Question

Advantages and disadvantages of bolted and welded connection

Answer 1

Some advantages of bolted joints:  

1) They are easily disassembled, as opposed to something like riveting or welding, which requires cutting.  

2) They can be designed to take tension loads, unlike riveting (by tightening the bolt/nut to develop a preload, you reduce the effects of fatigue due to cyclic loading, which you can't do with a rivet; plus, rivets can easily pull through a hole when loaded in tension).  

3) Welds require heating a metal, which can change the properties in the heat-affected zone, and can also create thermal stresses. Bolts avoid this problem. You're also not likely to start a fire (welds) or breathe toxic fumes (welds and adhesive joints) when you're installing a bolt.  

4) Bolted joints aren't particularly sensitive to the condition of the parent material. With welds and adhesive joints, the parent material needs to be clean, free of oils, etc (and obviously, it has to be metal to weld).

Some disadvantages:  

1) They require access to both sides of the joint (although this can be overcome using studs or special bolts like Hi-Loks). Welding, adhesive joints, and some types of riveting can be done with access to only one side of the joint.  

2) They can become loose over time as the nut backs off (this can be addressed to some extent by using the proper preload and thread-locking features) or as the material creeps. Welding and adhesive joints don't have this problem.  

3) They require holes, which introduce stress concentrations and more failure modes; drilling the holes may create cracks which will grow over time to cause failure. Welding and adhesive joints don't require holes. Also, welds and adhesive joints are continuous, so they don't concentrate load like a bolt does.  

4) Preload can be tough to measure accurately - it depends on the method of tightening, the friction between the threads of the bolt and the nut, etc.

Answer 2

Advantages of welded joints:

• This joint is much more effective than the bolted joints with no threat of being loose with time as it is in case of bolted joints.
• There is no need of of drawing holes in the metal pieces and increase the stress concentration at that point as the two metal parts are thoroughly joined.

Disadvantages of welded joints:

• Toxic fumes are generated by the joint is being made which can be breathed in by the the person welding it.
• Unlike the bolted joint they cannot be easily assemble to dismantled whenever there is a requirement.

Advantages of Bolted joints

• Less man power is needed when compared to rivet connection.
• Higher strength bolts are more stronger to the rivets.

Disadvantages of Bolted joints:

• Bolted connection has very lesser strength in the axial tension as the root net area of thread is less.
• Under the vibratory loads, the strength is reduced if the connections are get very loosened.

To know more:

Advantages and disadvantages of bolted connection over riveted connection

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