Ultrasonic metal welding - serration wear name

[dculp1]

In ultrasonic metal welding, a serrated tip engages the top workpiece and causes it to oscillate, typically at 20000 Hz. The tip amplitude may be in the range of 10 to 50 micrometers, peak-to-peak. Meanwhile, a serrated anvil engages the bottom workpiece to restrain it from vibrating. A compressive force of up to 500 pounds is applied to the workpieces between the tip and anvil. No lubricant is present.

During this process the serrations of the tip and anvil wear (see attached photo). The serration temperatures may become high, possibly enough to soften the serrations. Also, the serrations may adhere to the workpiece, possibly by welding. Fatigue of the serrations may also be involved. The rate of wear depends on the serration materials (typically hardened steel), the workpiece materials, and the process parameters. In some cases many thousands of workpieces can be processed before significant wear occurs; in other cases significant wear may occur after relatively few workpieces have been processed.

What is the best name that describes this type of wear? Galling? (Neither "abrasion" nor "fretting" seems appropriate. However, fretting does involve oscillatory motion.)

Thanks,
Don C.

 

[metengr]

The term you are looking for is called fretting wear.

 

[EdStainless]

we referred to it as fretting also.
Since the loads are actually fairly low and the process involved intermittent sticking.
Macro-failure of the horn and anvil were sometimes fatigue.

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P.E. Metallurgy, Plymouth Tube

 

[dculp1]

Fretting usually assumes small amplitudes which the ultrasonic welding would seem to satisfy (10 to 50 micrometers, peak-to-peak). For fretting, is there any assumption about the maximum velocity (which would be related to the rate of wear) - i.e., that if the velocity exceeds some upper value then it is no longer considered fretting? (For the given amplitudes at 20 kHz, the peak velocities range from 0.6 to 3.1 m/sec.)

EdStainless --

It sounds as though you have had experience with this type of wear in ultrasonic welding. Is this so?

 

[EdStainless]

I used to UTW high performance thermo-plastics (carbon loaded PPS and PEEK).
It was hell on tooling.
We used many materials, carbide (solid, not bonded), H13 tool steel, and cobalt alloys.
The Co alloys worked very well even though they weren't as hard, they resist wear fantastically.

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P.E. Metallurgy, Plymouth Tube

 

[dculp1]

EdStainless --

UTW = Ultrasonic Thermoplastic Welding?

Do you have particular Co alloys that you would recommend? What heat treatment would you apply? (This info would be very helpful for continuing development of

http://ultrasonic-resonators.org/miscellaneous/wear/wear.html.

Any additional info would also be helpful.) Thanks.