Vibration Analysis to detect shaft/tool failures?

[BfdDan]

Hello- I am in the cold rolling industry and want to know if anyone has any experience using vibration analysis tools to detect early shaft/tooling failures. We use shaped rolls to form steel into custom shapes and often a cracked tool is not detected until it completely fails. I would like to develop a way to detect the crack earler.

 

[GregLocock]

You might have some luck using a very high frequency accelerometer - the technique was called acoustic emissions by B&K, which was not very helpful. Do you have any idea how much warning there is? I'm guessing not much.

Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[Strong]

I have detectd shaft cracks in gearboxes using demodulated vibration spectrum. This is jst another way of processing high frequency vibrations.

Walt

 

[GregLocock]

I'd guess you'd see a once or twice per revolution high frequency spike, just before failure.

Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[Strong]

Another method is to detect change in shaft natural frequency (bending vibration mode) using vibration spectrum analysis. Regardless of the detection method, you still have to deal with background vibrations, speed/load variations, and work/process cycle. Audible sound or ultrasound for noncontact measurement may also be feasible.

Walt

 

[GregLocock]

But a crack that is about to grow rapidly (ie fracture) may not be big enough to affect the resonant frequency of the shaft.

In fact I'd go so far as to say that a frighteningly large crack would have a tiny effect on resonant frequency.

Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[NVAPORMAN]

I am curious as to the rotational speeds,size of shafts,bearings,components or any pictures of the equipment.