REG NASA-HDBK-7004 REV C-2012 FORCE LIMITED VIBRATION TESTING.pdf

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1、APPROVED FOR PUBLIC RELEASEDISTRIBUTION IS UNLIMITEDNASA TECHNICAL HANDBOOK NASA-HDBK-7004C National Aeronautics and Space Administration Approved: 11-30-2012 Washington, DC 20546-0001 Superseding NASA-HDBK-7004B FORCE LIMITED VIBRATION TESTING MEASUREMENT SYSTEM IDENTIFICATION: METRIC (SI)/ENGLISH

2、Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-NASA-HDBK-7004CAPPROVED FOR PUBLIC RELEASEDISTRIBUTION IS UNLIMITED2 of 63DOCUMENT HISTORY LOG Status Document Revision Approval Date Description Baseline 5-16-2000 Baseline Release Revision A 11-5-2002

3、 Added New Section 6.0 “Comparison of Flight and Ground Vibration Test Data,” which includes force data measured in two flight experiments. The flight data provide validation of the force limiting methodology. Made minor editorial changes. Revision B 1-31-2003 Page 8, Changed Equation 1(a) from: f =

4、 fo to:f fo and Equation 1(b) from: f = foto: f foRevision C 11-30-2012 Reorganized document; added section 5.6 on impedance method; added section 6, Guidelines; added section 7.3 on GLAST spacecraft flight force data; moved material on Complex TDOF System and the spreadsheet example to Appendix C.

5、Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-NASA-HDBK-7004CAPPROVED FOR PUBLIC RELEASEDISTRIBUTION IS UNLIMITED3 of 63FOREWORD This Handbook is published by the National Aeronautics and Space Administration (NASA) as a guidance document to provid

6、e engineering information; lessons learned; possible options to address technical issues; classification of similar items, materials, or processes; interpretative direction and techniques; and any other type of guidance information that may help the Government or its contractors in the design, const

7、ruction, selection, management, support, or operation of systems, products, processes, or services. This Handbook is approved for use by NASA Headquarters and NASA Centers, including Component Facilities and Technical and Service Support Centers. This Handbook establishes a common framework for cons

8、istent practices across NASA programs. This third revision of the Handbook includes several advances in the calculation and application of vibration force limits, guidelines for the application of force limiting, and data from a third flight experiment that involved measuring the forces and accelera

9、tions at the interface between a spacecraft and launch vehicle. The primary goal of vibration tests of aerospace hardware is to identify problems that, if not remedied, would result in flight failures. This goal can best be met by implementing a realistic (flight-like) test with a specified positive

10、 margin. Usually, this goal is not well served by traditional acceleration-controlled vibration tests that historically do an adequate job of screening out flight failures but often result in failures that would not occur in flight. Vibration tests that are unrealistic and too severe are responsible

11、 not only for the cost and schedule overruns associated with hardware failures during unrealistic tests but also for the weight and performance penalties associated with designing for unrealistic tests. It has been known for 40 years that the major cause of overtesting in aerospace vibration tests i

12、s associated with the large mechanical impedance of the shaker and the standard practice of controlling the input acceleration to the frequency envelope of the flight data (Blake, 1954 1; Salter, 1964 2; Murfin, 1968 3; Ratz, 1966 4; Heinricks, 1967 5; Painter, 1967 6). This approach results in unre

13、alistic, large base reaction forces and other large responses at the fixed-base resonance frequencies of the test item. The conventional method of alleviating this problem is to measure and limit the acceleration responses in the test to those predicted for flight, but this approach is highly depend

14、ent on the analysis that the test is supposed to validate and usually requires limiting the acceleration responses at many locations on large test items. This Handbook describes an improved vibration testing method that has been facilitated by two technological developments, circa 1980-1990: the adv

15、ent of both three-axis piezoelectric force gages and shaker control systems with real-time response limiting. The subject method involves inserting the ring-shaped force gages under the test item to measure the reaction force between the test item and the shaker and limiting the measured force to a

16、specification that is designed to replicate the flight environment. For most of the frequency range, the test is controlled, as in a conventional vibration test, by the input acceleration specification; but at the test item resonance frequencies, the force limit usually results in a reduction of the

17、 input acceleration (notching). Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-NASA-HDBK-7004CAPPROVED FOR PUBLIC RELEASEDISTRIBUTION IS UNLIMITED4 of 63Since the mid-1990s, force limited vibration testing has been utilized on many projects, at the

18、Jet Propulsion Laboratory (JPL), Goddard Space Flight Center (GSFC), other NASA Centers, and at other government laboratories and aerospace contractors. This Handbook describes the rationale and methodology of force limited vibration testing, so that the benefits of applying this relatively new tech

