• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.60 no.9
• /
• pp.1684-1692
• /
• 2011

Recently, several vector hysteresis models such as vector Preisach, vector Jiles-Atherton and dynamic E&S model have been proposed to describe vector magnetic properties of electrical steel sheets. However, it is still difficult to find an adequate vector hysteresis model in finite element application for both the Non-oriented and Grain-oriented electrical steel sheets under alternating and rotating field conditions. In this paper, an improved E&S vector hysteresis model is suggested to describe the vector magnetic properties of both Non-oriented and Grain-oriented electrical steel sheets under various magnetic field conditions including alternating and rotating magnetic field conditions. The validity of the proposed model is tested through comparisons with the experimental results under various magnetic field conditions.

• Structural Engineering and Mechanics
• /
• v.13 no.1
• /
• pp.75-90
• /
• 2002

Many existing concrete structures suffer from low quality of concrete and inadequate confinement reinforcement. These deficiencies cause low strength and ductility. Wrapping concrete by carbon fiber reinforced polymer (CFRP) composite sheets enhances compressive strength and deformability. In this study, the effects of the thickness of the CFRP composite wraps on the behavior of concrete are investigated experimentally. Both monotonic and repeated compressive loads are considered during the tests, which are carried out on strengthened undamaged specimens, as well as the specimens, which were tested and damaged priorly and strengthened after repairing. The experimental data shows that, external confinement of concrete by CFRP composite sheets improves both compressive strength and deformability of concrete significantly as a function of the thickness of the CFRP composite wraps around concrete. Empirical equations are also proposed for compressive strength and ultimate axial deformation of FRP composite wrapped concrete. Test results available in the literature, as well as the experimental results presented in this paper, are compared with the analytical results predicted by the proposed equations.

• Smart Structures and Systems
• /
• v.19 no.6
• /
• pp.695-703
• /
• 2017

In this paper, based on first-order shear deformation theory, the governing equations of motion for a sandwich curved beam including an elastic core and two piezo-magnetic face-sheets are presented. The curved beam model is resting on Pasternak's foundation and subjected to applied electric and magnetic potentials on the piezo-magnetic face-sheets and transverse loading. The five equations of motion are analytically solved and the bending and vibration results are obtained. The influence of important parameters of the model such as direct and shear parameters of foundation and applied electric and magnetic potentials are studied on the electro-mechanical responses of the problem. A comparison with literatures was performed to validate our formulation and results.

• Journal of the Korea Safety Management & Science
• /
• v.18 no.1
• /
• pp.167-177
• /
• 2016

The CEO leadership and employee's concerning and participation to quality management innovation activity is critical factor for improving the business performance. This empirical study is aims to find that whether the quality management activity is significant or not in the automotive parts suppliers. To perform this research, we distributed 250 sheets totally, and withdraw 194 sheets. We analysed 169 sheets that we could use for this research using SPSS 18.0 and AMOS 18.0. We had the results that CEO leadership is significantly positive effects on the employees's participation to quality management. And the result of process improvement have positively effective and significant effects on the product improvement result and business performance of firms.

• Journal of Welding and Joining
• /
• v.15 no.2
• /
• pp.89-99
• /
• 1997

Spot welding is one of the important welding processes for the construction of thin metal sheet. Because of low investment cost, alternating welding current is widely applied for power source. Direct current type could be, however, recommened for high quality weldment. In this study, the effect of welding current type on the weldability and the electrode life in spot welding of aluminium alloy were investigated. Various welding tests were done by using three phase direct and alternating welding current, respectively. In spite of high variation of welding force, weld quality and electrode life with alternating welding current were shown better results than those with direct current for 2mm thick alumininum alloy sheets. This was due to excessive erosion of the positive electrode in direct welding current compared with the negative one. On the contrary to 2mm sheets, the welding parameters of alternating current for 1mm sheets must be carefully selected.

• Journal of Korea Technical Association of The Pulp and Paper Industry
• /
• v.36 no.3
• /
• pp.67-73
• /
• 2004

Effect of calendering on structural and surface properties of sheets made of various pulp was investigated. BKP, BCTMP and KOCC were used as raw materials for handsheets and sheets were calendered at the different calendering temperature and pressure conditions. Caliper, air permeability, and PPS roughness were reduced by calendering, but their effects were a little different depending on pulp type and calendering condition. Increase of density with increase of calendering Pressure was remarkable on sheet made of BCTMP or KOCC, and the effect of temperature was more significant than pressure. PPS roughness of sheet made of BCTMP or KOCC was reduced by calendering, but BKP sheet showed little reduction of roughness at higher calendering pressure. The compressibility of sheet increased logarithmetically with calendering pressure and surface compressibility of KOCC sheet was relatively higher than other pulps.

• Transactions of Materials Processing
• /
• v.7 no.4
• /
• pp.354-363
• /
• 1998

In order to analyze the stretch forming characteristics of tailored blanks, laser welded blanks of different thickness and strength combinations were prepared and stretching tests were done. The stretching formability of laser welded blanks was reduced as increasing the deformation restraining force ($strength{\times}thickness$) ratio between two welded sheets. Weld line movement was attributed to strain concentration at weaker sheets and resulted in fracture at weaker sid, so that fracture could be predicted by the forming limit of the weak sheet. In the case of a welded blank with the similar deformation restraining force rations between two welded sheets, crack occurred at weld and its forming limit was about 15% less than the base sheet. The effects of lubrication and weld line position on stretch-ing formability were also investigated by experiments. Lower friction did not always give better formability for tailored blanks. Stretching formability was observed to be improved as increasing the area of weak sheet.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2004.05a
• /
• pp.74-79
• /
• 2004

The shape of cold rolled steel sheets is the degree of flatness, and the flatter, the better. Because undesirable strip shapes of cold rolled steel sheets can affect not only visible problem but also automatic working process in customer's lines, the requirement of the customers is more and more stringent. So we usually used the tension leveler to make high quality of strip flatness. For the improvement of the quality of strip flatness, this report developed three-dimensional FEM (Finite Element Method) simulation model, and analysis about the strain and stress distribution of strip in the tension leveling process.

• Journal of ILASS-Korea
• /
• v.2 no.1
• /
• pp.8-17
• /
• 1997

A study has been carried out on the instability of a conical liquid sheet by using the linear instability theory. Various analytical methods using the Kelvin-Helmholtz instability theory were tried to examine the wave growth on cylindrical liquid sheets. Cylinderical liquid sheets were extended to the case with the conical sheets. Perturbations due to tangential motion as well as longitudinal one were taken into account. And it was assumed the the breakup occurs when amplitude ratio exceeds exp(12), drop sizes were predicted only by theoretical approach. The predicted drop size agreed well with the measured Sauter mean diameter, $D_{32}$.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2005.11a
• /
• pp.161-164
• /
• 2005

The flexural behavior of a strengthened beam, that is a reinforced. concrete beam with externally bonded fiber sheets, was theoretically and experimentally investigated. The effects of the amount of glass fiber sheets varying from 1 to 4 plies on the flexural capacity of the strengthened beam are also examined. The flexural rigidity of the strengthened beam was enhanced compared with RC beam. In addition, the failure mode and load-deflection relationship for the strengthened beam and the comparison of analysis with experiment are extensive investigated. Finally, the determination of the nominal moment capacity $M_n$ of the strengthened beam will be discussed