REQUIREMENTS FOR THREADED FASTENING SYSTEMS IN …

1 METRIC/SI (ENGLISH). NASA TECHNICAL STANDARD NASA-STD-5020A. w/CHANGE 1: Office of the NASA Chief Engineer ADMINISTRATIVE/. EDITORIAL CHANGE. 2019-02-11. Approved: 2018-09-04. Superseding NASA-STD-5020. (Baseline). REQUIREMENTS FOR THREADED FASTENING . SYSTEMS IN SPACEFLIGHT HARDWARE. APPROVED FOR PUBLIC RELEASE DISTRIBUTION IS UNLIMITED. NASA-STD-5020A w/CHANGE 1. DOCUMENT HISTORY LOG. Status Document Change Approval Date Description Revision Number Baseline 2012-03-12 Initial Release Revision A 2018-09-04 Significant changes were made to this NASA Technical Standard.

2 It is recommended that it be reviewed in its entirety before implementation. Key changes were: The format of the baseline version has been modified to provide better flow of the REQUIREMENTS language. This includes the order of the REQUIREMENTS from the baseline version. Some REQUIREMENTS have been merged due to redundancy or deleted. 1 2019-02-11 Editorial Changes Corrected decision box No. 2 in Appendix , Figure 8, Determining Whether a Joint Separates before Rupture When Loaded Solely in Tension, to state Pp-max *Ptu-allow (vs. ), which aligns with the previous revision and the justification in the text.

3 Corrected the symbol for phi to (vs. ( ) in equation 47. Unbolded two equations in Appendix APPROVED FOR PUBLIC RELEASE DISTRIBUTION IS UNLIMITED. 2 of 114. NASA-STD-5020A w/CHANGE 1. FOREWORD. This NASA Technical Standard is published by the National Aeronautics and Space Administration (NASA) to provide uniform engineering and technical 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.)

4 This NASA Technical Standard is approved for use by NASA Headquarters and NASA Centers and Facilities, and applicable technical REQUIREMENTS may be cited in contract, program, and other Agency documents. It may also apply to the Jet Propulsion Laboratory (a Federally Funded Research and Development Center (FFRDC)), other contractors, recipients of grants and cooperative agreements, and parties to other agreements only to the extent specified or referenced in applicable contracts, grants, or agreements. This NASA Technical Standard establishes criteria for ensuring the integrity of THREADED FASTENING SYSTEMS in launch and space vehicles and their associated equipment.

5 Requests for information should be submitted via Feedback at Requests for changes to this NASA Technical Standard should be submitted via Marshall Space Flight Center (MSFC) Form 4657, Change Request for a NASA Engineering Standard. _____Original signed by_____ _____09/04/2018_____. Ralph R. Roe, Jr. Approval Date NASA Chief Engineer APPROVED FOR PUBLIC RELEASE DISTRIBUTION IS UNLIMITED. 3 of 114. NASA-STD-5020A w/CHANGE 1. TABLE OF CONTENTS. SECTION PAGE. DOCUMENT HISTORY 2. FOREWORD .. 3. TABLE OF 4. LIST OF APPENDICES .. 5. LIST OF FIGURES.

6 6. LIST OF TABLES .. 7. 1. SCOPE .. 9. Purpose .. 9. 9. Tailoring .. 9. 2. APPLICABLE DOCUMENTS .. 10. General .. 10. Government Documents .. 10. Non-Government Documents .. 10. Order of Precedence .. 11. 3. ACRONYMS, ABBREVIATIONS, SYMBOLS, AND. DEFINITIONS .. 11. Acronyms, Abbreviations, and 11. Definitions .. 12. Definition of 12. Definition of Terms .. 14. 4. REQUIREMENTS .. 16. FASTENING system Control Plan .. 17. Design 17. FASTENING system Preload .. 20. Strength REQUIREMENTS .. 26. Fatigue Life .. 36. Locking Features .. 37. Part Selection Criteria.

7 40. Quality Assurance .. 42. APPROVED FOR PUBLIC RELEASE DISTRIBUTION IS UNLIMITED. 4 of 114. NASA-STD-5020A w/CHANGE 1. LIST OF APPENDICES. APPENDIX PAGE. A. EXPLANATION AND JUSTIFICATION OF FASTENER. ANALYSIS CRITERIA .. 46. Purpose of Appendix A .. 46. Accounting for Preload Variation when Installing Fasteners with Torque Control (Supplement to Section ) .. 46. Short-Term Relaxation of Preload (Supplement to Section ) .. 51. Use of a Load-Introduction and Stiffness Factor (Supplement to Sections and ) .. 51. Bolt Analysis: Separation before Rupture (Supplement to Section ).

8 60. Ultimate Margin of Safety for Tensile Loading with Linear Theory (Supplement to Section ) .. 64. Omission of Preload in Shear and Interaction Analyses (Supplement to Sections and ) .. 65. Theoretical Treatment of Interaction Equations (Supplement to Section ) .. 66. Determining if Fastener Yielding is Detrimental for Separation or Joint Slip (Supplement to Section ) .. 70. Margin of Safety for Joint Slip (Supplement to Sections and ) .. 73. Margin of Safety for Bolted Joint Separation (Supplement to Section ) .. 75. Load Redistribution within a Fastened Joint.

9 75. B. BEST PRACTICES FOR LOCKING FEATURES .. 83. Purpose of Appendix B .. 83. Background and Introduction .. 83. Best Practices for Mechanical Locking Features .. 84. Best Practices for Prevailing Torque Locking Features .. 85. General .. 85. Prevailing Torque Locking Devices .. 86. Inspect .. 89. Installation and Verification .. 90. Best Practices for Adhesive Locking Features .. 90. Adhesives .. 90. Process Validation .. 92. Inspect .. 94. Clean .. 94. Prime (for anaerobic adhesives only) .. 94. Installation .. 94. APPROVED FOR PUBLIC RELEASE DISTRIBUTION IS UNLIMITED.

10 5 of 114. NASA-STD-5020A w/CHANGE 1. LIST OF APPENDICES (Continued). APPENDIX PAGE. Verification .. 95. General .. 95. Best Practices for Free 96. C. JUSTIFICATION FOR LOW LIKELIHOOD OF FATIGUE. FAILURE .. 97. Purpose of Appendix C .. 97. Justification .. 97. D. REFERENCES .. 101. Purpose of Appendix D .. 101. Reference Documents .. 101. E. REQUIREMENTS COMPLIANCE MATRIX .. 106. Purpose of Appendix E .. 106. LIST OF FIGURES. FIGURE PAGE. 1 Logic Flow for Minimum Separation Factor of 20. 2 Dimensional Considerations in Selecting FASTENING Hardware.