A novel theoretical model for obtaining Norton's law of creep materials using different small specimens

Abstract

The test method for evaluating the creep properties of a material using small specimens mostly relies on an empirical correlation equation derived through uniaxial tests, and it is difficult to obtain a unified theoretical model for creep specimens with different configurations. We propose a novel and unified theoretical model that describes the creep displacement–time curves based on the energy density equivalent principle, which can be expressed as h = h*B(P/A*)vt. A simple expression of the model parameters related to sizes was established for cantilever beam, ring compression, and flat small punch specimens using finite element analysis (FEA). Forward and reverse verification using FEA and experimental validation of the model using small specimens of a zinc alloy (ZA27) at 27°C were conducted. The results revealed that the Norton's law parameters predicted using the new creep model are in good agreement with the results obtained using the uniaxial creep test. The new model does not require an empirical correlation between the displacement and uniaxial reference equivalent strain and has a uniform characterization for four types of specimens with different configurations and sizes.