APPLICATIONS NEWS

Air Force feels good vibrations with LMS

25 June 2008



The Brazilian Institute of Aeronautics and Space (IAE), is deploying LMS Test.Lab testing systems and LMS Virtual.Lab simulation software to better identify critical vibration modes on ground vibration tests (GVT).

Implementation, applications assistance and on-going technical support services are being provided by LMS regional representative SMARTtech, which was instrumental in securing the contract for LMS International.

In efforts to increase safety and improve pre-test predictive capabilities, IAE (one of the research organisations of the Brazilian Air Force) plans to use advanced LMS technology to identify the dynamic behaviors of aeronautical and aerospace structures investigated.

IAE researchers typically predict resonant frequencies of structures using finite-element models updated with frequency response function (FRF) measurement data. In the LMS implementation to improve this process, IAE will use LMS Virtual.Lab simulation software at the pre-test stage to accurately identify critical points of measurement, and subsequently to correlate and update the analysis models. LMS Test.Lab will be used by researchers in performing experimental modal analysis post-processing. The measurements are acquired by a 112-channel LMS SCADAS III front-end with built-in versatile LMS signal-conditioning capabilities.

The system includes LMS PolyMAX, a modal parameter estimator that quickly highlights resonances as coloured spikes on amplitude versus frequency plots, allowing researchers to spot Eigen frequencies in seconds instead of spending hours pouring through raw FRF data.

Automation of this task saves time, yields more consistent results and enables engineers to easily spot resonances that otherwise might not be readily identified. ‘LMS PolyMAX saves a significant amount of time and enables us to identify vibration modes that previously might have gone undetected with our former manual methods,’ said Dr Everaldo Barros, manager of the IAE Experimental Modal Analysis Test Group. ‘This allows us to more closely correlate test measurements with analysis predictions in updating the mathematical models. When applying LMS Test.Lab and LMS Virtual.Lab, our productivity is increased, the engineering group has greater confidence in the results and the system added considerable value in reaching higher analysis accuracy in our projects.’

LMS was able to cover all the functional requirements with a single integrated solution. This enables IAE to establish a unified approach in identifying modal frequencies in the investigated structures and updating the analysis models. ‘LMS came up with the most advanced tools and best integrated process solution in addressing the challenge of structural dynamics for our aerospace applications,’ Barros added.

‘The integration of these technologies into a unified system allows us to efficiently prepare test campaigns, perform the data acquisition with high number of channels, adequately cover all the various excitation modes, accurately identify resonances and easily compare them with those predicted by the FE model. Overall, LMS has enabled us to significantly increase the precision of our mathematical predictions in aerospace applications where accuracy is an absolute must.’

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