What tension is put on a weld stud when torquing is applied?
What tension is put on a weld stud when torquing is applied?
(OP)
I have a CD weld stud that requires a 3.1NM torque test. I torque the stud with out anything assembled and it passes the 3.1NM torque (weld holds)
When My team assembles the part and they attempt to torque the same stud with hardware the downward force causes the weld to fail and stud to fall off. Is there a conversion to measure the upward pull on the weld when I am assembling? I want to send these back to the welder but every test that they can perform passes the simple torque test. The failure I am sure is in the upward tension.
Thanks
When My team assembles the part and they attempt to torque the same stud with hardware the downward force causes the weld to fail and stud to fall off. Is there a conversion to measure the upward pull on the weld when I am assembling? I want to send these back to the welder but every test that they can perform passes the simple torque test. The failure I am sure is in the upward tension.
Thanks





RE: What tension is put on a weld stud when torquing is applied?
So you are winding a nut down until it jams on the threads ?
Tables for Approximate bolt tension/clamping force vs torque are all over the place.
Here is one, for inch threads.
https://spaenaur.com/pdf/sectionD/D48.pdf
Here is one for metric fasteners.
https://www.fastenal.com/content/feds/pdf/Torque-T...
Many posts will follow that remind us how variable the torque/tension relationship is due to friction.
RE: What tension is put on a weld stud when torquing is applied?
Maybe you should do test and tighten the same equipment down.
One thing that might be happening, are the studs when being assembled being lubricated on the threads? if so that might be the problem, you might be testing the stud dry and they pass but your colleges are tightening the threads with lubricant on either by accident or intentional.
“Do not worry about your problems with mathematics, I assure you mine are far greater.” Albert Einstein
RE: What tension is put on a weld stud when torquing is applied?
RE: What tension is put on a weld stud when torquing is applied?
Well if the threads get lubricated at assembly then the tensile load for the same torque can double and hence yes failure will ensue.
Find out of any lubricant is getting on the threads at assembly stage.
“Do not worry about your problems with mathematics, I assure you mine are far greater.” Albert Einstein
RE: What tension is put on a weld stud when torquing is applied?
RE: What tension is put on a weld stud when torquing is applied?
If you simply twist / apply a torque to the rod after welding (e.g. hold the bottom plate still and twist the rod) the weld will only be seeing shear load, distributed over the weld length (e.g. rod circumference).
When you start to turn a nut down the rod, and try to tighten it against something, the torque you are applying to the nut presses the nut and rod threads together. As you continue to try and turn the nut down the rod (e.g. apply more torque), an upward (tension) force is generated in the rod. The weld at the bottom of the rod is therefore now experiencing a tensile load, which is determined by the amount of torque applied to the nut. As the torque on the nut increases (e.g. as you tighten it more against whatever is below the nut) the tension in the rod also increases.
There is a standard equation for this relationship. From my old metric structural standards (check whether this is applicable for your case!) the equation is:
Torque (Nm) = 0.2 x bolt tension (kN) x bolt dia (mm)
The 0.2 factor is the 'friction factor' or 'k-value' and is 0.2 for threads in an 'as delivered / slightly oily' condition.
You will be able to rearrange this to determine what tension is being applied for a given nut tightening torque.
RE: What tension is put on a weld stud when torquing is applied?
It's entirely possible that the test load is inappropriate as an installation load. Without knowing the fastener size it's not possible to tell more.
Weld studs are typically in tension.
RE: What tension is put on a weld stud when torquing is applied?
RE: What tension is put on a weld stud when torquing is applied?
Follow the link it gives procedures for testing stud welds.
https://www.pfsno.com/blog/2015/12/15/procedures-f...
“Do not worry about your problems with mathematics, I assure you mine are far greater.” Albert Einstein
RE: What tension is put on a weld stud when torquing is applied?
From what I read, it sounds like the approach used is to run a nut down to the end of the threads and trying to "twist" the stud. I believe that is not the typical means of testing a stud correctly.
The attached file is extracted from AWS D1.1. It may not be applicable to your situation, but then again, maybe it is.
Best regards - Al
RE: What tension is put on a weld stud when torquing is applied?
Best regards - Al