Papers by Keyword: Isotropic

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Authors: Marian Gaiceanu, Emil Rosu
Abstract: In this paper a voltage control strategy based on the optimal control theory, for isotropic rotor permanent magnet synchronous motor (PMSM) drives, is proposed. The complete optimal control of the three phase permanent magnet synchronous machine (PMSM) consists of three components: the state feedback, the feed forward compensation of the load torque and the reference to achieve the desired state. The control assures a smooth dynamic response, in order to achieve the desired state in steady state, the fast compensation of the load torque, and the energy minimization. The obtained solution by integrating the matrix Riccati differential equation (MRDE) is orientated towards the numerical implementation (by using a zero order hold) and it is computed on-line. The optimal control strategy is applied to PMSM drives and verified by simulations.
Authors: Jun Lin Li, Shao Qin Zhang, Wei Yang Yang, Jing Zhao
Abstract: This paper is concerned in semi-infinite interface crack of orthotropic and isotropic bi-materials and using the composite material fracture complex function method. By means of constructing special stress functions with two real singularity index and solving the problem of a class of generalized bi-harmonic equations , the stress and displacement fields of two dissimilar materials are obtained .Results demonstrate that the stress and displacement fields near the crack tip show mixed crack characteristics without oscillation.
Authors: Marian Gaiceanu, Emil Rosu
Abstract: The paper aims to underline the importance of applying complete optimal control to electric drives, in particular to Permanent Magnet Synchronous Motor (PMSM). The proposed optimal control has three components: the feedback componentassures energy minimization; the forcing component assures the zero steady state; the feedforward compensating component assures fast compensation of the disturbance. The methodology of obtaining this type of the advanced optimal control is based on variational calculus. The solution is a nonrecursive one, avoiding memorizing it from the final time to the initial time, as in the recursive case. Moreover, the solution is orientated to numerical implementation by using a zero order hold in order to solve adequately the matrix Riccati differential equation (MRDE). The practical implication of using the proposed method is the on-line computing possibility of the optimal control solution. The influences of the control weighted matrix upon the manipulated variable of the PMSM electric drive are shown by numerical simulation.
Authors: Bao Sheng Zhao, Gui Xian Lu, Xiue Wu
Abstract: In this paper, the axisymmetric general steady-state solution for porous media is presented. And the completeness of the P-Ns representation for the axisymmetric displacement field equation is proved directly from the equations governing the displacement field, which can be applied to homogeneous and isotropic poroelastic materials. At last, the Boussinesq general solution and Timpe general solution are obtained from P-N General Solution.
Authors: Evgeny Barkanov, Andris Chate, Sandris Ručevskis, Eduards Skukis
Abstract: An inverse technique based on vibration tests to characterise isotropic, orthotropic and viscoelastic material properties of advanced composites is developed. An optimisation using the planning of experiments and response surface technique to minimise the error functional is applied to decrease considerably computational expenses. The inverse technique developed is tested on aluminium plates and applied to characterise orthotropic material properties of laminated composites and viscoelastic core material properties of sandwich composites.
Authors: Marco Alfano, Leonardo Pagnotta, Giambattista Stigliano
Abstract: The use of non destructive techniques for the elastic characterization of isotropic materials is continuously increasing and those based on the modal vibration testing of plate-like specimens is very widespread. In the present paper, an optimized search procedure is proposed which allows the material constants of isotropic plates to be non-destructively identified from vibration testing data and using finite element analyses. The identification process is performed by an optimizing algorithm in which the error function to be minimized depends on the difference between the natural frequencies obtained by finite element analyses and the measured ones. In order to verify the proposed identification procedure a comparison with the results reported in literature has been made.
Authors: Manish Kr. Khandelwal, P. Bera
Abstract: A comprehensive numerical investigation on the natural convection in an isotropic porous enclosure is presented. All the walls of the enclosure are adiabatic except the bottom wall which is partially heated and cooled by sinusoidal temperature profile. The governing equations were written under assumption of Brinkman-extended non-Darcy model, including material derivative, and then solved by numerically using spectral element method (SEM). The heat transfer and fluid flow mechanisms in isotropic case are governed by periodicity parameter (N) Rayleigh Number (Ra), Darcy number (Da), aspect ratio (A), Prandtl number (Pr) and media permeability (K). The main emphasize is given on effect of N on local heat transfer as well as mechanism of heat transfer and fluid flow in enclosure. The results shows that, as the periodicity is decreased on increasing N the absolute value of Nux at the bottom left corner point increases. For odd values of N, the local heat transfer profile is symmetric about the line x=0.5, which is consequence of symmetric boundary condition at the bottom wall of the enclosure. The entire flow is governed by two type convective cells: (i) rotating clockwise (ii) rotating anticlockwise. Furthermore for even values of N cells rotating anticlockwise are dominated and covered the entire domain. In particular the present analysis shows that, different periodicity of temperature boundary condition has the significant effect on the flow mechanism and consequently on the heat transfer rate.
Authors: Kari Thangaratnam, Evangeline Kumar
Abstract: In this research article, semiloof shell element was used to study the behaviour of plate and shells under mechanical and thermal load for stress, free vibration, initially stressed vibration, mechanical buckling, and non-linear vibration. In the above cases, the material properties: Isotropic, Composite and Functionally Graded Material (FGM) were considered. Wherein, the material property for the FGM shells was assumed to vary through the thickness of the shell by varying the volume fraction of the constituent, whereas, for composites, classical laminated theory was used. Utilizing the semiloof shell element, and the above material properties, the package COMSAP was developed. From the obtained results, we have observed that with coarse meshes, semiloof shell elements present better results, and it is especially effective in the case of thin plates and shells.
Authors: Somsak Siwadamrongpong, Usanee Kitkamthorn, Chaiyapak Sajjawattana
Abstract: The most important factors in hard disk drive suspension manufacturing is the suspension preload, so call “gram load”. The suspensions were generally made from cold rolled stainless steel (SUS304). The suspensions were formed by mechanical forming and gram load was adjusted by mechanical bending until reached a specification. The material properties in mechanical bending simulation of thin stainless steel were usually as isotropic for simple calculation. But the properties of thin stainless steel should be defined as orthotropic materials. Therefore, this work aimed to study gram load results of using isotropic and orthotropic properties. The thin stainless sheet was cut and test for mechanical properties in rolling and transverse directions. The properties of the thin sheet were applied to simulation model. It was found that orthotropic material properties shows a good agreement with the experimental results more than using isotropic material properties. Therefore, the results of this work could be used to explain and predict the mechanical response on the suspension manufacturing.
Authors: Muntaz Hana Ahmad Khairi, Saiful Amri Mazlan, Ubaidillah, Siti Aishah Abdul Aziz, Norhiwani Mohd Hapipi
Abstract: This study introduces a sucrose acetate isobutyrate (SAIB) as an additive of magnetorheological elastomers (MREs) to be added in silicone rubber matrix and carbonyl iron particles (CIPs) as their filler. The CIPs were fixed at 60 wt% and two types of MREs sample were fabricated which are isotropic and anisotropic. Rheological properties related to shear storage modulus were measured using a rheometer (MCR 302, Anton Paar). The experimental results demonstrated that the magnetorheological (MR) effect of anisotropic MREs-based Silicone/SAIB was 126 % as compared to isotropic MREs-based Silicone/SAIB, 64%. The fabricated MREs samples were frequency and strain dependent. The relative MR effect for both samples showed decreasing trend with the increment of strain amplitude and excitation frequency.
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