3. Conclusion

Based on the forces exerted by machine components and the shapes of the parts used to distribute and transmit stresses, the materials used here (especially steels) are reminded of their brittle characteristics.

Beyond a certain strength limit, cracks and fractures appear, reflecting stresses, shapes and materials. The morphology of fractures thus provides two types of information: one mechanical, the other metallurgical.

This enabled us to identify the notions of ductility and brittleness, crack progressivity and safety, but above all it enabled us to identify the onset of cracks.

The metallurgical study of the starter, combined with the morphological map of the entire fracture, enables us to attribute the cause of the degradation to the metal, whether or not it is due to the material or its processing.