Small Punch Testing for Creep: Progress in Europe

The small punch or disk bend test has particular value in life prediction of operating equipment since the test requires very small amounts of material (a common test specimen disk is 0.5 mm thick with a diameter of 6 to 10 mm), and usually the required volume of material can be acquired from operating equipment in a virtually nondestructive manner. The application of the small punch (SP) test for creep has gained significant interest in the last decade, primarily as a result of research in Europe. The CEN (one of three European standardization organizations recognized by the EC) has been working to develop a Code of Practice for the small punch test. The Code documents, very recently completed, focus on use of the test for creep rupture and tensile and toughness properties. This paper summarizes the European round-robin work leading to the Code of Practice and key aspects of the Code. Included is a description of the currently recommended semi-empirical interpretation of data from the multiaxially-loaded small punch test specimens, less straightforward than that from conventional uniaxial specimens. As the SP test sees more field use and as the specimen and test configurations achieve better uniformity, we can expect that its application to creep life prediction will increase.

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Determination of Norton Creep Law From Small Punch Test

Volume 6A: Materials and Fabrication ◽

10.1115/pvp2014-28189 ◽

2014 ◽

Cited By ~ 1

Author(s):

Xiangsai Feng ◽

Yanfeng Qin ◽

Kai Ma ◽

Kaishu Guan

Keyword(s):

Nuclear Power ◽

Engineering Application ◽

Small Punch Test ◽

Creep Tests ◽

Small Punch ◽

Code Of Practice ◽

Punch Test ◽

Membrane Stretch ◽

Creep Curves

The present work focused on a miniature test named small punch creep test which have been employed to electric power, petro-chemical, nuclear power and other fields widely in the last three decades. Under normal circumstances, engineering application pay more closer attention to the Norton creep law. To determine the Norton creep law, at least three creep curves were needed by traditional method, it’s time consuming and uneconomic. In present paper, the small punch creep tests were carried out following the CEN code of practice. Based on Chakrabarty’s membrane stretch model and Norton power law, the results of small punch creep tests and finite element method have been compared and discussed. A completely novel and economical approach was proposed to determine the parameters of Norton creep law more accurately and conveniently. The results show that, if scopes of parameters known, the Norton creep law could be determined accurately even from one creep curve only.

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Modeling a Small Punch Testing Device

Engineering, Technology & Applied Science Research ◽

10.48084/etasr.416 ◽

2014 ◽

Vol 4 (2) ◽

pp. 612-617 ◽

Cited By ~ 1

Author(s):

S. Habibi ◽

A. Ziadi ◽

A. Megueni

Keyword(s):

Ultimate Load ◽

Geometrical Parameters ◽

Small Punch Test ◽

Small Punch ◽

Code Of Practice ◽

Punch Test ◽

Matlab Program ◽

European Code ◽

Ductile Steel ◽

Practical Constraints

A small punch test of a sample in miniature is implemented in order to estimate the ultimate load of CrMoV ductile steel. The objective of this study is to model the ultimate tensile strength and ultimate load indentation according to the geometrical parameters of the SPT using experimental data. A comparison of the model obtained with the two models (European code of practice and method of Norris and Parker) allows the design and dimensioning of an indentation device that meets the practical constraints. Implemented as a Matlab program, allows the investigation of new combinations of test variables.

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Determination of Creep Properties from Small Punch Test with Reverse Algorithm

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.734.212 ◽

2017 ◽

Vol 734 ◽

pp. 212-236 ◽

Cited By ~ 3

Author(s):

Ying Zhi Li ◽

Paul Stevens ◽

Jin Feng Geng ◽

Dong Fang Ma ◽

Liang Xu

Keyword(s):

