Structural acoustic response of finite rib-reinforced plates

Abstract

The structural acoustic response of finite fluid-loaded flat plates with arbitrary attached rib stiffeners was formulated. The ribs were modeled as simple inertial reactions providing transverse forces to the plate structure. The plate response and the surface acoustic pressure distribution were written as expansions in terms of the in vacuo plate eigenfunctions. The expansion coefficients were obtained by solving a set of simultaneous complex linear algebraic equations. Results were obtained for an unribbed steel plate, and for a steel plate with a set of uniform ribs, in response to harmonic line-force excitation. The results demonstrated the potential for significant reductions in the vibration level by approximately 90% at certain frequencies because of the presence of the attached ribs. These reductions were attributed to the interaction of two nearly resonant modes in a ‘‘beating’’ phenomenon. It was shown that this ‘‘beating’’ arises because of the presence of the ribs. In order to quantify this effect, a quantity called the ‘‘rib function’’ was defined and was shown to be dependent upon the rib masses, their locations, and the in vacuo mode shapes.