Small Punch Testing - The Transition from a Code of Practice to a European Testing Standard

Matocha, Karel; Hurst, Roger Christopher

doi:10.4028/www.scientific.net/kem.734.3

Cited by 13 publications

(5 citation statements)

References 52 publications

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“…where R is the radius of the receiving hole, r is the radius of the punch indenter, h 0 is the test-piece thickness and k sp is small punch creep test correlation factor. This relationship is derived from the Chakrabarty's stretch membrane theory and complicated regression analyses [25,26]. The empirical correlation factor, k sp , is introduced in order to take into account the different creep ductilities of different materials.…”

Section: Comparative Study On the Two Sets Of Data Both In Small Punc...mentioning

confidence: 99%

Assessment of Creep Properties Using Small Punch Test for a 9%Cr-Mo-Co-B Power Plant Steel

Xiao

Zhang

et al. 2021

Metals

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The present study provides a feasible method to evaluate creep properties for a 9%Cr-Mo-Co-B power plant steel by comparing two sets of data obtained from small punch tests and conventional uniaxial creep tests. The method includes three steps: firstly, conduct a series of small punch tests and conventional creep tests in different load and temperature conditions; secondly, convert the load and central deflection data obtained from the small punch test to stress and strain data; thirdly, determinate the best fit correlation factor by comparing the two sets of data in selected creep models. It is found that two sets of data show a similar trend in stress–rupture time relation, stress–minimum strain rate relation and LMP–stress relation. The correlation factor, ksp, can effectively bridge the gap between the load in small punch test and the stress in conventional creep test. For a high-Cr martensitic heat-resistant steel named as CB2, the ksp value 1.4 can make a good prediction for rupture time, while for minimum creep rate and the Larson–Miller parameter, the ksp value 1.4 will lead a conservative prediction in the low-stress range.

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Section: Comparative Study On the Two Sets Of Data Both In Small Punc...mentioning

confidence: 99%

Assessment of Creep Properties Using Small Punch Test for a 9%Cr-Mo-Co-B Power Plant Steel

Xiao

Zhang

et al. 2021

Metals

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“…An open problem regarding small punch creep testing is the correlation between the load level applied to the small disc specimen and the stress induced in a conventional uniaxial creep test that exhibits the same time to rupture. Some equations for data interpretation have been proposed in the CEN CWA 15627 and are here reported in the section ‘Small punch creep test’, but the procedure is still not totally accepted for industrial applications and further investigation on the complex behaviour of the specimen during testing is ongoing [25].…”

Section: Specialised Small Specimen Creep Testingmentioning

confidence: 99%

The role of small specimen creep testing within a life assessment framework for high temperature power plant

Morris

Cacciapuoti

Sun

2017

International Materials Reviews

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The safe operation of components operating at high temperature and pressure faces numerous challenges associated with ageing materials and maintaining commercial viability whilst economies transition to a lower carbon future as part of their climate change commitments. Due to these challenges the plant operator faces increasing pressure to ensure that any capital or operational expenditures are optimised and must ensure that they duly recognise plant age, condition, operating regime and ultimately the planned closure date.This review, for the first time, describes how small specimen creep testing can be applied within a practical and deployable life assessment framework and in conjunction with other assessment techniques. The current state of the art for small specimen creep testing is critically reviewed; this also includes a review of traditional techniques used on site for the metallurgical assessment of material condition, with examples from site investigations and assessment campaigns in both conventional and nuclear plant applications.In order to enhance the current practice for assessing the condition of creep ageing components this review proposes the more proactive use of small specimen testing methods for the in-service condition assessment of power plant materials, notably earlier in the plant lifecycle and within a holistic life assessment framework. This is intended to provide a means of calibrating the time dependent response of the component or system being monitored, thereby providing a key reference in-service strain rate measurement, or material property evaluation, that can subsequently be used with other traditionally deployed assessment methods to define a more targeted and cost-effective forward inspection plan. The review describes how small specimen creep testing methods and other complementary tools can be use in a new and structured approach to life management.The current status of small specimen testing methods, for both conventional and nuclear applications, is described along with a detailed discussion on current practice for in-service creep life assessment, with a case study used to illustrate the main principals. A case study is presented for ageing CMV (0.5%Cr0.5%Mo0.25%V) main steam pipework due to the extensive amount of through life data available, which highlights the particular challenges associated with the interpretation of various types of site outage inspection data, in conjunction with on-load plant operational data. The current approach to the assessment of component condition follows well established inspection based practices defined in various industry good practice guides, with expert elicitation and experience used to judge the condition of the component, system and operational risk on return to service.This review proposes a new approach to the holistic life assessment of high temperature plant, with a particular emphasis on more proactive use of small specimen testing. In addition, the review has 2 highlighted other aspects of the current approach to in-...

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“…Reliability and repeatability of testing has been a strong focus within the research community, leading to the establishment of a European Code of Practice. [3] Results from small punch creep (SPC) tests are typically shown through time/displacement curves, which while appearing comparable to that of conventional uniaxial creep curves, in reality are quite different due to the differing creep mechanisms present in each of these test techniques. This is because uniaxial test specimens are only subjected to a single tensile stress state, while in the SPC test the specimen experiences a multiaxial stress state.…”

Section: Introductionmentioning

confidence: 99%

An Investigation into the Correlation of Small Punch and Uniaxial Creep Data for Waspaloy

Williams

Evans

Harrison

2021

Metall Mater Trans A

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Within the aerospace sector, the understanding and prediction of creep strains for materials used in high-temperature applications, such as Nickel-based super alloys, is imperative. Small punch testing offers the potential for understanding creep behavior using much less material than conventional uniaxial testing but in contrast to uniaxial creep tests, the stress in small punch creep (SPC) tests is multiaxial. SPC testing can be a valuable tool for validating models of creep deformation, but the key to unlocking its full capability is through the accurate correlation of the creep material properties measured through both techniques. As such, the focus of this paper is to correlate the creep behavior of Waspaloy obtained through conventional uniaxial testing to that obtained via small punch creep testing. Recently, and for low chrome steels, this has been achieved through use of the ksp method, but there are good reasons for believing this technique will not work so well for Nickel-based super alloys. This paper shows this to be the case for Waspaloy and proposes some alternative methods of correlation based on combining the Monkman–Grant relation and the Wilshire equations for both uniaxial and small punch creep. It was found that this latter approach enabled the accurate conversion of SPC minimum displacement rates to equivalent uniaxial minimum creep rates which, when combined with the Wilshire equations, enabled SPC test loads to be converted into equivalent uniaxial stresses (and visa versa) with levels of accuracy that were significantly reduced when compared to using the ksp method. Further, the random error associated with these conversions were dramatically increased.

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Small Punch Testing - The Transition from a Code of Practice to a European Testing Standard

Cited by 13 publications

References 52 publications

Assessment of Creep Properties Using Small Punch Test for a 9%Cr-Mo-Co-B Power Plant Steel

Assessment of Creep Properties Using Small Punch Test for a 9%Cr-Mo-Co-B Power Plant Steel

The role of small specimen creep testing within a life assessment framework for high temperature power plant

An Investigation into the Correlation of Small Punch and Uniaxial Creep Data for Waspaloy

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