Linear elastic stress-strain

[pocoyo]

I wonder is there any kind of materials that experimentally exhibit linear stress-strain relationship with strain of 5% or more?
Many thanks in advance,

pocoyo

[Jorgen]

If by linear stress-strain you mean purely linear (that is, not viscous or any other non-linearity), then I would think that there are virtually no material that is purely linear for strains > 5%.

-Jorgen