FIRST WORKSHOP. Airbus A320 Main Landing Gear Door Ground Vibration Testing. Delft, September 10, 2015 Presenter: Pascal Lubrina (ONERA)

Transcription

1 FIRST WORKSHOP Airbus A320 Main Landing Gear Door Ground Vibration Testing Delft, September 10, 2015 Presenter: Pascal Lubrina (ONERA)

2 Airbus A320 Main Landing Gear Door Ground Vibration Testing Pascal Lubrina ONERA Aeroelastic and Structural Dynamics Department 2

3 Summary 1. Generalities Why a Ground Vibration Test of an aircraft? Why a Main Landing Gear Ground Vibration Test in AFLoNext? 2. Tests specifications 3. GVT Means, Measurements and Methods 4. Results 5. Conclusions 3

4 Why a Ground Vibration Test of an aircraft? Typically, the GVT of a complete aircraft is realized on the prototype before its 1 st flight. The objective of such non destructive test is to deliver the structural dynamic parameters (resonance frequencies, mode shapes, structural damping coefficient, modal masses ) necessary to - anticipate the aeroelastic stability, warn and prevent the aircraft from flutter risks - update the mathematical model of the aircraft (Finite Element Model) to be used for aeroelastic stability, loads predictions, passenger comfort, sustained engine imbalance risks NH90 (1996) A (2005) A350 XWB 900 (2013) A320 Neo (2014) UAV Sagem (1998) WT model (1999) Fan blade (2006) 4

5 Why a Main Landing Door GVT in AFLoNext? AFLoNext WP3 Technical Context : The main landing gear doors of aircraft as civil Airbus can be damaged during operations due to unsteady aerodynamic high level excitations from vortex generated by the Nose Landing Gear deployed with possible amplifications due to cavity resonances of the volume liberated by the Main Landing Gear when extended. FOI computation AFLoNext WP3 Objective : To improve the unsteady aerodynamic and structural dynamic knowledge to predict the structural behavior of the future main landing gear doors. To make safer structural designs and easier aerodynamic and/or structural modifications Objective of the Main Landing Gear Door GVT : To deliver the partners with the experimental modal analysis of the MLG door for updating the FEM (Finite Element Model). This updated structural mathematical model being propitious to improve the predictions of the vibratory responses. 5

6 Test specifications Aircraft concerned : the Airbus A320 'ATRA' owned by DLR, on nominal pressure tire conditions on ground (no specific soft suspension) Location of the GVT : DLR facilities in Braunschweig Period of the GVT : April 2015 GVT duration : 5 working days MLG door concerned : the left hand side MLG door Right hand side MLG door closed (thanks to adaptation on the green circuit and serious preparation work by Airbus, its assistances and DLR Braunschweig) General view GVT measurement site 6

7 GVT Equipments : Sensor installation Main Sensors = 90 mono axial accelerometers 19 sites on MLG door and immediate vicinity 9 sites on aircraft 3 mono-axial accelerometers / site + others sensors/signals as 1 strain gauge, 2 forces sensors Accelerometers on the MLG door and immediate vicinity Accelerometers sites on the aircraft 7

8 GVT Equipments : Exciter installations fixed by Airbus : Max Force level 150N and max accelerations not to overpass (6 g and 51 g) Y Lateral excitation Z bottom excitation X bottom excitation Test equipment intrusiveness (mass of sensors, mass and stiffness of the coil of the shaker ) are known or measured. This must be considered in the FEM updating task (mass of the door ~50 kg) Acquisition system: LMS Scadas III with V12L modules Second acquisition systems used to monitor the vibration cycles 8

9 GVT Equipments : Bungee installation Why installing a bungee? To vanish as far as possible the backlash (free-play) then : - Reducing the impact of strong non-linear behavior - Making easier (conform to the standard linear theory) the modal identification Remarks: - the bungee must be as flexible as possible not to impact the resonance frequencies of the modes - in flight, the static aerodynamic forces block the free-plays - in the FEM available there is no free-play characteristics: 1 long rope f 9 mm 6,0 m long + 50% extension 21 N/m stiffness Harm level for the attachment of a long flexible bungee View of the bungee in between the MLG door and a heavy structure 9

