Abstract
Premature cracking of the first stage turbine blades in the HPFTP of the SSME have caused greater than expected repair costs. It is expected that the operational life of these blades can be extended by redesigning the platform friction dampers that are used to reduce the vibration response of the blades. Vibratory excitation of the resonance modes of the blades is induced by their passage through the wakes of the front bearing support struts and the first stage nozzles of the turbopump. Analytical studies, by the lumped mass method, of friction damper effectiveness, and spin pit tests of a bladed disk have been performed. Test blades were instrumented with strain gauges and were excited magnetically. Methodologies used in the program are described. Preliminary results show that the effectiveness of the blade platform dampers can be increased if the frequency and amplitude of the most damping forcing functions (s) can be defined. [Work sponsored by Marshall Space Flight Center of NASA.]
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