Design and Drafting of Riveted Joints

Definition

A riveted joint is a permanent mechanical connection used to join two or more plates or structural members by inserting a metal pin, known as a rivet, through aligned holes and deforming its tail end to create a secure head.

Main Content

1. Types of Riveted Joints

• Lap Joint: The plates to be joined overlap each other. Single or double rows of rivets can be used based on strength requirements.
• Butt Joint: The plates are kept in line and are joined using cover plates (straps) on one or both sides of the main plates.

2. Rivet Head Profiles

• Snap Head: Most commonly used for structural work; it provides a smooth, rounded appearance.
• Countersunk Head: Used where a flush surface is required, such as in aerospace or automotive exterior paneling to reduce drag.

3. Failure Modes of Riveted Joints

• Tearing of Plate: The plate might tear along the line of rivet holes (the margin) due to excessive tensile stress.
• Shearing of Rivet: The rivet itself may be cut or "sheared" across its cross-section due to the forces pulling the plates in opposite directions.

[Visual representation of Shear Failure]
   Plate 1 --->
   __________________
   |      |   |      |
   |      | O |      |  <-- Rivet shears here
   |______|___|______|
          |   |
   <--- Plate 2

Working / Process

1. Preparation of Plates

• Plates are marked and center-punched to indicate the exact location of the rivet holes.
• Holes are drilled or punched to a diameter slightly larger (typically 1.5 mm to 2 mm) than the nominal diameter of the rivet shank.

2. Assembly and Heating

• The plates are aligned, and the rivet (often heated to a cherry-red color for large diameters) is inserted through the aligned holes.
• Heating makes the metal ductile, allowing it to be easily shaped while filling the hole completely.

3. Forming the Tail

• The tail end of the rivet is hammered or compressed using a die (snap) to form a new head.
• As the rivet cools, it contracts, pulling the plates tightly together, creating a high clamping force known as residual tension.

Advantages / Applications

• Permanent Connection: Unlike bolts, rivets are difficult to remove without destruction, ensuring structural integrity in high-vibration environments.
• Material Compatibility: Riveting allows for the joining of dissimilar materials or non-weldable alloys.
• Industrial Usage: Extensively used in shipbuilding, bridge construction, aircraft fuselages, and pressure vessel manufacturing.

Summary

Riveted joints are a traditional yet highly reliable method of permanently fastening structural components. By utilizing the shear strength of the rivet and the clamping force generated during cooling, these joints provide excellent resistance to fatigue and vibration.

• Key takeaways: Riveted joints rely on the shearing and bearing strength of the rivet and the tensile strength of the joined plates.
• Process: The process involves aligning, inserting a ductile rivet, and forming a second head to lock the assembly in place.
• Important terms:
  • Pitch: Distance between center of one hole to the next.
  • Margin: Distance from the edge of the plate to the center of the nearest hole.
  • Shear Stress: The force tending to cut the rivet.