Small punch testing and Its numerical simulations under constant deflection force conditions
A comparison of results of small punch tests on miniaturized discs under a constant force with their simulation by means of FEM is presented. A heat resistant steel of type CSN 41 5313 (EN 10CrMo9-10) was selected for our investigations. The small punch tests as well as the necessary conventional c...
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Інститут проблем міцності ім. Г.С. Писаренко НАН України
2008
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| Cite this: | Small punch testing and Its numerical simulations under constant deflection force conditions / P. Dymacek, K. Milicka // Проблемы прочности. — 2008. — № 1. — С. 32-35. — Бібліогр.: 7 назв. — англ. |
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| author | Dymacek, P. Milicka, K. |
| author_facet | Dymacek, P. Milicka, K. |
| citation_txt | Small punch testing and Its numerical simulations under constant deflection force conditions / P. Dymacek, K. Milicka // Проблемы прочности. — 2008. — № 1. — С. 32-35. — Бібліогр.: 7 назв. — англ. |
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| description | A comparison of results of small punch tests on miniaturized discs under a constant force with their simulation by means of FEM is presented. A heat resistant steel of type CSN 41 5313 (EN 10CrMo9-10) was selected for our investigations. The small punch tests as well as the necessary conventional creep tests on massive specimens were performed at 873 K. For simulations, the Norton power-law and the exponential relationships were applied in the FEM model of the SPT arrangement. Parameters of both relationships were derived from stress dependences of minimum creep rate obtained from the conventional creep tests. While at higher loads the Norton power-law yields results more comparable with those obtained from experiments, at lower loads the exponential relationship gives better results. The investigation also confirms the simple relation between stress in conventional tests and force in small punch tests resulting in identical time to fracture of both types of tests.
Сопоставляются результаты испытаний на изгиб миниатюрных дисков при постоянном усилии и данные моделирования таких испытаний методом конечных элементов (МКЭ). Для исследования выбрана жаропрочная сталь типа СБЫ 41 5313 (БЫ 10СгМо9-10). Испытания на изгиб миниатюрных образцов (ИИМО) и необходимые традиционные испытания на ползучесть массивных образцов проводились при температуре 873 К. Для моделирования применяли степенную зависимость Нортона и экспоненциальную зависимость в модели МКЭ для схемы ИИМО. Параметры для обеих зависимостей были получены из соотношений напряжения и минимальной скорости ползучести, установленных по данным обычных испытаний на ползучесть. При повышенных нагрузках степенная зависимость Нортона обеспечивает более близкое совпадение с экспериментальными данными, а при меньших нагрузках лучшие результаты получены с использованием экспоненциальной зависимости. Исследование подтверждает также простую связь между напряжением при обычных испытаниях и усилием при испытаниях миниатюрных образцов, что приводит к идентичности величины наработки до разрушения в обоих типах испытаний.
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UDC 539. 4
S m a l l P u n c h T e s t in g a n d I t s N u m e r ic a l S im u la t io n s u n d e r C o n s t a n t
D e f le c t io n F o r c e C o n d it io n s
P. D y m a cek 1,a and K . M ilick a 1,b
1 Institute o f Physics o f Materials, Academy o f Sciences o f the Czech Republic, Brno, Czech
Republic
a pdymacek@ipm.cz, b milicka@ipm.cz
A comparison o f results o f small punch tests on miniaturized discs under a constant force with their
simulation by means o f FEM is presented. A heat resistant steel o f type CSN 41 5313 (EN 10CrMo9-10)
was selected fo r our investigations. The small punch tests as well as the necessary conventional creep
tests on massive specimens were performed at 873 K. For simulations, the Norton power-law and
the exponential relationships were applied in the FEM model o f the SPT arrangement. Parameters
o f both relationships were derived from stress dependences o f minimum creep rate obtained from
the conventional creep tests. While at higher loads the Norton power-law yields results more
comparable with those obtained from experiments, at lower loads the exponential relationship gives
better results. The investigation also confirms the simple relation between stress in conventional
tests and force in small punch tests resulting in identical time to fracture o f both types o f tests.
