Irreconcilability of uniaxial test data with irreversibility of loading and unloading

Abstract

Uniaxial material properties of macroscopic average stress and strain invoke monoscale global equilibrium. The procedure does not hold for microscopic uniaxial stress and strain test specimens. There lacks direct connection between the measured stress and strain at the macro and micro scales. Scale transmissibility of stress and strain must be validated by models and/or laws. Material testing philosophy of the 18th century are not valid for the 21st century applications, where microscopic and nanoscopic effects enter into design. Simply put, the dual scaling of distortion (micro) and dilatation (macro) is no longer uncommon.The use of true versus engineering stress and strain (S&S) can be troublesome as they entail contrasting physical interpretation for the same material, say for the 4130 steel for example. The true S&S curve shows hardening while the engineering S&S curves exhibit softening. The fictitious concept of elastic and plastic unloading also renders different meanings. Dissipated and available energy density from the uniaxial data can yield positive and negative efficiencies for 4130 steel. The benefit of micro and/or nano effects to macro properties can depend on the sustainable time of the test data. The active holding time of the nano interface reinforcement depends on manufacturing know-how, a highly guided trade secret that cannot be commonly acquired without the analytical skill and knowledge of non-equilibrium mechanics and metallurgy.The competition of the 21st century rests on energy efficiency for the use of super strength materials and structural systems. The axiomaticism of material testing can no longer walk alone without the emphasis of “identifiability and synchronicity” (I&S) of I-Ching or the Books of Changes. Uncertainties are not likely to be revealed by postulating and testing models without a knowledge of I&S. Physical events are biased by synchronicity, a property that can mitigate uncertainty. As application is extended from the macro to the nano or even smaller scale, multiscaling models will be the rules in material science research rather than the exception.