scholarly journals On the interpretation of results from small punch creep tests

2010 ◽  
Vol 45 (3) ◽  
pp. 141-164 ◽  
Author(s):  
T H Hyde ◽  
M Stoyanov ◽  
W Sun ◽  
C J Hyde
Keyword(s):  
Finite Element ◽  
Creep Behaviour ◽  
Test Material ◽  
Complex Nature ◽  
Small Punch Test ◽  
Creep Tests ◽  
Linear Processes ◽  
Small Punch ◽  
Punch Test ◽  
Uniaxial Creep

The small punch creep testing method is highly complex and involves interactions between a number of non-linear processes. The deformed shapes that are produced from such tests are related to the punch and specimen dimensions and to the elastic, plastic, and creep behaviour of the test material, under contact and large deformation conditions, at elevated temperature. Owing to its complex nature, it is difficult to interpret the small punch test creep data in relation to the corresponding uniaxial creep behaviour of the material. One of the aims of this paper is to identify the important characteristics of the creep deformation resulting from ‘localized’ deformations and from the ‘overall’ deformation of the specimen. Following this, the results of approximate analytical and detailed finite element analyses of small punch tests are investigated. It is shown that the regions of the uniaxial creep test curves dominated by primary, secondary, and tertiary creep are not those that are immediately apparent from the displacement versus time records produced during a small punch test. On the basis of the interpretation of the finite element results presented, a method based on a reference stress approach is proposed for interpreting the results of small punch test experimental data. Future work planned for the interpretation of small punch tests data is briefly addressed.

Small punch test: An approach to solve the inverse problem by deformation shape and finite element optimization

2007 ◽  
Vol 40 (1) ◽  
pp. 33-39 ◽  
Author(s):  
Patrick Egan ◽  
Maurice P. Whelan ◽  
Fereydoun Lakestani ◽  
Michael J. Connelly
Keyword(s):  
Inverse Problem ◽  
Finite Element ◽  
Small Punch Test ◽  
Small Punch ◽  
Punch Test

Determination and Validation of Gurson-Tvergaard Model Parameters for Finite Element Simulation of Small Punch Test

2015 ◽  
Vol 750 ◽  
pp. 59-68 ◽  
Author(s):  
Yan Yan Lu ◽  
Liang Chen ◽  
Kai Shu Guan
Keyword(s):  
Finite Element ◽  
Finite Element Simulation ◽  
Model Parameters ◽  
Displacement Curve ◽  
Small Punch Test ◽  
Test Technique ◽  
Small Punch ◽  
Punch Test ◽  
Element Simulation ◽  
Load Displacement

Small punch test (SPT) is a miniature sample test technique which can evaluate in-service material properties with an almost non-destructive method. Since the deformation behavior of the small punch specimen is complicated, finite element simulation embedded with Gurson-Tvergaard (GTN) model is adopted to simulate elastic-plastic behaviour until fracture. Choosing the proper GTN parameters is crucial for the small punch simulation, which directly influence the precision of load-displacement curve obtained from simulation. In this paper, load-displacement curve is divided into five stages and the parameters identification process is done by adjusting the simulation curve with experimental load-displacement curve in different stages which controlled by separately parameters. The results show that the parameters determined based on this criterion are not unique. In order to validate the reliability of this method, specimen’s minimum thickness of cross-section after fracture was introduced as an extra criterion which turned out to be feasible. Load-displacement curves cannot serve as the only criterion to verify the GTN parameters.

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

Metals ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 1996
Author(s):  
Xiao Tian ◽  
Saifei Zhang ◽  
Hui Xu ◽  
Taijiang Li ◽  
Baixun Yang ◽  
...  
Keyword(s):  
Power Plant ◽  
Stress Rupture ◽  
Correlation Factor ◽  
Rupture Time ◽  
Good Prediction ◽  
Small Punch Test ◽  
Creep Tests ◽  
Creep Properties ◽  
Small Punch ◽  
Punch Test

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.

Determination of Norton Creep Law From Small Punch Test

2014 ◽  
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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