Fasterner's tighening torque measurement in real time at high temperature

[dragonliu2]

Dear all,

Does anyone know how to measure the fastener’s torque at 1200 degree Celsius or even higher?
Are there any torque transducers about this? Or are there any companies can provide this kinds of service?

Thank you.

 

[dragonliu2]

Strong,thank you. The high temperature strain gage can also be used to measure clamping force of the fastener. This is one of the solutions I am looking for.

Though the clamping force of the fastener or the strain of the fastener shank cannot be measured directly since the shank is hidden inside the fastener hole, I can add a block between the nut and the joint plate and measure out the block's strain. With the selection of the material of the block and some calculations, the influence of the block can be decreased to be ignorable.

 

[rb1957]

how about witness marks, to detect changes in the nut position.

another day in paradise, or is paradise one day closer ?

 

[dragonliu2]

rb1957, the optical method can be used to judge/measure the rotation between the nut and the shank but it may be difficult to be used to measure the difference between the deformation of the fastener and the joint plates. The deformation difference can also make the nut loose if the deformation of the shank is larger than those of the joint plates in the thickness direction of the joint plates.

Thank you for your contribution.

I now have 3 methods to try:
1)Measure the torque of the nut using long bar with heat insulating section;
2)Measure the torque of the nut firstly as it is cold, and then heat the joint and after certain heating cycles, cool the joint down and measure the torque again. Repeat this process again and again. This method can judge whether the nut is loosen or not after some cycles of heating but can not tell the torque value when the temperature is very high(about 1000 oC or higher);
3)Add a block between the nut and one of the joint plate, and measure the compression strain in real time using the high-temperature strain gages, and then eliminate the block's influence by selection the block(both dimension and material) and calculation.

Thank you all.

 

[rb1957]

if the nut doesn't turn, has the torque changed ?

another day in paradise, or is paradise one day closer ?

 

[dragonliu2]

rb1957,the torque may increases when the temperature is changed, for example the joint plates expand larger than the fastener shank along the axis direction of the shank though there is no movement between the nut and shank, and vice visa.

 

[desertfox]

http://www.boltscience.com/pages/untightening.htm

http://mguler.etu.edu.tr/MAK205_Chapter4.pdf

Above are a couple of sites that might help with your problem[pre][/pre]

“Do not worry about your problems with mathematics, I assure you mine are far greater.” Albert Einstein

 

[desertfox]

Sorry should of said in the second link have a look at example 4.11

“Do not worry about your problems with mathematics, I assure you mine are far greater.” Albert Einstein

 

[rb1957]

thermal expansion is "just" another factor to take into account when defining preload; well understood.

is the question about preload or torque ? as torque in the nut won't change with temperature.

why the need to measure in the oven ? why not remove from oven (and handle with care) ?

another day in paradise, or is paradise one day closer ?

 

[desertfox]

Hi rb1957

What I was alluding to with those links that it's possible to calculate the increased stresses in both the clamped parts and the bolt after assembly due to increased temperature, not sure how accurate it would be but you can calculate it by hand using the assumption for the area of the clamped parts being based on 2.5 times the bolt diameter (Roy Mech site).
I've used calculations in the past based on this and had no problems albeit my materials were copper or aluminium being clamped with steel bolts.

“Do not worry about your problems with mathematics, I assure you mine are far greater.” Albert Einstein

 

[rb1957]

yes, there are analytical approaches of varying accuracy. I was replying to the OP's post.

another day in paradise, or is paradise one day closer ?

 

[3DDave]

Another tweak to this is that the material properties will likely change, particularly the coefficient of expansion is not linear over large temp changes and I expect the modulus of elasticity isn't constant either. If multiple materials are used, getting the data for the analytic solutions is going to be interesting.

 

[desertfox]

hi 3DDave

I agree about the material properties however I get the impression they are all the same grade of ceramic but we need that confirming.
At least if OP does a ball park calculation by hand it gives a starting point the hand calculation might show the joint is a non starter but who knows.

“Do not worry about your problems with mathematics, I assure you mine are far greater.” Albert Einstein