Non-destructive techniques for damage analysis in standards and hybrid bearings

Technological progress in automotive has led to the continuous development of manufacturing industries. Nowadays, electrical, and mechanical components require new standards. Rolling bearings are used as key factors in the automotive field guaranteeing vehicles performance enhancement, heavy load bearing, and friction reduction. Therefore, the manufacturing process of bearings presents new challenges, as well as the main building blocks as the rolling elements. In this frame, the bearing balls manufacturing industry is demanding improvement in materials, geometry, and process. Now, more than ever, only a well-established production network enables to respond to customer needs and contributes to preserving the global environment. Rolling elements precision is essential to reach the high quality of assembled products as the market requests. Higher required performance and expectations increased due to the demand for noise reduction and low vibration performance needs. This drives an increasing request for precision balls and rollers. Moreover, power source diversification and an environmentally friendly focus perspective make room for hybrid bearings with fine, light, and tough ceramics rolling elements. This scenario has thus motivated this Ph.D. research activity with the aim to handle the problem of improving the quality and yield of existing products in the direction of zero defects conditions. The activity has been carried out with a working approach which has meant to keep in mind the main industrial needs: productivity, time and cost savings, and reliability of the results obtained. Therefore, the present work consists of a monitoring study from the raw material, production process over the finished product for rolling elements in the automotive field, in particular standard steel and ceramics balls. The primary goal pursued has been therefore focusing on standard and hybrid bearings production, process, and product development. The present thesis through the proposition of a working methodology, which encompasses theoretical, numerical, and experimental aspects, together with the related scientific literature studies on the subject can be made easily accessible to the ball manufacturing field. The primary goal pursued for steel balls has been therefore to trace the entire design of the manufacturing machine and process of the component, from the modelling phase to the quality of finished product estimation; moreover, the impact on vibration and noise level of bearings, suggesting more efficient processing parameters in the different steps and discussing capabilities and drawbacks. For hybrid bearings, the goal was to research and identify new abrasive coatings and new deposition techniques for ceramic balls production. The research activity described in the thesis aims to address the challenge of improving the quality and yield of existing products towards zero defects conditions. The approach taken considers industrial needs such as productivity, time and cost savings, and reliability of results. The thesis proposes a working methodology that integrates theoretical, numerical, and experimental aspects, as well as a review of scientific literature on the subject, to benefit the ball manufacturing field. For steel balls, the primary goal is to trace the entire design of the manufacturing machine and process, from modeling to estimating the quality of the finished product. The impact on vibration and noise levels in bearings is also investigated, with suggestions for more efficient processing parameters and discussions on capabilities and drawbacks.