Angular ball bearings are commonly used whenever there is a demand to increase stiffness of bearing. The aforementioned can be achieved by obtaining proper preload in bearings. In common belief, has negative consequence: it increases the load rolling elements, which must lead lower durability bearing compared situation before use.

The sensitive and quantitative measurement method will be important to evaluate the lubrication condition and to predict the remaining bearing life-time. Observations of the size and number of damage or wear particle, and the fluctuation of the ball load are useful for the quantitatively evaluation of operation abnormalities in a ball bearing. The vibration and AE (Acoustic Emission) method are...