One of the most challenging tasks in Condition Monitoring is to assess health conditions of critical components like roller bearings. Bearing Vibration behaviour under defective condition involves several parameters such as temperature, lubricant viscosity, loading conditions, operating conditions, defect size and location.  After decades of studies on the subject, bearings dynamic behaviour under conventional operating conditions (speed, temperature, etc.) is now very well defined. But as soon as we leave the conventional operating ranges, a new phenomenon appears and affects the vibratory response of the components modifying the expected vibration signature.

In this paper, we will study the bearing behaviour under high speed condition; present a new twenty degree of freedom model simulating the spindle bearing system during high speed machining accounting for the gyroscopic effect arising at high speeds.

Demonstration will be made that the static natural frequencies (measured when the machine is off, or in conventional speed <6000CPM) will duplicate and drift according to speed. Moreover, the developed model is used to generate vibration response of a defective bearing, and to assess its transmissibility from one housing to another. Numerical simulations as well as experimental tests were conducted on a high speed milling CNC operating at 30000 CPM to validate the dynamic behaviour.

Béchir Badri (Ph.D; M.Ing) is the cofounder of BETAVIB, a company specialized in the development of vibration products for condition monitoring and expertise. He has been involved in the field of vibration analysis for the last 18 years, and is an active member of the CMVA (Canadian Machinery Vibration Association). His primary area of expertise covers advanced signal processing, mechanical modeling, structural dynamics as well as reliability management. He has written 12 articles for scientific reviews with evaluation committee in the field of vibration monitoring and bearings defects diagnosis.