1、APPROVED FOR PUBLIC RELEASE DISTRIBUTION IS UNLIMITED NASA TECHNICAL STANDARD NASA-STD-5020 National Aeronautics and Space Administration Approved: 03-12-2012 Washington, DC 20546-0001 REQUIREMENTS FOR THREADED FASTENING SYSTEMS IN SPACEFLIGHT HARDWARE MEASUREMENT SYSTEM IDENTIFICATION: METRIC/SI (E
2、NGLISH) Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-NASA-STD-5020 APPROVED FOR PUBLIC RELEASE DISTRIBUTION IS UNLIMITED 2 of 88 DOCUMENT HISTORY LOG Status Document Revision Approval Date Description Baseline 03-12-2012 Initial Release Provided b
3、y IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-NASA-STD-5020 APPROVED FOR PUBLIC RELEASE DISTRIBUTION IS UNLIMITED 3 of 88 FOREWORD This Standard is published by the National Aeronautics and Space Administration (NASA) to provide uniform engineering and techn
4、ical requirements for processes, procedures, practices, and methods that have been endorsed as standard for NASA programs and projects, including requirements for selection, application, and design criteria of an item. This Standard is approved for use by NASA Headquarters and NASA Centers, includin
5、g Component Facilities and Technical and Service Support Centers. This Standard establishes criteria for ensuring the integrity of threaded fastening systems in launch and space vehicles and their associated equipment. Requests for information, corrections, or additions to this Standard should be su
6、bmitted via “Feedback” in the NASA Standards and Technical Assistance Resource Tool at http:/standards.nasa.gov. Original Signed By: 03-12-2012 _ _ Michael G. Ryschkewitsch Approval Date NASA Chief Engineer Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS
7、-,-,-NASA-STD-5020 APPROVED FOR PUBLIC RELEASE DISTRIBUTION IS UNLIMITED 4 of 88 SECTION TABLE OF CONTENTS PAGE DOCUMENT HISTORY LOG . 2 FOREWORD . 3 TABLE OF CONTENTS . 4 LIST OF FIGURES . 8 LIST OF TABLES . 9 1. SCOPE . 10 1.1 Purpose . 10 1.2 Applicability . 10 1.3 Tailoring . 10 2. APPLICABLE DO
8、CUMENTS . 10 2.1 General . 10 2.2 Government Documents . 11 2.3 Non-Government Documents 11 2.4 Order of Precedence . 11 2.4.1 Document Conflicts 11 3. ACRONYMS AND DEFINITIONS . 12 3.1 Acronyms and Abbreviations . 12 3.2 Definitions 12 3.2.1 Definitions of Variables . 12 3.2.2 Definition of Terms 1
9、5 4. GENERAL REQUIREMENTS 19 4.1 Strength 19 4.1.1 Ultimate Design Loads . 19 4.1.2 Yield Design Loads 19 4.2 Fracture Control and Fatigue Life 20 4.3 Joint Separation 21 4.4 Locking Features 21 4.5 Fastening System Control Plan 22 5. DESIGN REQUIREMENTS AND CONSIDERATIONS . 22 5.1 Materials . 22 5.
10、2 Specification of Lubricants, Coatings, and Sealants 22 5.3 Thread Form Compatibility 23 5.4 Use of Washers and Chamfered Bolt Holes . 23 5.5 Locking Features 23 5.6 Thread Engagement, Dimensions, and Tolerances 24 Provided by IHSNot for ResaleNo reproduction or networking permitted without license
11、 from IHS-,-,-NASA-STD-5020 APPROVED FOR PUBLIC RELEASE DISTRIBUTION IS UNLIMITED 5 of 88 SECTION TABLE OF CONTENTS (Continued) PAGE 5.6.1 Fastener Length Selection for Thread Engagement . 24 5.6.2 Bolt Grip Selection to Prevent Interference . 25 5.7 Fastener Installation Specification and Control .
