• Journal of The Korean Society of Agricultural Engineers
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• v.50 no.4
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• pp.67-75
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• 2008

In construction facilities such as bridges, the fluid boundary layer(or water film) is formed at the structure-soil interface by the inflow into the system due to rainfall or/and rising ground-water. As a result, the structure-soil interaction(SSI) state changes into the structure-fluid-soil interaction(SFSI) state. In general, construction facilities may be endangered by the inflow of water into the soil foundation. Thus, it is important to predict the dynamic SFSI responses accurately so that the facilities may be properly designed against such dangers. It is desired to have the robust tools of attaining such a purpose. However, there has not been any report of a method for the SFSI analyses. The objective of this study is to propose an efficient method of finite element modelling using the new interface element named hybrid interface element capable of giving reasonable predictions of the dynamic SFSI response. This element enables the simulation of the limited normal tensile resistance and the tangential hydro-plane behaviour, which has not been preceded in the previous studies. The hybrid interface element was tested numerically for its validity and employed in the analysis of SFSI responses of the continuous bridge subjected to seismic load under rainfall or/and rising ground-water condition. It showed that dynamic responses of the continuous bridge resting on direct foundation may be amplified under rainfall condition and consequently lead to significant variation of stresses.

• Composites Research
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• v.26 no.4
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• pp.223-229
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• 2013

Hybrid composite strut tower was designed to prevent permanent deformation of upper mount by the impact from the uneven road. When exceeding energy absorption capacity of tire and suspension systems, residual impact is delivered to upper mount. Especially, in case of using high-rigidity suspension system for high driving performance, the conventional strut tower can be easily deformed due to reduction of energy absorption capacity of suspension systems. In this study, optimal design of hybrid composite strut tower which made of back-up metal and carbon fiber reinforced composite was suggested by using finite element analysis, and low velocity impact test was performed to investigate their dynamic characteristics. Also, 3D measuring and ultra c-scanning methods were carried out to diagnose damages in the strut towers.

• Journal of Magnetics
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• v.21 no.3
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• pp.379-386
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• 2016

To satisfy the requirement of magnetically suspended control moment gyroscope (MSCMG) that magnetic bearing can provide torque, a novel 4DOF hybrid magnetic bearing (HMB) with integrated structure was designed. Mathematical models of forces and torques are established by using equivalent magnetic circuit method. The current stiffness, displacement stiffness, tilting current stiffness and angular stiffness of the 4DOF hybrid magnetic bearing are derived by the mathematical models. Equivalent magnetic circuit method and finite element method (FEM) simulation results indicate that the force has a good linear relationship with both displacement and current, and the torque has a good linear relationship with angular displacement and current. The novel 4DOF HMB is capable of achieving control in both two radial translational degrees of freedom (DOF) and also two radial rotational DOFs. The 4DOF HMB is well adapted to MSCMG system, exhibiting advantages in the controllable DOF, light weight and easy to control.

• Journal of Ocean Engineering and Technology
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• v.24 no.6
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• pp.92-96
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• 2010

Recently, the application of aluminum alloys has been increasing for lightweight and high quality transport vehicles. Therefore, the proposal has been made to apply high speed hybrid welding methods to the marine grade aluminum alloy (A5052) used for shipbuilding by combining a 3-KW CW Nd : YAG laser and the MIG welding process. In this study, the characteristics of the welding parameters were investigated for a hybrid butt joint. This paper also describes the determination of the heat distribution in a weldment and the welding residual stress using a finite element method. Mechanical experimentation was also used to ascertain the reliability of the weldment.

• Steel and Composite Structures
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• v.26 no.3
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• pp.265-272
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• 2018

A detailed study was carried out on the tensile properties of the single-lap joint of a steel panel bolted/bonded to a composite laminate with a flanging. Finite element model (FEM) was established to predict the strength and to analyze the damage propagation of the hybrid joints by ABAQUS/Standard, which especially adopted cohesive elements to simulate the interface between the laminate and adhesive. The strength and failure mode predicted by FEM were in good agreement with the experimental results. In addition, three influence factors including adhesive thickness, bolt preload and bolt-hole clearance were studied. The results show that the three parameters have effect on the first drop load of the load-displacement curve, but the effect of bolt-hole clearance is the largest. The bolt-hole clearance should be avoided for hybrid joints.

