• Journal of the Korean Society of Safety
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• v.30 no.3
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• pp.7-12
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• 2015

CFRP composites are used as primary structural members in various industrial fields because their specific strength and specific stiffness are excellent in comparison to conventional metals. Their usage is expanding to high added-value industrial fields because they are more than 50% lighter than metals, and have excellent heat resistance and wear resistance. However, when CFRP composites suffer impact damage, destruction of fiber and interface delamination occur. This causes an unexpected deterioration of strength, and for this reason it is very difficult to ensure the reliability of the excellent mechanical properties. Therefore, for the destruction mechanism in bending with impact damage, this study investigated the reinforcement data regarding various external loads by identifying the consequential strength deterioration. Specimens were damaged by impact with a steel ball propelled by air pressure. Decrease in bending strength caused by the tension and compression of the impact side, and depending on the lamination direction of fiber and interface inside the specimen. From the bending test it was found that the bending strength reduced when the impact energy increased. Especially in the case of compression on the impact side, as tensile stress occurred at the damage starting point, causing rapid failure and a substantially reduced failure strength.

• Korean Journal of Applied Biomechanics
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• v.21 no.3
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• pp.327-334
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• 2011

The objective of this study was to develop a scientific approach for investigating Korean dance in detail, and to examine the intense expressions and various movements, which are based on Danjeon breathing. For the purpose, we analyzed the movement changes and distribution of forces resulting from the switch in movement between exhalation and inhalation while bending, which is the most basic movement in Korean dance. The following conclusions were drawn from this study. In Korean dance, bending with breathing involves less back-and-forth-movement and more up-and-down movement, as compared to bending without breathing; this indicates greater body stability and a wider range of movements while bending with breathing. In addition, less time is required for bending with breathing at the point of switching from exhalation to inhalation, and it involves less movement of the supporting leg; thus, vending with breathing involves faster switching from bending movements to extending movements. While bending, the raised leg goes through a less smooth curve while breathing, which indicates stronger movement of the toes. Bending with breathing requires a greater braking force than bending without breathing, and the vertical force, generated by switching from exhalation to inhalation, is transferred to extending movements using the ground load. The results of this study can be potentially employed to investigate the expressions used in Korean dance on th basis of its principle of forces. Korean dance has evolved into various creative forms, and basic analytical studies of these diverse forms and related breathing methods re required in the future.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.31 no.4
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• pp.425-431
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• 2007

[ $Al_2O_3/SiC$ ]composite ceramics were sintered to evaluate the bending strength and elastic wave characteristics. The three-point bending test was carried out under room temperature. The elastic wave was detected by fracture wave detector. The crack healing behavior was investigated from 1373 K to 1723 K. The bending strength of $Al_2O_3/SiC$ composite by nanocomposite is higher than that of $Al_2O_3$ monolithic. Crack-healing behavior depended on an amount of additive powder $Y_2O_3$. In $Al_2O_3/SiC$ composite ceramics with 3 wt. % $Y_2O_3$ for additive powder, the bending strength at 1573 K is about 100% increase than that of the smooth specimens. From the result of wavelet analysis of elastic wave signal, the smooth specimen and heat treated specimen of $Al_2O_3$ monolithic and $Al_2O_3/SiC$ composite ceramics showed characteristics of frequency about 58 kHz. The strength of $Al_2O_3/SiC$ composite ceramics was a little higher than those of $Al_2O_3$ monolithic. The dominant frequencies were high with increasing of $Y_2O_3$ for additive powder. The dominant frequencies had direct connection with the bending strength.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.3
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• pp.901-907
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• 2013

In this study, flexural strength properties of concrete under biaxial stress state were experimentally investigated. Tests for size effect and fatigue behaviour of concrete under biaxial stress were carried out by the ASTM C 1550 and the biaxial flexure test(BFT). The results given by the biaxial tests were compared to those by the third-point bending test. Test results showed that biaxial flexural strengths obtained from the ASTM C 1550 and the biaxial flexure test are greater than the strength by the third-point bending test. As the size increases, the uniaxial and biaxial flexural strength decreases. However, the slope of the size effect of the biaxial strength was greater than that of the uniaxial strength. Finally, the fatigue response of concrete under the biaxial stress state was similar with that for uniaxial stress state.

• Journal of the Korean Institute of Gas
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• v.3 no.3 s.8
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• pp.1-8
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• 1999

Three-point bending fatigue properties of austenitic 304 stainless steel sheets were investigated at room temperature and LNG temperature($-162^{\circ}C$) in the strain range from 0.43 to $1.7\%$. The fatigue properties at $-162^{\circ}C$ were superior to those at room temperature due to the higher volume fractions of deformation-induced martensite. The cyclic hardening behavior owing to the deformation- induced martensite transformation was detected in both specimens. In room temperature testing, the mean load amplitude increased steadily with cycles, meaning that cumulative plastic incubation strain was required for martensite transformation. On the contrary, in $-162^{\circ}C$ tested specimen, the mean load amplitude increased rapidly within a few cycles due to the rapid transformation of martensite, and slightly decreased after the maximum is reached probably due to dynamic recovery.

