• 한국금형공학회:학술대회논문집
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• 2008.06a
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• pp.23-26
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• 2008

In order to examine the deformation characteristics of Al circular pipe underthe biaxial compression, the horizontal biaxial compression die for the experiment was manufactured. From this, in the various compressive strain rate (1 mm/min. ${\sim}$ 400 mm/min.)conditions, the circular pipes, which were made by Al materials, were investigated based on the properties change of cross section area, punch load and deformation behavior. The tensile and compressive strains were evaluated from micro Vickers hardness tester. From these results, the punch load and deformation characteristic of Al circular pipes were highly changed in the compressive strain rate about 200 mm/min. The Al circular pipes had the tendency that the punch load decreased with increasing the compressive strain rate. In addition, following as the change of the shape and position of neutral axis due to the deformation proceeding of the circular pipe, the special point of the internal circular pipe at maximum load showed the maximum deformation strain and the maximum measured hardness value. The CAE (computer aided engineering) simulation using Deform-2D program was performed on the circular pipe in order to know and verify the exact compressive deformation behavior. From these results, the experimentally measured results were reasonably in good agreement with the simulation results.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.18 no.5
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• pp.29-36
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• 2019

In modern society in which the fourth industrial revolution has come to the fore and rapid technology innovations are taking place, a phenomenon of making and selling small quantities of various products that consumers want instead of mass producing one item has emerged. As the market is moving toward the multi-item small-sized production system, there is a need for a system in which a machine independently judges and carries out machining and post-processing. In order for a machine to judge processing on its own, it is necessary to measure the force applied to a product. This study aimed to develop a large-scale dynamometer that enables three-axis measurement using octagonal ring load cells. As for the device's configuration, four octagonal ring load cells, which were previously researched, were used to enable three-axis measurement. It was reconfigured by modifying the attachment position of the octagonal ring load cells' strain gauge and the Wheatstone bridge of each axis, and a system was set up to allow the monitoring of data measured through the monitor. The configured device calculated a strain rate by an experiment, and this rate was compared with the theoretical strain rate to find a correction value. The correction value was entered into a formula, deriving a modified formula. The modified formula was entered into the device, which completed the large-scale dynamometer.

• Structural Engineering and Mechanics
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• v.70 no.3
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• pp.257-267
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• 2019

Expressions for the calculation of ductility index for concrete girders with different ratios of prestressed and classical reinforcement were proposed using load-displacement, load-strain and load-curvature relation. The results of previous experimental static tests of several large-scale concrete girders with different ratio of prestressed and classical reinforcement are briefly presented. Using the proposed expressions, various ductility index of tested girders were calculated and discussed. It was concluded that the ductility of girders decreases approximately linearly by increasing the degree of prestressing. The study presents an expression for the calculation of the average ductility index of classical and prestressed reinforced concrete girders, which are similar to the analysed experimental test girders.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2004.04a
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• pp.275-280
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• 2004

Shape optimization was performed to obtain the precise shape of cutouts including the internal shape of cutouts in laminated composite plates by three dimensional modeling using solid element. The volume control of the growth-strain method was implemented and the distributed parameter chosen as Tsai-Hill fracture index for shape optimization. The volume control of the growth-strain method makes Tsai-Hill failure index at each element uniform in laminated composites under the initial volume. Then shapes optimized by Tsai-Hill failure index were compared with those of the initial shapes for the various load conditions and cutouts. The following conclusions were obtained in this study. (1) It was found that growth-strain method was applied efficiently to shape optimization of three dimensional cutouts in a laminate composite, (2) The optimal shapes of the various load conditions and cutouts were obtained, (3) The maximum Tsal-Hill failure index was reduced up to 67% when shape optimization was peformed under the initial volume by volume control of growth-strain method.

• Journal of The Korean Society of Agricultural Engineers
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• v.54 no.4
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• pp.39-46
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• 2012

The objectives of this study is intended to analyze stresses using the boundary element method and probability analysis for agricultural structure. Loads and material properties are an important factor when analyzing the structure. Until now, designing structure, loads and material properties are applied deterministic value. However, load and material properties involve uncertainties due to those change probabilistic and deterministic methods could not consider uncertainties. To solve these problems, the reliability analysis based on probability properties scheme was developed. Reliability analysis is easy to approach to analysis frame structure, however it has limitation when solving plane stress strain problems a kind of agricultural structures. The BEM (Boundary Element Method) is able to analysis plane strain problems by boundary conditions. Thus, this study applied boundary element method to analysis plane strain problem, load and material properties as a probabilistic value to calculate the analytical model using Monte Carlo simulations were developed.

