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Vibration Testing Fixtures - The vibration testing blindspot

Presentation at A2LA Tech Forum 2021 by Paragon Systems Testing to answer the why we perform vibration tests, what we need to perform a vibration test, ISO 17025 definition of equipment, how vibration fixture affects a vibration test result and vibration fixture blind spot<br>https://paragonsystems.net/testing-services/vibration-fixtures-manufacturer/<br>

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Vibration Testing Fixtures - The vibration testing blindspot

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  1. Vibration Testing Fixtures The Vibration Testing Blindspot Tony Araujo – Paragon Systems Testing August 2, 2021

  2. If you see this icon… It means that the information on this slide could be REALLY important. Take a picture so you can keep it for future reference! 2 Navigating the waters of accreditation

  3. Visit to see our mobile App! 3 Navigating the waters of accreditation

  4. Agenda • Why do we perform vibration testing? • What do we need to perform a vibration test? • ISO 17025 definition of “Equipment” • Can a vibration fixture affect a vibration test result? • The vibration fixture blind spot • Conclusions • Questions/Comments 4 Navigating the waters of accreditation

  5. Why Do We Perform Vibration Testing? “The vibration test is designed to simulate the vibration damage that the DUT will experience during its life time.”* *Hunter, N.F., “Vibration Testing – Reviewing the State of The Art-Prospects and Challenges”, Proceedings of the SD 2000 Conference LA-UR-99- 3413 06/23/99 5 Navigating the waters of accreditation

  6. Why Do We Perform Vibration Testing?  Engineering development  Component selection  Design verification  Failure modes  Reliability qualification  Warranty  Recalls  Liability 6 Navigating the waters of accreditation

  7. What’s Required to Perform a Vibration Test? • Actuator • Produces mechanical oscillation • Power Amplifier • Supplies electrical energy to drive the shaker • Accelerometer • Measures the output from the shaker • Controller • Takes accelerometer signal and regulates output from amplifier • Vibration Fixture • Attaches DUT to shaker 7 Navigating the waters of accreditation

  8. What’s Required to Perform a Vibration Test? • Test method • What is the test environment? • Tolerances? • The device which requires a vibration test (DUT) 8 Navigating the waters of accreditation

  9. ISO 17025 Definition of “Equipment” 6.4.1 The laboratory shall have access to equipment (including, but not limited to, measuring instruments, software, measurement standards, reference materials, that is required for the correct performance of laboratory activities and that can influence the results. 9 Navigating the waters of accreditation

  10. ISO 17025 Definition of “Equipment” In the vibration testing context what can “influence results” is commonly interpreted to mean Controller accuracy Accelerometer accuracy 10 Navigating the waters of accreditation

  11. ISO 17025 Definition of “Equipment” 6.4.4 The laboratory shall verify that equipment conforms to specified requirements before being placed or returned into service. 6.4.5 The equipment used for measurement shall be capable of achieving the measurement accuracy and/or measurement uncertainty required to provide a valid result 11 Navigating the waters of accreditation

  12. ISO 17025 Definition of “Equipment” 1 What “specified requirements” or “measurement accuracy” are we trying to achieve? Typically +/- 3dB allowing for the instrument error* 0.1 PSD (g²/Hz) 0.01 0.001 0.0001 10 100 1000 *IEC 60068-2-64 Part 2, Environmental Testing, Test Fh: Vibration, broad-band random (digital control) and guidance, Section 4.3.4 Vibration Tolerance Frequency (Hz) 12 Navigating the waters of accreditation

  13. ISO 17025 Definition of “Equipment” Frequently confirmation of the +/- 3dB tolerance is interpreted as having being achieved if the vibration test level is within this tolerance on the shaker test surface 13 Navigating the waters of accreditation

  14. ISO 17025 Definition of “Equipment” IEC 60068-2-64 Environmental Testing Part 2 Test Fh: Vibration, broad-band (digital control) and guidance The required characteristics apply to the complete vibration system, which includes the power amplifier, vibrator, test fixture, specimen and control system when loaded for testing. 14 Navigating the waters of accreditation

  15. Can a vibration fixture affect a vibration test?  Absolutely!  All vibration energy enters the DUT through the vibration fixture.  Depending on the fixture resonant performance or the vibration control method used, the DUT can be tested well outside of the control profile tolerance.  The DUT “shall be mechanically connected to the mounting surface either directly or by means of a rigid test fixture… or as stated in the relevant specification.”* *IEC 60068-2-47 Tests – Mounting of specimens for Vibration, Impact and Similar Dynamic Tests, Section 6 Mounting, where the specimen is equipment and other articles. 15 Navigating the waters of accreditation

