• KIEAE Journal
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• v.8 no.3
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• pp.77-83
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• 2008

The effective mixture of structural laminated timber and other materials is expected to extend the potentials of building structures because of the potentials to realize high performance in structural safety. The classical joint types using drift pin and bolts are occurred local failures due to the small bearing area. In result, new joints using H shaped steel were suggested in this research. The objective of this study is to evaluate elasto-plastic behaviors by strengthening types of wood frames with new joints connecting structural laminated timber with H shaped steel. A total of five specimens of about one-second scale were tested. Specimens had columns with 1,050 height and $84mm{\times}100mm$ section, and a beams with 1,950mm length and $130mm{\times}100mm$ section. Also, the specimens were stiffened by brace, hwang-toh brick, and autoclaved lightweight concrete. The results of the test showed that the specimen stiffened with autoclaved lightweight concrete was characterized by fairly good strength and stiffness than those of the other specimens. Initial stiffness of H-2.0D-NS specimen with 2 times inserting length of beam height showed 1.33 times than that of H-1.5D-NS specimen. However, the strength of H-2.0D-NS specimen has not improved too much than H-1.5D-NS specimen.

• Steel and Composite Structures
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• v.45 no.1
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• pp.83-100
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• 2022

Timber is one of the few natural, renewable building materials and glulam is a type of engineering wood product. In the present work, timber-based braces are applied for retrofitting midrise Special Moment Resisting Frame (SMRF) using two types of timber base braces (Timber base glulam, and hybrid Timber-Steel-BRB) as alternatives for retrofitting by traditional steel bracings. The improving effects of adding the bracings to the SMRF on seismic characteristics of the frame are evaluated using load-bearing capacity, energy dissipation, and story drifts of the frame. For evaluating the retrofitting effects on the seismic performance of SMRF, a five-story SMRF is considered unretofitted and retrofitted with steel-hollow structural section (HSS) brace, Glued Laminated Timber (Glulam) brace, and hybrid Timber-Steel BRB. Using OpenSees structural analyzer, the performance are investigated under pushover, cyclic, and incremental loading. Results showed that steel-HSS, timber base Glulam, and hybrid timber-steel BRB braces have more significant roles in energy dissipation, increasing stiffness, changing capacity curves, reducing inter-story drifts, and reducing the weight of the frames, compared by steel bracing. Results showed that Hybrid BRB counteract the negative post-yield stiffness, so their use is more beneficial on buildings where P-Delta effects are more critical. It is found that the repair costs of the buildings with hybrid BRB will be less due to lower residual drifts. As a result, timber steel-BRB has the best energy dissipation and seismic performance due to symmetrical and stable hysteresis curves of buckling restrained braces that can experience the same capacities in tension and compression.

• Journal of Powder Materials
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• v.21 no.4
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• pp.301-306
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• 2014

Titanium alloys are extensively used in high-temperature applications due to their excellent high strength and corrosion resistance properties. However, titanium alloys are problematic because they tend to be extremely difficult-to-cut material. In this paper, the powder synthesis, spark plasma sintering (SPS), bulk material characteristics and machinability test of hybrid $Ti_2AlC$ ceramic bulk materials were systematically examined. The bulk samples mainly consisted of $Ti_2AlC$ materials with density close to theoretical value were synthesized by a SPS method. Random orientation and good crystallization of the $Ti_2AlC$ was observed at $1100^{\circ}C$ for 10 min under SPS sintering conditions. Scanning electron microscopy results indicated a homogeneous distribution and nano-laminated structure of $Ti_2AlC$ MAX phase. The hardness and electrical conductivity of $Ti_2AlC$ were higher than that of Ti 6242 alloy at sintering temperature of $1000^{\circ}C{\sim}1100^{\circ}C$. Consequently, the machinability of the hybrid $Ti_2AlC$ bulk materials is better than that of the Ti 6242 alloy for micro-EDM process of micro-hole shape workpiece.

• Journal of Electrical Engineering and Technology
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• v.10 no.1
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• pp.155-164
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• 2015

In this paper, two rotor configurations including different amount of magnet and reluctance parts are presented. The rotors are constituted by means of a flexible hybrid motor structure. Considerable features of the hybrid structure are that the combination of the magnet and reluctance parts can be suitably modified and the mechanical angle (${\beta}$) between the parts can also be varied. Two hybrid rotor configurations have been considered in this study. First, finite element (FE) simulations were carried out and the torque behaviors of the motors were predicted. The average torque ($T_{avg}$) and maximum torque ($T_{max}$) curves were obtained from FE simulations in order to find suitable ${\beta}$. Mathematical model of the motors was formed in terms of a,b,c variables considering the amount of the magnet and reluctance parts on the rotor and simulations were performed. Rotor prototypes, motor drive and drive method were introduced. Torque profiles of the motors were obtained by static torque measurement and loaded tests were also realized. Thus, simulation results were verified by experimental study. There is a good match between predictions and measurements. The proposed motors are operated with electrical $120^{\circ}$ mode as a brushless DC motor (BLDC) and torque versus speed characteristics show a compound DC motor characteristic. The motors can be named as brushless DC compound motors.

