Design & Analysis of Bolted Joints
09/24/2019 8:30 am
$1990 per person
Just about everyone involved in developing hardware for space missions (or any other purpose, for that matter) has been affected by problems with joints using threaded fasteners. Common problems include structural failure, fatigue, galling, inadequate preload, fasteners losing preload or falling out completely, low or nonlinear stiffness, joint slipping or loss of alignment, excess weight, procurement cost and lead time, incompatibility with the space environment, and time-consuming assembly.
This three-day course includes many examples and class problems. Participants should bring calculators.
Who should attend:
Mechanical design engineers, structural analysts, and others interested in or involved with bolted joints.
- Overview. Common problems with bolted joints. A process for designing a bolted joint. Bolting as a method of attachment. General design guidelines. The importance of preload. Introduction to NASA-STD-5020. Key definitions. Top-level requirements from NASA-STD-5020. Factors of safety, fitting factors, and margin of safety. Establishing internal standards and criteria.
- Introduction to Threaded Fasteners. History of screw threads. Thread forms and compatibility. Rolled vs. cut threads. Bolt features and geometry. Tensile-stress area. Fine threads vs. coarse threads.
- Developing a Concept for the Joint. General types of joints and fasteners. Configuring the joint. Designing a stiff joint. Shear clips and tension clips. Avoiding problems with fixed fasteners.
- Calculating Bolt Loads when Ignoring Preload. How a preloaded joint carries load. Temporarily ignoring preload. What about friction as a load path? Common assumptions and their limitations. Finite element modeling of a bolted joint. An effective process for calculating bolt loads in a compact joint.
- Failure Modes & Assessment Methods. Understanding stress analysis. An effective process for strength analysis. Bolt tension and shear. Tension joints. Shear joints. Identifying potential failure modes. Fastened shear joints with composite materials.
- Thread Stripping & Pull-out Strength. How threads fail. Computing shear engagement areas. Including a knock-down factor. Test results.
- Selecting Hardware & Detailing the Design. Selecting compatible materials. Selecting the nut. Commonly used threaded inserts. Use of washers. Selecting fastener length and grip. Recommended fastener hole sizes. Guidelines for simplifying assembly. Establishing bolt preload. Torque-preload relationship. Locking features and NASA-STD-5020. Maintaining preload.
- Mechanics of a Preloaded Joint. Mechanics of a preloaded joint under applied tension. Estimating bolt stiffness and clamp stiffness. Understanding the loading-plane factor. Worst case for steel-aluminum combination. Key conclusions regarding load sharing. Effects of bolt ductility. How temperature change affects preload.
- Analysis Criteria per NASA-STD-5020. Objectives and summary. Calculating maximum and minimum preloads. Tensile loading: ultimate-strength analysis. Separation analysis. Tensile loading: yield-strength analysis. Shear loading: ultimate-strength analysis. Interaction of tension, shear, and bending. Shear loading: joint-slip analysis. Low-risk classification for fastener fatigue.
- Design Tables: Preliminary Bolt Sizing, Based on NASA-STD-5020 Analysis Criteria. Objectives for generating design tables. Setting up a spreadsheet. Assumptions and equations. Typical driving parameters. Design tables for selected situations.
If this course is not on the current schedule of open enrollment courses and you are interested in attending this or another course as an open enrollment, please contact us at (410) 956-8805 or email@example.com. Please indicate the course name, number of students who wish to participate. and a preferred time frame. ATI typically schedules open enrollment courses with a 3-5 month lead time. For on-site pricing, you can use the request an on-site quote form, call us at (410) 956-8805, or email us at firstname.lastname@example.org.
Tom Sarafin has worked full time in the space industry since 1979. He worked over 13 years at Martin Marietta Astronautics, where he contributed to and led activities in structural analysis, design, and test, mostly for large spacecraft. Since founding Instar Engineering in 1993, he’s consulted for NASA, DigitalGlobe, Lockheed Martin, AeroAstro, and other organizations” to “… NASA, DOD Space Test Program, DigitalGlobe, Lockheed Martin, and other organizations. He’s helped the U. S. Air Force Academy design, develop, and verify a series of small satellites and has been an advisor to DARPA. He was a member of the core team that developed NASA-STD-5020. He is the editor and principal author of Spacecraft Structures and Mechanisms: From Concept to Launch and is a contributing author to Space Mission Analysis and Design. Since 1995, he has taught over 200 courses to more than 4000 engineers and managers in the space industry.
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