Electric Power ◽

Power Plants ◽

Small Punch Test ◽

Plastic Properties ◽

Creep Properties ◽

Small Punch ◽

Material Parameters ◽

Code Of Practice ◽

Punch Test ◽

Acceptable Method

In the early 1980’s, the small punch technique was developed in USA and Japan. This technique has been applied to nuclear reactors, electric power plants for safety assessments. European researchers have carried out the pioneer work on SP creep testing in the 1990’s. European Code of Practice (CoP) documents have become available in 2006, which provides a guide line to perform small punch tests for metallic materials, and introduces methods for estimation of tensile properties, fracture toughness and creep properties. Since then several conferences and symposiums have been held to exchange ideas and experiences, and several efforts have been made to improve the approaches for interpreting the material properties from test results. However, due to the complexity of the small punch test itself and lack of systematic test data for verification, especially in the creep region, up to now there is no common acceptable method to interpret creep properties. This paper discusses some of the problems commonly encountered in the small punch creep test (SPCT) analysis, such as the uniqueness in reverse creep analysis for identification of material parameters, how to consider effects of large deformation and strain hardening, how to separate deflection into a part caused by loading and a part caused by creep, and how to estimate the elastic-plastic properties of a material in the creep temperature region. Based on these considerations, several existing approaches for interpreting creep properties have been re-evaluated. In addition, a software package, based on the optimization toolbox of Matlab has been developed for identification of material parameters automatically. Verifications are performed by checking the agreement between properties derived by small punch test and uni-axial tests. Discussions on problems of existing approaches and how to improve them further, are described in the paper. Experimental data are provided by JRC Petten, Netherlands, and Henan Electric Power Research Institute, China. Recently a working group led by JRC Petten is engaged in upgrading the CoP to a European standard. It is expected that in the future more data will become available for further verification.

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Computational Simulation of Small Punch Test

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.232.497 ◽

2012 ◽

Vol 232 ◽

pp. 497-501

Author(s):

Jindřich Petruška ◽

Jiří Hůlka ◽

Kubik Petr

Keyword(s):

Mechanical Properties ◽

Numerical Simulation ◽

Computational Simulation ◽

Testing Procedure ◽

Penetration Test ◽

Small Punch Test ◽

Small Punch ◽

Code Of Practice ◽

Punch Test ◽

Basic Evaluation

The paper deals with numerical simulation of Small Punch Test (SPT). SPT is a penetration test used to determine basic mechanical properties from a tiny piece of material. The testing procedure drew a great interest in the last decade, nevertheless there are no generally accepted standards for this type of testing until now. “Code of Practice” was created as a consequence of the CEN Workshop 2007, recommending both geometry, experiment performance and its basic evaluation. To obtain other mechanical properties like flow curve, yield stress, ductility and ultimate strength, it is necessary to realize a numerical simulation of the test to identify the mentioned material parameters. As the SPT results are generally influenced by many other parameters besides material behaviour, we try to quantify their relevance to make the material identification more rigorous.

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

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.734.3 ◽

2017 ◽

Vol 734 ◽

pp. 3-22 ◽

Cited By ~ 6

Author(s):

Karel Matocha ◽

Roger Hurst

Keyword(s):

Mechanical Properties ◽

Test Method ◽

Metallic Materials ◽

Small Punch Test ◽

Test Technique ◽

Small Punch ◽

Code Of Practice ◽

Punch Test ◽

Early Results ◽

Miniature Testing

The development and practical use of the Small Punch test technique for the evaluation of mechanical properties of metallic materials in Europe resulted in the publication of the CEN document CWA 15627 Small Punch Test Method for Metallic Materials in 2007. The evaluation of the actual mechanical properties of metallic materials from the results of such tests according to CWA 15627 were presented at the first three International conferences SSTT "Determination of Mechanical Properties by Small Punch and other Miniature Testing Techniques" held in Ostrava (2010, 2012) and Castle Seggau in Austria (2014). In the present paper the motivation and the steps taken to lead to the setting up of a working group and programme facilitating the transformation of CWA 15627 Small Punch Test Method for Metallic Materials into an EN standard are summarized along with early results of the programme.

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Determination of Creep Properties From Small Punch Test

Volume 3: Design and Analysis ◽

10.1115/pvp2008-61437 ◽

2008 ◽

Cited By ~ 12

Author(s):

Yingzhi Li ◽

Roman Sˇturm

Keyword(s):

Power Plants ◽

Research Work ◽

Small Punch Test ◽

Creep Properties ◽

Small Punch ◽

Code Of Practice ◽

Punch Test ◽

Starting Point ◽

European Code

The small punch test is one of the techniques, which can directly assess the current material properties of components on situ. The main advantages of this method are that only small amount of material is needed and no repair is required afterwards. In addition, the test itself is rather simple to perform. Since early 1980’s, the technique has been developed and applied to nuclear reactors, electric power plants for safety assessment. European researchers have carried out the pioneer work on small punch testing at the creep region. Recently the European Code of Practice documents are available for both high and low temperature properties, which summarizes the international experiences in last 20 years and provides a guide line to perform small punch test for metallic materials. This paper gives an overview of the research work on determination of creep properties from small punch test. Verification is performed by comparison of creep properties derived by small punch test and uni-axial tests. An agreement is found and shows that small punch test is able to predict reasonable creep properties of materials. Considerations how to improve the approach are also addressed. Further work is needed as available tests are still limited. This paper makes a starting point that others can improve further.

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