DAMPING AND FATIGUE PERFORMANCE OF ADDITIVE MANUFACTURED PARTICLE DAMPER INFUSED INSTRUMENTATION RAKE

Recently, laser powder bed fusion (LPBF) has been implemented as an enabling technology to create intentional large cavities during the print process to leave behind sections with embedded metal powder to act as particle dampers within the component. This novel application of particle damping has been applied to beam specimens with the additive manufactured (AM) particle damper technology and shown to attenuate resonant excitation and therefore stress in the component by up to 90% when compared to fully fused parts subjected to the same base excitation. More recently however, the AM damping technology has been applied to turbine engine relevant blade and hardware geometries. In this work, the damping and fatigue performance of a representative aerodynamic instrumentation rake are investigated. Four successful builds of the rakes were performed with and without internal pockets as well as with 0- and 45-degree printing orientations. Four internal configurations of the rakes are printed to include a 0:254mm, 0:381mm, 0:508mm, "fully fused" or 0mm pocket thicknesses. Each specimen is first scanned and three dimensionally reconstructed and analyzed to compare the nominal CAD drawing to as-printed and received geometry using blue light and CT scanning. Vibrational tests for the rake specimens are performed on a 20,000lb Unholtz-Dickie shaker and a OFV-505 single-point laser vibrometer and strain gages are utilized to measure the velocity and strain response respectively of the rake specimens. Sine wave down-chirp sweeps are conducted to excite the specimen in a 2nd bend mode to collect amplification and Q factor, or quality factors, to evaluate the damping performance amongst the rakes. Finally, vibration fatigue tests are performed, in the 2nd bend mode, to validate the improved fatigue performance of inherently damped rake components compared to the fully fused control group and demonstrate the novel additive damping technology to a commonly used experimental instrumentation fixture.