Small punch tensile testing of curved specimens: Finite element analysis and experiment

- Small punch test applied to nuclear fuel cladding type specimens.
- The same UTS values obtained from tube and flat small punch specimens.
- Yields stress estimates stronger affected by clamping than UTS estimates.
- Difficult to obtain a reliable yield stress using small punch.

The Small Punch (SP) technique is a miniature test used for characterizing irradiated materials or when a testing material is available only in small quantities. In this work Finite Element (FE) models are developed to support the parametric analysis of SP fuel cladding tube specimens in comparison to standard flat ones. FE analysis shows that there are practically no differences between circular and rectangular flat specimens. The tube specimen results in only slightly higher maximal force (Fm). However, Fm is attained at significantly lower displacements. This is attributed to the curvature of the specimen. The friction linearly increases the Fm and to a lesser extent the displacement at Fm. FE analysis also shows that the yield stress and different hardening, while keeping ultimate tensile strength constant, practically do not affect the Fm. Significant specimen deformation can be expected at already small (0.1 mm) puncher deflection, which could limit the applicability of the small punch test to ductile materials. Varying degree of clamping in the experimental procedure can cause large scatter in the yield stress estimates. In all cases good agreement between the simulation and experimental results was obtained, best with a friction coefficient of 0.2.