• Structural Engineering and Mechanics
• /
• v.76 no.2
• /
• pp.153-162
• /
• 2020

Aiming at the mechanical and structural characteristics of the contact zone composite rock, the shear tests and numerical studies were carried out. The effects of the differences in mechanical properties of different materials and the normal stress on shear properties of contact zone composite samples were analyzed from a macro-meso level. The results show that the composite samples have high shear strength, and the interface of different materials has strong adhesion. The differences in mechanical properties of materials weakens the shear strength and increase the shear brittleness of the sample, while normal stress will inhibit these effect. Under low/high normal stress, the sample show two failure modes, at the meso-damage level: elastic-shearing-frictional sliding and elastic-extrusion wear. This is mainly controlled by the contact and friction state of the material after damage. The secondary failure of undulating structure under normal-shear stress is the nature of extrusion wear, which is positively correlated to the normal stress and the degree of difference in mechanical properties of different materials. The increase of the mechanical difference of the sample will enhance the shear brittleness under lower normal stress and the shear interaction under higher normal stress.

• Korean Journal of Human Ecology
• /
• v.22 no.1
• /
• pp.131-140
• /
• 2013

Eco-friendly and health-functional clothing is now becoming the target of the worldwide hot trends. The purpose of this study is to develop an eco-friendly textiles to decrease environmental pollution and to be harmless for human health by investigating how the natural chorangak liquid treatment affects the changes of mechanical properties and the hand of silk fabrics according to different treatment conditions. Treatment was varied with various temperatures ($85^{\circ}C$, $90^{\circ}C$, $95^{\circ}C$) for 90 seconds after degumming. The results were as follows: 1) The natural chorangak liquid is the most effective at the ratio of glacial acid 200ml with eggshell 20g minimizing the time limit and sludge reduction. Its treatment of silk fabrics is optimized at $90^{\circ}C$ for 90 seconds with 25% conc. after degumming when considering tenacity and elongation. 2) After the treatment, tenacity and elongation of specimen are increased compared with those of degummed silk fabrics. 3) After analyzing the effect of the treatment on the characteristic values of basic mechanical properties of silk fabrics, mechanical properties (tensile, bending, shearing, compression, surface) are overall improved. The properties of thickness and weight are increased as well. 4) Based on the clear analysis on effects of the treatment on the mechanical properties and the hand of silk fabrics, the level of THV was enhanced from good to excellent. Therefore, chorangak liquid can be utilized satisfactorily as a new finishing agent for developing eco-friendly textiles.

• Geotechnical Engineering
• /
• v.11 no.1
• /
• pp.41-50
• /
• 1995

In situ clay soils with Ko condition have anisotropic characteristics, varying the response according to the principal stress direction upon loading. But because of their practicality and simplicity, consolidated isotropic undrained compression tests are commonly used in practice to determine the behavior of cohesive soils. In this study to investigate the anisotropic characteristics and the effects of consolidation stress states on the response of normally consolidated clay soils during shearing, triaxial compression and extension tests after consolidating the undisturbed clay soil samples, which are obtained as a block sample to normalized consolidation states under isotropic or Ko state, were carried out. As a result of tests, the anisotropy of the undrained strength was confirmed. Comparing the soil responses between isotropic and Ko consolidation, the undrained strength by isotropic consolidation is overestimated because of its higher mean consolidation pressure. And isotropic consolidation reduces the anisotropy of soil response and influences on the stress-strain behavior and pore pressure response because the animotropic soil structure is partially collapsed during isotropic consolidation process. Also, OCR in overconsolidated soils is decreased by isotropic consolidatiorL Friction angle in eztension is higher than that in compression, but regression analysis shows that friction angle with cohesion in extension is almost the same as that without cohesion in compresslon.

