Component replacement TPA: A transmissibility-based structural modification method for in-situ transfer path analysis

In-situ transfer path analysis is a diagnostic method used to analyse the propagation of noise and vibration through complex built-up structures. Its defining feature is the independent characterisation of an assembly’s active components (i.e. vibration sources) by their blocked forces. This independent characterisation enables the downstream structural modification of an assembly without affecting the sources’ operational characteristics. In practical engineering structures, however, there is often a need to alter or replace components that reside within a vibration source, for example resilient mounts. An upstream structural modification of this sort would alter the blocked force and thus invalidate any response predictions made thereafter. Hence, an alternative approach is required. In the present paper a transmissibility-based structural modification method is introduced. We derive a set of equations that relate the blocked force and forward transfer functions obtained from an initial assembly, to those of an upstream modified assembly. Exact formulations are provided, together with first and zeroth order approximations for resiliently coupled structures. These component replacement expressions are verified by numerical examples.