Bolts of Uniform Strength – Design of Bolted Joints – Design of Machine

Bolts of Uniform Strength – Design of Bolted Joints – Design of Machine


Hello friends here in this video we will see what is meant by Bolts of Uniform strength I’ll write the topic name Bolts of uniform strength as for the name when we are having the bolts they should be of uniform strength to explain this here I will draw our diagram This is the diagram of bolt of a simple bolt which I am drawing this is the bolt head know as we can see in the diagram of this bolt here we have a threaded section and then this section is plain it does not have threads now this portion which do not have threads it is called as shank after the shank here we have the threaded section when the load is acting over this bolt this bolt would be failing at a minimum area or we can say where the area is not uniform if we look at the shank the diameter of the shank is uniform but if we look at the threaded portion here we are having uneven area so it is very much clear that failure will start in this threaded section this bolt will not fail at the shank it will fail at the threads and by failing we mean that the threads they are going to break now looking into this diagram since I can say that stress will be maximum where area is minimum now if we compare your this is the minimum diameter which we call it as the Cole diameter D suffix C and then we have the outer diameter called as the nominal diameter D oh so what will happen is that when the load is acting over this bolt the threaded section stresses will accumulate in this section and because of this when the load is applied at the core diameter as we can see the diameter is less so even area is less so when we apply a load there are chances of breaking of threads at the core the threads will break at the core like this now if we look into the diagram the diameter of the shank is equal to the outer diameter of the threads that is the nominal diameter and we are left with D C which is the minimum diameter it means the shank has sufficient strength similarly outer diameter is having strength but DC it is weaker section so failure will start at this weakest section so here I can say that this much portion the threaded section it is the weakest section so we if we need to avoid this condition that is if you want to avoid the breaking of this threads because what is happening is that in the bolt half of the part up to the shank it is a stronger part whereas the threaded portion they are weaker so the load distribution is non-uniform and even the stress distribution is non-uniform threaded section will have more stress compared to the shank which is the plain portion so what we have to do we have to make such a bolt which has uniform strength that is the strength is same throughout now how that can be done one of the method is to reduce the shank diameter up to the cold diameter I will draw it and explain here I am explaining one of the methods to get bolts of uniform strength these are the threaded section now here previously the shank diameter was equal to the outer diameter now what we are doing we are removing the material at the shank and making the shank diameter equal to the core diameter as we can see in this diagram now when the load will be acting load will not concentrate only in the threaded portion but it would be uniform because the diameter of the shank the shank diameter is equal to the core diameter smaller diameter DC so when you make the shank diameter equal to core diameter then that would be called as bolt of uniform strength under the action of load this bolt width would be equally stressed in the shank and in the threaded portion so the chances of failure of such a bolt is less as compared to the previous one where the hole diameter was less and shank diameter was equal to the nominal diameter now one more method to get bolts of uniform strength is that in this same diagram suppose if we are not making the shank diameter equal to the core diameter the other method is to drill a hole inside the shank passing through the bolt head like this see this is one more method like where we are drilling a hole this is the drilled hole so another method of getting bolts of uniform strength is in the simple bolt where the shank is equal to the diameter which is the nominal diameter we can simply drill a hole so now what will happen when this is subjected to load along with the weakest section even this section where there is hole stress would be distributed and in this way the stress would be uniformed so in this video we have seen what are made by bolts of uniform strength

14 Replies to “Bolts of Uniform Strength – Design of Bolted Joints – Design of Machine”

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