In order to ensure the safety and evaluate lifetime extension of nuclear power plants,it is fundamentally significant to accurately surveillance the mechanical properties of the in-pile components.Irradiation hardening and embrittlement is a major concern[1].For the in-pile surveillance specimen test,it is convenient to use miniaturized specimens(with reduced radioactivity)to characterize the mechanical properties.For irradiation experiments using energetic ion beams as a surrogate method,the limited area of the ion beam and the limited depth of ion range make it compulsory to develop miniaturized specimen technique to evaluate the mechanical properties of materials.Among all the small specimen test technique,small punch test(SPT)is the most attractive and widely used,which employs disc specimens firmly gripped between two dies and deformed vertically into a circular hole by a spherical punch[2;3].The sample strength and ductility can not be obtained straightforward due to the complicated stress state and the load deflections curve(LDC).Data are generally interpreted by semi-empirical formulations[4].To characterize the constitutive relation and directly observe the deformation mechanism of the ion irradiated material is a challenging work.
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