• Proceedings of the Korean Institute of Building Construction Conference
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• 2006.11a
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• pp.53-56
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• 2006

The objection of this study is to investigate the properties of cement mortar with the kinds and addition of expansive additives. 3 kinds of expansive additives produced in our country and 0, 5, 10, 15, 20% of ratio of addition rate are selected for this experiment. According to experimental results, flow of cement mortar with expansive additives is nearly same with flow of plain mortar and compressive strength, tensile strength, bend strength of cement mortar with expansive additives at 28 days is higher than that of plain mortar.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.18 no.6
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• pp.658-663
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• 2009

Metal/ceramic composites structures have many attractive properties with great potential for applications that demand high stiffness as well as chemical and biological stability, thermal and electrical insulation. They are currently in use for mechanical and thermal protection in cutting tool and engine parts. Thus, determination of adhesive properties for coating part is one of the most important problems for the extension of the use of coated materials. In this work, bending strength of Functionally Graded Materials(FGM) are evaluated by means of bending strength tester. The graded layer according to the load condition showed the change of the bend strength.

• Proceedings of the Korean Institute of Industrial Safety Conference
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• 1998.05a
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• pp.31-36
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• 1998

It is very important to have exact informations on the properties and characteristics of the sintered steel as a new material of machine elements. The bending fatigue tests are performed for sintered steel bend specimens and spur gears, which are notched by using a slicing blade. The fatigue test at a constant stress amplitude is performed by using an electrohydraulic servo-controlled pulsating tester Consequently, the S-N curves are obtained and the fatigue strength. is compared with flaw depth. Accordingly, this study presents the fatigue strength of sintered spur gears, the critical notch depth of sintered steel and the effects of flaw depth on the bending fatigue strength. The enhancement of fatigue strength due to carburized treatment is clarified.

• Journal of the Korean Society of Safety
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• v.13 no.4
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• pp.34-40
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• 1998

It is very important to have exact informations on the properties and characteristics of the sintered steel as a new material of machine elements. The bending fatigue tests are performed for sintered steel bend specimens and spur gears, which are notched by using a slicing blade. The fatigue test at a constant stress amplitude is performed by using an electrohydraulic servo-controlled pulsating tester. Consequently, the S-N curves are obtained and the fatigue strength is compared with flaw depth. Accordingly, this study presents the fatigue strength of sintered spur gears, the critical notch depth of sintered steel and the effects of flaw depth on the bending fatigue strength. The enhancement of fatigue strength due to carburized treatment is clarified.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2003.05a
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• pp.109-113
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• 2003

In this experiment, we distribute the bending angle to 60$^{\circ}$, 90$^{\circ}$, 120$^{\circ}$, and we separate it in to two groups. One is straightening right after bending and the other is straightening after one week. The bars we will use are HD13 and HD16. The number of tests will be 60 times. In the case of HD16, the increase of bending angle decreased yield strength and maximum strength. And compared with thinner bars, HD16 showed bigger differences in yield strength and maximum strength when the 'being bent' duration got longer. So it shows that when we bend and after straighten a bar, stress change takes place on the surface of the bar. At the beginning it shows it's ductility after that it deforms while transforming it's character to destroying. And also, if we straighten a bar after bending, it doesn't get straighten like the original form. So it makes torsion and this torsion makes moments in different areas.

• Structural Engineering and Mechanics
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• v.54 no.6
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• pp.1201-1216
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• 2015

This paper presents the details of size independent fracture energy and bi-linear tension softening relation for nano modified high strength concrete. Nano silica in powder form has been used as partial replacement of cement by 2 wt%. Two popular methods, namely, simplified boundary effect method of Karihaloo et al. (2003) and RILEM (1985) fracture energy with P-${\delta}$ tail correction have been employed for estimation of size independent fracture energy for nano modified high strength concrete (compressive strength ranges from 55 MPa to 72 MPa). It is found that both the methods gave nearly same values, which is an additional evidence that either of them can be employed for determination of size independent fracture energy. Bi-linear tension softening relation corresponding to their size independent fracture energy has been constructed in an inverse manner based on the concept of non-linear hinge from the load-crack mouth opening plots of notched three-point bend beams.

