• Steel and Composite Structures
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• v.35 no.1
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• pp.77-92
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• 2020

The present paper outlined a procedure for geometrically nonlinear dynamic analysis of functionally graded graphene platelets-reinforced (GPLR-FG) nanocomposite cylinder subjected to mechanical shock loading. The governing equation of motion for large deformation problems is derived using meshless local Petrov-Galerkin (MLPG) method based on total lagrangian approach. In the MLPG method, the radial point interpolation technique is employed to construct the shape functions. A micromechanical model based on the Halpin-Tsai model and rule of mixture is used for formulation the nonlinear functionally graded distribution of GPLs in polymer matrix of composites. Energy dissipation in analyses of the structure responding to dynamic loads is considered using the Rayleigh damping. The Newmark-Newton/Raphson method which is an incremental-iterative approach is implemented to solve the nonlinear dynamic equations. The results of the proposed method for homogenous material are compared with the finite element ones. A very good agreement is achieved between the MLPG and FEM with very fine meshing. In addition, the results have demonstrated that the MLPG method is more effective method compared with the FEM for very large deformation problems due to avoiding mesh distortion issues. Finally, the effect of GPLs distribution on strength, stiffness and dynamic characteristics of the cylinder are discussed in details. The obtained results show that the distribution of GPLs changed the mechanical properties, so a classification of different types and volume fraction exponent is established. Indeed by comparing the obtained results, the best compromise of nanocomposite cylinder is determined in terms of mechanical and dynamic properties for different load patterns. All these applications have shown that the present MLPG method is very effective for geometrically nonlinear analyses of GPLR-FG nanocomposite cylinder because of vanishing mesh distortion issue in large deformation problems. In addition, since in proposed method the distributed nodes are used for discretization the problem domain (rather than the meshing), modeling the functionally graded media yields to more accurate results.

• Journal of the Korean Geotechnical Society
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• v.20 no.6
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• pp.61-73
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• 2004

The coefficient of permeability of natural clay shows a nonlinear property which is related to various stress level of soils, and this nonlinear property has effect on the period of consolidation and the property of deformation in clay soils under loading. Thus, in this paper the numerical analysis was conducted by FEM-using coupled theory which incorporated Biot's consolidation theory into modified Cam-clay model- to consider the effects of nonlinear permeability on the behavior of clay soils under loading. The result of this paper showed that nonlinear permeability had different effects on the deformation and excess pore water pressure in clay soils according to the change of ratios of coefficients of permeability which was presented a degree of nonlinear property, and average coefficients of permeability of soils. Therefore, it was concluded that nonlinear permeability should be considered according to both the change of ratios of coefficients of permeability and average coefficients of permeability to conduct more simultaneous analyses to field conditions.

• The Transactions of the Korean Institute of Power Electronics
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• v.6 no.4
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• pp.333-340
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• 2001

This paper presents a calculating method for inductance of the Switched Reluctance Motor(SRM) for torque characteristics and driving by analytical model. The torque generating characteristics of the SRM depend on the phase current and the inductance variation features, but Its nonlinear magnetic characteristics make it difficult to calculating inductance. Recently, The approaches for calculating inductance have taken vary from detailed finite element method(FEM) and Fitting method in magnetization curves using complex nonlinear magnetic circuit models. But those methods have not satisfactory approach for machine performance calculations, because of having a long time and remodeling for analyses, therefore thus an alternative approach is required. So it is suggested simply calculating method of the inductance based on designed data of machinery by analytical model in unaligned and aligned rotor. In order to prove the calculating, there are compare with analytical FEM. direct measurement, this method, and simulation. The compared result is shown to obtain good accuracy.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.14 no.4
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• pp.703-710
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• 1994

A nonlinear FEM analysis of steel members under very-low-cycle loading has been performed in conjunction with experimental works. This analysis is an FEM tracing toward cracking of steel members under cyclic loads such as a strong earthquake. After verifying the procedure by comparing global hysteretic behaviors from the analytical and experimental results, the local stress-strain hysteresis at critical sections for large cyclic deformations was traced by the numerical analysis. Local strain history was discussed in relation to cracking. Based on the experimental and analytical results, a new approach to seismic safety assessment for steel members was proposed in this paper.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2002.05a
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• pp.778-781
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• 2002