• Composites Research
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• v.34 no.5
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• pp.269-276
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• 2021

PCM (Prepreg Compression Molding) process is a high-speed molding technology that can manufacture high-quality CFRP (Carbon Fiber Reinforced Plastic) parts. Compared to the autoclave process, it generates less waste and can significantly reduce cycle time, so various studies are being conducted in the aerospace and automobile industries. In this study, in order to improve the quality of the PCM process, a molding method was developed to increase the compression pressure of the press step by step according to the curing behavior of the prepreg. It was confirmed that this multi-stage compression molding technology is a good means to produce high-quality CFRP products and shorten cycle times. And, the laminated prepreg at room temperature was immediately put into the mold and preheated and molded at the same time, so that it could be molded without a separate preheating process. In addition, as a result of applying the same process conditions optimized for flat plate molding to three-dimensional shapes, a product similar to a flat plate in appearance could be made without the process of establishing process conditions.

• Structural Engineering and Mechanics
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• v.16 no.5
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• pp.557-580
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• 2003

Laminated composite structures find wide range of applications in many branches of technology. They are much suited for weight sensitive structures (like aircraft) where thinner and lighter members made of advanced fiber reinforced composite materials are used. The orientations of fiber direction in layers and number of layers and the thickness of the layers as well as material of composites play a major role in determining the strength and stiffness. Thus the basic design problem is to determine the optimum stacking sequence in terms of laminate thickness, material and fiber orientation. In this paper, a new optimization technique called Cellular Automata (CA) has been combined with Genetic Algorithm (GA) to develop a different search and optimization algorithm, known as Cellular Genetic Algorithm (CGA), which considers the laminate thickness, angle of fiber orientation and the fiber material as discrete variables. This CGA has been successfully applied to obtain the optimal fiber orientation, thickness and material lay-up for multi-layered composite hybrid beams plates and shells subjected to static buckling and dynamic constraints.

• Computers and Concrete
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• v.25 no.4
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• pp.303-310
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• 2020

In this research, a hybrid mathematical model is derived using the higher-order polynomial kinematic model in association with soft computing technique for the prediction of best fiber volume fractions and the minimal mass of the layered composite structure. The optimal values are predicted further by taking the frequency parameter as the constraint and the projected values utilized for the computation of the eigenvalue and deflections. The optimal mass of the total layered composite and the corresponding optimal volume fractions are evaluated using the particle swarm optimization by constraining the arbitrary frequency value as mass/volume minimization functions. The degree of accuracy of the optimal model has been proven through the comparison study with published well-known research data. Further, the predicted values of volume fractions are incurred for the evaluation of the eigenvalue and the deflection data of the composite structure. To obtain the structural responses i.e. vibrational frequency and the central deflections the proposed higher-order polynomial FE model adopted. Finally, a series of numerical experimentations are carried out using the optimal fibre volume fraction for the prediction of the optimal frequencies and deflections including associated structural parameter.

• Steel and Composite Structures
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• v.29 no.6
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• pp.749-758
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• 2018

This article derived a hybrid coupling technique using the higher-order displacement polynomial and three soft computing techniques (teaching learning-based optimization, particle swarm optimization, and artificial bee colony) to predict the optimal stacking sequence of the layered structure and the corresponding frequency values. The higher-order displacement kinematics is adopted for the mathematical model derivation considering the necessary stress and stain continuity and the elimination of shear correction factor. A nine noded isoparametric Lagrangian element (eighty-one degrees of freedom at each node) is engaged for the discretisation and the desired model equation derived via the classical Hamilton's principle. Subsequently, three soft computing techniques are employed to predict the maximum natural frequency values corresponding to their optimum layer sequences via a suitable home-made computer code. The finite element convergence rate including the optimal solution stability is established through the iterative solutions. Further, the predicted optimal stacking sequence including the accuracy of the frequency values are verified with adequate comparison studies. Lastly, the derived hybrid models are explored further to by solving different numerical examples for the combined structural parameters (length to width ratio, length to thickness ratio and orthotropicity on frequency and layer-sequence) and the implicit behavior discuss in details.

• Composites Research
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• v.32 no.2
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• pp.113-119
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• 2019

The objective of this research is to study the mechanical and vibration characteristics of vibration damping aluminum panels for automotive parts. For this purpose, the test and simulation results of aluminum-resin hybrid materials and aluminum sheet materials were compared. Tensile strength and elastic modulus of the hybrid material were approximately 10% lower than aluminum sheet. Also, it was showed that the hybrid material have lower natural frequency than aluminum sheet, and it was confirmed that loss factor increases as the thickness of resin increases. Finally, it is confirmed that the test results and the analysis results are similar with each other and the performance prediction of the materials are possible by FEA.

• International Journal of Precision Engineering and Manufacturing
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• v.1 no.1
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• pp.33-41
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• 2000

Fiber reinforced metal laminates(FRMLs) were new type of hybrid materials. FRMLs consist of high strength metals(Al 5052-H34) and laminated fiber with structural adhesive bond. The effect of resin mixture ratios on the fatigue crack propagation behavior and mechanical properties of aramid fiber reinforced aluminum composites was investigated. The epoxy, diglycidylether of bisphenol A(DGEBA), was cured with methylene dianiline(MDA) with or without an accelerator(K-54). Eight kinds of resin mixture ratio were used for the experiment ; five kinds of FRMLs(1)(mixture of epoxy and curing agent) and three kinds of FRMLs(2)mixture of epoxy, curing agent and accelerator). The characteristic of fatigue crack propagation behavior and mechanical properties FRMLs(2) shows more effecting than that of FRMLs(1).