
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• v.1 no.2
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• pp.181-189
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• 1994

The compacts of pure and phosphorus-coated iron powder with 0~0.8%C were sintered at $1100^{\circ}C$ for 40 min. in cracked ammonia gas atmosphere. The tensile and impact strengths were measured and the relationship of the results with carbon content, phosphorus, quenching and tempering was investigated. The results obtained can be summarized as follows : (1) The tensile strength of sintered compacts increased slowly with carbon content. Increase in tensile strength by heat treatment was evident especially in the low carbon specimen. The specimen with phosphorus showed higher strength compared to pure iron compacts value. (2) No inflection point of elasticplastic deformation on stress-strain curve was observed in sintered steel. The elastic modulus of sintered steel had the same tendency as tensile strength. But the elongation showed the opposite tendency. (3) The impact absorption energy of sintered steel without addition of phosphorus decreased successively with carbon content and by quenching and tempering. On the contrary, addition of phosphorus resulted in an increase of the impact absorption energy. Quenching and tempering did not affect the impact energy especially in high carbon content. (4) The main fracture source was pore in specimen and the propagation of crack occured mostly along the grain boundaries. But the intragranular fracture was also observed in high carbon, quenched and tempered specimen, and especially in the specimen with phosphorus.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.21 no.6
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• pp.60-66
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• 2022

The optimal strain energy function was obtained by comparing the results of the analysis using the strain energy functions obtained by uniaxial tensile and equibiaxial tensile tests on gasket materials used in hydrogen fuel cells, with the results measured using a contact pressure measurement sensor. At this time, even when only the uniaxial tensile test was conducted, Yeoh could obtain the most accurate results even by conducting only the uniaxial tensile test. Using this, an analysis of the cross section of the gasket used in stack confirmed a safe contact pressure and no deformation on the separator. In the future, research will be conducted to verify the gasket durability by reliability evaluation.

• Transactions of the Korean hydrogen and new energy society
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• v.33 no.2
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• pp.176-182
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• 2022

Since the various characteristics of the polymer electrolyte membrane are not clearly identified, it is difficult to predict and design applications for various conditions. In this study, as a previous study on the aging of the polymer electrolyte membrane, a study was conducted on the change of mechanical properties according to the aging of the polymer electrolyte membrane. Through the tensile test of Nafion 117, the mechanical properties change due to aging was confirmed. As a result of the tensile test, it was confirmed that the aged Nafion 117 had reduced tensile strength. Through DSC measurement, aged Nafion confirmed that the glass transition temperature and enthalpy change were low, which is thought to be the effect of molecular motion and transition due to the lapse of time. The effect is thought to cause a difference in the amount of change in enthalpy, resulting in a difference in mechanical properties during tension.

• Corrosion Science and Technology
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• v.22 no.6
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• pp.457-465
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• 2023

Irradiation-assisted stress corrosion cracking (IASCC) is one of the main degradation mechanisms of austenitic stainless steels, which are used as reactor internal materials. Slow strain rate testing (SSRT) has been widely applied to evaluate the IASCC initiation characteristics of proton-irradiated tensile specimens. Tensile specimens require low surface roughness for micro-crack observation, and electropolishing is the most important specimen pre-treatment process used for this. In this study, optimal electropolishing conditions were examined through analyzing results of polarization experiments and surface roughness measurements after electropolishing. Corrosion cell and electropolishing equipment were fabricated for polarization tests and electropolishing experiments using SSRT specimens. The experimental parameters were electropolishing time, current density, electrolyte temperature, and stirring speed. The optimal electropolishing conditions for SSRT tensile specimens made of type 316 stainless steel were evaluated as a polishing time of 180 seconds, a current density of 0.15 A/cm², an electrolyte temperature of 60 ℃, and a stirring speed of 200 RPM.