Successfully estimating tensile strength by small punch testing


Successfully estimating tensile strength by small punch testing

Holmström, S.; Simonovski, I.; Baraldi, D.; Bruchhausen, M.; Altstadt, E.; Delville, R.

The Small Punch (SP) test is a relatively simple test well suited for material ranking and material property estimation in situations where standard testing is not possible or considered too material consuming. The material tensile properties, e.g. the ultimate tensile strength (UTS) and the proof strength are usually linearly correlated to the force-deflection behaviour of a SP test. However, if the test samples and test set-up dimensions are not according to standardized dimensions or the material ductility does not allow the SP sample to deform to the pre-defined displacements used in these correlations the standard formulations can naturally not be used. Also, in cases where no supporting UTS data is available the applied correlation factors cannot be verified. In this paper a formulation is proposed that enables estimation of UTS without supporting uniaxial tensile strength data for a range of materials, both for standard type and for curved (tube section) samples. The proposed equation was originally developed for estimating the equivalent stress in small punch creep but is now shown to also found to robustly estimate the UTS of several ductile ferritic, ferritic/martensitic and austenitic steels. It is also shown that the methodology can be further applied on non-standard test samples and test set-ups and to estimate the properties of less ductile materials such as 46% cold worked 1515Ti cladding steel tubes. In the case of curved samples the UTS estimates have to be corrected for curvature to equal the corresponding flat specimen behaviour. The geometrical correction factors are dependent on tube diameters and wall thicknesses and were solved by finite element simulations. The outcome of the testing and simulation work shows that the UTS can be robustly estimated both for flat samples as well as on thin walled tube samples. The usability of the SP testing and assessment method for estimating tensile strength of engineering steels in general and for nuclear claddings in specific has been verified.

Keywords: small punch test; tensile strength

  • Contribution to proceedings
    5th International Small Sample Test Techniques (SSTT) Conference 2018, 10.-12.07.2018, Swansea, United Kingdom
    Conference Proceedings of 5th International Small Sample Test Techniques Conference SSTT 2018, Swansea

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