Method for low-cycle fatigue life assessment of metallic materials under multiaxial loading

A new method of fatigue life assessment under multiaxial low-cycle regular and irregular loading is proposed, which is based on the modified Pisarenko-Lebedev criterion, the linear damage accumulation hypothesis, and the nonlinear Manson approach. The results of low-cycle fatigue tests of titanium a...

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Дата:2008
Автори: Shukaev, S., Gladskii, M., Zakhovaiko, A., Panasovskii, K.
Формат: Стаття
Мова:English
Опубліковано: Інститут проблем міцності ім. Г.С. Писаренко НАН України 2008
Назва видання:Проблемы прочности
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Цитувати:Method for low-cycle fatigue life assessment of metallic materials under multiaxial loading / S. Shukaev, M. Gladskii, A. Zakhovaiko, K. Panasovskii // Проблемы прочности. — 2008. — № 1. — С. 56-59. — Бібліогр.: 3 назв. — англ.

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spelling irk-123456789-484602013-08-19T22:48:42Z Method for low-cycle fatigue life assessment of metallic materials under multiaxial loading Shukaev, S. Gladskii, M. Zakhovaiko, A. Panasovskii, K. Научно-технический раздел A new method of fatigue life assessment under multiaxial low-cycle regular and irregular loading is proposed, which is based on the modified Pisarenko-Lebedev criterion, the linear damage accumulation hypothesis, and the nonlinear Manson approach. The results of low-cycle fatigue tests of titanium alloy VT9 under irregular proportional and non-proportional biaxial loading are given. The tests were carried out at three Mises strain levels (0,6, 0,8, and 1,0%) with various combinations of proportional and non-proportional strain paths. All the tests were carried out at room temperature. The proposed method turned out to be effective and to allow for such factors as strain state type, strain path type and loading irregularity. Предложен новый метод оценки усталостной долговечности в условиях многоосного равномерного и неравномерного нагружения, который основан на модифицированном критерии Писаренко-Лебедева, линейной гипотезе накопления повреждений и нелинейном подходе Мэнсона. Приведены результаты испытаний титанового сплава ВТ9 на малоцикловую усталость при неравномерном пропорциональном и непропорциональном двухосном нагружении. Испытания проводились при трех уровнях деформаций по критерию Мизеса: 0,6; 0,8; 1,0% с различными сочетаниями пропорциональной и непропорциональной траекторий деформации. Все испытания выполнялись при комнатной температуре. Установлено, что предлагаемый метод является эффективным и позволяет учитывать такие факторы, как вид деформированного состояния, тип траектории деформации и неравномерность нагружения. 2008 Article Method for low-cycle fatigue life assessment of metallic materials under multiaxial loading / S. Shukaev, M. Gladskii, A. Zakhovaiko, K. Panasovskii // Проблемы прочности. — 2008. — № 1. — С. 56-59. — Бібліогр.: 3 назв. — англ. 0556-171X http://dspace.nbuv.gov.ua/handle/123456789/48460 539. 4 en Проблемы прочности Інститут проблем міцності ім. Г.С. Писаренко НАН України
institution Digital Library of Periodicals of National Academy of Sciences of Ukraine
collection DSpace DC
language English
topic Научно-технический раздел
Научно-технический раздел
spellingShingle Научно-технический раздел
Научно-технический раздел
Shukaev, S.
Gladskii, M.
Zakhovaiko, A.
Panasovskii, K.
Method for low-cycle fatigue life assessment of metallic materials under multiaxial loading
Проблемы прочности
description A new method of fatigue life assessment under multiaxial low-cycle regular and irregular loading is proposed, which is based on the modified Pisarenko-Lebedev criterion, the linear damage accumulation hypothesis, and the nonlinear Manson approach. The results of low-cycle fatigue tests of titanium alloy VT9 under irregular proportional and non-proportional biaxial loading are given. The tests were carried out at three Mises strain levels (0,6, 0,8, and 1,0%) with various combinations of proportional and non-proportional strain paths. All the tests were carried out at room temperature. The proposed method turned out to be effective and to allow for such factors as strain state type, strain path type and loading irregularity.
