International Journal of Applied Electromagnetics and Mechanics - Volume 52, issue 1-2

Authors: Sun, Feng | Zhang, Ming | Jin, Junjie | Duan, Zhenyun | Jin, Jiaqi | Zhang, Xiaoyou

Article Type: Research Article

Abstract: A three-degree of freedom (DOF) same-stiffness permanent magnetic spring is proposed, which comprises three groups of permanent annular and cylindrical magnets. The three groups of magnets are symmetrically arranged on a concentric circle. In each group, the permanent cylindrical and annular magnets are coaxial and the same magnetic poles are opposite. The repulsive force in the radial direction is regarded as the magnetic spring force between the permanent cylindrical and annular magnets. The repulsive forces of three groups of magnets can realize the three DOF same-stiffness magnetic spring forces on a plane. In this paper, a mathematical model of the …magnetic spring force is established for one group of magnets. The mechanical characteristics of the magnetic spring force are analyzed by calculations with the mathematical model, simulations with the FEM (finite-element method) model, and verifications with the experimental prototype. The results suggest that the force characteristics of the magnetic spring resemble those of a mechanical spring and the different stiffness of the magnetic spring force can be obtained by changing the structural parameters. Show more

Keywords: Stiffness, magnetic spring, permanent magnet, finite-element method

DOI: 10.3233/JAE-162026

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 52, no. 1-2, pp. 667-675, 2016

Authors: Uchimoto, Tetsuya | Takagi, Toshiyuki | Wu, Xiaoyang | Feng, Hao | Urayama, Ryoichi

Article Type: Research Article

Abstract: In applying eddy current testing to evaluation of fatigue cracks in austenite stainless steels, various influential factors are needed to be considered, such as martensite transformation of austenitic phase, crack closure, and oxide formation between crack faces, and so on. In this study, influential factors of heating of fatigue cracks in type 316 austenitic stainless steels are evaluated through experimental and numerical analysis. Signal phase shift and amplitude decrease by heating is systematically discussed.

Keywords: Eddy current testing, fatigue crack, austenitic stainless steel, heat treatment, martensitic phase

DOI: 10.3233/JAE-162044

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 52, no. 1-2, pp. 677-684, 2016

Authors: Zhang, Jingjing | Dong, Longlei | Guirong, Yan | Shao, Kang

Article Type: Research Article

Abstract: An unsuitable value of k may lead to a series of wrong manifolds after dimensionality reduction in local linear embedding (LLE). In order to improve the accuracy of dimensionality reduction in LLE, an improved LLE algorithm (ILLE) is proposed, which determins the optimal number of nearest neighbors k and decreases its sensitivity. In this paper, ILLE is applied to identify the modal shapes of two complex structures and the results show that ILLE identifies the modal shape more accurately than LLE.

Keywords: LLE, modal identification, complex structures

DOI: 10.3233/JAE-162152

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 52, no. 1-2, pp. 685-690, 2016

Authors: Wang, Cheng | Yu, Fei | Tao, Lin | Guo, Wangping | Wang, Jianying | Lai, Xiong-Ming | Zhang, Huizhen | Yan, Guirong | Chen, Weibin | Wang, Tian

Article Type: Research Article

Abstract: Due to the ill-conditioned inverse characteristics of uncorrelated multi-source random dynamic load identification problem, there are large condition number and large identification errors for classic least-squares of generalization method at inherent natural frequencies. In order to avoid its illness and singularity, this multi-objective optimization inverse problem is turned into single-objective optimization forward problem by criterion function of minimization maximum relative errors of all response measuring points, and we adopt genetic algorithm to search this optimal solution then. Results of uncorrelated multi-source vibration load identification on cylindrical shell CAE simulation data set show that this new method is much better in …precision and is less sensitive for measurement noise than classic least-squares of generalization method. Show more

Keywords: Random dynamic load identification, uncorrelated multi-source, frequency domain, multi-objective optimization, matrix least-squares inverse, minimization maximum relative errors, genetic algorithm

DOI: 10.3233/JAE-162213

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 52, no. 1-2, pp. 691-699, 2016

Authors: Guan, Wei | Wang, Cheng | Wang, Tian | Zhang, Huizhen | Luo, Xiangyu | Xiang, Liang | Liu, Yan | Xie, Xiaodong

Article Type: Research Article

Abstract: Based on the theory of ``time-frozen'', this paper proposes a novel operational modal analysis (OMA) for linear time-varying structure using limited memory principal component analysis (LMPCA). Compared with modal coordinate decomposition of non-stationary response signals for linear time-varying continuous beam structure, it is found that PCA can be decomposed to extract time-varying instantaneous modal parameters, which reveal structure characteristics in limited memory window length L. Numerical simulations results on a cantilever beam with slow time-varying mass are presented to verify the TV instantaneous natural frequencies and modal shapes identification capability of the LMPCA.

