What is riveted joints?
There are different Types of riveted joints used to joint two steel or timber member.
Rivets are the non-threaded strong joints that are generally made up of aluminum or steel consisting of head and shank. And, riveted joints are the joints that are permanent, consisting of mainly two components that are controlled together by the rivet, head at the top, and tail (cylindrical stem) at the bottom.
Riveted joints are called fasteners as head enables the rivet function as a fastener, formed on the free end by a setting. It has an appearance like a metal pin.
It was not often used in the past but due to its significant improvements in welding and bolted joints, it is now generally used in structures. They are generally made up of low carbon, nickel steel, brass, copper, and aluminum.
Geometry of riveted joint:
- It is made up of wrought iron of soft steel due to lower hardness.
- Also, in corrosive environment copper, aluminum is used for ductility, toughness, and hardness.
- For structural purposes, rivet up to 40mm dia is used.
Mechanism of riveted joints:
- It is made up of die and backup die and rivet are kept in between them by the help of force that makes the rivet placed in the part to be set.
- Rivet is deformed by equal and opposite mechanical force so that the tail part is converted to head at the bottom. Thus, the complete rivet is placed in the plates. This process is called the shop head.
- The part that is to be joined are drilled first by drilling machine and clearance are considered as:
|12 to 24 mm||1.5 mm|
|24 to 48 mm||2 mm|
Depending on the thermal condition of rivet, riveting process can be done on two ways:
If the cold rivet is used in normal temperature during the riveting process, it is known as cold riveting. The cold riveting is done in normal structural joints, woodworks, etc. in ambient temperature.
Condition to use:
- If steel rivet has a diameter less than 10mm,
- If the rivet is made up of ductile materials like aluminum, copper, brass, etc.
Advantages of cold riveting:
- In this process no heat is involved so will require less time.
- Joined material is not affected by temperature.
Disadvantages of cold riveting:
- Requires more energy as it needed more hammering force
- Joined part will have the less gripping force
- Is not suitable for the leak-proof joint.
If rivet shank is heated to red hot before sliding into metal plates then such process is called hot riveting process. Its reduction on length is prevented by heads rested on a plate, reduction may have occurred due to the shrinkage while cooling.
Due to this the connected parts get compressed because of increased tensile stress and result in riveted parts holding tightly. Hot riveting is generally used in fluid-tight joints.
Condition to use:
- Steel rivet having the diameter more than 10mm,
- If the rivet is made up of less ductile materials.
Advantages of hot riveting:
- Less hammering force is required,
- Clamp are joined tightly,
- Useful for the leak-proof joint.
Disadvantages if hot riveting:
- Not appropriate for heat-sensitive working,
- External heating source is also required to heat rivet,
- Due to the rivet shank heating process, it takes a long time.
Types of riveted joints
According to position of plates:
- Lap Joint
- Butt Joint
In these types of riveted joints, plates are kept face to face so that overlaps exist where the rivet is inserted. Rivet joints are classified according to the numbers of rows such as single riveted joint, double-riveted joints, etc. and this number of rows gives strength to the joint.
The arrangement of rivets between rows can be,
Chain riveting: rows will have rivet in same transverse line
Zig-zag riveting: rivets in the rows will staggered.
In these types of riveted joints (butt joints), rivets are placed in such a way that they do not form any overlap and are placed in each plate and one or two cover plates.
They may be of single strap or double strap butt joints that are according to the number of cover plates. In this joint, rivets can be arranged as a single row, double or triple chain or zigzag.
According to purpose:
- Strong joint:
They are used in engineering structures such as beams, trusses, and machine frames. As they as used in strong structure so-known as strong joints.
- Tight joint:
They are used in providing strength and leak proof against low pressures. They are generally used in reservoirs, containers, and tanks.
- Strong tight joints:
This joint is used in the boilers and pressure vessels to ensure both strength and leak proofness.
Types of rivet
Generally, eight types of rivets are used as the joints:
- Blind rivets:
They are also known as hollow or pop rivets that are used where we can’t see the next side of the join. They can be applied very fast and can be used in aerospace, shipbuilding, and electronics.
- Drive rivets;
They have a short mandrel to protrudes from the head. The end is inserted into the hole to flare by using the hammer.
- Flush rivet:
They are also known as countersunk rivets as they use countersunk heads and countersunk hole. They are mainly used for the external surfaces for providing a good appearance and to eliminate aerodynamic drag.
- Friction lock rivet:
They are early forms of a blind rivet having a dome-shaped structure. They are generally used in aerospace as an expanding bolt.
- Oscar rivet:
They have a structure of splits along with the hollow shaft and splits usually available in three sets. This is because the shaft to bend and flare outwards as the mandrel needs to be drawn into the rivet.
- Self-piercing rivets:
This rivet ends includes a chamfered poke to pierce materials so it doesn’t need a drill or punched hole. They can pierce through the top sheet by creating water or gas-tight joint but cannot perfectly pierce the bottom sheet of the materials.
- Solid rivets:
It is also known as round head rivets that are the oldest rivet, from the bronze age. They are very good and reliable types of fasteners.
- Structural steel rivets:
This has been replaced nowadays as it requires the high skilled workers to install and tighten these bolts. They were used in joining structural steels.
Types of failure in different types of riveted joints
The failure mainly occurs in four location due to stress. They are:
- Shearing stress failure:
Due to exerting the tensile stress by the plates on the rivets, they shear off as they cannot resists the stress.
- Tearing of plate at edge:
Due to tearing at edge, the joint may fail. To overcome this failure, we can keep margin, m= 1.5d,
d = diameter of rivet hole.
- Tearing of plate across rows:
The plates can tear off across the row due to low resistance to the tensile stress in main plates. To overcome this failure, we consider one pitch length of the plate.
- Crushing of rivets:
Rivets may be crushed without shear under the tensile stress causing an oval hole on the rivets and losing the joints.
Advantages of riveted joint
- Fabrication cost is cheaper
- Maintenance cost is low
- Non-metallic joints can be used in riveted joints
- It is more durable
- Flexibility in design
- Easy inspection
Disadvantages of riveted joint
- Required skilled manpower
- Leakage may occur
- Requires more workspace
- Structural weight increases
- Aesthetic finish lacked
Application of different types of riveted joints
- Boiler shells
- In structures members
- In bridge parts
- Railways wagons
- Buses and trucks
I hope this article remains helpful for you.
Happy Learning – Civil Concept
Civil Engineer – Shreya Parajuli