19、nology can be maximized and the method can be applied throughout NASA in a consistent manner. The Handbook is organized so that those already familiar with force limiting may use it as a reference and those who are new to this technology may use it as a textbook. In either case, it is not a Standard

20、 and therefore should be used only for guidance and not to justify a given approach or a specific numerical value. Section 6 of this Handbook gives three explicit guidelines based on years of experience conducting and overseeing force limited vibration tests. Requests for information, corrections, o

21、r additions to this Handbook should be submitted via “Feedback” in the NASA Standards and Technical Assistance Resource Tool at http:/standards.nasa.gov. Original Signed By: 11-30-2012 Michael G. Ryschkewitsch NASA Chief EngineerApproval DateProvided by IHSNot for ResaleNo reproduction or networking

22、 permitted without license from IHS-,-,-NASA-HDBK-7004CAPPROVED FOR PUBLIC RELEASEDISTRIBUTION IS UNLIMITED5 of 63SECTIONTABLE OF CONTENTS PAGEDOCUMENT HISTORY LOG . 2 FOREWORD . 3 TABLE OF CONTENTS . 5 LIST OF FIGURES . 6 LIST OF TABLES . 7 1. SCOPE. 8 1.1 Purpose . 8 1.2 Applicability . 8 1.3 Rati

23、onale . 9 2. APPLICABLE DOCUMENTS . 10 2.1 General 10 2.2 Government Documents 11 2.3 Non-Government Documents (References) . 11 2.4 Order of Precedence . 14 3. ACRONYMS AND DEFINITIONS 14 3.1 Acronyms and Abbreviations . 14 3.2 Definitions 16 4. FORCE GAGES . 17 4.1 Force Gage Characteristics . 17

24、4.2 Force Gage Installation . 18 4.3 Force Gage Preload 22 4.4 Force Gage Calibration . 22 5. FORCE LIMITS. 23 5.1 Response Limiting and Notching . 24 5.2 Apparent, Effective, Residual, and Asymptotic Masses 25 5.3 Semi-Empirical Force Limit Equation . 29 5.4 Simple TDOF System Method of Deriving Fo

25、rce Limits 31 5.5 Complex TDOF System Method of Deriving Force Limits . 33 5.6 Equivalent Circuit Impedance Method of Deriving of Force Limits . 33 5.7 Flight and Ground Test Scaling of C2in Semi-Empirical Method . 37 5.8 FEM Analysis of Force Limits. 38 5.9 Quasi-Static Load Limits 39 6. THREE GUID

26、ELINES 40 6.1 Guideline 1: Use Force Limiting only for Highly Resonant Test Articles . 40 6.2 Guideline 2: Use Appropriate Rationale for Deriving Force Limits 40 6.3 Guideline 3: Avoid Excessive Notching 41 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS

27、-,-,-NASA-HDBK-7004CAPPROVED FOR PUBLIC RELEASEDISTRIBUTION IS UNLIMITED6 of 637. FLIGHT AND GROUND VIBRATION TEST DATA. 41 7.1 Shuttle Vibration Force (SVF-2) Experiment on Space Shuttle Space Transportation System-96 (STS-96) . 41 7.2 Cosmic-Ray Isotope Spectrometer (CRIS) Instrument on Advanced C

28、omposition Explorer (ACE) Spacecraft . 46 7.3 GLAST Spacecraft on Delta II Launch Vehicle . 49 APPENDICESA Calculation of Effective Mass . 55 B Equations for Calculating the Simple TDOF System Force Limit . 57 C Tables for Complex TDOF System Method of Calculating Force Limits 58 D Sweitzers Notchin

29、g Criterion 62 FIGURELIST OF FIGURES PAGE1 Deep Space One Spacecraft Mounted on 24 Small Force Transducers . 19 2 Mars Exploration Rover Mounted on Eight Medium Force Transducers 20 3 CASSINI Spacecraft Mounted on Eight Large Force Transducers 21 4 Reduction of SDOF System RMS Response by Notching .

30、 25 5 Complex TDOF System with Residual and Modal Masses . 27 6 Apparent Mass, Asymptotic Mass, Modal Mass, and Residual Mass of Longitudinally Vibrating Rod, Excited at One End and Free at Other End . 28 7 Simple TDOF System of Coupled Oscillators . 31 8 Normalized Force Specification from Simple T

31、DOF System 32 9 Impedance Method Results for TDOF System with Two Identical Oscillators . 35 10 SVF-2 Experiment on STS-96 42 11 Hitchhiker Canister for SVF-2 . 42 12 Force Limit in Vibration Test of SVF-2 Canister . 43 13 Acceleration Input in Vibration Test of SVF-2 Canister 44 14 Y-Axis Accelerat

32、ion at Top of SVF-2 45 15 Total Y-Axis Force in SVF-2 Flight . 45 16 CRIS Instrument on ACE Spacecraft Bus 46 17 Total Vertical Force in CRIS Random Vibration Test . 47 18 Notched Acceleration Input in CRIS Random Vibration Test . 47 19 Spectral Density of Flight Normal Acceleration Measured near On