  16. Can a vibration fixture affect a vibration test? Vibration fixture experiment DUT 4U Rackmount chassis (19” rack) Test Profile ISO 16750-3 Test IV – Passenger Car, Sprung Masses (Vehicle Body) reduced to -6 dB (10 Hz to 1,000 Hz) to 1.5grms; Z-axis only tested for brevity Vibration Monitoring Locations External - Vibration table surface, DUT Mounting Flange, Internal - HDD and Power Supply 16 Navigating the waters of accreditation

  17. Can a vibration fixture affect a vibration test? Vibration fixture experiment DUT Mounting Methods 1. Simple sandwich clamp to vibration table surface (Condition 1) 2. Qualified vibration fixture simulating actual DUT installation method Condition 2A & 2B) 17 Navigating the waters of accreditation

  18. Can a vibration fixture affect a vibration test? Vibration fixture experiment DUT Mounting Methods 1. Simple sandwich clamp to vibration table surface (Condition 1) 2. Qualified vibration fixture simulating actual DUT installation method Condition 2A & 2B) 18 Navigating the waters of accreditation

  19. Can a vibration fixture affect a vibration test? Vibration fixture experiment Control Strategies 1. Accelerometer mounted to vibration table surface (Condition 1 & 2A) 2. Multi-point averaging with accelerometers mounted to vibration table surface + mounting flange of DUT (Condition 2B) Vibration Table Surface 19 Navigating the waters of accreditation

  20. Can a vibration fixture affect a vibration test? Vibration fixture experiment DUT Mounting Flange Control Strategies 1. Accelerometer mounted to vibration table surface (Condition 1 & 2A) 2. Multi-point averaging with accelerometers mounted to vibration table surface + mounting flange of DUT (Condition 2B) Vibration Table Surface 20 Navigating the waters of accreditation

  21. Can a vibration fixture affect a vibration test? Experiment Setup (Fixtured) 21 Navigating the waters of accreditation

  22. Can a vibration fixture affect a vibration test? Vibration fixture resonant performance 6.0 • Control on vibration table surface; fixture monitored adjacent to flange mount. • 0.5g sine sweep • Two resonances evident, one at 444 Hz and a second at 489 Hz. • Presence of a third resonance just beyond 1,000 Hz 5.0 Control (g) Acceleration (g) Fixture (g) 4.0 3.0 2.0 1.0 0.0 10 100 1000 Frequency (Hz) 22 Navigating the waters of accreditation

  23. Can a vibration fixture affect a vibration test? Test Condition 1 • DUT ‘sandwich” clamped to vibration table surface • Does not reflect design intent mounting • Control on vibration table surface Flange Control 23 Navigating the waters of accreditation

  24. Can a vibration fixture affect a vibration test? Test Condition 1 Results 10 HDD Power Supply 1 Tolerance bands at +/- 3dB 0.1 PSD (g²/Hz) 0.01 0.001 0.0001 0.00001 10 100 1000 Frequency (Hz) 24 Navigating the waters of accreditation

  25. Can a vibration fixture affect a vibration test? Test Condition 2A • DUT attached to vibration fixture using chassis flanges • Design intent mounting • Control on vibration table surface Flange Control 25 Navigating the waters of accreditation

  26. Can a vibration fixture affect a vibration test? Test Condition 2A Results 10 HDD Power Supply 1 Tolerance bands at +/- 3dB 0.1 PSD (g²/Hz) 0.01 0.001 0.0001 0.00001 10 100 1000 Frequency (Hz) 26 Navigating the waters of accreditation

  27. Can a vibration fixture affect a vibration test? Test Condition 2B • DUT attached to vibration fixture using chassis flanges • Design intent mounting • Control averaged between vibration table surface and mounting flange Flange & Control Averaged 27 Navigating the waters of accreditation

  28. Can a vibration fixture affect a vibration test? Test Condition 2B Results 10 1 Tolerance bands at +/- 3dB 0.1 PSD (g²/Hz) 0.01 0.001 0.0001 0.00001 10 100 1000 Frequency (Hz) 28 Navigating the waters of accreditation

  29. Can a vibration fixture affect a vibration test? 10 PSD (g²/Hz) Internal results on the HDD and Power Supply appear similar, but are they? 0.1 0.001 0.00001 10 100 1000 Frequency (Hz) Condition 2A 10 PSD (g²/Hz) 10 PSD (g²/Hz) 0.1 0.1 0.001 0.001 0.00001 0.00001 10 100 1000 10 100 1000 Frequency (Hz) Condition 1 Frequency (Hz) Condition 2B 29 Navigating the waters of accreditation