• Journal of the Korean Home Economics Association
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• v.34 no.2
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• pp.183-199
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• 1996

The objective of this study was to provide fundamental data on somatotype for elderly women by classifying the somatotype and analysing the 3 characteristics of their somatotype. The subject were 368 women of 60~84 years old, they were analyzed indirect photography. To find out differences among the age groups, the 368 subjects were grouped into two age groups (Group 1 ; age 60 to 69, Group 2 ; aged 70 to 84). Data were analyzed using Factor analysis, Cluster analysis, duncan test and Analysis of variance. Through the factor analysis, 27 items from photometric measurements respectively. Cluster analysis was applied for classification of somatotype. The results of this study were as follows. 1. The characteristics of Elderly women's somatotype were bending of the upper-torso, fatness of the waist and abdomen, drooping of the bust and shoulder and hip. In addition, height, girth, depth and width items were decreased in their sizes respectively. 2. The characteristics of clusters were as follows. Type 1 was straight somatotype in which the plumb line through tragion, the bust depth and under bust depth region laterally. Type 2 was swayback somatotype in which the upper portion of protruding point on the back was bent forward but the lower portion of protruding point had a characteristics of turning over somatotype. Type 3 was bending somatotype. Namely, this type was shorter than average and below the average fatness. Generally, the lateral view silhouette of elderly women was the straight type and changed into bending type as the age increases.

• Steel and Composite Structures
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• v.46 no.3
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• pp.353-366
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• 2023

This paper presents a finite-element analysis (FEA) of aluminum alloy rectangular hollow sections (RHSs) and square hollow sections (SHSs) with circular through-openings under three-point and four-point bending. First, a finite-element model (FEM) was developed and validated against the corresponding test results available in the literature. Next, using the validated FE models, a parametric study comprising 180 FE models was conducted. The cross-section width-to-thickness ratio (b/t) ranged from 2 to 5, the hole size ratio (d/h) ranged from 0.2 to 0.8 and the quantity of holes (n) ranged from 2 to 6, respectively. Third, results obtained from laboratory test and FEA were compared with current design strengths calculated in accordance with the North American Specifications (NAS), the modified direct strength method (DSM) and the modified Continuous strength method (CSM). The comparison shows that the modified CSM are conservative by 15% on average for aluminum alloy RHSs and SHSs with circular through-openings subject to bending. Finally, a new design equation is proposed based on the modified CSM after being validated with results obtained from laboratory test and FEA. The proposed design equation can provide accurate predictions of flexural capacities for aluminum alloy RHSs and SHSs with circular through-openings.

• Computers and Concrete
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• v.17 no.3
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• pp.407-421
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• 2016

This paper presents numerical modeling of the structural behavior of CFRP (carbon fiber reinforced polymer) strengthened RC (reinforced concrete) beams under four-point bending. Simulation of debonding at the CFRP-concrete interface was focused, as it is the main failure mode of CFRP strengthened RC beams. Here, cohesive layer was employed to model the onset of debonding, which further helps to describe the post debonding behavior of the CFRP strengthened RC beam. In addition, the XFEM approach was applied to investigate the effects of crack localization on strain field on CFRP sheet and rebar. The strains obtained from the XFEM correlate better to the test results than that from CDP (concrete damaged plasticity) model. However, there is a large discrepancy between the experimental and simulated loaddisplacement relationships, which is due to the simplification of concrete constitutive law.

• Journal of Welding and Joining
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• v.32 no.4
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• pp.34-38
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• 2014

Carburizing treatments are the important way to developing fatigue strength and wear resistance. It is well known that the case depth is one of the most significant parameters determining fatigue strength. In this study, 3-point bending fatigue test was conducted to evaluate fatigue strength for the carburized depth with 18CrNiMo7-6 steel. As a result, fatigue strength increased with effective case depth decreased. It is shown that hardness in case hardened layer played principal role in the fatigue strength.

• Journal of the Korea Concrete Institute
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• v.12 no.3
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• pp.67-75
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• 2000

It was well recognized that the damages associated mainly with the aging of civil infrastructures were one of very serious problems for assurance of safety and reliability. Recently carbon fiber sheet(CFS) has been widely used for reinforcement and rehabilitation of damaged concrete beam. However, the fundamental mechanism of load transfer and its load-resistant for carbon fiber sheet reinforced concrete are not fully understood. In this study, three point bending test has been carried out to understand the damage progress and the micro-failure mechanism of CFS reinforced mortars. For this purpose, four different types of specimens are used, that is, mortar, steel bar reinforced mortar, CFS reinforced mortar, and steel bar and CFS reinforced morter. Acoustic Emission(AE) technique was used to evaluate the characteristics of damage progress and the failure mechanism of specimens. in addition, two-dimensional AE source location was also performed to monitor crack initiation and propagation processes for these specimens.