• Magazine of the Korean Society of Agricultural Engineers
• /
• v.34 no.1
• /
• pp.41-48
• /
• 1992

Various soil behaviors usually occurring in the geotechnical problems, such as, cutting and embankments, stability of slope, seepage, consolidations, shearing failures and liquefaction, should be predicted and analyzed in any way. An approach of these predictions may be followed by the development of the constitutive equations as first and subsequently solved by numerical methods. The purpose of this paper is develop the constitutive equation of sands uder monotonic or cyclic loadings. The constitutive equation which is based on elasto-plastic theory, modified anisotropic consolidated stress parameter by Sekiguchi et al and Pender's theory is derived. And the equation is included a new stress parameter, hardening function, Bauschinger's effects and Pender's theory. The model is later evaluated and confirmed the validity by the test data of Ottawa sand, Banwol sand Hongseong sand. The following conclustions may be drawn: 1. The consititutive equation which is based on elasto-plastic theory, modified anisotropic consolidated stress parpameter by Sekiguchi et al and Pender's theory is derived. The equation in included a new stress parameter, hardening function, Bauschinger's effect and Pender's theory. 2. For Ottawa sand, the result of the constitutive equation shows a better agreement than that of Oka et al. The result of axial strain agrees well with the tested data. However, the result of horizontal strain is little bit off for the cyclic loadings or large stress. It is thought that the deviation may be improved by considering Poisson's ratio and precise measurement of shear modulus. 3. Banwol sand is used for the strain and stress tests with different relative densitites and confining pressures. The predeicted result shows a good agreement with the tested data because the required material parameters were directly measurd and determined form this laboratory. 4. For Hongseong sand, the tests under same amplitude of cyclic deviatoric stress shows a similar result with the tested data in absolute strain. It shows the acute shape of turning point because the sine wave of input is used in the test but the serrated wave in prediction.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.19 no.3
• /
• pp.55-63
• /
• 2015

Post-installed concrete set anchors are installed after the concrete hardened. These anchors increasing usage in development of construction equipment and flexible construction. The anchor loaded in shearing exhibits various failure modes such as steel failure, concrete failure, concrete pryout, depending on the shear strength of steel, the strength of concrete, edge distance and anchor interval, etc,. In this study, the objective is to investigate the effects of the variations like anchor embedment depth, edge distance and concrete strength on experimental and finite element analysis of shear failure behavior of post-installed concrete set anchor for light load embedded in concrete. The results of embedment depth experiments show that concrete strength has much affection on the shallow embedment depth. Concrete strength has no much affection with anchor interval and edge distance parameter and both experimental results occurred same failure mode. By comparing the experimental results that occurred steel failure mode show that as strong as concrete strength are the displacement results are small.

• Geotechnical Engineering
• /
• v.8 no.2
• /
• pp.45-58
• /
• 1992

An elasto-plastic constitutive model for geological materials, which satisfies the flezibility and stability at the same time, can be used in a number of geotechnical problems. Using the spacing ratio of critical state, a flexible model is proposed based on the stability of modified Camflay model. The spacing ratio of critical state can be simply evaluated, and practically used in describing the undrained shearing behavior of clay. The proposed model has precisely predicted the stress paths and stress -strain relationships, compared with the modified Camflay model, with respect to undrained triaxial test results. Besides, the effects of strain rate, creep, and relaxation can also be considered. Using the quasi-state boundary surface, the constitutive relations are well predicted. Therefore, it is found that the assumption of associative flow rule is well posed for undrained behavior of normally consolidated clay.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.17 no.5
• /
• pp.284-293
• /
• 2016

One of the most efficient procedures for the solution of partial differential equations is the method of differential quadrature. The differential quadrature method (DQM) has been applied to a large number of cases to overcome the difficulties of complex algorithms of computer programming, as well as the excessive use of storage due to the conditions of complex geometry and loading. The in-plane vibrations of curved beams with extensibility of the arch axis, including the effects of rotatory inertial and shear deformation, are analyzed by the DQM. The fundamental frequencies are calculated for members with various slenderness ratios, shearing flexibilities, boundary conditions, and opening angles. The results are compared with the numerical results obtained by other methods for cases in which they are available. The DQM gives good mathematical precision even when only a limited number of grid points is used, and new results according to diverse variations are also suggested.

