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

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

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

(OP)
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.

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

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

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

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

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

(OP)
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.

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

What is the fastener material ?

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

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

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

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.

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

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

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

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.

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

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.

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

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.

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

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

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

(OP)
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.

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

See the insulators?

[img https://www.1stdibs.com/furniture/dining-entertain...]

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

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

See sketch of device to transmit torque while isolating thermally.

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

Rev A.

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

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

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

laser interferometer can measure extremely small distances

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

(OP)

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.







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

(OP)

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.

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

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

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

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

(OP)
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.

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

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

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

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

(OP)
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.

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

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

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

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 ?

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

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

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

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 ?

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

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.

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


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

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