• Proceedings of the Korea Concrete Institute Conference
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• 1995.10a
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• pp.215-218
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• 1995

This paper presents an experimental study on the strength and deformation of concrete-filled circular steel short columns. Six specimens of concrete-filled circular short columns were tested under concentric compressive load. For comparsion, three specimens of circular steel short columns were also loaded to failure. The ultimate strength, ductility, and confinement mechanism of columns were compared. In the comparison, the effect of witch-thickness ratio and concrete compressive strength on the behavior of colimns were examed. As a result, the axial load verse axial average strain relationship of concrete-filled circular steel columns was very stable, because of interactions between the concrete and steel, the strength are 13% and 30% larger than the strength extimated by simply superimposed method of the concrete and steel. The ratio of the circumferential to longitudinal strain increment, both measured on the steel suface, was 0.28 up to the longitudinal strain of 0.1%, increases from 0.3 to 0.8 between the strain of 0.1% to 0.3%, and 0.8 beyond the strain of 0.3%

• Transactions of the Korean Society of Mechanical Engineers A
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• v.33 no.12
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• pp.1357-1365
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• 2009

In this study, we enhance the numerical approach of Lee et al.$^{(1)}$ to spherical indentation technique for property evaluation of hyper-elastic rubber. We first determine the friction coefficient between rubber and indenter in a practical viewpoint. We perform finite element numerical simulations for deeper indentation depth. An optimal data acquisition spot is selected, which features sufficiently large strain energy density and negligible frictional effect. We then improve two normalized functions mapping an indentation load vs. deflection curve into a strain energy density vs. first invariant curve, the latter of which in turn gives the Yeoh-model constants. The enhanced spherical indentation approach produces the rubber material properties with an average error of less than 3%.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2017.05a
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• pp.158-159
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• 2017

In this study, it evaluate the strain properties of fiber reinforced concrete and fiber reinforced cement composite. The types of fiber are Hooked steel fiber and it was mixed 0.5, 1.0 vol.% in concrete and 1.0, 2.0 vol.% in cement composites. The impact test was conducted by using a projectile (diameter: 25mm, velocity: 170m/s) and strain properties on the rear side of each specimen was evaluated by strain gage. After the impact test, fracture grade, fracture depth was evaluated.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.132-137
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• 2004

In this work, effects of hyper-elastic rubber material properties on the indentation load-deflection curve and subindenter deformation are first examined via [mite element (FE) analyses. An optimal data acquisition spot is selected, which features maximum strain energy density and negligible frictional effect. We then contrive two normalized functions. which map an indentation load vs. deflection curve into a strain energy density vs. first invariant curve. From the strain energy density vs. first invariant curve, we can extract the rubber material properties. This new spherical indentation approach produces the rubber material properties in a manner more effective than the common uniaxial tensile/compression tests. The indentation approach successfully measures the rubber material properties and the corresponding nominal stress.strain curve with an average error less than 3%.

• Steel and Composite Structures
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• v.16 no.5
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• pp.455-480
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• 2014

Sixteen concrete filled square CFRP-steel tubular (S-CFRP-CFST) stub columns under axial compression were experimentally investigated. The experimental results showed that the failure mode of the specimens is strength loss of the materials, and the confined concrete has good plasticity due to confinement of the CFRP-steel composite tube. The steel tube and CFRP can work concurrently. The load versus longitudinal strain curves of the specimens can be divided into 3 stages, i.e., elastic stage, elasto-plastic stage and softening stage. Analysis based on finite element method showed that the longitudinal stress of the steel tube keeps almost constant along axial direction, and the transverse stress at the corner of the concrete is the maximum. The confinement effect of the outer tube to the concrete is mainly focused on the corner. The confinements along the side of the cross-section and the height of the specimen are both non-uniform. The adhesive strength has little effect both on the load versus longitudinal strain curves and on the confinement force versus longitudinal strain curves. With the increasing of the initial stress in the steel tube, the load carrying capacity, the stiffness and the peak value of the average confinement force are all reduced. Equation for calculating the load carrying capacity of the composite stub columns is presented, and the estimated results agree well with the experimental results.