Keywords: Operation modal analysis, slow time-varying structure, time-frozen, instantaneous modal parameters, limited memory principal component analysis

DOI: 10.3233/JAE-162085

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 52, no. 1-2, pp. 701-709, 2016

Authors: Wang, Cheng | Wang, Jianying | Zhong, Bineng | Ying, Hui | Yan, Guirong | Chen, Weibin | Peng, Jialin

Article Type: Research Article

Abstract: In order to separate multiple random fault sources only from mixed vibration measurement response signals of mechanical system, Negentropy and Gradient iteration based fast independent component analysis (FastICA) is applied for blind signal separation (BSS). After finding the association between independent components (ICs) matrix and multiple random fault sources, multiple random fault sources identification problem is turned into ICA of the stationary random vibration response signals of mechanical system. This method uses negative entropy maximization as criterion of independence, Gradient iteration as optimization method to extract random fault sources one by one. Simulation experiment results verified that this method could …identify and separate multiple random fault sources only from mixed vibration measurement response signals of mechanical system correctly and effectively. Show more

Keywords: Blind signal separation, fast independent component analysis, multiple random fault sources, blind identification and separation, vibration measurement response signals, negentropy, gradient iteration

DOI: 10.3233/JAE-162200

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 52, no. 1-2, pp. 711-719, 2016

Authors: Ge, Gen | Li, Ze Peng | Xu, Jia

Article Type: Research Article

Abstract: One buckled simply supported giant magnetostrictive material (GMM) laminated thin film beam model subject to axial colored noise excitations is proposed. Applying the Hamilton principle and Galerkin approach the model is expressed as a one dimensional vibrating model with parametrical random excitation. The stochastic averaging method is used to obtain the probability density function (PDF) of the amplitude when the vibration is around the buckled position and the amplitude of the oscillation is small. The reliability of the system was also studied. The numerical simulation verified the theoretical analysis.

Keywords: GMM film, buckled beam, colored noise, stochastic averaging method

DOI: 10.3233/JAE-162142

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 52, no. 1-2, pp. 721-729, 2016

Authors: Li, Yilun | Yang, Shiyou

Article Type: Research Article

Abstract: In this paper, a hybrid topology optimization methodology based on ON/OFF method and Genetic Algorithm (GA) is proposed. To cater to the topology optimization, improvements are made on both the ON/OFF method and genetic algorithm. The proposed methodology is applied to the topology optimization of a magnetic actuator to maximize the magnetic force in a specific direction to verify its feasibility and effectiveness. The numerical results have demonstrated that the performance of the proposed methodology is significantly superior to those of available techniques.

Keywords: Topology optimzation, ON/OFF method, genetic algorthim

DOI: 10.3233/JAE-162081

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 52, no. 1-2, pp. 731-738, 2016

Authors: Rotinat, René | Moulart, Raphaël | Nunio, François | Vedrine, Pierre

Article Type: Research Article

Abstract: This study deals with an experimental methodology developed in order to identify the elastic properties of superconducting ring-shaped windings, constituents of the main coil winding of a magnetic resonance imaging magnet (MRI). Mechanical tensile tests were conducted on real scale specimens associated to an optical full-field displacement measurement technique (stereo image correlation). Strain fields were then obtained from the measured displacement fields by numerical differentiation. Finally, the four in-plane orthotropic stiffnesses of the windings were determined using the Virtual Fields Method (VFM). Experimental set-up also allows detecting a possible occurrence of a delamination thanks to in-plane displacement fields.

Keywords: Full-field measurement, DIC, orthotropic elasticity, VFM, superconductors, MRI

DOI: 10.3233/JAE-162060

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 52, no. 1-2, pp. 739-745, 2016

Authors: Yamaoki, Toshihiko | Ma, Mingxue | Nitta, Kouichi | Matoba, Osamu

Article Type: Research Article

Abstract: For extracting the absorber information in a scattering medium, we investigate the temporal-spatial characteristics of optical intensity distribution ratio by solving the time-dependent photon diffused equation. Numerical results indicated the output power ratio distribution with short accumulated time is effective to obtain the reconstructed absorber with the narrow width. There is no influence of the temporal and spatial widths of the input pulsed light on the reconstructed property. In the numerical conditions used in the paper, the short accumulated time provides 60% of reconstructed absorber size obtained at the saturated time.

Keywords: Imaging through turbid media, tomographic imaging, scattering measurements

DOI: 10.3233/JAE-162145

Citation: International Journal of Applied Electromagnetics and Mechanics, vol. 52, no. 1-2, pp. 747-754, 2016