Development of Seals for Rocket Engine Turbopumps

An investigation was conducted to determine the effect of frequency and amplitude of axial vibration and of bearing axial play in producing fretting damage in unlubricated ball bearings at constant temperature and humidity. A study was also made of the impact forces occurring within the bearings due to these vibrations. A simplified analog simulation model of the ball bearing and the vibration exciter system was also developed.

Frequency, amplitude, time, and a derived parameter GxI (the product of acceleration and impact frequency) had a very significant influence on fretting damage, indicated statistically at a confidence level of ninety-nine percent. Although axial play had little effect on fretting damage for the range of axial plays of the test bearings, it had significant effect on the acceleration levels obtained within the bearings. Fretting damage was measured with a bearing torque analyzer. The experimental test vibrations were accurately reproduced on the analog model.