Finite differences software for the numeric analysis of a non-destructive electromagnetic testing system
In this paper, theoretical bases for the development of a software for electromagnetic effects simulation based on the approximation method of finite differences using Scilab are presented. A methodology for programming the algorithm is discussed and a simulation test is conducted in order to validate it, which consists of a coil with a ferromagnetic core. Finally, this software is used in studies related to magnetic flux leakage by a simulation of a system for the measurement of magnetic flux density in plates with different defects, which include both 2D and 3D and defects with orientation of 45 degrees.
Feasibility study for nondestructive evaluation of magnetic properties and hardness of two-layered specimens by magnetic single-yoke probe
Abstract This work is a feasibility study for the application of a single-yoke magnetizing technique for in situ measurements of thick bulk specimens. We consider variations in the magnetic properties near the surface and inside the specimens. The magnetic properties of two-layered sheet specimens, which have different magnetic properties in each layer, are examined, and a simple summation law is consequently found concerning the relation between the magnetic parameters of the first and second layers measured by the single yoke. The relation between magnetic properties and the Vickers hardness in each layer is also inferred by regression analysis. An estimation of the hardness in each layer using a magnetic measurement by single-yoke probes is then successfully performed. These results show the possibility of nondestructive evaluation for inhomogeneous characteristics of structural materials.
Fast Simulation of 3D Electromagnetic Problems Using Potentials
We consider solving three-dimensional electromagnetic problems in parameter regimes where the quasi-static approximation applies, the permeability is constant, the conductivity may vary significantly, and the range of frequencies is moderate. The difficulties encountered include handling solution discontinuities across interfaces and accelerating convergence of traditional iterative methods for the solution of the linear systems of algebraic equations that arise when discretizing Maxwell's equations in the frequency domain. We use a potential-current formulation (A, ? ,?) with a Coulomb gauge. The potentials A and ? decompose the electric field E into components in the active and null spaces of the ??operator. We develop a finite volume discretization on a staggered grid that naturally employs harmonic averages for the conductivity at cell faces. After discretization, we eliminate the current and the resulting large, sparse, linear system of equations has a block structure that is diagonally dominant, allowing an efficient solution with preconditioned Krylov space methods. A particularly efficient algorithm results from the combination of BICGSTAB and an incomplete LU-decomposition. We demonstrate the efficacy of our method in several numerical experiments.