K eyw o rd s : sm all punch test, finite elem ent m ethod, parametric study, creep, fracture
mechanics.
In troduction . Small punch tests (SPT) on thin disk specim ens can be considered as
one o f the promising methods for the determination o f the residual - or at least guaranteed -
life o f exposed parts o f pow er generation and thermal facilities. D ue to sm all specim en
dim ensions it m ay be classified as a non-destructive m ethod in this industrial sector.
Recently, there have been significant efforts by European and U S research groups to
standardize the dim ensions and test conditions o f SPT at low, ambient, and high
temperatures [1]. Currently, a good progress has been achieved in the num erical m odeling
o f the SPT at room and low temperatures, for the SPT at constant deflection rate
conditions [2, 3]. Preliminary results at IPM demonstrated that SPT-CDF (at constant
deflection force conditions) represent an apt too l for obtaining local creep properties at
operational temperatures. It w as show n that the results o f these tests can be correlated
w ith the results o f conventional tests on m assive specim ens [4, 5]. Thus, the sm all punch
technique should provide important inform ation for safety procedures. H ow ever, the
currently applied relations betw een results o f conventional testing and sm all punch tests
are purely empirical. The aim o f this w ork w as to apply the finite elem ent m ethod (FEM)
for the verification and better understanding o f the sm all punch test application in the
assessm ent o f the creep resistance and either the residual or guaranteed life tim e for heat
resistant steels.
P rocedures. The material chosen for this study w as a low alloy heat resistant steel
C SN 415313 (EN equivalent 10CrM o9-10), w hich is w id ely used in the C zech power
generation industry. The testing temperature w as set to be 600oC (873 K), w hich is the
m axim um recom m ended operation temperature for this steel in long-term service. In order
to obtain accurate relationships betw een the results o f conventional and sm all punch tests,
the com parison o f their results obtained on the sam e heat o f steel w ith identical heat
treatment as w ell as m echanical treatment w as necessary. Therefore, both types o f tests
were performed under conditions leading to comparable values o f tim e to rupture (up to
1000 hr). Stress (load) ranges were 80 to 200 M Pa for conventional creep tests and 200 to
500 N for SPT. Several conventional tensile tests at the testing temperature were also
performed in order to determine the static material properties, nam ely the Young modulus.
© P. DYMACEK, K. MILICKA, 2008
32 ISSN 0556-171X. npo6n.eubi npounocmu, 2008, № 1
mailto:pdymacek@ipm.cz
mailto:milicka@ipm.cz
Small Punch Testing and Its Numerical Simulations
R esu lts and D iscu ssion . A com parison o f the experim ental values o f the force F
and the stress o resulting in identical tim e to fracture in both types, i.e ., SPT, and
conventional creep tests (see Fig. 1) confirm ed the sim ple relation betw een the force and
stress in the form [4, 5]:
F = W o , (1)
w here the factor W reaches values close to 2.6 for som e heat-resistant steels. The value
W = 2.5 w as obtained from the present experim ents. The p lot o f experim ental and
num erical results show n in Fig. 2 w ill be d iscussed further.
Fig. 1 Fig. 2
Fig. 1. Comparison o f the load and stress at identical time to fracture for conventional creep tests
and SPT.
Fig. 2. Comparison o f the load vs. time to fracture for experimental and calculated SPT data.
Fig. 3 Fig. 4
Fig. 3. A 2D axisymmetric FE model o f the SPT arrangement, expanded to 3D.
Fig. 4. Equivalent creep strain plot for a specimen loaded with F = 500 N at t = 13,525 s.
