Bolt Preload, Completely: Torque, Friction, Joint Diagrams and Fatigue

Everything a bolted joint is doing, with numbers. Stiffness from Hooke's law, the joint as two springs, the joint diagram, the load split that keeps a preloaded bolt out of fatigue, separation and prying, and then the tightening side: where torque goes, the nut factor, scatter, oil, angle tightening, torque to yield and direct measurement.

It closes with the slow failures, loosening, embedding and temperature, and the preload budget a designer actually writes down.

In this video

• Bolt and joint stiffness, the joint diagram
• Load split: 10 kN external, 1 kN on the bolt
• Separation, prying and fatigue
• Torque split 50/40/10 and the nut factor
• ±30 % scatter, lubrication, angle and yield tightening
• Loosening, embedding, thermal effects
• Writing a preload budget and a tightening spec