CHARACTERIZATION OF SHAKER TEST FOR ENVIRONMENTAL TEST

Transcription

1 CHARACTERIZATION OF SHAKER TEST FOR ENVIRONMENTAL TEST Washington de Lima, PhD Melanie N. Ambrose National Security Campus operated by Honeywell FM&T June, Spacecraft and Launch Vehicle Dynamic Environments Workshop The Department of Energy s National Security Campus is operated and managed by Honeywell, LLC under contract number DE-NA

2 NSC PDRD Project Experimental characterization and simulation of system for shock and vibration environmental test The focus of this presentation is on experimental characterization of random vibration system Honeywell, LLC manages and operates the Department of Energy s National Security Campus under contract DE-NA

3 NSC E-lab Shakers Characterization Characterize the shakers at NSC E-lab driver voltage consumption metric for spatial variation shaker-to-shaker variation NSC E-lab Shakers Characterization tools Driver voltage of single point control on the center of empty shaker. Operational deflection shape (ODS) on the surface of an empty shaker Operational deflection shape (ODS) on the top surface of a shaker adapter Operational deflection shape (ODS) on the top of slip table connected to shaker 2 Test Spec => Workmanship Random (0.001 g 2 /Hz from 10Hz to 4000Hz) Four shakers (UD T2000) were tested : shakers 1,2 and 3 are 1.5 inch stroke limit and shaker 4 is 3 inch stroke limit 1/15/15 Washington de Lima 3

4 Driver Voltage [V^2/Hz] E-08 1E-09 Driver Voltage Empty Shaker shaker1 [ Vrms = 0.22V] shaker2 [ Vrms = 0.29V] shaker3 [ Vrms = 0.20V] shaker4 [ Vrms = 0.36V] Empty Shaker Test Armature Resonances Small shaker-to-shaker variation Frequency [Hz] Region difficult to control High shaker-to-shaker variation Higher shaker-to-shaker variation is presented in frequency range above 2kHz with substantial variation above 3kHz. There are tests that will not run because the maximum driver voltage will be reached due to the high peak values between 3.5 to 4.0 khz. The peaks at the driver voltage may be stressing the shaker amplifier and reducing life of shaker armature 1/15/15 Washington de Lima

5 Driver Voltage Empty Shaker Mode Shape at 2064 Hz Armature Resonance Mode shape at 3560Hz localize motion at coil Nodal surface at the shaker table at 3500 Hz range 1/15/15 Washington de Lima

6 ODS Empty Shaker Control accelerometer is at center armature [ ]. The response acceleration was measured in all other 28 shaker point connections [ ] using LMS TestLab The ODS calculates the motion of all shaker point connection [ ] relative to motion of control accelerometer [ ] Envelope FRF quantifies the spatial variation EEEEEEEEEEEEEEEE FFFFFF = 11 pppppppppppp mmmmmmmm wwwwwwww cccccccccccccc 11 pppppppppppp mmmmmmmm iiiiiiiiiiiiiiiiiiiiiiiiii oooo tttttt cccccccccccccc 1/15/15 Washington de Lima 6

7 ODS Empty Shaker (Cont.) Envelope FRF] Hz FRF Shaker Hz Frequency Hz ODS at 270 Hz ODS at 3500 Hz Similar result for all other four shakers 1/15/15 Washington de Lima 7

8 ODS Empty Shaker (Cont.) Small Spatial Variation High Spatial Variation For all four shakers the response points are in phase with the control up to 2.8kHz Above 2.8kHz the response points are not in phase with control point and there is a great shaker to shaker variation in the FRF behavior 1/15/15 Washington de Lima 8

9 ODS Empty Shaker (Cont.) Off Axis Response Point 37 Control Point Off axis response indicates if the shaker motion is not unidirectional and will transfer energy to the DUT in a direction not specified in the test requirement X and Y axes are off axis directions We present the off-axis responses in the control location [ ] and in a non-controlled point (point 37 ) 1/15/15 Washington de Lima 9

10 ODS Empty Shaker (Cont.) Off Axis Control Location [ ] X Off axis direction Y Off axis direction Z Control direction Point 37 Control Point Minimum off axis response at the control location. Shaker 1 presented off axis response higher than the control response around 3.6kHz 1/15/15 Washington de Lima 10

11 ODS Empty Shaker (Cont.) Off Axis Non Control Location [ ] X Off axis direction at Non- Controlled point Y Off axis direction at Non- Controlled point Z control direction at Non- Controlled point Z Control direction at Control point Point 37 Control Point All four shakers presented off-axis direction response higher than the control direction in frequency range above 2kHz Off-axis may be responsible for crack propagation 1/15/15 Washington de Lima 11

12 ODS in Adapter on Shakers 1. The shaker adapter is a 9 x 9 inch 70lb cube. 2. Measurement at 25 points on top surface adapter and 8 points on the shaker 3. Control location at the center of the adapter top surface. Actual Test Set up LMS Test Lab Mesh Top surface Shaker table 1/15/15 Washington de Lima 12

13 ODS in Adapter on Shakers (cont.) National Nuclear Security Administration Envelope FRF Shaker Hz 270 Hz Frequency[Hz] 270 Hz 3500 Hz The shaker and the adapter move in phase The acceleration of shaker table is much higher than the acceleration of the adapter. Note that the motion is amplified for better visualization. 1/15/15 Washington de Lima 13

