• Journal of Korea Foundry Society
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• v.30 no.6
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• pp.241-246
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• 2010

The viscosity of foam metal is necessary to get the pores, but it is difficult to manufacture net-shape foam, because the fluidity decreases by increasing viscosity. In this study, the A356 alloy which has good fluidity and less defect was selected and fabricated to foam metal. To understand about effect of thickening agent on foaming and mechanical properties, quantity of thickening agent was changed. The pore size, porosity and distribution of foam metal were measured by i-solution program. And compression test were performed by UTM. In case of 3.0wt% Ca in thickening agent, it is found that most of foam consist of homogeneous shape, and the growth height had the highest value of 204 mm in the all fabricated foams. The porosity was 93% and compressive strength was 3.1 MPa. In the microstructure, the $Al_2Si_2Ca$ intermetallic compound and Ti were observed. The vickers hardness value rose with increasing viscosity value.

• Steel and Composite Structures
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• v.37 no.2
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• pp.253-258
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• 2020

Vibration response in a sandwich plate with a nanocompiste core covered by magnetic layer is presented. The core is armed by functionalyy graded-carbon nanotubes (FG-CNTs) where the Mori-Tanaka law is utilized assuming agglomeration effects. The structure plate is located on elastic medium simulated by Pasternak model. The governing equations are derived based on Mindlin theory and Hamilton's principle. Utilizing diffrential quadrature method (DQM), the frequency of the structure is calculated and the effects of magnetic layer, volume percent and agglomeration of CNTs, elastic medium and geometrical parameters of structure are shown on the frequency of system. Results indicate that with considering magnetic layer, the frequency of structure is increased.

• Journal of the Korean Society for Precision Engineering
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• v.28 no.11
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• pp.1297-1308
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• 2011

The light-weight design of UTM (Urban Transit Maglev)-02 car-body frames are performed, based on initial configuration. The thicknesses of fourteen sub-structures are defined as design variables and the loading condition is considered according to weight of sub-structures, electronic and pneumatic modules and passengers. For efficient and robust process of design optimization, objective function and constraints are approximated by response surface approximation. Structural analysis is performed at some sampling points to construct the approximated objective function and constraints composed of design variables. Design space is changed to find many optimal candidates and best optimal design can be found eventually. The Matlab Optimization Toolbox is used to find optimal value and sensitivity analysis about each design variable is also performed.

• Journal of the Korean Society of Industry Convergence
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• v.2 no.1
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• pp.27-33
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• 1999

Effects of spinning speed and draw ratio on structure and mechanical properties of PP filament. A The crystalline structure and mechanical properties of uniaxially deformed polypropylene filament has been examined by XRD, birefringence, UTM and density method. Uniaxially deformed PP filament was prepared of various spinning speeds (300, 600, 900m/min.) and draw ratio(x2, x3, x4). From the results of these studies, it found the following facts. Firstly, it was found that the crystallinity and crystallite size (110plane) of the samples were increased with increasing of spinning speed and draw ratio, especially, it was rapidly increased between as spun yarn and 2 times draw ratio. Secondly, birefringence value was increased with increasing of spinning speed and draw ratio. The mechanical properties of initial modulus, tensile strength were increased with increasing of spinning speed and draw ratio also, but the degree of elongation decreased as spinning speed and draw ratio.

• Journal of the Korea Institute of Military Science and Technology
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• v.12 no.5
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• pp.660-666
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• 2009

Thermoplastic polyurethane elastomer(PU-TPE) and energetic thermoplastic polyurethane Elastomer(E-PU-TPE) were prepared from Hexamethylene diisocyanate(HDI), 1,4-BD/AA ester polyol and glycidyl azide polymer(GAP-2400) as an energetic material by the addition polymerization. The PU-TPE and E-PU-TPE were characterized by FT-IR and GPC. Viscometer, DSC and UTM were used to investigate the viscose behavior with a various solvent, thermal properties and mechanical properties of PU-TPE and E-PU-TPE, which are of potential interest for the development of high performance binder of energetic solid propellants. It was found that $M_w$ of PU-TPE and E-PU-TPEs are over 100,000 and decreased with increase of GAP-2400 contents. $T_m$ and ${\Delta}H$ as thermal properties decreased and also tensile strength and elongation at break as mechanical properties decreased with increase of GAP-2400 contents.

• Korean Journal of Materials Research
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• v.9 no.2
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• pp.181-187
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• 1999

In this study, the effect of residual stress on mechanical strength was investigated with 1 kind of whiteware body and 4 kinds of glazes which are produced in succeeding ceramic art place. Using dipping method, the body was coated for different times in order to manipulate the coating thickness and sintered in the different temperatures ($1200^{\circ}C$, $1250^{\circ}C$, $1300^{\circ}C$, $1350^{\circ}C$) for two thus hours. The sintered bodies were characterized by XRD, EPMA, FEM and UTM in order to study the forming of reaction layer between body and glazes, residual stresses and the effects of residual stresses on mechanical strength of pottery. At $1300{\circ}C$, we obtained maximum density and mechanical strength. By the finite element method, the residual stresses in surface of body were minimum in specific thickness of glazes and the mechanical strength of body in that thickness of glazes showed maximum when the firing temperature was settled.

