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For testing a conductive pipeline, remote field eddy current testing (RFECT) is used, which is composed of solenoidal exciter coil and receiving sensor coils. In RFECT, there is remote field zone where the eddy current distributions are concentrated on the external surface of the pipe wall. Therefore, it is possible to detect a defect that occurs on the external surface of the pipe wall even if the receiving coils are located inside the pipe. From the measured coil signals, it is necessary to decompose background offset and predict the pattern of defect signal in order to estimate the defect size for the maintenance of underground pipelines eventually. In the process, the amplitude variations of the induced magnetic field at sensor coils are closely related to defect depth. Therefore, it is important to analyze and eliminate distortions of measured RFECT signals. This paper analyzes the effects of the induced magnetic field on the sensing signals with respect to different depth sizes in the RFECT system. The amplitude and the distribution pattern of defect signals are computed by a 3-D finite-element method and the method to eliminate the signal distortions caused by induced magnetic fields are presented. Simulated results in this paper agreed well with measuring ones. [ABSTRACT FROM AUTHOR]

This paper presents a new topology optimization method based on basis functions for design of rotating machines. In this method, the core shape of a given rotating machine is represented by the linear combination of the basis functions. The shape is then freely deformed by changing the weighting coefficients to the basis functions to find the optimal shape. The proposed method is compared with the conventional shape optimization based on polygon morphing. The former is shown to outperform the latter in both interior permanent magnet and synchronous motor models. [ABSTRACT FROM AUTHOR]

In this paper, a finite-element implementation of linear second-strain gradient elasticity is introduced based on a Hellinger-Reissner variational principle in order to use standard finite-element methods. Displacement boundary conditions are applied to one or more vertices of different polyhedrons. As a result, a smooth deformation around deformed vertices of the polyhedrons can be observed, in contrast to the appearance of singularities in the first-order theory, i.e., a Cauchy continuum, where strain singularities appear in such cases. [ABSTRACT FROM AUTHOR]

In this paper, a new eight-unknown shear deformation theory is developed for bending and free vibration analysis of functionally graded plates by finite-element method. The theory based on full 12-unknown higher order shear deformation theory simultaneously satisfies zeros transverse stresses at top and bottom surfaces of FG plates. A four-node rectangular element with 16 degrees of freedom per node is used. Poisson's ratios, Young's moduli, and material densities vary continuously in thickness direction according to the volume fraction of constituents which is modeled as power-law functions. Results are verified with available results in the literature. Parametric studies are performed for different power-law indices, side-to-thickness ratios. [ABSTRACT FROM AUTHOR]

Composites of multi-walled carbon nanotubes (MWCNTs) and cement layers were manufactured by grinding carbon nanotubes and cement powder in a planetary ball mill. Tiny cement nanoparticles were fabricated using an ethylene-glycol-assisted synthesis procedure with successive hydrolysis and condensation reactions. Cement-nanotube nanocomposites were then produced by adding functionalized nanotube powder to the colloidal cement nanoparticles suspended in ethylene glycol (weight ratio of nanotubes to cement $$=$$ 1:1). Modal analysis of five-walled carbon nanotube nanocomposites with 1-5 cement layers was performed via the finite-element method. The five-walled carbon nanotube nanocomposites with different shapes were modelled using three-dimensional elastic beams of carbon bonds, nodal carbon point masses and cement layer shell elements. The natural frequency, von Mises stress and strain energy of the elements were calculated by considering the Van der Waals forces between the carbon atoms in the hexagonal lattice. In the modal analysis, the greatest variation in displacement was observed along the x-axis, and the maximum values of the total displacement appeared to be larger at the cement layers than at the MWCNTs. The cement-nanotube nanocomposites exhibited a gradual decrease in deformation and vibration as the number of cement layers was increased. [ABSTRACT FROM AUTHOR]