# Reference source of study for welding clamping force calculation

• Nitheeswar
Nitheeswar
TL;DR Summary
I need to know reference source about clamping forces required to hold the welding components
What are the factors considered while calculating clamping force requirement ?
Clamping force for welding based on thickness - 48*s^3
s- thickness
what are other factors considered along with thickness and i need a detail source/reference books?

That is a huge question. There can be no one reference book.
Most clamping force will be very specific, and based on experience.

F = k * width * (thickness)^3 .
But that ignores the clamp position and distance between the clamps.

What material ?
What welding process ?
Clamping parts together, to eliminate air gap ?
Or clamping a part to a fixing table without distorting the table ?

DeBangis21
Material is SS and process is MAG
We are clamping sheet to fixed table which has a resting base

Is this formula F=12*b*s^3 is valid for only thickness upto 6mm or more?

Nitheeswar said:
Is this formula F=12*b*s^3 is valid for only thickness upto 6mm or more?
The force needed to bend the beam, to close air gaps, prior to welding, is a function of s^3, so it should work for any thickness, s. The parameter not specified are the number and position of clamps.
Nitheeswar said:
We are clamping sheet to fixed table which has a resting base
You may know what you mean by that, but there are too many possible interpretations for me to make any sensible comment. Maybe we could have a picture or detailed diagram.
What are you welding to what, with what type of joint?
Do you use a backing strip of brass or copper?
Manual or robot process?

We can consider one sheet rested on table and clamped from top
Another sheet rested on bottom plate and also clamped from side which has rest plates on opposite side of clamping
We can consider two plates as L shape of length 1.5 m
It's a manual process and it is a fillet weld

My motive is to not only for one case
We want to study about clamping forces required for different orientations, thickness,lengths,weld sizes,positions etc,.

Nitheeswar said:
We want to study about clamping forces required for different orientations, thickness,lengths,weld sizes,positions etc,.
Then you need to study the elasticity of engineering materials, and the deflection of materials subjected to loads.
You will then be able to calculate the force required to straighten a part, and hold it in that position, while it is being welded.

https://en.wikipedia.org/wiki/Elasticity_(physics)
https://en.wikipedia.org/wiki/Young's_modulus
https://en.wikipedia.org/wiki/Euler–Bernoulli_beam_theory

Nitheeswar said:
My motive is to not only for one case
We want to study about clamping forces required for different orientations, thickness,lengths,weld sizes,positions etc,.
Another alternative is to hire a very experienced welder (a few decades worth of varied experience) and turn him loose on building the project.
(or at least join the team)

Baluncore said:
Then you need to study the elasticity of engineering materials, and the deflection of materials subjected to loads.
You will then be able to calculate the force required to straighten a part, and hold it in that position, while it is being welded.

https://en.wikipedia.org/wiki/Elasticity_(physics)
https://en.wikipedia.org/wiki/Young's_modulus
https://en.wikipedia.org/wiki/Euler–Bernoulli_beam_theory

Baluncore said:
Then you need to study the elasticity of engineering materials, and the deflection of materials subjected to loads.
You will then be able to calculate the force required to straighten a part, and hold it in that position, while it is being welded.

https://en.wikipedia.org/wiki/Elasticity_(physics)
https://en.wikipedia.org/wiki/Young's_modulus
https://en.wikipedia.org/wiki/Euler–Bernoulli_beam_theory
ok. we are deciding clamping force based on the deflection using concepts of deflection of materials subjected to loads
how deflection is found ? what are inputs for finding deflection?

Nitheeswar said:
how deflection is found ? what are inputs for finding deflection?
Look for problems of fit by using a feeler gauge, or look for light passing through a gap that is due to imperfect stock or preparation.

A competent welder will know what is required. They should work with a mechanical engineer, to design the jigs and fixtures needed for a routine assembly.

Allowance will need to be made for shrinkage of the weld. As a weld fillet cools, it will close the angle slightly. The support jig will need to allow for that deformation.

Take a look at:
Title: Jigs and Fixtures Design Manual
Author: Prakash Hiralal Joshi.
McGraw-Hill Professional Publishing (2002)
ISBN: 0071405569
See: Chapter 10. Welding and Assembly Fixtures.

Lnewqban
Here my question is,
If we are welding without clamping, then this causes some b deflection
To avoid deflection we are clamping the parts
For clamping force calculation, we are using deflection as input
how we can find the deflection caused due to welding?

Nitheeswar said:
Here my question is,
If we are welding without clamping, then this causes some b deflection
To avoid deflection we are clamping the parts
For clamping force calculation, we are using deflection as input
how we can find the deflection caused due to welding?
As explained above, there is no simple answer or general calculation for that heat induced deflection.
It is a case by case analysis, where the skill of the welder and the temperature used make a big difference.

Wherever steel gets red, but is restricted to expand, it will deform (or shrink).
It will then contract when cooled down, pulling the surrounded material with same force that it tried to pushed it away when hot (previously to becoming red and plastic).

If you have a production line, where similar parts are welded together, experimentation with jigs and welding techniques (pre-spot welds along the joints, low temperature, etc.) will reveal the sweet spot to you quicker than inaccurate calculations.

https://www.engineeringtoolbox.com/stress-restricting-thermal-expansion-d_1756.html

https://www.engineeringtoolbox.com/linear-thermal-expansion-d_1379.html

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