Durability of rubber dust cover in the ball joint for automotive suspension parts were analyzed by FEM and compared with experimental data. Upper open area of ball joint is sealed by dust cover for preventing outflow of the lubricating oil and intrusion of send, dust, water, etc. This rubber cover undergoes repeated loadings such as tension and compression while the car is running. Analysis about rubber material needs to consider every kinds of nonlinearities arise in finite element analysis, which are geometric nonlinearity due to large displacement and small strain, materially nonlinearity and nonlinear boundary condition such as contact. So in the study, the deformation behavior of dust cover was analysed by using the commercial finite element program MARC. This program could solve these kinds of nonlinear analysis accurately. Finite element model of dust cover is considered as 3-dimensional half model based on 2-dimensional axisymmetric model. Material property of rubber was modeled by Ogden model and input data for calculation takes form uniaxial tension test of rubber specimen, The final object of the study is obtaining the design specification of dust covers and the result of analysis should be a useful data to design of rubber

• Steel and Composite Structures
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• v.32 no.4
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• pp.423-441
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• 2019

This study aims to accurately predict the first ply failure loads of laminated composite hypar shell roofs with different boundary conditions. The geometrically nonlinear finite element method (FEM) is used to analyse different symmetric and anti-symmetric, cross and angle ply shells. The first ply failure loads are obtained through different well-established failure criteria including Puck's criterion along with the serviceability criterion of deflection. The close agreement of the published and present results for different validation problems proves the correctness of the finite element model used in the present study. The effects of edge conditions on first ply failure behavior are discussed critically from practical engineering point of view. Factor of safety values and failure zones are also reported to suggest design and non-destructive monitoring guidelines to practicing engineers. Apart from these, the present study indicates the rank wise relative performances of different shell options. The study establishes that the angle ply laminates in general perform better than the cross ply ones. Among the stacking sequences considered here, three layered symmetric angle ply laminates offer the highest first ply failure load. The probable failure zones on the different shell surfaces, identified in this paper, are the areas where non-destructive health monitoring may be restricted to. The contributions made through this paper are expected to serve as important design aids to engineers engaged in composite hypar shell design and construction.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.11a
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• pp.205-209
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• 2008

In this study, very accurate computational mechatronics method has been developed for typical N.C. machine model applying to manufacturing industry in these days. Computation analysis of high speed machine tools like N.C. machine needs consideration about mechatronical features because the machine shows close interaction between dynamic behavior of the mechanical structure, drives and numerical control. For this, nonlinear structural analysis tools based on FEM are linked numerical control program to control the dynamic behavior. In this study, we studied the dynamic feature of N.C. machine by using SAMCEF as nonlinear computational structural analysis tool and simulink as drivers.

• Journal of The Korean Digital Architecture Interior Association
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• v.3 no.2
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• pp.47-54
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• 2003

A Steel plate shear wall can be used as one of the lateral force resistant elements in buildings. It have many advantages from a structural point of view such as ductility, energy absorption capacity and initial stiffness etc. In this study to grasp the behavior of steel plate shear wall considering material and geometrical non-linearity, the FEM analyses were carried out using ANSYS(ver. 5.6) program. The analysis results were fully discussed and compared with test results to verify the validity of analysis method. The object of this study is to find out analytically the elasto-plastic behavior of un-stiffened steel plate shear wall.

• Proceedings of the KIEE Conference
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• 1998.11a
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• pp.70-72
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• 1998

Because of using PWM inverters and converters. The problems of insulation breakdown is emerging in both high voltage motors and general motors. In conventional methods, the viewpoint of surge problems is wave propagation with or without cable and inverter. For the purpose of knowing the situation of insulation breakdown, the end-turn coil of windings in the motor winding insulation structure is modelled by FEM, and field analysis of that is done. For first step, only end-turn coil is modelled and the model is simulated with FEM by approximating the resistivity of metallic foil surrounding insulation layers with having nonlinear property. Next, the result of simulation with nonlinear resistivity are compared with the result of linear resistivity. Because of microscope analysis, there is the problem of generalization but the situation of corona discharge in end-turn coil will be explained from this simulation.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2009.04a
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• pp.517-520
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• 2009

본 연구에서는 비선형 FEM 해석을 이용하여 PSC(Prestressed concrete)와 강으로 구성된 혼합구조 보의 휨 실험을 검증하였다. 혼합구조 보의 거동에 가장 큰 영향을 미치는 연결부는 Perfobond rib로 구성된 경우와 스터드로 구성된 경우를 고려하였다. 이종 재료가 접하는 경계면의 상호 작용에 대해 완전합성과 부분합성인 경우를 고려하여 혼합구조 보의 비선형 해석을 수행한 후 해석 결과와 실험 결과를 비교하였다. 하중-처짐관계, 파괴 형상 등의 해석 결과를 실험 결과와 비교한 결과, 부분합성을 고려한 모형이 실험 결과와 유사한 거동을 보였으며 또한 Perfobond rib를 갖는 실험체가 스터드를 갖는 실험체보다 해석 결과와 비교 시 안전측의 결과를 나타냈다.