A mode count procedure for mid-frequency analysis of complex vibro-acoustic systems

A component mode synthesis based hybrid method for the dynamic analysis of complex systems

“…The limit between the low and the high frequency responses for each sub-structure is defined by the sub-structure high frequency limit that is calculated using an SEA high frequency condition [10]. This leads to the definition of a mode wavelength limit used to classify the set of modes of each sub-structure into global and local modes.…”

“…Some alternatives are used to improve results from SEA or from FEM into the medium frequency range. The hybrid approaches [5][6][7][8]10,16] belong to this group, combining FEM and SEA techniques to solve the mid-frequency problems.…”

“…If the system is characterized by low damping, the mode count N m is found to be a good indicator of the high frequency limit [10,23], as values above a critical mode count (typically 5 modes in the band [3,4]) ensure high values of the modal overlap. In cases of extremely low damping values, the modal overlap should be used as main high frequency parameter, as it constitutes the most restrictive criterion.…”

“…Langley and co-workers [5][6][7][8] have developed a hybrid deterministic-statistical modelling framework in which each sub-structure is defined with a different numerical formulation linked by hybrid junctions, as the ones proposed by Shorter and Langley [7]. Later, it has been shown how the mid-frequency range can be accurately determined from the set of frequencies from which each sub-structure fulfils the SEA conditions [9,10].…”

“…Each sub-structure modal base is sub-divided into a global and a local set of modes, depending on a limit wavelength defined from the sub-structure high frequency limit [10]. Global modes are those whose associated wavelengths are longer than this limit wavelength.…”