Sigma Limiting Effects on the Response of a Ceramic Matrix Beam

High sigma events were studied in the narrowband random response of a cantilevered beam excited by an electrodynamic shaker. The effects of truncating the input signal to the shaker with a BlackglasTM beam are discussed. Tests were conducted with the shaker option of the shaker controller sigma limiting turned off, sigma limited to 2.5, and sigma limited to 3.5. Large data files were recorded and analyzed. The results were compared with similar previous tests with an aluminum alloy beam. The sigma values calculated varied considerably with the record lengths. When a fatigue failure was assumed, the cumulative fatigue damage was computed as a function of the sigma value of the response peak probability density function. Very little damage was found for the high sigma peaks compared to the damage that occurred with the many smaller peaks.