12、 25 5.8 Installation Torque Specification and Control . 26 6. CRITERIA FOR ANALYSIS OF THREADED FASTENING SYSTEMS . 26 6.1 Nominal, Maximum, and Minimum Preload . 27 6.2 Strength Under Ultimate Design Loads . 31 6.2.1 Ultimate-Strength Analysis for Tensile Loading . 31 6.2.2 Ultimate-Strength Analys
13、is for Shear Loading 33 6.2.3 Ultimate-Strength Analysis for Interaction of Tension, Shear, and Bending 34 6.3 Strength Under Yield Design Loads 35 6.4 Friction as a Load Path for Shear Loading: Joint-Slip Analysis 36 6.5 Joint Separation Analysis . 38 7. QUALITY ASSURANCE 38 7.1 As-Built Documentat
14、ion 38 7.2 Training 39 7.3 Installation Tools and Instruments . 39 7.4 Calibration of Installation Tools and Instruments 39 7.5 Threaded Fastening System Hardware Inspection . 39 7.6 Locking Feature Verification . 39 7.7 Fastening System Hardware Procurement, Inspection, and Storage 40 Provided by I
15、HSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-NASA-STD-5020 APPROVED FOR PUBLIC RELEASE DISTRIBUTION IS UNLIMITED 6 of 88 APPENDICES A. EXPLANATION AND JUSTIFICATION OF FASTENER ANALYSIS CRITERIA .41 A.1 Purpose of Appendix A . 41 A.2 Accounting for Preload Var
16、iation when Installing Fasteners with Torque Control (Supplement to Section 6.1) 41 A.2.1 Rationale for Eqs. (6.5b) and (A.2-3b) 46 A.3 Short-Term Relaxation of Preload (Supplement to Section 6.1) 47 A.4 Use of a Load-Introduction Factor (Supplement to Section 6.2.1.2) 47 A.5 Bolt Analysis: Separati
17、on Before Rupture (Supplement to Section 6.2.1) . 48 A.6 Ultimate Margin of Safety for Tensile Loading with Linear Theory (Supplement to Section 6.2.1.2) 53 A.7 Omission of Preload in Shear and Interaction Analyses (Supplement to Section 6.2.2) 55 A.8 Theoretical Treatment of Interaction Equations (
18、Supplement to Section 6.2.3) .56 A.9 Determining if Fastener Yielding is Detrimental for Separation or Joint Slip (Supplement to Section 6.3) 61 A.10 Margin of Safety for Joint Slip (Supplement to Section 6.4) 64 A.11 Margin of Safety for Bolted Joint Separation (Supplement to Section 6.5) 66 A.12 U
19、se of a Fitting Factor. 66 B. BEST PRACTICES FOR LOCKING FEATURES 68 B.1 Purpose of Appendix B . 68 B.2 Background and Introduction 68 B.3 Best Practices for Mechanical Locking Features 70 B.4 Best Practices for Prevailing Torque Locking Features 70 B.4.1 General 70 B.4.2 Prevailing Torque Locking D
20、evices 71 B.4.3 Inspect . 74 B.4.4 Installation and Verification 74 B.5 Best Practices for Adhesive Locking Features 75 B.5.1 Adhesives 75 B.5.2 Process Validation 76 B.5.3 Inspect . 78 B.5.4 Clean . 78 B.5.5 Prime (for anaerobic adhesives only) 78 B.5.6 Installation . 79 B.5.7 Verification . 79 B.5
21、.8 General 79 B.6 Best Practices for Free Spinning . 80 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-NASA-STD-5020 APPROVED FOR PUBLIC RELEASE DISTRIBUTION IS UNLIMITED 7 of 88 APPENDICES (Continued) C. JUSTIFICATION FOR THE LOW-RISK FATIGUE CLASS
22、IFICATION 81 C.1 Purpose of Appendix C . 81 C.2 Conclusions . 84 D. REFERENCES 85 D.1 Purpose of Appendix D . 85 D.2 Reference Documents . 85 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-NASA-STD-5020 APPROVED FOR PUBLIC RELEASE DISTRIBUTION IS UN
23、LIMITED 8 of 88 FIGURE LIST OF FIGURES PAGE 1 Logic Flow for Minimum Separation Factor of Safety 21 2 Dimensional Considerations in Selecting Fastening Hardware 25 3 Ultimate Strength Analysis of Fasteners Under Shear Loading 33 4 Dimensions Used to Calculate Load-Introduction Factor 48 5 Determinin
24、g Whether a Joint Separates Before Rupture When Loaded Solely in Tension 48 6 How to Quantify Ductility of a Fastening System from a Tension Test 49 7 Preloaded Joint in Which the Bolt Load Increases by a Relatively High Percentage of Applied Tensile Load 50 8 Separation Before Rupture for a Brittle
25、 Threaded Fastening System 51 9 Separation Before Rupture for a Ductile Threaded Fastening System. 52 10 Bolt Tensile Load versus Applied Tensile Load 53 11 Separation Before Rupture with Linear Theory . 54 12 Rupture Before Separation with Linear Theory . 55 13 Stress Distribution at Collapse Due t
26、o Combined Bending and Tension . 59 14 Comparison of Interaction Between Circular and Rectangular Cross Sections at Collapse 60 15 Effect of Fastener Yielding on the Separation Load 62 16 Loss of Preload Resulting from Fastener Yielding 63 17 Fastener Yielding Under an Applied Load that Exceeds the
27、Separation Load 64 18 Locking Feature Selection Flowchart 69 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-NASA-STD-5020 APPROVED FOR PUBLIC RELEASE DISTRIBUTION IS UNLIMITED 9 of 88 TABLE LIST OF TABLES PAGE 1 Analytical Adjustments of Maximum and
28、 Minimum Preloads 28 2 Two-Sided 90/95 Tolerance Limit Factors for a Normal Distribution (Odeh and Owen, 1980) 44 3 Sample Data from 30 Torque-Tension Tests (Actual Test Data) 45 4 Hypothetical Applied-Loading Spectrum Used to Justify the Low-Risk Classification for Faster Fatigue. 82 5 Results of F
29、astener Fatigue Analysis for the Hypothetical Joint and Loading Spectra 83 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-NASA-STD-5020 APPROVED FOR PUBLIC RELEASE DISTRIBUTION IS UNLIMITED 10 of 88 REQUIREMENTS FOR THREADED FASTENING SYSTEMS IN SPA
30、CEFLIGHT HARDWARE 1. SCOPE 1.1 Purpose The purpose of this Standard is to specify requirements for design and analysis of threaded fastening systems in NASA spaceflight hardware. 1.2 Applicability This Standard is applicable to all NASA programs and projects. This Standard may not be applicable to g
