Applications of Holography to Dynamics: High-Frequency Vibrations of Plates

The techniques of holographic interferometry are applied to study the high-frequency transverse vibrations of a simply supported rectangular plate. Over 110 vibration modes were identified using stored beam holography, at frequencies ranging from 162 cps to 20,000 cps. In addition, three very high modes were identified at frequencies up to 76.8 kcps. The corresponding modal numbers were m = 17, n = 31, for the highest mode identified. Time average holograms were made of these and other modes, and photographs made from the holograms are included herein. The experimental mode shapes and frequencies were generally in agreement with classical plate theory, except for the three highest modes. The latter agreed with Mindlin’s plate theory, which includes rotary inertia and shear effects. Other applications of holography to dynamics are briefly discussed.