Random Decrement Signal Processing of Modal Impact Test Data

Abstract

When performing modal impact tests on mechanical systems many practioners utilize hardware based digital signal processors to rapidly estimate average spectral properties from a set of repeated impact and response time traces. However, if the complete set of time traces is saved as is commonly done when performing impact tests on civil structures then more generalized analysis and triggering conditions can be used to process the dataset. One such more general triggering condition can be referred to as random decrement signal processing. In this paper it is explained and illustrated how random decrement signal processing can be used to accept double hit impact and overlapping responses and it is shown that in many cases, the estimated transfer function are estimated with higher accuracy then using traditional triggering/averaging techniques.