• Journal of Welding and Joining
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• v.15 no.5
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• pp.104-114
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• 1997

The microstructure and bond strength were investigated on the SiC/SiC and SiC/mild steel joints brazed by Ag-5at%Ti alloy. Ag-5at%Ti-2at%Fe and -5at%Fe brazing alloys were also used to see the effects of Fe addition on the bond strength of SiC/SiC brazed joints. Brazing temperature and brazing gap were selected and examined as brazing variables. The microstructure of SiC/SiC brazed joints was affected by Fe addition to the Ag-5at%Ti alloy, but the bond strength was not. Increasing brazing temperature also changed the microstructure of $Ti_5Si_3$ reaction layer and brazing alloy matrix of the SiC/SiC and SiC/mild steel joints, but not the bond strength. Brazing gap had a great effects on the bond strength. Decreasing brazing gap from 0.2 mm to 0.1 mm in SiC/SiC brazing increased the bond strength from 187 MPa to 263 MPa and, in SiC/mild steel brazing, from 189 MPa to 212 MPa. It was concluded that the most important parameter on the bond strength in SiC/SiC and SiC/mild steel brazing was the relative ratio between brazing gap and specimen size.

• Korean Journal of Materials Research
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• v.29 no.1
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• pp.43-51
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• 2019

Nacre of abalone shell features a "brick-and-mortar" microstructure, in which micro-plates of calcium carbonate are bonded by nanometers-thick layers of chitin and proteins. Due to the microstructure and its unique toughening mechanisms, nacre possesses an excellent combination of specific strength, stiffness and toughness. This study deals with the possibility of using nacre fragments obtained from abalone shell for making a bulletproof armor system. A composite plate laminated with abalone shell fragments is made and compression and bend tests are carried out. In addition, a bulletproof test is performed with hybrid armor systems which are composed of an alumina plate, a composite plate, and aramid woven fabric to verify the ballistic performance of nacre. The compressive strength of the composite plate is around 258.3 MPa. The bend strength and modulus of the composite plate decrease according to the plate thickness and are about 149.2 MPa and 50.3 GPa, respectively, for a 4.85 mm thick plate. The hybrid armor system with a planar density of $45.2kg/m^2$, which is composed of an 8 mm thick alumina plate, a 2.4 mm thick composite plate, and 18 layers of aramid woven fabric, satisfy the NIJ Standard 0101.06 : 2008 Armor Type IV. These results show that a composite plate laminated with abalone shell fragments can be used for a bulletproof armor system as an interlayer between ceramic and fabric to decrease the armor system's weight.

• PNF and Movement
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• v.17 no.2
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• pp.303-310
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• 2019

Purpose: This study aimed to investigate the correlation between abdominal muscle strength and measures of respiratory function in stroke patients. Methods: The study participants comprised 17 (male: 12, female: 5) stroke patients hospitalized at W rehabilitation hospital in Busan, South Korea. Abdominal muscle strength was assessed using a digital manual dynamometer for 5 seconds contacting the sternal notch of the participants to bend the trunk. Respiratory function (forced vital capacity, forced expiratory volume in one second, forced expiratory volume in one second/forced vital capacity, and peak expiratory flow) was assessed using a spirometer. The collected data were analyzed using Pearson's correlation analysis, and the significance level was set 0.05. Results: A statistically significant correlation was found between abdominal muscle strength and forced vital capacity, forced expiratory volume in one second, and peak expiratory flow. However, abdominal muscle strength and forced expiratory volume in one second/forced vital capacity were not significantly correlated. Conclusion: This study demonstrated that there is a relationship between abdominal muscle strength and respiratory function. Exercise programs to strengthen the abdominal muscles are therefore necessary to improve respiratory function in stroke patients.

• Journal of Industrial Technology
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• v.24 no.A
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• pp.9-15
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• 2004

The flexural strength from 3-point bend test and fatigue properties were measured to evaluate mechanical properties of metal/ceramic interface of the multilayer ceramic package produced through tape casting. From the results, the specimens with three electrode layers showed the highest strength. The temperature distribution with time during thermal cycle and thermal stresses with the change of electrode's shape have been estimated by mathematical modelling. Specimen affected by thermal shock, produced microcracks by the difference of thermal expansion coefficient. The results of tensile test and fatigue test showed the rupture at pin. The fact that the pin brazed specimens were always fractured at the pin proved the good bonding condition between pin and electrode.