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Summer Students 2007 Student Session. Experimental Modal Analysis of the CMS Beam Pipe. Etienne Castanié. Experimental Modal Analysis of the CMS beam pipe. The CMS beam pipe Introduction to modal analysis Measurements Analysis Results Conclusion Mechanical Measurement Laboratory.
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Summer Students 2007 Student Session Experimental Modal Analysis of the CMS Beam Pipe Etienne Castanié
Experimental Modal Analysisof the CMS beam pipe • The CMS beam pipe • Introduction to modal analysis • Measurements • Analysis • Results • Conclusion • MechanicalMeasurementLaboratory NO HIGGS NO SUSY
The CMS beam pipe • How will this structure move during LHC operation ? • What is its dynamic mechanical behavior ? Innermost Detector End Cap Pipe HF Pipe CT2 Pipe Beam line Vacuum Chamber IP 5 Central Pipe (Be)
(Basic) Introduction to experimental modal analysis Mode shapes Measurements Time graphs FRF You want to know resonant frequencies, damping and mode shapes of a structure ? Frequency (Hz) Magnitude
Measurements We need: • Some accelerometers (3 here) • A spectrum analyzer • A way to hit the beam pipe Accelerometers
Analysis: Modal parameters estimation Curve Fitting Modal peak function Information about resonant frequencies and damping All the frequency response functions Information about mode shapes ξ3 ξ1 ξ2 Mode shapes Frequency response matrix
Results First bending mode of the entire structure (5Hz) First bending mode of the {End Cap + HF} pipe (47Hz)
Conclusion • 3 kind of mode shapes: • Global (the 3 pipes move together) • Semi-global (2 of the 3 pipes move) • Local (only 1 pipe moves) • About 10 “forbidden frequencies” below 100Hz • Experimental modal analysis consider complex structures • with real mounting conditions or cabling.
Mechanical Measurement Laboratory I have also worked on these projects: ATLAS Pixel Detector (vibration monitoring) Inner Triplets (strain measurements) ATLAS End Cap Toroïd (tilt monitoring) T2K Experiment (modal analysis)
