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Theta-Like Specimens for Measuring Mechanical Properties at the Small-Scale: Effects of Non-Ideal Loading



David Henann, Li Ma, Lin-Sien H. Lum


As material structures and devices build from them shrink to the nano-scale, it is ever more difficult to measure accurately mechanical properties and behavior. Such mechanical properties data are needed for designing small-scale devices and for assessing their mechanical reliability. A particularly promising small-scale mechanical testing configuration for localized measurements of tensile properties is that of a Greek theta-like geometry loaded vertically in compression, thereby subjecting the horizontal ligament to uniaxial tension. The stress distribution in such specimens, particularly in the tensile gauge section is examined via finite element analysis. As it is difficult to load uniformly a small-scale structure with an articulating load platen, alternative loading configurations are considered, progressing from a double-articulating surface contact to a single-articulating line contact and to a point contact via a spherical loading tip. As one's ability to achieve the prerequisite loading configuration improves, the state of stress in the test gauge section deteriorates. In each case the influence of non-ideal load application (i.e., non-articulation of the loading fixtures and off-center load application) is elucidated. Additionally, two alternative loading schemes are considered: the inclusion of a compliant layer to mitigate misalignment and the addition of an extended upper loading tab. The latter configuration yields the most favorable stress state and the most tolerant to non-ideal loading, while having the advantage of the simplest load application: a spherical loading tip on a flat specimen top.
Journal of the Mechanics and Physics of Solids


alignment, articulation, finite element analysis, mechanical properties, tensile testing, theta specimen


Henann, D. , Ma, L. and Lum, L. (2021), Theta-Like Specimens for Measuring Mechanical Properties at the Small-Scale: Effects of Non-Ideal Loading, Journal of the Mechanics and Physics of Solids (Accessed June 18, 2024)


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Created October 12, 2021