• Journal of Magnetics
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• v.2 no.1
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• pp.12-15
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• 1997

Fe-(3∼6.5wt%) Si alloy powders having a high magnetic induction(Bs) and a low core loss value for high frequency use were obtained by an extractive melt spinning as well as a centrifugal atomization technique. Sintered core rings made by the rapidly solidified Fe-6.5wt% Si powders exhibited the high frequency magnetic properties : megnetic induction(B8) of 1.23 T, coercivity(Hc) of 0.12 Oe, relative permeability(${\mu}$a) of 6321, and core loss(W10/50) of 1.27 W/kg from the rings of 1.1 mm thick. The magnetic induction values were found to be almost identical to those of non-oriented Fe-6.5wt% Si steel sheet and double the value of 6.5wt% Si sheet prepared by the CVD technique. The high frequency core losses(W) up to 10 kHz(W10/10k) were measured to be competitive to those of grain-oriented Fe-6.5wt% Si steel sheet.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.59 no.2
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• pp.151-153
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• 2010

This paper is presented for the development of the brushless DC(BLDC) motor for the spindle motor of hard disk drives(HDD). A new BLDC Motor has the use of insulated, compacted, and iron powder for the armature core material of BLDC motors. Insulated iron powder in this paper is generally called soft magnet composite(SMC). The SMC is used for the stator of the motor instead of the laminated steel core. The motor used by SMC can have the good advantages in condition of the high frequency input power and small sized motor. It gets much more high efficiency than laminated steel core at same input power. The proposed motor has a technique of speed sensorless control. Experimental results show the performance of the proposed BLDC motors for an HDD.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.57 no.10
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• pp.1752-1758
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• 2008

This paper deals with the reduction of friction torque in permanent magnet motors by using the heat treatment of stator core. The stator core is made of electrical steel sheared by the punching die. From the punching process, large mechanical stress acting on the edge of stator tooth induces significant plastic and elastic deformation and then cause the change of magnetization properties. Then, the mechanical and magnetic unbalance in the sheared region of stator tooth produced by material cutting has influence on the friction torque. This paper investigated the effect of the punching process on the magnetization process and the mechanical deformation, and then proposed the stress relief annealing method for the reduction of friction torque among one of motor characteristics.

• Computers and Concrete
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• v.19 no.5
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• pp.567-577
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• 2017

This study presents investigation of the behavior of moderately thick reinforced concrete slabs having hollow cores with different parameters. The experimental part of this investigation includes testing eight specimens of solid and hollow-core slab models having (2.05 m) length, (0.6 m) width and (25 cm) thickness under two monotonic line loads. Load versus deflection was recorded during test at mid span and under load. Numerically, the finite element method is used to study the behavior of these reinforced concrete slabs by using ANSYS computer program. The specimens of slab models are modeled by using (SOLID65) element to represent concrete slabs and (LINK180) element to represent the steel bars as discrete axial members between concrete nodes. The finite element analysis has showed good agreement with the experimental results with difference of (4.71%-8.68%) in ultimate loads. A parametric study have been carried out by using ANSYS program to investigate the effects of concrete compressive strength, size and shape of core, type of applied load and effect of removing top steel reinforcement.

• Steel and Composite Structures
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• v.39 no.3
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• pp.229-241
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• 2021

This work focused on aluminum foam sandwich (AFS) with different foam core densities and different face-sheet thicknesses subjected to constant amplitude three-point bending cyclic loading to study its fatigue performance. The experiments were conducted out by a high frequency fatigue test machine named GPS-100. The experimental results showed that the fatigue life of AFS decreased with the increasing loading level and the structure was sensitive to cyclic loading, especially when the loading level was under 20%. S-N curves of nine groups of AFS specimens were obtained and the fatigue life of AFS followed three-parameter lognormal distribution well. AFS under low cyclic loading showed pronounced cyclic hardening and the static strength after fatigue test increased. For the same loading level, effects of foam core density and face-sheet thickness on the fatigue life of AFS structure were trade-off and for the same loading value, the fatigue life of AFS increased with aluminum foam core density or face-sheet thickness monotonously. Core shear was the main failure mode in the present study.

