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 the 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 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 15-15Ti cladding steel tubes. In the case of curved samples the UTS estimates have to be corrected for curvature to match the corresponding flat specimen behaviour. The geometrical correction factors are dependent on tube diameters and wall thicknesses and were determined 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 for 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.
The orientation relationship of an austenite-to-ferrite phase transformation in 316L stainless steels induced by the loss of austenite stabilizers resulting from the steel dissolution corrosion in ...liquid Pb-Bi eutectic was studied by means of electron backscatter diffraction. The misorientations at the austenite/ferrite interface were compared to the prevailing orientation relationship models in steels. The Pitsch orientation relationship model was found to be predominant, which is unusual for austenite-to-ferrite bulk transformations in steels. The nature of this particular transformation, which involves loss of steel alloying elements and the presence of an interfacial liquid metal layer, is discussed to explain this finding.
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Functional interfaces are at the core of research in the emerging field of 'domain boundary engineering' where polar, conducting, chiral, and other interfaces and twin boundaries have been ...discovered. Ferroelectricity was found in twin walls of paraelectric CaTiO
3
. We show that the effect of functional interfaces can be optimized if the number of twin boundaries is increased in densely twinned materials. Such materials can be produced by shear in the ferroelastic phase rather than by rapid quench from the paraelastic phase.
Celotno besedilo
Dostopno za:
BFBNIB, DOBA, GIS, IJS, IZUM, KILJ, KISLJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
A sharp drop in hysteresis is observed for shape memory alloys satisfying the compatibility condition between austenite and martensite, i.e.
λ
2
=
1, where
λ
2 is the middle eigenvalue of the ...transformation strain matrix. The present work investigates the evolution of microstructure by transmission electron microscopy as the composition of the Ti
50Ni
50−
x
Pd
x
system is systemically tuned to achieve the condition
λ
2
=
1. Changes in morphology, twinning density and twinning modes are reported along with twinless martensite and exact austenite–martensite interfaces.
Considering positive Maxwell problems, we propose a substructured version of the Hiptmair-Xu preconditioner based on a new formula that expresses the inverse of Schur systems in terms of the inverse ...matrix of the global volume problem.
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