10 GVT Measurements and Methods Excitations Lateral near actuator attachment PRM swept sine Conf psi "1st mode" - 6 Force levels "2nd mode" - 5 Force levels "5th mode" - 6 Force levels [150 Hz : 5 Hz] - 3 Force levels Conf psi "1st mode" - 5 Force levels "2nd mode" - 3 Force levels Conf 2 0 psi "1st mode" - 3 Force levels "2nd mode" - 3 Force levels Vertical Bottom PRM swept sine "3rd mode" - 6 Force levels "4th mode" - 5 Force levels "6th mode" - 5 Force levels [150 Hz : 15 Hz] - 3 Force levels "3th mode" - 3 Force levels "3th mode" - 3 Force levels X Bottom PRM "2nd mode" - 1 Force level swept sine [150 Hz : 15 Hz] - 3 Force levels New Lateral rear part of the door PRM swept sine looking for add. Torsion mode No add. Torsion mode observed [150 Hz : 48 Hz] - 1 Force level PRM : Phase Resonance Method (Modal Tuning or Appropriation) from stabilized sine excitations PSM : Phase Separation Method (here Polymax) from swept sine excitation runs 10

11 Videos Y Lateral excitation of the 1 st mode 11

12 Videos X bottom excitation of the 2 nd mode Low motion effect due to the ~25 Hz of the mode = 1/16 x 400Hz record freq of the camera 12

13 Results : Comparative Table damping coef. damping coef. freq. freq. freq. FEM PRM CONF1 PSM Selection CONF1 1 13,60 Hz 1 8,60 Hz 5,69% 1 8,47 Hz 5,76% 2 25,69 Hz 2 23,69 Hz 5,23% 2 23,95 Hz 3,95% 3 27,47 Hz 0,98% 4 61,91 Hz 3 42,15 Hz 2,56% 4 43,41 Hz 3,65% 5 44,78 Hz 1,43% 6 51,60 Hz 6,01% 7 53,15 Hz 3,67% 3 40,47 Hz 8 54,63 Hz 3,16% 9 59,04 Hz 3,68% 10 66,60 Hz 4,98% 11 68,46 Hz 4,29% 12 70,55 Hz 2,19% 13 76,31 Hz 2,06% 4 88,59 Hz 4,33% 14 92,81 Hz 4,16% 5 103,15 Hz 15 98,23 Hz 3,51% ,13 Hz 3,40% ,67 Hz 1,65% 6 109,38 Hz 5 107,56 Hz 3,16% ,53 Hz 2,98% ,11 Hz 3,06% ,37 Hz 3,99% 7 121,45 Hz 8 137,79 Hz 6 142,32 Hz 2,38% ,41 Hz 1,67% ,53 Hz 1,00% 0 Hz 20 Hz 40 Hz 60 Hz 80 Hz 100 Hz 120 Hz 140 Hz 160 Hz FEM PRM PSM 13

14 Results : Comparisons Mode comparisons by MAC Modal Assurance Criteria MAC = 1 (red columns) for strictly identical mode shapes This mode identified at 27,47 Hz not tuned by PRM but from swept excitation runs (PSM) CrossMAC between the 6 PRM modes and the 10 FEM modes CrossMAC between the 6 PRM modes and the 22 PSM modes 14

15 Results : Vibration modes from PRM and PSM Selected Mode shapes 3D plots 15

16 Results : Vibration modes from PRM and PSM Selected Mode shapes 3D plots 16

17 Results : Vibration modes from PRM and PSM Selected Mode shapes 3D Animation 17

18 Results : Participation of the aircraft in the modes max(ac) / max(mlgd) max(near MLGD- AC) / max(mlgd) freq. freq. freq. FEM PRM CONF1 PSM Selection CONF1 max(ac) / max(mlgd) max(near MLGD-AC) / max(mlgd) 1 13,60 Hz 1 8,60 Hz 3,9% 1,0% 1 8,47 Hz 0,9% 2,5% 2 25,69 Hz 2 23,69 Hz 1,0% 2,4% 2 23,95 Hz 0,3% 2,7% 3 27,47 Hz 3,0% 7,2% 4 61,91 Hz 3 42,15 Hz 1,1% 1,9% 4 43,41 Hz 1,7% 3,0% 5 44,78 Hz 1,3% 6,1% 6 51,60 Hz 6,6% 11,8% 7 53,15 Hz 5,1% 19,8% 3 40,47 Hz 8 54,63 Hz 3,6% 14,8% 9 59,04 Hz 3,9% 17,0% 10 66,60 Hz 8,1% 15,4% 11 68,46 Hz 4,6% 24,0% 12 70,55 Hz 5,9% 8,7% 13 76,31 Hz 9,6% 23,2% 4 88,59 Hz 0,3% 3,1% 14 92,81 Hz 0,8% 3,5% 5 103,15 Hz 15 98,23 Hz 1,0% 7,0% ,13 Hz 0,6% 7,0% ,67 Hz 1,7% 11,6% 6 109,38 Hz 5 107,56 Hz 0,4% 4,6% ,53 Hz 0,6% 6,2% ,11 Hz 1,8% 24,5% ,37 Hz 1,3% 18,2% 7 121,45 Hz 8 137,79 Hz 6 142,32 Hz 0,5% 7,2% ,41 Hz 1,2% 10,4% ,53 Hz 10,3% 57,5% 18