14 ODS in Adapter on Shakers (cont.) National Nuclear Security Administration Adapter Torsional Mode Adapter Mode For all four shakers the response points are in phase with the control up to 1.8kHz Above 1.8kHz the response points are not in phase with control point and there is a great shaker to shaker variation in the FRF behavior 1/15/15 Washington de Lima 14

15 ODS in Adapter on Shakers (cont.) National Nuclear Security Administration Off Axis Control Location [ ] X Off axis direction Y Off axis direction Z Control direction Control Point Point 14 Minimum off axis response at the control location. For all four shakers the off axis response at around 700Hz approaches the control response (adapter has a resonance around 700Hz whose participation factor is in x and y direction) 1/15/15 Washington de Lima 15

16 ODS Empty Shaker (Cont.) Off Axis Non Control Location[ ] X Off axis direction at Non- Controlled point Y Off axis direction at Non- Controlled point Z control direction at Non- Controlled point Z Control direction at Control point Control Point Point 14 All four shakers presented off-axis direction response equal or higher than the control direction in the higher frequency range 1/15/15 Washington de Lima 16

17 ODS in Slip Table on Shaker 2 National Nuclear Security Administration Actual Test Set up Table-shaker connection LMS Test Lab Mesh Z X 1.5 x1.5 grid Y X Y Control location in Y direction 1/15/15 Washington de Lima 17

18 ODS in Slip Table on Shaker 2 National Nuclear Security Administration Y X Control location in Y direction 1/15/15 Washington de Lima 18

19 ODS in Slip Table on Shaker 2 National Nuclear Security Administration Nodes Resonances 1/15/15 Washington de Lima 19

20 ODS in Slip Table on Shaker 2 National Nuclear Security Administration FRF = 1 up to 1685 Hz => the responses points move in phase with control 1/15/15 Washington de Lima 20

21 ODS in Slip Table on Shaker 2 National Nuclear Security Administration 200 Hz 3790 Hz 200 Hz 200 Hz 3790 Hz All response points seems to move in phase with the control location All response points seems to move not in phase with the control location. High level of lateral motion (x and z) 1/15/15 Washington de Lima 21

22 ODS in Slip Table on Shaker 2 National Nuclear Security Administration 1763 Hz 2271 Hz 3790 Hz 1/15/15 Washington de Lima 22

23 NSC E-lab Shakers Characterization Conclusion Higher shaker-to-shaker variation is presented in frequency range above 2kHz with substantial variation above 3kHz. The off-axis response can be higher than the control response in the frequency range above 2kHz. Envelope FRF can be used as simple quantification of the spatial variation. There will be 4kHz tests that will not be able to run since it will reach the maximum driver voltage of the control. Some random test will need to use limit channel capability. 1/15/15 Washington de Lima

24 Armature Crack Creation and Propagation 1/15/15 Washington de Lima 24

25 Armature Modes (FEM) and Possible scenario for crack propagation National Nuclear Security Administration Goals : Answer the question: How a 4kHz random test can create a crack in the armature? 1/15/15 Washington de Lima

26 Armature Modes (FEM) and Possible Scenario for crack Propagation Armature Crack 1/15/15 Washington de Lima

27 Armature Modes (FEM) and Possible Scenario for crack Propagation Mode at 2064 Hz Armature Resonance Mode shape at 3560Hz localize motion at coil At frequency range above 3.5kHz the modal shapes have high lateral motion and lower axial motion 1/15/15 Washington de Lima

28 Armature Modes (FEM) and Possible Scenario for crack Propagation Mode shape at 3560Hz localize motion at coil Mode shape at 3675Hz localize motion at coil At frequency range above 3.5kHz the modal shapes have high lateral motion and lower axial motion 1/15/15 Washington de Lima

29 Off Axis Response X Off axis direction at Non- Controlled point Y Off axis direction at Non- Controlled point Z control direction at Non- Controlled point Z Control direction at Control point Point 37 Control Point High off-axis response (measured I the shaker table) at frequency range above 2kHz 1/15/15 Washington de Lima 29

30 Possible Scenario for Crack Propagation National Nuclear Security Administration ODS shows that there is high off axis motion above 2kHz on the shaker table FEM shows that there are a lot of modes above 2 khz with high off axes motion on the bottom of the armature (coil) Possible Scenario An event (over stroke limit shocks, armature was dropped) created a notch on the bottom of the armature creating stress concentration Crack Initiator High off-axis motion above 2 khz accelerated the propagation of the crack 1/15/15 Washington de Lima

31 Conclusion It looks like an event (unrelated to 4kHz) created a notch on the bottom of the armature (coil) and the notch (tip stress concentration) initiated the crack propagation. The FEM suggests that at high frequency (above 2 khz) if the armature table(top of the shaker) shows off-axis response then the armature coil (bottom of the armature) will have off-axes response too, and it will be higher than the off-axes response of the armature table. The data so far suggest that 4kHz tests do not create a crack in the armature but it will contribute to the crack propagation and consequently the shaker will fail. A test below 2kHz may not contribute to the propagation of the crack even if a notch is created in armature No information (data) that explains the relation between amplifier failure and armature crack. 1/15/15 Washington de Lima