Preconditioning characteristics of porcine aortic tissue

Repeated, cyclic loading, or "preconditioning" is used to place a material in a repeatable reference state for subsequent mechanical testing. Methods vary, however, because there is no well defined preconditioned state. Through the testing of strips of fresh porcine aortic valve leaflets the authors find that even at small loads there is slight migration of sequential elongation curves in the positive strain direction, likely due to creep. It is concluded that a small but constant migration per cycle can still constitute a preconditioned state.