Development of a load cell based on fiber Bragg gratings sensors

The goal of this work is the development of a new application of fiber Bragg gratings sensors (FBG), in order to measure the pre-load transmitted to a couple of roll bearings, inside an high speed electro-mandrel. FBG sensors has been preferred to classical electrical strain gauges because of their intrinsic immunity to electromagnetic fields. This last are very strong in the application here considered, and moreover its effect cannot be easily filtered because it occur at the same frequency of the phenomena to observe. The mechanical component design, used to convert the preloading forces in measurable strain, is also illustrated. On this component the fiber optic sensor is installed and the load cell obtained is calibrated. An uncertainty value equal to 1% of the full scale, is obtained. The effective pre-load value induced by the tightening system on the rolling bearings has been measured with the system developed.