• Steel and Composite Structures
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• v.45 no.5
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• pp.767-774
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• 2022

A geometrically nonlinear stability analysis of sandwich annular plates with cellular core and particle-reinforced composite layers has been performed in the present research. The particles are powders of graphene oxide (GOP) which act as nanoscale filler of epoxy matrix. To this regard, Halpin-Tsai micromechanical scheme has been used to define the material properties of the layers. A square shaped core has been considered for which the material properties have been defined based on the relative density concept. Large deflection theory of thin shells has been selected to develop the complete formulation of sandwich plate. The geometrically nonlinear stability analysis of sandwich annular plates has been carried out by indicating that the buckling load is dependent on particle amount, thickness of layer and core relative density.

• International Journal of High-Rise Buildings
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• v.7 no.3
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• pp.223-232
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• 2018

Two novel types of construction detailings, including using the distributive beam and the inner ring diaphragm in the joint between large-section CFT columns and outrigger truss to enhance the transferring efficiency of huge vertical load, and using the T-shaped stiffeners in the steel tube of large-section CFT columns to promote the local buckling capacity of steel tubes, were tested to investigate their working mechanism and design methods. Experimental results show that the co-working performance between steel tube and inner concrete could be significantly improved by setting the distributive beam and the inner ring diaphragm which can transfer the vertical load directly in the large-section CFT columns. Meanwhile, the T-shaped stiffeners are very helpful to improve the local bulking performance of steel tubes in the column components by the composite action of T-shaped stiffeners together with the core concrete under the range of flange of T-shaped stiffeners. These two approaches can result in a lower steel cost in comparison to normal steel reinforced concrete columns. Finally, a practical engineering case was introduced to illustrate the economy benefits achieved by using the two typical detailings.

• Steel and Composite Structures
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• v.25 no.5
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• pp.545-556
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• 2017

The tubed steel reinforced concrete (SRC) column is a composite column in which the outer steel tube is mainly used to provide confinement on the core concrete. This paper presents experimental and analytical studies on the behavior of circular tubed SRC (TSRC) columns subjected to axial compression. Eight circular TSRC columns were tested to investigate the effects of length-to-diameter ratio (L/D) of the specimens, diameter-to-thickness ratio (D/t) of the steel tubes, and use of stud shear connectors on the steel sections. Elastic-plastic analysis on the steel tubes was used to investigate the mechanism of confinement on the core concrete. The test results indicated that the tube confinement increased the strength and deformation capacity for both short and slender columns, and the effects on strength were more pronounced for short columns. A nonlinear finite element (FE) model was developed using ABAQUS, in which the nonlinear material behavior and initial geometric imperfection were included. Good agreement was achieved between the predicted results using the FE model and the test results. The test and FE results were compared with the predicted strengths calculated by Eurocode 4 and the AISC Standard. Based on the analytical results, a new design method for this composite column was proposed.

• Steel and Composite Structures
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• v.34 no.6
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• pp.783-794
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• 2020

Steel-concrete-steel sandwich composite wall is composed of two external steel plates and infilled concrete core. Internal mechanical connectors are used to enhance the composite action between the two materials. In this paper, the compressive behavior of a novel sandwich composite wall was studied. The steel trusses were applied to connect the steel plates to the concrete core. Three short specimens with different truss spacings were tested under compressive loading. The boundary columns were not included. It was found that the failure of walls started from the buckling of steel plates and followed by the crushing of concrete. Global instability was not observed. It was also observed that the truss spacing has great influence on ultimate strength, buckling stress, ductility, strength index, lateral deflection, and strain distribution. Three modern codes were introduced to calculate the capacity of walls. The comparisons between test results and code predictions show that AISC 360 provides significant underestimations while Eurocode 4 and CECS 159 offer overestimated predictions.

• Steel and Composite Structures
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• v.34 no.4
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• pp.547-559
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• 2020

Buckling restrained braces (BRBs) were developed as an enhanced alternative to conventional braces by restraining their global buckling, thus allowing development of a stable quasi-symmetric hysteretic response. A wider adoption of buckling restrained braced frames is precluded due to proprietary character of most BRBs and the code requirement for experimental qualification. To overcome these problems, BRBs with capacities corresponding to typical steel multi-storey buildings in Romania were developed and experimentally tested in view of prequalification. The first part of this paper presents the results of the experimental program which included sub-assemblage tests on ten full-scale BRBs and uniaxial tests on components materials (steel and concrete). Two different solutions of the core were investigated: milled from a plate and fabricated from a square steel profile. The strength of the buckling restraining mechanism was also investigated. The influence of gravity loading on the unsymmetrical deformations in the two plastic segments of the core was assessed, and the response of the bolted connections was evaluated. The cyclic response of BRBs was evaluated with respect to a set of performance parameters, and recommendations for design were given.