Interpretation of non-conventional miniaturized creep test: derivation of equivalent gauge length

The objective of this paper is to clarify the nature of the equivalent gauge length of miniaturized creep test methods. A mechanics-based approach was employed to allow conventional uniaxial creep data to be obtained from non-conventional miniaturized creep tests, under steady-state creep. The data interpretation is based on the reference stress method. On this basis, the theoretical derivation of the equivalent gauge lengths for a range of miniature specimen types is presented, including sub-size uniaxial, small punch, impression, small rings, miniature 2 bars, and miniature bending beams and plate. Then the effect of geometry change due to the creep test on the conversion parameters is evaluated. Finally, several theoretical and practical aspects, related to specimen deformation modes, the basis of the correlation methods, the sensitivity of “strain measurements”, the effective volumes, the choice of test methods, etc, are addressed.