Determination of creep damage properties from small punch creep tests considering pre-straining effect using an inverse approach

Abstract

Although the small punch creep test (SPCT) has been commonly accepted as an effective small specimen material characterisation technique (e.g. the European Code of Practice (CoP) for small punch test was produced in 2006 to provide a practical guideline for the experimental work and data interpretation of small punch test), the conversion from the experimental results obtained from the SPCT, i.e. displacement-time data, to the corresponding strain-time data obtained from conventional uniaxial creep tests has not been thoroughly understood due to the complex nature of the deformation and material failure mechanisms involved in the SPCT, e.g. contact mechanism, material nonlinearity, large deformation and initial plasticity damage. The current paper presents an inverse method to determine the creep properties directly from the SPCT experimental results, without converting them to the uniaxial creep test data. A finite element (FE) model taking account of the conventionally overlooked pre-straining effects has been employed for an inverse optimisation method for the first time. The inverse method has been proven to be capable of effectively predicting the creep behaviours of a P91 steel at 600⁰C with a good agreement to the experimental results. Keywordssmall punch creep test; creep damage properties; pre-straining effect; inverse approach Manuscript region of origin Europe

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