33、e Mounting Foot of CRIS Instrument 48 20 Spectral Density of Flight Normal Force Measured under CRIS Instrument 49 21 GLAST Spacecraft Sine Vibration Test . 50 22 GLAST Spacecraft X-axis (Lateral) Interface Flight Accelerations 51 23 GLAST Spacecraft X-axis (Lateral) Base Flight Forces 51 24 GLAST S

34、pacecraft Z-axis (Thrust) Interface Flight Accelerations . 52 25 GLAST Spacecraft Z-axis (Thrust) Flight Base Forces . 52 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-NASA-HDBK-7004CAPPROVED FOR PUBLIC RELEASEDISTRIBUTION IS UNLIMITED7 of 6326 GLA

35、ST Spacecraft Thrust Z-Axis Apparent Mass Measured in Ground Vibration Test and in Three Flight Regimes 54 27 GLAST Spacecraft Lateral X-Axis Apparent Mass Measured in Ground Vibration Test and in Two Flight Regimes 54 TABLELIST OF TABLES PAGE1 Summary Table for C2Values in 29 38 2 Force Limit Spect

36、rum for Complex TDOF System with Q=50 . 59 3 Force Limit Spectrum for Complex TDOF System with Q=20 . 60 4 Force Limit Spectrum for Complex TDOF System with Q=5 . 61 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-NASA-HDBK-7004CAPPROVED FOR PUBLIC R

37、ELEASEDISTRIBUTION IS UNLIMITED8 of 63FORCE LIMITED VIBRATION TESTING 1. SCOPE 1.1 Purpose The purpose of force limited vibration testing is to alleviate overtesting associated with the unrealistically high base reaction forces that occur at the test item resonances in conventional base-drive vibrat

38、ion tests (Blake, 1954 1; Salter, 1964 2; Murfin, 1968 3; Ratz, 1966 4; Heinricks, 1967 5; Painter, 1967 6); Smallwood, 1989 7; Scharton, et al., 1989 8; Smallwood, 1990 9; Scharton, 1995 10). The purpose of this Handbook is to provide an approach that may be consistently followed by those desiring

39、to use force limiting, without having to conduct an extensive literature search or research and development effort before conducting the test. This Handbook describes the rationale behind force limiting, the hardware required for implementation, the various methods for deriving force-limit specifica

40、tions, and three flight experiments in which the base reaction forces were measured. The disparity in the mechanical impedances of the flight and the vibration test mounting configurations is usually the most important cause of overtesting in vibration tests. However, it may not be the only cause. A

41、 second contributor 2 to vibration overtesting is the uniformity of the motion at the various attachments of the test item to the vibration test fixture, which uniformity is often in contrast to the uncorrelated motion of the attachments in the flight-mounting configuration. The degree of overtestin

42、g associated with the uniformity of the attachment motion in the test is usually greater at the higher frequencies and when the flight-mounting configuration involves relatively wide-spread attachments to lightweight flight structure excited with an uncorrelated source, such as acoustic noise. Final

43、ly, overtesting can simply be the result of unrealistic test specifications, e.g., caused by the cascading of margins associated with the individual steps in the process used to develop the specifications. Neither of these latter two sources of overtesting is discussed further in this handbook. 1.2

44、Applicability This Handbook is applicable to all force limited vibration tests of National Aeronautics and Space Administration (NASA) flight and non-flight hardware, including but not limited to built-up spacecraft, spacecraft experiments and components, aircraft and launch vehicle equipment, launc

45、h vehicle pads, and Ground Support Equipment (GSE). This Handbook is approved for use by NASA Headquarters and NASA Centers, including Component Facilities and Technical and Service Support Centers. This Handbook may also apply to the Jet Propulsion Laboratory (JPL) or to other contractors, grant re

46、cipients, or parties to agreements only to the extent specified or referenced in their contracts, grants, or agreements. This Handbook, or portions thereof, may be referenced in contract, program, and other Agency documents for guidance. When this Handbook contains procedural or process requirements

47、, they may be cited in contract, program, and other Agency documents for guidance. Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-NASA-HDBK-7004CAPPROVED FOR PUBLIC RELEASEDISTRIBUTION IS UNLIMITED9 of 63For the purpose of this Handbook, a force lim

48、ited vibration test is any vibration test in which the reaction force at the base of the test item is measured and limited. In addition, a force limited vibration test almost always involves measuring and controlling the acceleration at the base of the test item and may also involve measuring and limiting the acceleration and/or force responses at other positions on the test item as well. For both analysis and test, it is usually convenient to think of the input acceleration as the control and of the base reaction force as a response, similar to the acceleration response