Fatigue lifetime of ADI from ultimate tensile strength to permanent fatigue limit
S — N curve of austempered ductile iron was obtained in the range of lifetime including low cycle fatigue domain and high cycle fatigue domain up to 108 cycles. Ultimate tensile strength is used as a limiting value of the curve. Symmetric push-pull fatigue and tensile tests were performed at room te...
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| Опубліковано в: : | Проблемы прочности |
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| Дата: | 2008 |
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Інститут проблем міцності ім. Г.С. Писаренко НАН України
2008
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| Цитувати: | Fatigue lifetime of ADI from ultimate tensile strength to permanent fatigue limit / J. Zapletal, S. Vechet, J. Kohout, K. Obrtlfk // Проблемы прочности. — 2008. — № 1. — С. 40-43. — Бібліогр.: 7 назв. — англ. |
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Digital Library of Periodicals of National Academy of Sciences of Ukraine| _version_ | 1859898668628312064 |
|---|---|
| author | Zapletal, J. Vechet, S. Kohout, J. Obrtlik, K. |
| author_facet | Zapletal, J. Vechet, S. Kohout, J. Obrtlik, K. |
| citation_txt | Fatigue lifetime of ADI from ultimate tensile strength to permanent fatigue limit / J. Zapletal, S. Vechet, J. Kohout, K. Obrtlfk // Проблемы прочности. — 2008. — № 1. — С. 40-43. — Бібліогр.: 7 назв. — англ. |
| collection | DSpace DC |
| container_title | Проблемы прочности |
| description | S — N curve of austempered ductile iron was obtained in the range of lifetime including low cycle fatigue domain and high cycle fatigue domain up to 108 cycles. Ultimate tensile strength is used as a limiting value of the curve. Symmetric push-pull fatigue and tensile tests were performed at room temperature on isothermally treated nodular cast iron alloyed with copper and nickel having positive impact on mechanical, technological and fatigue properties of austempered ductile iron. Suitable functions for the fit of experimentally determined points were tested and their parameters were calculated. The best results were obtained using the Palmgren function and the function introduced by Kohout and Vechet. Since the loading frequency in high-cycle region is two orders higher than in low-cycle region, the effect of loading cycle frequency on fatigue behavior of the studied material is also studied. A possibility of discontinuity of experimental data between low-cycle and high-cycle regions is discussed.
Получена кривая усталости аустенитно-отпущенного ковкого чугуна (ADI) в диапазоне долговечности, включая области малоцикловой и многоцикловой усталости до 108 циклов. В качестве предельного значения указанной кривой используется предел прочности при растяжении. Проведены испытания на усталость при симметричном растяжении-сжатии и на растяжение при комнатной температуре изотермически термообработанного чугуна с шаровидным графитом, с добавками меди и никеля, которые оказывают положительное влияние на механические, технологические и усталостные свойства ADI. Осуществлена проверка соответствующих функций для описания экспериментально определенных точек; выполнен расчет параметров указанных функций. Наилучшие результаты получены при использовании функции Пальмгрена и функции, предложенной Когутом и Вечетом. Исследовано также влияние частоты циклов нагружения на усталостное поведение рассматриваемого материала с учетом того, что частота нагружения в многоцикловой области на два порядка превышает частоту нагружения в малоцикловой области. Рассмотрена также возможность отсутствия непрерывности в экспериментальных данных на участке между малоцикловой и многоцикловой областями.
|
| first_indexed | 2025-12-07T15:56:26Z |
| format | Article |
| fulltext |
UDC 539. 4
F a t ig u e L ife t im e o f A D I f r o m U lt im a te T e n s i le S tr e n g th to P e r m a n e n t
F a t ig u e L im it
J. Z a p le ta l,1a S. V ech et,1b J . K oh ou t ,2 c and K . O brtlfk3 d
1 Brno University o f Technology, Brno, Czech Republic
2 University o f Defence, Brno, Czech Republic
3 Institute o f Physics o f Materials, Academy o f Sciences o f the Czech Republic, Brno, Czech
Republic
a pepa.sanguis@centrum.cz, b vechet@fme.vutbr.cz, c jan.kohout@unob.cz, d obrtlik@ipm.cz
S — N curve o f austempered ductile iron was obtained in the range o f lifetime including low cycle
fatigue domain and high cycle fatigue domain up to 108 cycles. Ultimate tensile strength is used as a
limiting value o f the curve. Symmetric push-pull fatigue and tensile tests were performed at room
temperature on isothermally treated nodular cast iron alloyed with copper and nickel having
positive impact on mechanical, technological and fatigue properties o f austempered ductile iron.