• Journal of the Korean Wood Science and Technology
• /
• v.49 no.2
• /
• pp.181-190
• /
• 2021

Screw-type fasteners are widely used to make connections between wood members or between wood and steel connectors because they can tolerate the applied loads by withdrawal or shearing. In this study, we evaluated the withdrawal resistances of the screw-type fasteners and analyzed the effects of the lead-hole size, relative grain direction (tangential, radial, and cross-sections) of the wood member, screw diameter, screw type, and species. Two wood species, including domestic larch and imported spruce, and three screw-type fasteners, including domestic lag screws (diameters of 9.46, 7.79, and 6.27 mm), domestic tapping screw (diameter, 6.3 mm), and imported Sherpa screw (diameter, 8.0 mm) were used. To assess the effect of lead-hole size, the lead holes with diameters corresponding to 68.7%, 70.8%, and 74.0% of the shank diameter of the lag screw were predrilled. The lead hole corresponding to 74% of the shank diameter was selected for this study because the smaller lead holes required higher rotational force for installation, which may cause damage in the screw neck, although there was no significant difference in the withdrawal resistance depending on the lead-hole sizes applied in this study. The lag screws installed on the tangential and radial surfaces showed similar withdrawal resistances to each other, which were greater than those installed on the cross-sectional surface. As the lag screw diameter increased from 6.27 mm to 9.46 mm, the withdrawal resistance also increased proportionally. The withdrawal resistance of the tapping screw having a diameter of 6.3 mm was almost 1.6 times higher than that of the lag screw having a similar diameter of 6.27 mm, while that of Sherpa screw having a diameter of 8.0 mm was around 1.4 times higher than that of the lag screw having a similar diameter of 7.79 mm.

• Korean Journal of Poultry Science
• /
• v.50 no.1
• /
• pp.63-72
• /
• 2023

This study was conducted to investigate the effect of vitamin E and nanoparticle-sized vitamin E (NVE) in a broiler diet on growth performance, blood profiles, and meat quality. A total of 45 one-day-old Arbor Acres broilers (initial body weight of 37.00 ± 0.41 g) were used in this experiment for 28 days. All broilers were randomly allocated into three dietary treatments in a randomized complete block design. The dietary treatments were as follows: a basal diet (CON), a basal diet supplementing with 380 mg/kg of vitamin E (T1), and a basal diet supplementing with 380 mg/kg of NVE (T2). Each treatment had five replicates with three birds per cage. On days 0-7, the T1 and T2 groups significantly increased (P<0.05) body weight gain compared to the CON group. Also, the T1 and T2 groups significantly increased (P<0.05) vitamin E content in blood and breast meat compared to the CON group. In shearing force, the T2 group showed a lower tendency (P=0.070) than the CON group. The T1 group showed a higher tendency (P=0.086) in the b* (yellowness) value than the T2 group. On day 7 after the end of the experiment, the T2 group significantly decreased (P<0.05) TBA values compared to the CON group. In conclusion, supplementation with vitamin E or NVE can improve broiler growth performance in the starter period, reduce TBA value through the antioxidant action of vitamin E, prevent lipid oxidation, and improve shelf life.

• Food Science of Animal Resources
• /
• v.27 no.4
• /
• pp.409-415
• /
• 2007

This experiment was conducted to investigate the effects of dietary enzyme mixture fortified with ${\beta}-glucanase$ on the growth performance, serum components and meat quality of broiler chicks. 31,800 Ross 208 male broiler chicks were randomly allotted into 2 groups, the control and 0.3% enzyme diet with ${\beta}-glucanase$ supplementation groups. Control group chicks were fed the control (corn-soybean meal based) diet and the treatment group chicks were fed the 0.3% enzyme mixture supplemented with ${\beta}-glucanase$. The growth performance, serum components and meat qualities such as pH, color, water holding capacity, cooking loss, and shearing force of meats were investigated. The results showed that the growth performance of chicks fed the 0.3% enzyme mixture diet were improved compared to that of the control group, as much as 5% in growth rate, 19% in average weight, 6.8% in performance index, and 5.5% in feed efficiency. Although, there were no significant differences in the muscle color degrees ($L^*a^*b^*$) and shearing force between the control group and experimental group, the water holding capacity and cooking loss of the experimental group were significantly higher than those of control group (p<0.05). The antibody titers in serum against the antigens of Newcastle disease and Infectious Bursal disease were higher in the experimental group than in the control group. Altogether, these suggest that the broiler diet containing 0.3% enzyme mixture fortified with ${\beta}-glucanase$ activity can improve the growth performance, immune reaction, and meat quality of broiler chicks.