Experimental Investigation of Al -Thin Shells Subjected to Random Vibrations

Experiments were conducted to obtain the modal damping ratios of two hollow cylinders of different thicknesses of Aluminum. An electro dynamic exciter with slip table is used to excite the hollow cylinders. The hollow cylinder (unit under test) is fastened to the exciter. The exciter is placed in the horizontal direction and connected to the slip table. A control accelerometer is placed at the bottom of the cylinder and a measured accelerometer is placed at the top of the cylinder. A control acceleration spectrum is applied at the base of the cylinder to obtain the response power spectrum at the tip. Charge type accelerometers (B&K 4383) are used to measure the acceleration responses along with the signal conditioners (B&K 2635). A lid is fasted to the cylinder to avoid the spilling of the water on the slip table. Tests are performed at different water levels in each cylinder. From each test, half power method is used to estimate the modal damping