Operational Replication of Strain Responses During MIMO Random Control Tests

The main goal of a successful environmental vibration control test is ultimately to replicate in the laboratory the same load path and stress responses that a test article experiences when subjected to operational vibrations. Poor replications can lead to an unacceptable time to failure estimation for the unit under test and different failure modes. When performing a vibration control test, it is however necessary to deal with the differences between real-life and testing boundary conditions and excitation mechanisms. In case of in-flight random vibration environments, these differences become particularly critical due to the distributed nature of the aerodynamic loads. Multi-input multi-output (MIMO) random vibration control is a technology that allows to explore new possibilities for the replication of these environments. With MIMO random control, it is possible to increase the number of inputs and the number of acceleration control channels on the structure; when combined with the operational impedance matching, the approach can lead to an optimal replication of the in-service acceleration responses. The main goal of this work is to show a new possibility in the MIMO random control testing practice: simultaneous control of multiple strain responses. The underlying idea is to directly target the replication of stress propagation mechanisms while making use of the well-known advantages of MIMO random control.