31、round support equipment. Additional requirements for fracture control, non-metallic structures, non-standard fasteners, and fasteners used in extravehicular activity (EVA) may apply. This Standard is approved for use by NASA Headquarters and NASA Centers, including Component Facilities and Technical
32、 and Service Support Centers, and may be cited in contract, program, and other Agency documents as a technical requirement. This Standard may also apply to the Jet Propulsion Laboratory or to other contractors, grant recipients, or parties to agreements only to the extent specified or referenced in
33、their contracts, grants, or agreements. Requirements are numbered and indicated by the word “shall.” Explanatory or guidance text is indicated in italics beginning in section 4. This document shall not supersede applicable laws and regulations unless a specific exemption has been obtained by the Off
34、ice of the NASA Chief Engineer. 1.3 Tailoring Tailoring of this Standard for application to a specific program or project shall be formally documented as part of program or project requirements and approved by the Technical Authority. 2. APPLICABLE DOCUMENTS 2.1 General The documents listed in this
35、section contain provisions that constitute requirements of this Standard as cited in the text. Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-NASA-STD-5020 APPROVED FOR PUBLIC RELEASE DISTRIBUTION IS UNLIMITED 11 of 88 2.1.1 The latest issuances of
36、cited documents shall apply unless specific versions are designated. 2.1.2 Non-use of specific versions as designated shall be approved by the responsible Technical Authority. The applicable documents are accessible via the NASA Standards and Technical Assistance Resource Tool at https:/standards.na
37、sa.gov or may be obtained directly from the Standards Developing Organizations or other document distributors. 2.2 Government Documents NASA NASA-STD-5001 Structural Design and Test Factors of Safety for Spaceflight Hardware NASA-STD-5019 Fracture Control Requirements for Spaceflight Hardware NASA-S
38、TD-6008 NASA Fastener Procurement, Receiving Inspection, and Storage Practices for Spaceflight Hardware NASA-STD-6016 Standard Materials and Processes Requirements for Spacecraft 2.3 Non-Government Document American Society of Mechanical Engineers (ASME) ASME B107.300-2010 Torque Instruments 2.4 Ord
39、er of Precedence This Standard establishes requirements for design and analysis of threaded fastening systems in NASA spaceflight hardware but does not supersede nor waive established Agency requirements found in other documentation. 2.4.1 Document Conflicts Conflicts between this Standard and other
40、 requirements documents shall be resolved by the responsible Technical Authority. Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-NASA-STD-5020 APPROVED FOR PUBLIC RELEASE DISTRIBUTION IS UNLIMITED 12 of 88 3. ACRONYMS AND DEFINITIONS 3.1 Acronyms an
41、d Abbreviations % percent F degrees Fahrenheit AC Advisory Circular AND Air Force-Navy Design ASME The American Society of Mechanical Engineers ASTM American Society for Testing and Materials CRES corrosion resistant steel EVA extravehicular activity FAA Federal Aviation Administration FS factor of
42、safety HDBK Handbook JSC Johnson Space Center MEK methyl ethyl ketone MS margin of safety MSFC Marshall Space Flight Center MIL Military NAS National Aerospace Standard NASA National Aeronautics and Space Administration NASM National Aerospace Standard (Metric) NSTS National Space Transportation Sys
43、tem SAE Society of Automotive Engineers STD Standard VDI Verein Deutscher Ingenieure (German acronym) 3.2 Definitions 3.2.1 Definitions of Variables uncertainty or scatter in initial preload a-max actual preload variation for maximum preload, as determined from a sample of torque-tension test data a
44、-min actual preload variation for minimum preload, as determined from a sample of torque-tension test data 90/95 uncertainty or scatter in initial preload (calculated from torque-tension test data) selected using 90-percent probability and 95-percent confidence intervals e elastic deformation of a f
45、astening system at rupture under tensile loading p plastic deformation of a fastening system at rupture under tensile loading stiffness factor Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-NASA-STD-5020 APPROVED FOR PUBLIC RELEASE DISTRIBUTION IS U
46、NLIMITED 13 of 88 coefficient of friction mean preload for a fastener nbp mean total preload for a joint standard deviation of preload for a fastener nbp standard deviation of total preload for a joint pi unbiased sample standard deviation for initial preload shear stress A cross-sectional area Am m
47、inimum minor-diameter area As cross-sectional area of the full diameter body At tensile stress area a scaling factor applied to the external loads that causes a zero-margin condition cmax a factor that accounts for the maximum value of the fasteners controlled installation parameter (e.g., effective
48、 torque), as allowed by the specified tolerance cmin a factor that accounts for the minimum value of the fasteners controlled installation parameter (e.g., effective torque), as allowed by the specified tolerance D nominal fastener diameter e minimum edge distance measured from center of hole to closest edge
