Computation accuracies of boundary element method and finite element method in transient eddy current analysis

The computation accuracies of the boundary-element method (BEM) and finite-element method (FEM) in transient eddy-current problems are compared by using a slot-embedded conductor model and a diffusion model that can be solved theoretically. For computing the vector potential or magnetic flux density it is shown that larger time-step width can be chosen in the BEM than in the FEM method for the same accuracy </p

Locally continuously perfect groups of homeomorphisms

The notion of a locally continuously perfect group is introduced and studied. This notion generalizes locally smoothly perfect groups introduced by Haller and Teichmann. Next, we prove that the path connected identity component of the group of all homeomorphisms of a manifold is locally continuously perfect. The case of equivariant homeomorphism group and other examples are also considered.Comment: 14 page

Computaton of 3-dimensional Eddy current problems by using boundary element method

The boundary element method for computing 3-dimensional eddy current distributions is presented. This method is based on Vector Green's Theorem, and unknown electric field vectors and magnetic flux density vectors are assumed on the boundaries of two materials, and unknown electric field vectors are assumed in the conductor regions. After determining these unknown vectors, 3-dimensional eddy current distributions in the conductors are computed. The computation results of a conducting sphere model by this method were examined in contrast to those of a coupled circuit model. </p

An analysis of 3-dimensional magnetic field distributions in a small-sized synchronous motor with a permanent magnet rotor

This paper describes an analysis of 3- dimensional magnetic field distributions in a small-sized synchronous motor with a permanent magnet rotor and a simulation of the rotor behavior. Here, the concept of a surface magnetic charge is introduced, and then the magnetic field distributions are computed by using the integral equation method. Next, the rotor displacement is computed by using Newmark's &#946;-parameter method. By the use of these techniques, simulation of the rotor behavior is performed. The results of the simulation are examined in contrast to those of the experiments. </p

The optimum design of electrode and insulator contours by nonlinear programming using the surface charge simulation method

A new method is presented for optimizing electrode and insulator contours. The contours are modified by using the iteration methods of nonlinear programming until the desired electric field distribution is obtained. The Gauss-Newton, quasi-Newton, conjugate gradient, or steepest descent method is used for the iteration. The electric-field distributions are computed by means of the surface charge simulation method. It is shown that the Gauss-Newton method gives very fast convergence </p

Techniques for boundary element analysis of three-dimensional eddy current distribution

An analysis of three-dimensional eddy-current distribution by a boundary-element method using field vector variables is described. A triangular element is used as a boundary element. The electric field vector and magnetic flux density vector are defined as the unknown vectors and are assumed to be constant on each triangular element. For forming simultaneous equations, the computation point on the triangular element is set at the null point, where the triangular element itself does not induce tangential components of the electric field and the magnetic flux density </p

Computation of three-dimensional electromagnetic field in the eddy-current testing of steel pipes

The computation of three-dimensional electromagnetic field distributions in the eddy-current testing for holes in steel pipes is described. A boundary element method with vector variables was used to compute the eddy-current and magnetic-flux-density distributions. Computed and experimental results for the magnetic flux density on the inner surface are compared, and the mechanism of defect detection in steel pipes is clarified </p

Effect of surface roughness on friction behaviour of steel under boundary lubrication

The friction behaviour of grinded and polished surfaces was evaluated by using a reciprocal sliding tester under lubrication with PAO, PAO + ZnDTP and PAO + ZnDTP + MoDTC. Friction coefficients on the smooth surfaces showed higher values compared to those on the rough surfaces. For lubrication incorporating PAO and PAO + ZnDTP + MoDTC, friction coefficients on both the smoothest and the roughest surfaces decreased with sliding time. On the other hand, friction coefficients between these extremes decreased with sliding time. In this paper, the effects of surface roughness on friction behaviour are discussed