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Test Module Working Group. Update on the MODAL ANALYSIS of the Test Module supporting system in the LAB. Modal Analysis Report EDMS 1184906: Courtesy of T. Kostamovaara. Strategy. Modal measurements for the supporting system of the Test Modules in the LAB :
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Test Module Working Group Update on the MODAL ANALYSIS of the Test Module supporting system in the LAB Modal Analysis Report EDMS 1184906: Courtesy of T. Kostamovaara
Strategy • Modal measurements for the supporting system of the Test Modules in the LAB: • GOAL: To analyze the modal behaviour of the different configurations of the supporting system (girders, V-shaped supports and cradles) and identify the existing eigenfrequencies of the supporting system sub-assemblies. • Sub-assemblies: • DB V-shaped supports; • MB V-shaped supports; • DB girder with integrated V-shaped supports and cradles assembled, • MB girder with integrated V-shaped supports and cradles assembled. • Methodology: • Accelerometers glued on the supporting components; • Excitation force ( < 50 N) imposed with a special impact hammer (plastic-end tip); • Signal received by the accelerometers and the impact hammer tip and then transmitted to a spectrum analyzer; • Dedicated software interprets and analyses the measurements. • Comparison of: • Preliminary simulation values/modes (EDMS doc : 1083833); • Simulation values/modes (EDMS doc :1098928); • Modal measurements/modes (EDMS doc : 1159189), • Modal measurements/modes (EDMS doc : 1184906).
Testing Configuration Courtesy of T. Kostamovaara Excitation method Accelerometers • The accelerometers were assembled on key positions for the modal measurements so as to identify the modal behaviour or the supporting system components (V-shaped supports, girder, cradles, etc.). Such key points are the 1, 6, 10, 15 and 20 of the figure. DB T-0 (LAB) Girder (Boostec)
Results Courtesy of T. Kostamovaara Rigid body mode: 8 Hz Rigid body mode: 15 Hz Rigid body mode: 19 Hz Rigid body mode: 37 Hz 1st simulated (bending) mode: 50 Hz 2nd mode: 141 Hz 1st (bending) mode: 59 Hz *RIGID BODY MODE: The distance between any two given points of a rigid body remains constant in time regardless of external forces exerted on it.
Results – Conclusions Courtesy of T. Kostamovaara • The simulated 1st and 2nd modal shapes are confirmed by the measurements. • Rigid body modes measured in between 0-50 Hz: Resonance ~50 Hz with smaller damping needs to be avoided. • The alignment plates under the cradles can generate a series of body modes. • Stability could be optimized by rigidifying the alignment plates (e.g. cast them in cement). • Increase the frequency of the 1st bending mode (if needed) by dedicated design optimization of the girder cross section.
Summary and Future steps • Summary of accomplished tasks: • Modal simulation for the Main Beam and the Drive Beam configurations of the LAB; • Modal analysis for the Main Beam and Drive Beam V-shaped supports; • Modal analysis of the sub-assembly of the Drive Beam girder, V-shaped supports and cradles. • Future tasks: • Modal analysis of the sub-assembly of the Main Beam girder, V-shaped supports and cradles; Comments are always welcome!