  30. Can a vibration fixture affect a vibration test? External results (Mounting Flange and Vibration Table surface) appear even closer together Location (Overall grms) Test Mounting Flange Control Condition 1 1.5 1.5 Regardless of mounting method the overall grms (area under the PSD curve) for the Control location is the same as the Mounting Flange location?? 2A 1.5 1.5 2B 1.5 1.5 30 Navigating the waters of accreditation

  31. Can a vibration fixture affect a vibration test? Test level at the Mounting Flange 10 1 Condition 1 Condition 2A Condition 2B Even though all three mounting methods have the same overall grms level (area under the PSD curve), noticeable out-of-tolerance conditions are evident for Condition 1 and 2A 0.1 PSD (g²/Hz) 0.01 0.001 0.0001 0.00001 10 100 1000 Frequency (Hz) 31 Navigating the waters of accreditation

  32. Can a vibration fixture affect a vibration test? Test level at the Mounting Flange 0.01 Condition 1 – Sandwich Clamp w/Table Control - Out of tolerance Condition 2A – Fixture mount w/Table Control - Out of tolerance Condition 2B - Fixture mount w/Multi-point avg. Control - In tolerance 0.001 PSD (g²/Hz) 0.0001 Condition 1 Condition 2A Condition 2B 0.00001 100 1000 Frequency (Hz) 32 Navigating the waters of accreditation

  33. Can a vibration fixture affect a vibration test? What’s happening inside of the DUT? Location Test PSD In Tolerance? HDD Power Supply Condition Overall grms %* Overall grms %* 1 NO 5.5 2.6 -5.2 -21.2 2A NO 4.5 4.4 -22.4 +33.3 2B YES 5.8 3.3 N/A N/A *% over or under the grms value for Test Condition 2B 33 Navigating the waters of accreditation

  34. Can a vibration fixture affect a vibration test? What’s happening inside of the DUT? Test PSD In Tolerance? HDD Condition (Peak g2/Hz at 20 Hz) %* 1 NO 7.1 97.2 2A NO 3.4 5.5 2B YES 3.6 N/A *% over or under the peak g2/Hz value at 20 Hz for Test Condition 2B 34 Navigating the waters of accreditation

  35. The Vibration Fixture Blind Spot  Equipment that can “influence results” is commonly understood to mean  Controller accuracy  Accelerometer accuracy  The vibration fixture can also significantly influence test results 35 Navigating the waters of accreditation

  36. The Vibration Fixture Blind Spot Equipment must conform to specified requirements and be capable of achieving measurement accuracy to provide a valid result Typically +/- 3dB allowing for the instrument error The vibration fixture can significantly influence test results 36 Navigating the waters of accreditation

  37. The Vibration Fixture Blind Spot IEC 60068-2-47 Tests – Mounting of specimens for vibration, impact and similar dynamic tests  The purpose of a vibration fixture is: “… to transmit faithfully the mechanical stimulation from the test apparatus to the specimen, and to ensure that the specification requirements can be met at the fixing points of the specimen” 37 Navigating the waters of accreditation

  38. The Vibration Fixture Blind Spot Consider how we normally perform a high temperature exposure test on electronic components Tolerance: 120C +/-2C 38 Navigating the waters of accreditation

  39. The Vibration Fixture Blind Spot Can we achieve + at the fixing points?/- 3dB And… Is the vibration energy entering the DUT in the manner the DUT was intended to receive it? 39 Navigating the waters of accreditation

  40. The Vibration Fixture Blind Spot Then consider… Tolerance: 120C +/-2C Will this approach influence results? 40 Navigating the waters of accreditation

  41. Conclusions The laboratory should consider the method of attachment of the DUT to the shaker when planning a vibration test The DUT attachment method should be representative of the manner the DUT is designed to receive vibration unless the specification specifies otherwise The dynamic performance of the attachment method can influence the control strategy employed 41 Navigating the waters of accreditation

  42. Conclusions Vibration fixtures correspond with the ISO 17025 definition of equipment, accordingly… The laboratory must treat the attachment method of the DUT in the same manner as all other equipment 42 Navigating the waters of accreditation

  43. Questions? Tony Araujo Vice President – Business Development Paragon Systems Testing tonya@paragonsystems.ca 43 Navigating the waters of accreditation

  44. Contact Us Thank You! Contact Us A2LA 5202 Presidents Court, Suite 220 Frederick, MD 21703 301 644 3248 Main 301 662 2974 Fax info@A2LA.org www.A2LA.org 44 Navigating the waters of accreditation

  45.   2021 by A2LA All rights reserved. No part of this document may be reproduced in any form or by any means without the prior written permission of A2LA. A Better World Through Accreditation

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