Tenue à la fatigue des composites métalliques

Composite beams : fatigue life study of chromium electroplated motor rings

Laboratoire de physique des matériaux, Institut supérieur des matériaux et de la construction mécanique (ISMCM), Saint-Ouen.

Abstract

Fatigue tests have been carried out on chromed piston rings. Chromium is electroplated on the outer cylinder of the rings.

The presence of a brittle metal on the surface (when the martensitic ductile iron does not present initial macroscopic defects), gives the beginning of the fatigue crack on this surface. In this case initiated crack in the chromium propagates easily in the cast iron.

The tests have been carried out in air, at the ambiant temperature and at an imposed forced displacement. They are of two types :

• —

  torque flexure combined tests, where the ring works as a helicoidal spring (TFC tests) ;

• —

  flexure tests on prestrained ring, where we open and close the gaps of the ring (FSP tests).