Structural Vibration Excitation using Rotating Magnet Arrays
Raytheon Technologies Research Center (RTRC) is Raytheon technologies central research organization. RTRC is located in East Hartford, CT and works in both commercial and government sectors. High cycle fatigue failures is a common issue plaguing jet engines and other aerospace systems. Typically, it requires test duration up towards 10 million load cycles and traditional servo hydraulic load frames operating at 10-20 Hz results in long test durations. It is desirable to develop methods that are capable of operation at 10X or higher frequencies. The team was tasked to design and build a non-contact excitation rig in which a stationary sample can be excited by a rotating magnet array. Magnets will be used as they can provide alternating force, which will provide non-contact excitation. The magnet array needs to be able to induce a vibration with a frequency near the object’s resonance to enable high stress in the material. Strain amplitude has to be accurately controlled through the test. The design uses one half of a magnetic coupling and its embedded permanent magnets which serve as the rotating magnet array. This is rotated by an AC electric motor controlled by LabVIEW. Initial testing had been conducted on a plain beam with a thinned out bending section fitted with a strain gage for stain monitoring through LabVIEW. A hall sensor is mounted near the magnetic coupling to record actual frequency. Utilizing this setup, non-contact fatigue and vibration testing is achieved.