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Permanent magnet bearing design: optimising the magnetisation direction

Di Puccio F.

International Journal of Applied Mechanics and Engineering

2004

Vol. 9, no 4

655-673

Permanent magnet bearings may be conveniently employed in several mechanical applications when friction and wear have to be avoided. The mechanical behaviour of these components is defined by the force acting between the elements of the bearing and by the stiffness of the system. In order to get the desired performance of the bearing a compromise of force and stiffness can be achieved, e.g. by selecting the magnetisation direction of the elements. The paper reviews some general criteria for permanent magnet bearing design and proposes a method for evaluating the most suitable magnetisation direction, based on the equivalent current method and employing Finite Element analyses. Three sample cases of annular and tapered bearing are reported, for which design maps for axial and radial bearings are also presented.

Analysis of a surface crack in rolling bearings

Bassani R., Ciulli E., Di Puccio F.

Applied Mechanics and Engineering

1999

Vol. 4, no spec.

305-310

Surface cracks may be detrimental in rolling bearings life. The paper present a linear elastic fracture mechanics approach, based in the weight function method for evaluating the stress intensity factors history during a load cycle. The real contact problem is simplified to a half-plane with an angled crack, and a load travelling over it, due to ehd or hertzian pressure distribution. Moreover the effect of a tractive force is also considered, with a friction coefficient equal to -0.05. The method is rather simple requiring only nominal stresses in the body, easily achievable also in an analytical form, e.g. Applying kolosov-muskhelishvili complex variable approach. Results show that hertzian and ehd pressure distribution causes similar stress intensity factors cycles, even if the first case crack propagation seems to be favoured.