Suitable functions fo r the f i t o f experimentally determined points were tested and their parameters
were calculated. The best results were obtained using the Palmgren function and the function
introduced by Kohout and Vechet. Since the loading frequency in high-cycle region is two orders
higher than in low-cycle region, the effect o f loading cycle frequency on fatigue behavior o f the
studied material is also studied. A possibility o f discontinuity o f experimental data between
low-cycle and high-cycle regions is discussed.
K eyw o rd s : austempered ductile iron, fatigue behavior, S — N curve, fatigue limit, low -cycle
fatigue tests, h igh-cycle fatigue tests, regression.
Introd uction . Nodular cast iron and its isothermally heat treated variant, austempered
ductile iron (A D I), are structural materials applied in m any branches o f m echanical and
civ il engineering and transportation. Com paring w ith other sorts o f cast iron, its advantage
consists in favorable shape o f graphite, w hich enables full exploitation o f m echanical
properties o f the m etal matrix. R ecently A D I has been used for the production o f
crankshafts, engine blocks, rotors o f electric generators, gas com pressor casings, large
gears, pressing dies, w heels o f colliery cars, etc. [1 ] .
E xp er im en ta l. The test bars for static m echanical tests in tension as w e ll as for
fatigue tests w ere m ade o f keel blocks o f alloyed nodular cast iron. Its chem ical
com position determ ined using quantometer is presented in Table 1 . Isothermal heat
treatment resulting in a bainitic structure w as performed in electric pot furnaces containing
salt bathes. A ustenization w as realized in the salt bath at a temperature o f 900°C for 1 h.
Isothermal decom position w as perform ed in the A S 140 salt bath at 400°C during 50 min
w ith aftercooling in water. The matrix o f the material studied consisted o f upper bainite
and stabilized retained austenite, w h ose content w as determ ined using quantitative phase
X -ray analysis to be 39 vol.% . For the determ ination o f the basic m echanical properties
at static tensile loading, cylindrical test bars 6 m m in diameter were tested. The elongation
o f the test bars w as m easured by an extensom eter w ith a gauge length o f 30 mm. Tests
were perform ed using a M od. TiraTest 2300 PC -controlled testing d evice at a stress rate
o f 30 M Pa/s. The basic stress and strain characteristics are sum marized in Table 2.
For the assessm ent o f low -cycle parameters the threaded bars o f diameter 8 m m and
a gauge length o f 12 m m w ere used. They were loaded using M TS 810 electro-hydraulic
PC-controlled test system in the regim e o f a controlled loading force w ith a sym metric
sinusoidal push-pull course at an average stress rate o f 4000 M Pa/s. D eform ation was
measured using an axial extensom eter w ith a gauge length o f 12 mm. A lso , h igh-cycle
© J. Z A PL E TA L , S. V fiC H ET, J. K O H O U T, K. O BR TLIK , 2008
40 ISSN 0556-171X. Проблемы прочности, 2008, № 1
mailto:pepa.sanguis@centrum.cz
mailto:vechet@fme.vutbr.cz
mailto:jan.kohout@unob.cz
mailto:obrtlik@ipm.cz
Fatigue Lifetime o f A D I from Ultimate Tensile Strength
fatigue tests were performed using 7-m m -diam eter bars w ith threaded heads. A Mod.
A m sler HFP 1478 high-frequency pulsator w as used to load the bars w ith a sym metric
push-pull loading cycle w ith a frequency o f about 200 Hz. A ll fatigue tests as w ell as
static tensile tests w ere carried out at room temperature.
T a b l e 1
Chemical Composition of Nodular Cast Iron under Study
Element C Mn Si P S Ni Cu Mg
wt.% 3.80 0.37 2.22 0.024 0.002 0.49 0.31 0.057
T a b l e 2
Static Mechanical Characteristics of ADI in Tension
Material Rp 0.2’ MPa Rm ’ MPa A,% Z , %
ADI 400°C/50 min 636 976 11.4 9.7
D ata P rocessing o f E xperim enta l R esults. The experimentally obtained dependence
o f the stress amplitude o ( N ) on the number o f cycles to fracture N in the range from 0.5
to 10 cycles w as fitted using tw o different regression functions: the Palmgren function
[2 ]
o ( N ) = a (N + B ) b + o ^ ( 1)
and the K ohout-V echet function [3]
IN + B xb
o ( N ) = ° “ liN + C ) • (2)
where a, b, B, C, and o x are the regression parameters. The m eaning o f all parameters
is unequivocal and w ith a close relation to geom etrical shape o f the curve on ly in the case
o f the K ohout-V echet function: o x m eans the permanent fatigue lim it for an infinite
number o f cycles to fracture (g iga-cycle fatigue is not considered here), B and C
represent the positions o f curve bends, and b is the curve slope at the point o f in flexion
w hen the curve is plotted in the lo g - lo g scale. In the case o f the Palmgren function, the
relation betw een parameter b and the slope is not so direct and the parameter a has a
rather com plicated meaning.
