A shaker can be used to simulate launch vibrations and check responses of structures forced at different frequencies. When vibrating at certain frequencies during tests, structural modes of the shaker table itself can cause the test to abort by accelerating too much or by pushing too much electrical gain through the system. Furthermore, structural modes can produce misleading data at these modal frequencies and cause the test article to be under-tested or over-tested. A modal roving hammer test of the horizontal shaker table is conducted to characterize these modes of the shaker table. Two cases were tested in an attempt to simulate the boundary condition of the table on the shaker: free-free and free-fixed. The free-free case revealed a stretching mode at 1334.2Hz while free-fixed showed two stretching modes at 576.7Hz and 1372.3Hz. A subsequent vibration test revealed controlling 20in from the shaker attachment point best controls these modes without drastically over-testing or under-testing.
Mechanical Engineering and Material Sciences Independent Study
Date of Submission
Mincks, Brian and Peters, David, "Modal Analysis and Vibration Test of NASA MSFC Shaker Table" (2018). Mechanical Engineering and Materials Science Independent Study. 81.