WHAT IS THE LIFETIME OF SUPERFICIAL TRIBOLOGICAL TRANSFORMATIONS IN THE RAILWAY PROBLEM? - FROM THE NUCLEATION AND GROWTH PROCESSES TO THE CONTACT FATIGUE CRACK

During the manufacturing processes (e.g. forming) or the use in service associated with the operation phases, some solids in contact subjected to repeated variable thermo-mechanical loads can undergo microstructural changes in the surface and under near-surface contact area. These changes in the materials, as known Supercial Tribological Transformations, have their origin in the presence of high mechanical and thermal gradients very close of the contact surface.