High Cycle Fatigue & Spin Pit Testing

SPONSOR: Naval Air Warfare Center ­ Aircraft Division

The laboratory's four foot diameter spin pit has been reactivated to perform high cycle fatigue tests for the Air Force and Navy. The pit can be induction heated and will be used to test various blade excitation devices as part of the HCF initiative.

The first test article (the previously tested M1 fuel-pump turbine rotor) was prepared for hanging in the pit. The control system and drive turbine were also overhauled as part of the refurbishment of the facility.

The M1 fuel-pump turbine rotor was successfully tested up to 8,000 rpm. Rotor shaft displacements and phasing measurements were obtained successfully, and orbital plots observed and recorded using a four-channel computer oscilloscope. Following the initial tests were a series of tests on the Vavra designed transonic fan, which was instrumented with strain gages and excited with both air jets and magnets in the vacuum spin pit. The magnetic blade excitation and non-contact blade vibration measurements were performed by Hood Technology. Fundamental vibrational frequencies were measured, and correlated to those determined by a finite-element modal analysis using ANSYS.

Future test articles are a turbine test rotor, whose blades have internal dampers and integrally bladed titanium fan rotor which is three feet in diameter. Both test articles are designed and built by Pratt & Whitney.