• Fibers and Polymers
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• v.3 no.4
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• pp.159-168
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• 2002

Polyurethane foams were produced by using a homogenizer as a mixing equipment. Effects of stirring speed on the foam structure were investigated with SEM observations. Variation of the bubble size, density of the foam, compressive strength, and thermal conductivity were studied. A hybrid foam consisting of polyurethane foam and commercial polystyrene foam is produced. Mechanical and thermal properties of the hybrid foam were compared with those of pure polyurethane foam. Advancement of flow front during mold filling was observed by using a digital camcorder. Four types of mold geometry were used for mold filling experiments. Flow during mold filling was analyzed by using a two-dimensional control volume finite element method. Variation of foam density with respect to time was experimentally measured. Creeping flow, uniform density, uniform conversion, and uniform temperature were assumed for the numerical simulation. It was assumed for the numerical analysis that the cavity has thin planar geometry and the viscosity is constant. The theoretical predictions were compared with the experimental results and showed good agreement.

• Journal of Mechanical Science and Technology
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• v.16 no.10
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• pp.1201-1210
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• 2002

A penalty frame method is proposed for the coupled analysis of finite elements with independently modeled substructures. Although previously reported hybrid interface method by Aminpour et al (IJNME, Vol 38, 1995) is accurate and reliable, it requires non-conventional special solution algorithm such as multifrontal solver. In present study, an alternative method has been developed using penalty frame constraints, which results in positive symmetric global stiffness matrices. Thus the conventional skyline solver or band solver can be utilized in the solution routine, which makes the present method applicable in the environment of conventional finite element commercial software. Numerical examples show applicability of the present method.

• Smart Structures and Systems
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• v.13 no.4
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• pp.587-614
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• 2014

In recent years the interest in online monitoring of lightweight structures with ultrasonic guided waves is steadily growing. Especially the aircraft industry is a driving force in the development of structural health monitoring (SHM) systems. In order to optimally design SHM systems powerful and efficient numerical simulation tools to predict the behaviour of ultrasonic elastic waves in thin-walled structures are required. It has been shown that in real industrial applications, such as airplane wings or fuselages, conventional linear and quadratic pure displacement finite elements commonly used to model ultrasonic elastic waves quickly reach their limits. The required mesh density, to obtain good quality solutions, results in enormous computational costs when solving the wave propagation problem in the time domain. To resolve this problem different possibilities are available. Analytical methods and higher order finite element method approaches (HO-FEM), like p-FEM, spectral elements, spectral analysis and isogeometric analysis, are among them. Although analytical approaches offer fast and accurate results, they are limited to rather simple geometries. On the other hand, the application of higher order finite element schemes is a computationally demanding task. The drawbacks of both methods can be circumvented if regions of complex geometry are modelled using a HO-FEM approach while the response of the remaining structure is computed utilizing an analytical approach. The objective of the paper is to present an efficient method to couple different HO-FEM schemes with an analytical description of an undisturbed region. Using this hybrid formulation the numerical effort can be drastically reduced. The functionality of the proposed scheme is demonstrated by studying the propagation of ultrasonic guided waves in plates, excited by a piezoelectric patch actuator. The actuator is modelled utilizing higher order coupled field finite elements, whereas the homogenous, isotropic plate is described analytically. The results of this "semi-analytical" approach highlight the opportunities to reduce the numerical effort if closed-form solutions are partially available.

• Journal of KSNVE
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• v.8 no.4
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• pp.654-662
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• 1998

To predict the radiating noise from the vibrating surface, it is required to know the velocity distribution of vibrating surface exactly as possible as it can. Although it can be obtained by finite element method, their accuracy is limited by theuncertainty of preparing input data such as material propoerties, damping, excitation, and the actual boundary conditions. Experimental values are accurate but are seldom available as many asthe data points compared to FEM mesh. Therefore, hybrid method of experiment and finite element method, called modal expansion technique, is investigated for the preparatin of accurate element method at specified frequencies and for the verification of this scheme, related experiment is performed. In high frequency range above 2000 Hz, piezo-electric material is used as an actuator.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.10a
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• pp.623-628
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• 2000

In this paper, the behavior for transfer girder of the upper-wall and lower-frame structures was studied by the nonlinear finite element analysis. It was analyzed and compared with the experimental results. Analysis results showed that failure modes were progressed by a initial diagonal crack in the shear span between the edges of the load and intermediate support plate. The nonlinear finite element analysis could predict deformation, principal stress, ultimate load and concrete crack. Also analysis results showed good agreement the test results.