Paper: Resonance Tracking of Nonlinear Structures by Amplitude Controlled Sine-Dwell Testing

Abstract

Sine-dwell testing is a common methodology in high cycle fatigue (HCF) testing. During a sine-dwell test the structure is excited with a single sine tone exactly at a resonance frequency until structural failure or sufficient time/cycles passed. When the resonance frequency shifts due to accumulated damage or temperature changes the controller tracks the resonance frequency by adjusting the drive frequency to maintain a defined phase relation between two channels.

Nonlinear systems are known to have modal parameters varying with the excitation amplitude. The evolution of the resonance frequency over the excitation level is often referred to as the backbone-curve of a system. Backbone-curves can provide useful insights into the physical mechanisms involved in the nonlinearity.

For many nonlinear structures, the backbone-curve can be experimentally determined using the sine-dwell method combined with amplitude control. In this approach, the resonance frequency is tracked as the excitation level is increased step by step.

This iterative phase control technique is an extension of traditional sine-dwell testing and is now available in the latest m+p VibControl software. It allows test engineers to better understand the nonlinear behavior of structures using familiar technology.