A tw o-dim ensional axisym m etric m odel o f the SPT arrangement w as formulated in
the A N S Y S FEM system [6 ]. The m odel is show n in Figs. 3 and 4. The contact betw een
the specim en and arrangement w as m odeled using surface to surface contact elem ents
w ith the friction coefficient f = 0.1. The parametric study o f various friction conditions
for SPT under constant deflection rate w as done in [7]. A pplication o f tw o types o f
constitutive creep m odels in the num erical analysis w as perform ed using the N orton
pow er-law (Eq. (2)) and the exponential relationship (Eq. (3)):
ISSN 0556-171X. npoôëeubi npounocmu, 2008, N 1 33
P. Dymâcek and K. Milicka
and
£ cr = B o n
o / m£ cr = Ce
(2 )
(3)
Both o f these equations are applicable m ostly to the secondary creep rates. From the
regression analysis o f the conventional creep test data w e obtained the coefficients
B = 3 .257-10 21, n = 6 .505 for the N orton pow er-law and C = 2 .6 8 -1 0 10, m = 21 .4 for
the exponential form.
The load cases were num erically so lved for the identical number o f load levels as the
performed SP testing. The experim ental SPT curves at tw o different load levels and the
relevant calculated curves are compared in Figs. 5 and 6 . The experim ental SPT curves
for the repeated tests at a load leve l o f 500 N are show n in Fig. 7, they demonstrate an
acceptably sm all scatter.
Fig. 5 Fig. 6
Fig. 5. Experimental and calculated SPT curves at F = 500 N.
Fig. 6 . Experimental and calculated SPT curves at F = 300 N.
Fig. 7 Fig. 8
Fig. 7. Experimental SPT curves at F = 500 N, illustration o f test reproducibility.
Fig. 8 . Experimental and calculated SPT deflection rate curves at F = 300 N.
34 ISSN 0556-171X. n poôëeu u npouHocmu, 2008, № 1
Small Punch Testing and Its Numerical Simulations
A very good correlation o f tim e to fracture w as obtained for the N orton constitutive
m odel, the exponential m odel g ives too conservative results for h igh load levels and
non-conservative ones for low er load levels (see Fig. 2). In spite o f this, for low er load
conditions the exponential m odel provides a better fit o f the analysis results w ith the
experim ent at the primary and secondary creep stages (as show n in Fig. 6 ). A com parison
o f creep deflection rates for load F = 300 N betw een the test and num erical analysis
results is show n in Fig. 8 .
The FE m odel does not include any damage m odeling. Therefore, the tertiary part o f
the calculated creep diagram is driven m ainly by the geom etrical softening (a local
decrease in the specim en thickness). This leads to a slightly different shape o f the tertiary
region o f the creep curve as compared to the test data. H ow ever, it does not seem to
influence substantially the calculated life-tim e to be m uch different from the life-tim e
m easured on the specim en. Im plem entation o f the damage m odeling, for exam ple w ith the
use o f a so-called elem ent death technique or application o f creep constitutive m odels that
account for dam age, could further im prove the capabilities o f the SPT FE m odel in order
to describe more realistically the tertiary creep stages.
C onclu sions. The SPT under constant deflection force can be w e ll sim ulated by
m eans o f the finite elem ent m ethod and relatively sim ple creep constitutive m odels such
as the N orton pow er-law or the exponential relationship. The adequacy o f the calculated
results can be further im proved either by including the damage m odeling in the SPT
m odel or using more com plex constitutive m odels that can w e ll describe all three creep
stages o f the material behavior.
1. Small Punch Test Method fo r Metallic Materials. Part A: A Code o f Practice fo r Small Punch
Creep Testing. Part B: A Code o f Practice fo r Small Punch Testing fo r Tensile and Fracture
Behavior, Documents o f CEN WS21, Brusseles (in press).
2. M. Abendroth and M. Kuna, Eng. Fract. M ech, 73, 710 (2006).
3. C. Sainte Catherine, J. Messier, Ch. Poussard, et al., in: M. A. Sokolov, J. D. Landes, and
G. E. Lucas (Eds.), Small Specimen Test Techniques, Fourth Volume, American Society for
Testing and Materials, West Conshohocken, PA (2002), p. 350.
4. K. Milicka and F. Dobes, Mat. Sci. Forum, 482, 407 (2004).
5. K. Milicka and F. Dobes, Int. J. Press. Vess. Piping, 83, 625 (2006).
6. ANSYS 9.0 Release Documentation, SAS IP (2004).
7. P. Dymacek, New Methods o f Damage and Failure Analysis o f Structural Part, TU Ostrava,
Czech Republic, September 4 -8 (2006), ISBN 80-248-1126-0, p. 269.
