Riveted joints make use of rivets to make the joints. This is one of the most widely used cold joining processes to fasten sheet metals. A rivet is a short cylindrical non-threaded mechanical device. Because of the presence of rivets, the joint is known as a riveted joint. In this article, we will explore more about riveted joints, their types, and applications.
What are Riveted Joints?
Riveted joints are permanent fastening joints for joining mainly two parts (plates or sheets). A rivet held the parts together with an integral head at the top and a narrow tail at the bottom. The short cylindrical part in between the head and tail is known as the shank. So, the riveted joint can be defined as a permanent joint between two sheet metals using rivets without any application of heat. As all the riveted joints use rivets as the primary component for joining, let’s learn a bit about the rivets.
What are Rivets?
A rivet is a well-known mechanical fastener having 3 parts (Fig. 1A); Head, Body or Shank, and Tail. Common materials used for producing rivets are Mild Steel, Copper, Brass, Aluminum, etc. The upper-most part known as the head can have various shapes depending on its applications. The bottom part known as the tail is usually tapered. The length of the tail is usually (1/4)D.
Based on the heads used on rivets, they are classified into various types as listed below:
- Snap head or cup head rivets
- Conical head rivets
- Pan head rivets
- Countersunk/Oval countersunk head rivets
- Flathead rivets
- Hollow head rivets.
- Biffurcated head rivet
Applications of Riveted Joints
Riveted joints are a popular choice wherever the application of heat /welding is not easily available or is prohibited. Some of the common applications of riveted joints are:
- Aircraft components and structures
- Boiler Shells
- Railway wagons and coaches
- Bridge parts
- Pressure Vessel Components
- Electronic Parts
Types of Riveted Joints
In general, there are two main types of riveted joints that are widely used. This classification is based on how the plates are used while joining.
- Lap Joint and
- Butt Joint
Lap Joint: In the lap joint type of riveted joint, the plates are slightly overlapped and joined by inserting the rivet through the coincident hole. The rivets make the connection in the overlapped region.
Butt Joint: In the butt joint type of riveted joint, the joining members do not create an overlap, rather they are placed edge to edge. External cover plates (also known as straps) are used while riveting.
Again, depending on how the riveted joints are done while joining (how rivets are arranged in the workpiece while joining), riveted joints are classified as the following types:
- Single Riveted Joints
- Double Riveted Joint
- Chain Riveted Joint
- Zig-zag Riveted Joint
- Diamond Riveted Joint
Single Riveted Joints: Single riveted joint is basically single row riveted joints. The plates are joined by riveting along a line using a single row using either a lap or butt joint.
Double Riveted Joints: As the name suggests, double riveted joints use two rows of rivets for joining each main plate. Both the rows are in the same line of axis. Double riveted joints can be lap or butt joints.
Chain Riveted Joints: In the case of chain riveted joints, the rivets in the adjacent rows are opposite to each other in the same transverse line.
Zig-zag Riveted Joint: When the rivets in the adjacent rows are staggered in such a fashion that every rivet is in the middle of two rivets of the opposite row the joint is known as a zig-zag riveted joint. They have a staggered pitch.
Diamond Riveted Joints: In a diamond riveted joint, the rivets are symmetrically arranged in a diamond pattern about the plate centerline. The number of rivets gradually decreases from the inner to the outer row. Bridge trusses usually use this type of riveting joint. The most common diamond riveted joints are butt joints.
Again, based on the condition of the rivets that are introduced between plates for joining, the riveting process can be of two types:
- Cold Riveting and
- Hot Riveting
While cold riveting is popular for structural joints. In hot riveting, the red hot rivet is introduced between plates to be joined.
For joining two plates by riveting, holes are punctured/drilled in both plates. The diameter of the holes is usually made 1.5mm larger than the nominal rivet diameter. In the next step, the hot or cold rivet is introduced between the arranged holes of the plates. Riveting can be performed by a riveting machine or by hand.
Assumptions for the Design of Riveted Joint
To simplify the process of the design of riveted joints, certain assumptions are made. Those are:
- Load among all the rivets is assumed to be uniformly distributed.
- The generated stress in the plate is considered to be uniform.
- The shear stress is assumed to be uniform throughout the gross area of rivets.
- Bearing stress between the contact surfaces of the plate and rivet is assumed to be uniform.
- The bending stress in the rivet is neglected.
- The rivet hole is assumed to be completely filled by the rivet.
- The friction force is assumed to be not present between plates.