Test R esu lts and D iscu ssion . The experim ental dependence o f the stress amplitude
on the number o f cycles to fracture w as fitted using both Eq. (1) and (2), see Figs. 1, 2,
and 3, w here both fits are compared. The values o f regression parameters together with
the calculated fatigue lim it for 10 cycles to fracture and the sum o f squares o f deviations
betw een m easured and fitted values S are presented in Table 3.
The difference in fits using different regression functions is evident at first sight: Eq.
(2) leads to a better fit than Eq. (1) does. This first im pression is supported by the values
o f the sum s o f squares: for Eq. (2) on ly 72% o f the value corresponding to Eq. (1) is
obtained. M oreover, tw o regions o f the numbers o f cycles to fracture are better described
2 5using Eq. (1): the low -cycle region from 10 to 10 cycles and the h igh-cycle region
above 10 cycles. It m eans that Eq. (2) has a better lim iting behavior than that o f Eq. (1).
Quantitatively it can be best expressed by the standard deviations o f the parameter o x
representing the lim iting behavior o f both equations: it w as calculated to be o x = (226.9
± 30.3) M Pa for Eq. (1) and o x = (310.1 ± 8 .8) M Pa for Eq. (2).
ISSN 0556-171X. npoôëeMbi npounocmu, 2008, № 1 41
J. Zapletal, S. Véchet, J. Kohout, and K. Obrtlik
T a b l e 3
Results of Regression Calculations
Parameter (Jœ, MPa b B a, MPa or C aC, MPa S
Eq. (1) 226.9 -0 .1882 65.02 1627.62 305.2 20,543
Eq. (2) 310.1 -0 .1086 33.11 1212,180 314.0 14,738
number o f cycles to fracture
Fig. 1. S — N curve o f the studied ADI, fitted by the Palmgren function (1).
10 10 10 10 10 10 10 10 10 10 10
number of cycles to fracture N
Fig. 2. S — N curve o f the studied ADI, fitted by the Kohout-Vechet function (2).
D iscontinuities betw een a low -cycle and h igh-cycle regions are often reported not
only as results o f experim ental tests [4, 5] but also as conclusions o f theoretical
considerations [6 , 7]. H ow ever, in Figs. 1, 2, and 3 both the low - and h igh-cycle results
are plotted com m only and it can be seen here that no discontinuity exists betw een them.
Even in tw o orders o f the number o f cycles to fracture the low - and h igh-cycle
experim ental points overlap and their link-up is ideal, w ithout any sign o f break or shift. It
can serve as an indirect evidence that both types o f tests w ere perform ed correctly and
responsibly.
42 ISSN 0556-171X. npoôëeubi npounocmu, 2008, N 1
Fatigue Lifetime o f A D I from Ultimate Tensile Strength
Generally, it is very hard to tell i f the above-m entioned discontinuities are only
experim ental artefacts or i f they can have a principal cause. It is m ost probable that at
least in som e cases the discontinuities can be attributable to changed experimental
conditions, inaccurate m easurem ents or incorrect conversion betw een low -cycle and
high-cycle data.
C on clu sion s
1. N o d iscontinuity w as found betw een the low - and h igh -cycle regions in
experim ental results o f A D I studied, even w hen the loading frequencies differ by two
orders o f magnitude (1 to 200 Hz).
2. The experim ental fatigue test results in the w hole range o f the number o f cycles to
fracture can be fitted using the Palmgren function and the K ohout-V echet function. The
latter provides a better fit in a low -cycle as w ell as h igh-cycle regions.
3. A relatively h igh value o f the fatigue lim it o c = 314 M Pa m eans that the
optim um regim e o f heat treatment w as applied.
Acknowledgements. The financial supports by the Ministry o f Defense o f the Czech Republic
within the Research Project No. MO0FVT0000404 and by the Grant Agency o f the Czech Republic
within the Grant Project No. 106/03/1265 are gratefully acknowledged.
1. E. Dorazil, High Strength Austempered Ductile Cast Iron, Horwood, London (1991).
2. W. Weibull, Fatigue Testing and Analysis o f Results, Pergamon Press, London etc. (1962).
3. J. Kohout and S. Vechet, Int. J. Fatigue, 23, 175 (2001).
4. D. S. Matsumoto and S. K. Gifford, J. Mater. Sci., 20, 4610 (1985).
5. R. Boukhili and R. Gauvin, J. Mater. Sci. Lett., 9, 449 (1989).
6. J. Pokluda, F. Kroupa, and L. ObdrZalek, Mechanical Properties and Structure o f Solids [in
Czech], PC-DIR, Brno (1994).
