isotropic vs kinematic hardening 1

[groveri]

Thin metal liner performance in filament wound pressure vessels is enhanced by autofrettage of the liner. The pressure vessel is loaded beyond the yield strength of the liner so that the liner is compressed when depressurized. The liner will then have a larger elastic range to operate in. More benefit can be obtained with a material that exhibits isotropic hardening because the compressive yield strength increases, increasing the total elastic range. Materials with kinematic hardening have decreased compressive yield strengths with no increase in the total elastic range. It is difficult to find which hardening model applies to various liner materials. Typical liner materials are austenitic stainless steels, various heat treated aluminums like 6061, 2219, non-heat treatable 1100-O aluminum, titanium, inconel and nickel. I'm looking for info as to which hardening model applies to any or all of these materials. Also, I could use a simple test method to determine the hardening model.

 

[CoryPad]

This is an advanced subject that will require some effort. In Mechanical Behavior of Materials by Dowling, he states "...the rheological models used are consistent with the behavior called kinematic hardening, the alternative choice of isotropic hardening not being employed as it is a poor model for real materials."

The topic is part of current research, a search on Scirus (

http://www.scirus.com)

will provide many results for further study. A recent thesis on the subject is available for free:

http://www.scirus.com/srsapp/scirus...0708102-185912/unrestricted/Araujo_thesis.pdf

Good luck.