Received 28. 06. 2007
ISSN 0556-171X. npo6neMbi npouHocmu, 2008, № 1 35
|
| id | nasplib_isofts_kiev_ua-123456789-48404 |
| institution | Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| issn | 0556-171X |
| language | English |
| last_indexed | 2025-12-01T18:55:58Z |
| publishDate | 2008 |
| publisher | Інститут проблем міцності ім. Г.С. Писаренко НАН України |
| record_format | dspace |
| spelling | Dymacek, P. Milicka, K. 2013-08-19T12:27:52Z 2013-08-19T12:27:52Z 2008 Small punch testing and Its numerical simulations under constant deflection force conditions / P. Dymacek, K. Milicka // Проблемы прочности. — 2008. — № 1. — С. 32-35. — Бібліогр.: 7 назв. — англ. 0556-171X https://nasplib.isofts.kiev.ua/handle/123456789/48404 539. 4 A comparison of results of small punch tests on miniaturized discs under a constant force with their simulation by means of FEM is presented. A heat resistant steel of type CSN 41 5313 (EN 10CrMo9-10) was selected for our investigations. The small punch tests as well as the necessary conventional creep tests on massive specimens were performed at 873 K. For simulations, the Norton power-law and the exponential relationships were applied in the FEM model of the SPT arrangement. Parameters of both relationships were derived from stress dependences of minimum creep rate obtained from the conventional creep tests. While at higher loads the Norton power-law yields results more comparable with those obtained from experiments, at lower loads the exponential relationship gives better results. The investigation also confirms the simple relation between stress in conventional tests and force in small punch tests resulting in identical time to fracture of both types of tests. Сопоставляются результаты испытаний на изгиб миниатюрных дисков при постоянном усилии и данные моделирования таких испытаний методом конечных элементов (МКЭ). Для исследования выбрана жаропрочная сталь типа СБЫ 41 5313 (БЫ 10СгМо9-10). Испытания на изгиб миниатюрных образцов (ИИМО) и необходимые традиционные испытания на ползучесть массивных образцов проводились при температуре 873 К. Для моделирования применяли степенную зависимость Нортона и экспоненциальную зависимость в модели МКЭ для схемы ИИМО. Параметры для обеих зависимостей были получены из соотношений напряжения и минимальной скорости ползучести, установленных по данным обычных испытаний на ползучесть. При повышенных нагрузках степенная зависимость Нортона обеспечивает более близкое совпадение с экспериментальными данными, а при меньших нагрузках лучшие результаты получены с использованием экспоненциальной зависимости. Исследование подтверждает также простую связь между напряжением при обычных испытаниях и усилием при испытаниях миниатюрных образцов, что приводит к идентичности величины наработки до разрушения в обоих типах испытаний. en Інститут проблем міцності ім. Г.С. Писаренко НАН України Проблемы прочности Научно-технический раздел Small punch testing and Its numerical simulations under constant deflection force conditions Испытания на изгиб малых образцов и их численное моделирование в условиях постоянного изгибающего усилия Article published earlier |
| spellingShingle | Small punch testing and Its numerical simulations under constant deflection force conditions Dymacek, P. Milicka, K. Научно-технический раздел |
| title | Small punch testing and Its numerical simulations under constant deflection force conditions |
| title_alt | Испытания на изгиб малых образцов и их численное моделирование в условиях постоянного изгибающего усилия |
| title_full | Small punch testing and Its numerical simulations under constant deflection force conditions |
| title_fullStr | Small punch testing and Its numerical simulations under constant deflection force conditions |
| title_full_unstemmed | Small punch testing and Its numerical simulations under constant deflection force conditions |
| title_short | Small punch testing and Its numerical simulations under constant deflection force conditions |
| title_sort | small punch testing and its numerical simulations under constant deflection force conditions |
| topic | Научно-технический раздел |
| topic_facet | Научно-технический раздел |
| url | https://nasplib.isofts.kiev.ua/handle/123456789/48404 |
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