7. A. Puskar and M. Hazlinger, Failure and Fractures o f Details [in Slovak], University of
Zilina, Zilina (2000).
Received 28. 06. 2007
ISSN 0556-171X. n poôëeu u npouuocmu, 2008, № 1 43
|
| id | nasplib_isofts_kiev_ua-123456789-48240 |
| institution | Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| issn | 0556-171X |
| language | English |
| last_indexed | 2025-12-07T15:56:26Z |
| publishDate | 2008 |
| publisher | Інститут проблем міцності ім. Г.С. Писаренко НАН України |
| record_format | dspace |
| spelling | Zapletal, J. Vechet, S. Kohout, J. Obrtlik, K. 2013-08-17T11:09:03Z 2013-08-17T11:09:03Z 2008 Fatigue lifetime of ADI from ultimate tensile strength to permanent fatigue limit / J. Zapletal, S. Vechet, J. Kohout, K. Obrtlfk // Проблемы прочности. — 2008. — № 1. — С. 40-43. — Бібліогр.: 7 назв. — англ. 0556-171X https://nasplib.isofts.kiev.ua/handle/123456789/48240 S — N curve of austempered ductile iron was obtained in the range of lifetime including low cycle fatigue domain and high cycle fatigue domain up to 108 cycles. Ultimate tensile strength is used as a limiting value of the curve. Symmetric push-pull fatigue and tensile tests were performed at room temperature on isothermally treated nodular cast iron alloyed with copper and nickel having positive impact on mechanical, technological and fatigue properties of austempered ductile iron. Suitable functions for the fit of experimentally determined points were tested and their parameters were calculated. The best results were obtained using the Palmgren function and the function introduced by Kohout and Vechet. Since the loading frequency in high-cycle region is two orders higher than in low-cycle region, the effect of loading cycle frequency on fatigue behavior of the studied material is also studied. A possibility of discontinuity of experimental data between low-cycle and high-cycle regions is discussed. Получена кривая усталости аустенитно-отпущенного ковкого чугуна (ADI) в диапазоне долговечности, включая области малоцикловой и многоцикловой усталости до 108 циклов. В качестве предельного значения указанной кривой используется предел прочности при растяжении. Проведены испытания на усталость при симметричном растяжении-сжатии и на растяжение при комнатной температуре изотермически термообработанного чугуна с шаровидным графитом, с добавками меди и никеля, которые оказывают положительное влияние на механические, технологические и усталостные свойства ADI. Осуществлена проверка соответствующих функций для описания экспериментально определенных точек; выполнен расчет параметров указанных функций. Наилучшие результаты получены при использовании функции Пальмгрена и функции, предложенной Когутом и Вечетом. Исследовано также влияние частоты циклов нагружения на усталостное поведение рассматриваемого материала с учетом того, что частота нагружения в многоцикловой области на два порядка превышает частоту нагружения в малоцикловой области. Рассмотрена также возможность отсутствия непрерывности в экспериментальных данных на участке между малоцикловой и многоцикловой областями. en Інститут проблем міцності ім. Г.С. Писаренко НАН України Проблемы прочности Научно-технический раздел Fatigue lifetime of ADI from ultimate tensile strength to permanent fatigue limit Усталостная долговечность изотермически отпущенного ковкого чугуна в интервале от предела прочности при растяжении до устойчивого предела выносливости Article published earlier |
| spellingShingle | Fatigue lifetime of ADI from ultimate tensile strength to permanent fatigue limit Zapletal, J. Vechet, S. Kohout, J. Obrtlik, K. Научно-технический раздел |
| title | Fatigue lifetime of ADI from ultimate tensile strength to permanent fatigue limit |
| title_alt | Усталостная долговечность изотермически отпущенного ковкого чугуна в интервале от предела прочности при растяжении до устойчивого предела выносливости |
| title_full | Fatigue lifetime of ADI from ultimate tensile strength to permanent fatigue limit |
| title_fullStr | Fatigue lifetime of ADI from ultimate tensile strength to permanent fatigue limit |
| title_full_unstemmed | Fatigue lifetime of ADI from ultimate tensile strength to permanent fatigue limit |
| title_short | Fatigue lifetime of ADI from ultimate tensile strength to permanent fatigue limit |
| title_sort | fatigue lifetime of adi from ultimate tensile strength to permanent fatigue limit |
| topic | Научно-технический раздел |
| topic_facet | Научно-технический раздел |
| url | https://nasplib.isofts.kiev.ua/handle/123456789/48240 |
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