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.

 

[btrueblood]

What are you fastening at that temperature? Why not let it cool off first?

 

[drawoh]

dragonliu2,

Why would a torque wrench not work? How big is the thing that is at 1200[°]C? Can you work near to it?

--
JHG

 

[dragonliu2]

Thank you,btrueblood and drawoh,I want to measure the tightening torque of the nut in real time and judge whether it is loosen during operation. The material of the connected parts of the mechanical joint are ceramics and the operation temperature fluctuates around 1200 degree Celsius. The high temperature and the temperature cycle make the nut loose and I need to find out how loose it is after a period of service.

I consulted companies such as HBM and they all said their torque transducer cannot used at such high temperature.

The contact pressure transducers as far I know cannot used at such high temperature either.

There may be some indirect measuring method.

Thank you again for your response.

 

[Tmoose]

What is the fastener material ?

 

[dragonliu2]

Tmoose: The material of the fastener is also ceramics currently, and it can also be high temperature alloy.
Thanks.

 

[3DDave]

Loosening is rarely a matter of torque and most often a matter of stretch or compression of the parts.

It might be easier to look at creep and elastic properties of the materials in a tensile test machine with a high temperature section.

 

[desertfox]

Hi dragonllu2

I am in agreement with 3DDave on this matter, it might be worth doing a calculation of thermal expansion of the components after the joint as been initially made, the calculation in my book would assume uniform heating although I don't know whether that's true or not in your case
I guess if uniform heating isn't applicable then you could use some heat transfer software to calculate what occurs in the joint.

Folowing my initial assumption I would calculate all the stresses in the joint and fastener at room temperature and then perform expansion calculations at the final temperature and check out the stresses both in the fastener and joint materials, loosening can be caused by the fastener going over its yield stress or the clamped materials going beyond yield.
If the temperature is cycled then the loosening might well be progressive.



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

 

[Compositepro]

You need to measure bolt stretch or tension not nut torque, which is meaningless except for the initial tigtening operation. There are tension indicating bolts and load washers available.

One design of tension indicating bolt has a pin inserted into a hole through the center of the bolt. Tightening the bolt stretches it but not the pin. The difference in length between the pin and bolt is easy to measure, and there should be no temperature limit to this technique.

 

[btrueblood]

Well...could you fabricate a wrench/socket/tool for tightening the bolt, and a suitably long extension (long enough to reduce the temperature at the working end of the tool) such that a person or tool could rotate the fastener while it's hot...and then apply a torque and measure shaft rotation at the cold end. You might need to do some repetitions after the first one, to see how much of the measured rotation is due to actual fastener loosening, and how much is due to slop in your tool string.

 

[moon161]

You could use some sort of insulating spacer in your works. I first thought of a ceramic socket or wrench to fit your nut or bolt, and long enough to poke out the peephole of your kiln, your could turn it with a normal torque wrench at close enough to room temp. IDK if that will withstand the torque, but maybe something to work with.

 

[EdStainless]

Since stretch is the real issue I would look at a fixed camera and reference marks on the fastener.
Perhaps one of the high resolution laser position sensors could be used for this also.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

 

[dragonliu2]

Thank you all!

EdStainless, you method may be ok to measure the rotation between the nut and the shank but cannot used to measure other tightening torque loosen mechanism such as the deformation of the fastener and the plates.

moon161,btrueblood , seems your method with long extension is the only direct method can be used now. I am still looking for some force sensors made of ceramics or Silicon that can withstand 1000 oC, but I did not find them yet. Anyway, I will try your methods if I have to.

 

[moon161]

See the insulators?

Because silver is the best thermal conductor ever, silver teapots need thermal isolator, otherwise you can't pick up the teapot.

 

[moon161]

See sketch of device to transmit torque while isolating thermally.

 

[moon161]

Rev A.

 

[EdStainless]

The torque tells you nothing, only elongation of the joint, relaxation of clamping, or some measure like that can tell you what you want to know.
You want to know if the connection loosens, well try to measure its position.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

 

[IFRs]

laser interferometer can measure extremely small distances

 

[dragonliu2]

moon161,thank you for your help and kindness.

EdStainless and IFRs, the optical method may be a good one. We thought of it and will try it when the condition is ok.

EdStainless,there usually be preload on the fastener and when the temperature-induced deformation of the fastener is larger than that of the joint plates, the fastener will loose. In this condition, both the clamping force of the fastener and tightening torque of the nut will decrease, therefore, the fastener loose can also be measured through the tightening torque of the nut. Also in this condition, there almost no relative movement between the nut and the fastener shank.

We can measure out the deformation of the fastener, but can not measure out the local deformation of the joint pleats around the hole. The area is under-covered by the nut and fastener head. The fastener loose is related to the contact relationship between the fastener and hole.

I also agree that different joint have different loosen mechanism and I will test out the loosen mechanism first.

Tmoose, sorry for the wrong information. The material of the joint plates are both ceramics matrix composite and the that of the fastener is high-temperate alloy. Ceramics fastener is a another design and will not be tested currently.

 

[Strong]

Did you contact:

http://www.hitecprod.com/pages/straingage_hfp.html

The bondable strain gage is rated less than 1200 C, but they may have some suggestions.

Walt