INTERNAL TRANSFER PATH ANALYSIS BASED ON IN-SITU BLOCKED FORCES AND TRANSMISSIBILITY FUNCTIONS

摘要

Transfer path analysis (TPA) is an established and valuable tool in automotive industry to determine the contributions of structure-borne and airborne sound sources to receiver responses at target positions. The classical TPA approach is based on contact forces at the interface between source and receiver to characterise the dynamic loads induced by the source and frequency response functions (FRFs) to quantify the transfer paths of the sound from the interface locations to the target positions. With knowledge of the determined contributions it is then possible to decide whether source loads or FRFs must be improved to optimise the target quantities. Recently a timesaving improvement to classical TPA has been proposed, where the loads are characterised using the in-situ blocked force method, so that dismantling of source and receiver is not necessary. This method is therefore called in-situ TPA. However, if the contributions of internal structure-borne sound sources to the overall vibro-acoustic behaviour of a product are desired it is of benefit if the target quantities are blocked forces. Thus it would be possible to virtually couple the product with the properties of an overall receiver. Therefore this paper presents a novel TPA approach called blocked force transmissibility TPA. The aim of the presented TPA is to determine the contribution of internal structure-borne sound sources to an overall target quantity of a product. The presented approach uses the vector of blocked forces measured externally at the contact interface of the overall product and a corresponding set of transmissibility functions relating the external coupling degrees of freedom (DOFs) to the internal source DOFs in order to propagate the external blocked forces back to multiple internal blocked forces. To prove the methodology of the presented approach a case study of a beam was carried out experimentally.