• Coupled systems mechanics
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• v.1 no.1
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• pp.39-57
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• 2012

This study intends to explore dynamic interaction behaviors between actively controlled maglev vehicle and guideway girders by considering the nonlinear forms of electromagnetic force and current exactly. For this, governing equations for the maglev vehicle with ten degrees of freedom are derived by considering the nonlinear equation of electromagnetic force, surface irregularity, and the deflection of the guideway girder. Next, equations of motion of the guideway girder, based on the mode superposition method, are obtained by applying the UTM-01 control algorithm for electromagnetic suspension to make the maglev vehicle system stable. Finally, the numerical studies under various conditions are carried out to investigate the dynamic characteristics of the maglev system based on consideration of the linear and nonlinear electromagnetic forces. From numerical simulation, it is observed that the dynamic responses between nonlinear and linear analysis make little difference in the stable region. But unstable responses in nonlinear analysis under poor conditions can sometimes be obtained because the nominal air-gap is too small to control the maglev vehicle stably. However, it is demonstrated that this unstable phenomenon can be removed by making the nominal air-gap related to electromagnetic force larger. Consequently it is judged that the nonlinear analysis method considering the nonlinear equations of electromagnetic force and current can provide more realistic solutions than the linear analysis.

• Smart Structures and Systems
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• v.18 no.3
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• pp.585-599
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• 2016

Steel cables serve as the key structural components in long-span bridges, and the force state of the steel cable is deemed to be one of the most important determinant factors representing the safety condition of bridge structures. The disadvantages of traditional cable force measurement methods have been envisaged and development of an effective alternative is still desired. In the last decade, the vision-based sensing technology has been rapidly developed and broadly applied in the field of structural health monitoring (SHM). With the aid of vision-based multi-point structural displacement measurement method, monitoring of the tensile force of the steel cable can be realized. In this paper, a novel cable force monitoring system integrated with a multi-point pattern matching algorithm is developed. The feasibility and accuracy of the developed vision-based force monitoring system has been validated by conducting the uniaxial tensile tests of steel bars, steel wire ropes, and parallel strand cables on a universal testing machine (UTM) as well as a series of moving loading experiments on a scale arch bridge model. The comparative study of the experimental outcomes indicates that the results obtained by the vision-based system are consistent with those measured by the traditional method for cable force measurement.

• Steel and Composite Structures
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• v.25 no.2
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• pp.245-255
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• 2017

The performance of an Industrialised Building System (IBS) consists of prefabricated reinforced concrete components, is greatly affected by the behaviour of the connection between beam and columns. The structural characteristics parameters of a beam-to-column connection like rotational stiffness, strength and ductility can be explained by load-rotation relationship of a full scale H-subframe under gravitational load. Furthermore, the connection's degree of rigidity directly influences the behaviour of the whole frame. In this research, rotational behaviour of a patented innovative beam-to-column connection with unique benefits like easy installation, no wet work, no welding work at assembly site, using a hybrid behaviour of steel and concrete, easy replacement ability, and compatibility with architecture was investigated. The proposed IBS beam-to-column connection includes precast concrete components with embedded steel end connectors. Two full-scale H-subframes constructed with a new IBS and conventional cast in-situ reinforced concrete system beam-to-column connections were tested under incremental static loading. In this paper, load-rotation relationship and ratio of the rigidity of IBS beam-to-column connection are studied and compared with conventional monolithic reinforced concrete connection. It is concluded that this new IBS beam-to-column connection benefits from more rotational ductility than the conventional reinforced concrete connection. Furthermore, the semi-rigid IBS connection rigidity ratio is about 44% of a full rigid connection.

• KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
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• v.27 no.2
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• pp.85-90
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• 2021

The gamma irradiation was on to Poly(butylene sebacate-co-terephthalate) (PBSeT), Poly(butylene adipate-co-terephthalate) (PBAT), Poly(lactic acid) (PLA) and casting polypropylene (CPP) at dose levels from 0 to 50 kGy. The properties of gamma irradiated samples were analyzed using DSC, TGA, UTM and FT-IR spectra. The mechanical and thermal properties of PBSeT and PBAT after gamma irradiation were less affected than CPP. The tensile strength and elongation of PBSeT was not affected by gamma irradiation, while these of PBAT, PLA and CPP were significantly decreased at 50 kGy gamma-ray dose. The thermal stability of PBSeT, PBAT, PLA and CPP showed a similar tendency to tensile strength. The glass transition temperature(T_g) and melting temperature(T_m) of PBSeT and PBAT were not altered by increasing gamma-ray dose, while these of PLA and CPP decreased. The chemical composition of all samples was not modified by gamma irradiation, and it was confirmed by FT-IR spectra. Based on mechanical and thermal stability studies of gamma irradiation on bioplastics, tested biodegradable packaging materials showed a potential to be used in sterilization process up to 35 kGy.