• Journal of Ocean Engineering and Technology
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• v.15 no.2
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• pp.72-78
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• 2001

The bead is used to provide properly restraining force in the sheet metal forming process. This bead process includes bending and geometrical non-linearity, and affects the state of binderwrap. Therefore, the analysis of bead process is very important to obtain the desired formability. In this paper, the research about the influence of the punch stroke of bead on the draw-bead process was conducted. Results from the analysis will give useful information to the effective tool design of blank forming process. To analyze the bead process, and elasto-plastic finite element formulation is constructed from the equilibrium equation and the considered boundary conditions involved a proper contact condition. The static-explicit finite element method as a numerical method for the analysis was applied to the analysis program code. It was found that this method could solve too much computation time and convergence problem owing to high non-linearity of bead forming process.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2016.10a
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• pp.913-914
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• 2016

This paper analyzes the impact of the satellite TWTA non-linearity charateristics for shared band transmission technology to improve spectral efficiency in satellite communication system. In shared band transmission technology for star network, a hub and terminals use same frequency band. In order to receive terminals's signal a hub have to remove the its own DVB-S2 carrier. In this paper the non-linearity impact of satellite TWTA is analyzed for self-interference cancellation.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.11a
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• pp.319-324
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• 2001

Free non-linear vibration of a rotating thin ring with a constant speed is analyzed when the ring has both the in-plane and out-of-plane motions. The geometric non-linearity of displacements is considered by adopting the Lagrange strain theory for the circumferential strain. By using Hamilton's principle, the coupled non-linear partial differential equations are derived, which describe the out-of-plane and in-plane bending, extensional and torsional motions. The natural frequencies are calculated from the linearized equations at various rotational speeds. Finally, the computation results from three non-linear models are compared with those from a linear model. Based on the comparison, this study recommends which model is appropriate to describe the non- linear behavior more precisely.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.36 no.8
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• pp.734-739
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• 2008

In this study, the nonlinear mechanical behavior of flexible textile composites was predicted by two-step analyses: micromechanics and mesomechanics. The effective material properties for fiber tows of flexible textile composite lamina were calculated in micromechanics, which were then used to calculate the effective tensile stress-strain curve of flexible textile composites in mesomechanics. A user defined material algorithm was developed and inserted in ABAQUS to account for the geometric non-linearity due to the large rotation and shear deformation of fiber tows in mesomechanics. It was found that the stress-strain behavior of flexible textile composites exhibited significant non-linearity. The effective tensile modulus agreed well with the test result.

• Structural Engineering and Mechanics
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• v.40 no.3
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• pp.347-371
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• 2011

This paper focuses on post-buckling analysis of Timoshenko beams with various boundary conditions subjected to a non-uniform thermal loading by using the total Lagrangian Timoshenko beam element approximation. Six types of support conditions for the beams are considered. The considered highly non-linear problem is solved by using incremental displacement-based finite element method in conjunction with Newton-Raphson iteration method. As far as the authors know, there is no study on the post-buckling analysis of Timoshenko beams under uniform and non-uniform thermal loading considering full geometric non-linearity investigated by using finite element method. The convergence studies are made and the obtained results are compared with the published results. In the study, the relationships between deflections, end rotational angles, end constraint forces, thermal buckling configuration, stress distributions through the thickness of the beams and temperature rising are illustrated in detail in post-buckling case.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.27 no.10C
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• pp.993-998
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• 2002

At Power amplifier, distortion of output is appeared because of non-linearlity, so we must study method of compensation for non-linearity. In this paper, it was studied about the characteristic of predistorter using serial schottky diode for an amplifier. As a result, we confirmed that power amplifier was able to linearize when we put predistorter using non-linearity of schottky diode before power amplifier. When input carrier level was low, input carrier was delivered directly into power amplifier but input carrier level was high, input carrier was delivered into power amplifier through predistorter with suppressed level. As a result power amplifier always was at saturation region. Through simulation using serenade 8.0, we have concluded that efficiency was improved about 3%, and predistorter got best linearity at 1.8㎓ between 800㎒∼2.2㎓.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.40 no.1
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• pp.23-31
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• 2015

In this paper, we design a SSD(simultaneous single band duplex) system using RF cancellation and digital cancellation. And then, we analyze performance of the SSD system using pre-distorter with HPA non-linearity. Also, we analyze digital cancellation performance of the SSD system using pre-distorter with HPA non-linearity. Additionally, digital cancellation cancels residual self-interference. In linear conditions, digital cancellation can cancel self-interference of 40dB. Therefore, the SSD system has good BER performance because most of self-interference is canceled. But, in HPA non-linearity conditions, digital cancellation cancels residual self-interference of 25dB. In this conditions, self-interference is greater than desired signal. Therefore, bit informations of distant station can not be received. But, we confirm that if the proposed system uses pre-distorter then bit information of distant station can be received by HPA non-linearity compensation. Also, we confirm that even though the proposed system uses pre-distorter, if HPA non-linearity increases then digital cancellation performance is degraded by imperfect compensation of HPA non-linerity.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2004.04a
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• pp.87-90
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• 2004

In this paper, geometrically non-linear finite element analyses were performed to study the mechanical behavior of the material system of the envelope of stratospheric airships. The microstructure of the load­bearing plain weave layer was identified and modeled. The Updated Lagrangian formulation was employed to consider the geometric non-linearity as well as the induced structural non-linearity for the fiber tows. The stress-strain behavior was predicted and the effective elastic modulus was calculated by numerical experiments. It was found the non-linear stress-strain curves were largely different from those by linear analysis with much higher non-linear elastic moduli. The difference was more distinguishable when the tow waviness was smaller.

• Computers and Concrete
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• v.15 no.4
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• pp.547-562
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• 2015

A two-dimensional multi-layered finite elements modeling of reinforced concrete structures at non-linear behaviour under monotonic and cyclical loading is presented. The non-linearity material is characterized by several phenomena such as: the physical non-linearity of the concrete and steels materials, the behaviour of cracked concrete and the interaction effect between materials represented by the post-cracking filled. These parameters are taken into consideration in this paper to examine the response of the reinforced concrete structures at the non-linear behaviour. Four examples of application are presented. The numerical results obtained, are in a very good agreement with available experimental data and other numerical models of the literature.

• Coupled systems mechanics
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• v.7 no.4
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• pp.441-453
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• 2018

Longitudinal fracture in a functionally graded beam configuration was studied analytically with taking into account the non-linear behavior of the material. A cantilever beam with two longitudinal cracks located symmetrically with respect to the centroid was analyzed. The material was functionally graded along the beam width as well as along the beam length. The fracture was studied in terms of the strain energy release rate. The influence of material gradient, crack location along the beam width, crack length and material non-linearity on the fracture behavior was investigated. It was shown that the analytical solution derived is very useful for parametric analyses of the non-linear longitudinal fracture behavior. It was found that by using appropriate material gradients in width and length directions of the beam, the strain energy release rate can be reduced significantly. Thus, the results obtained in the present paper may be applied for optimization of functionally graded beam structure with respect to the longitudinal fracture performance.