permanent set from cyclic loading?
permanent set from cyclic loading?
(OP)
I have a LDPE part that is subjected to a periodic compressive stress varying between about 20% of its yield strength and 0. When the machine is not running, it is subjected to a constant compressive stress of about 1% of its yield. Is it reasonable to expect this part to have no permanent set after millions of cycles and a few years sitting there? How about with a different polymer?





RE: permanent set from cyclic loading?
RE: permanent set from cyclic loading?
All thermoplastics are subject to flow or creep under load. PE is one of the most susceptible. Acetal is one of the least susceptible.
If you can use a cross linked material you will have much better elastic recovery.
PE can be obtained in cross linkable form as can polyurethane and many rubbers. The middle ground are the vulcanized rubber filled alloys, the most well known being Santoprene.
50 deg C is relatively hot for LDPE
Regards
Pat
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RE: permanent set from cyclic loading?
patprimmer,
Strange thing happen on the way to the Forum. I was on the phone with an engineer at the local Santoprene Plant when I open ths thread and read your post. He said thanks for the recommendation.
RE: permanent set from cyclic loading?
RE: permanent set from cyclic loading?
Regards
Pat
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RE: permanent set from cyclic loading?
As 90% of our products in any table we always ran compatibility tests which included a test for permanent set