Modeling vibrational energy transmission at bolted junctions between a plate and a stiffening rib.

An analytical model is presented for structure-borne sound transmission at a bolted junction in a rib-stiffened plate structure. The model is based on the wave approach for junctions of semi-infinite plates and calculates coupling loss factors required by statistical energy analysis. The stiffening rib is modeled as a plate strip and the junction is represented by an elastic interlayer with a spatially dependent stiffness. Experimental verification is carried out on a series of Plexiglas plate structures with varying rib depth and bolt spacing. A well-defined connection length at the junction was created by inserting thin spacers between the plate and the rib at each bolt. Comparison between numerical and experimental data for this case showed good agreement. Measured results for the bolted junction without spacers suggested that structure-borne sound transmission could be modeled as a series of connections characterized by a finite connection length. This concept is explored further by determining an equivalent connection length which gives the best agreement between numerical and experimental data.