19 Bottom X excit. Resonance Frequency Lateral excit. Results : Vibration modes tuned (PRM) Linearity plots (dependencies with Excitation Forces) The 6 modes tuned for diff. force levels AFLONEXT WP322 - MLG Door GVT - CONF psi 160 Hz 140 Hz 6th mode 5th mode 4th mode Bottom Z excit. 120 Hz 100 Hz 80 Hz 3rd mode 2nd mode 1st mode Lateral excit. Bottom Z excit. Bottom Z excit. 60 Hz 40 Hz Bottom Z excit. Bottom X excit. 20 Hz 0 Hz 0 W 1 W 10 W 100 W Excitation Power (W) Lateral excit. Lateral excit.

20 Structurlal Damping Coefficients Results : Vibration modes tuned (PRM) Linearity plots (dependencies with Excitation Forces) The 6 modes tuned for diff. force levels AFLONEXT WP322 - MLG Door GVT - CONF psi 7,0% 6,0% 5,0% 4,0% 6th mode 5th mode 4th mode 3rd mode 2nd mode 1st mode 3,0% 2,0% 1,0% 0,0% 0 W 1 W 10 W 100 W Excitation Power (W) 20

21 Resonance Frequency Stuctural Damping Coefficient Results : Vibration modes tuned (PRM) Linearity plots (dependencies with Excitation Forces) AND Actuator pressures The 1 st mode tuned ("MLG dor rotation") AFLONEXT WP322 MLG Door GVT - 1st mode AFLONEXT WP322 MLG Door GVT - 1st mode 9,0 Hz 8,5 Hz 8,0 Hz 3000 psi 1500 psi 0 psi 10,0% 9,0% 8,0% 7,0% 6,0% 3000 psi 1500 psi 0 psi 7,5 Hz 5,0% 7,0 Hz 4,0% 3,0% 6,5 Hz 2,0% 1,0% 6,0 Hz 0 W 1 W 2 W 3 W 4 W 5 W 6 W Excitation Power (W) 0,0% 0 W 1 W 2 W 3 W 4 W 5 W 6 W Excitation Power (W) 21

22 Resonance Frequency Stuctural Damping Coefficient Resonance Frequency Stuctural Damping Coefficient Results : Vibration modes tuned (PRM) Linearity plots (dependencies with Excitation Forces) AND Actuator pressures The 2 nd and 3rd modes tuned AFLONEXT WP322 MLG Door GVT - 2nd mode AFLONEXT WP322 MLG Door GVT - 2nd mode 26,0 Hz 3000 psi 6,0% 25,5 Hz 1500 psi Série4 5,0% 25,0 Hz 24,5 Hz 24,0 Hz 4,0% 3,0% 2,0% 3000 psi 1500 psi 0 psi 23,5 Hz 1,0% 23,0 Hz 0 W 2 W 4 W 6 W 8 W 10 W 12 W 14 W 16 W 18 W 20 W 0,0% 0 W 2 W 4 W 6 W 8 W 10 W 12 W 14 W 16 W 18 W 20 W Excitation Power (W) Excitation Power (W) AFLONEXT WP322 MLG Door GVT - 3rd mode AFLONEXT WP322 MLG Door GVT - 3rd mode 43,0 Hz 42,5 Hz 3000 psi 1500 psi 0 psi 5,0% 4,0% 3000 psi 1500 psi 0 psi 3,0% 42,0 Hz 2,0% 41,5 Hz 1,0% 41,0 Hz 0 W 10 W 20 W 30 W 40 W 50 W 60 W 70 W 80 W 90 W 100 W Excitation Power (W) 0,0% 0 W 10 W 20 W 30 W 40 W 50 W 60 W 70 W 80 W 90 W 100 W Excitation Force 22

23 Conclusions GVT performed, many data acquired, planning respected, no damage on ATRA, no injurie on people concerned Gap between Experimental results and FEM : Additional flexibilities observed at low frequencies, Additional flexibilities from aircraft not considered in the FEM Low structural dynamic impact of the pressure from 3000 to 1500 psi Intrusivity of the exciter to be considered for excitations introduced at the bottom of the door for modes above 90 Hz FEM updating task potentially difficult??? Reduce the objective of FEM updating (to consider the 1st 3 or 4 modes)??? Additional GVT on another/available MLG door in free-free conditions outlook on Flight vibrations Tests Optimization of accelerometer positions can be established Strain gauge installed on the actuator is OK can be reproduced 23

24 Thank you! For more information : Contact ONERA pascal.lubrina@onera.fr or Contact@AFLonext.eu GVT crew members 24

25 This project has received funding from the European Union s Seventh Framework Programme for research, technological development and demonstration under grant agreement No , AFLONEXT project. 25