format Article
author Shukaev, S.
Gladskii, M.
Zakhovaiko, A.
Panasovskii, K.
author_facet Shukaev, S.
Gladskii, M.
Zakhovaiko, A.
Panasovskii, K.
author_sort Shukaev, S.
title Method for low-cycle fatigue life assessment of metallic materials under multiaxial loading
title_short Method for low-cycle fatigue life assessment of metallic materials under multiaxial loading
title_full Method for low-cycle fatigue life assessment of metallic materials under multiaxial loading
title_fullStr Method for low-cycle fatigue life assessment of metallic materials under multiaxial loading
title_full_unstemmed Method for low-cycle fatigue life assessment of metallic materials under multiaxial loading
title_sort method for low-cycle fatigue life assessment of metallic materials under multiaxial loading
publisher Інститут проблем міцності ім. Г.С. Писаренко НАН України
publishDate 2008
topic_facet Научно-технический раздел
url http://dspace.nbuv.gov.ua/handle/123456789/48460
citation_txt Method for low-cycle fatigue life assessment of metallic materials under multiaxial loading / S. Shukaev, M. Gladskii, A. Zakhovaiko, K. Panasovskii // Проблемы прочности. — 2008. — № 1. — С. 56-59. — Бібліогр.: 3 назв. — англ.
series Проблемы прочности
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AT gladskiim methodforlowcyclefatiguelifeassessmentofmetallicmaterialsundermultiaxialloading
AT zakhovaikoa methodforlowcyclefatiguelifeassessmentofmetallicmaterialsundermultiaxialloading
AT panasovskiik methodforlowcyclefatiguelifeassessmentofmetallicmaterialsundermultiaxialloading
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fulltext UDC 539. 4 A M e th o d fo r L o w - C y c le F a t ig u e L ife A s s e s s m e n t o f M e ta l l ic M a te r ia ls u n d e r M u lt ia x ia l L o a d in g S. S h u k aev ,1a M . G lad sk ii,1b A . Z a k h o v a ik o ,1c and K . P a n a so v sk ii1,d 1 National Technical University o f Ukraine “Kiev Polytechnic Institute,” Institute o f Mechanical Engineering, Department o f Machine Dynamic and Strength o f Materials, Kiev, Ukraine a shukayev@users.ntu-kpi.kiev.ua, b’d gladsky@gmail.com, c zakhov@users.ntu-kpi.kiev.ua A new method o f fatigue life assessment under multiaxial low-cycle regular and irregular loading is proposed, which is based on the modified Pisarenko-Lebedev criterion, the linear damage accumulation hypothesis, and the nonlinear Manson approach. The results o f low-cycle fatigue tests o f titanium alloy VT9 under irregular proportional and non-proportional biaxial loading are given. The tests were carried out at three Mises strain levels (0,6, 0,8, and 1,0%) with various combinations o f proportional and non-proportional strain paths. All the tests were carried out at room temperature. The proposed method turned out to be effective and to allow fo r such factors as strain state type, strain path type and loading irregularity. K e y w o r d s : m ultiaxial low -cy c le fatigue, irregular loading, titanium alloys, damage accum ulation, lim it state criteria. In trod u ction . M achine and construction elem ents often undergo irregular m ultiaxial cycle loading. Though m ultiaxial fatigue o f materials has been studied for a long tim e and sufficient experim ental data has been accumulated, the problem o f including a loading irregularity in a low -cycle fatigue area is still important. N um erous attempts to describe fatigue damage process have been made, resulting in the developm ent o f a large number o f damage accum ulation m odels. The m ost generally em ployed is the linear damage accum ulation concept proposed b y Miner, w hereby dam ages D per cycle at a variable loading amplitude are added linearly and the failure happens w hen D = ' ^ . n i / N f = 1, w here n { is the number o f on e-level loading cycles and N f is number o f cycles to failure under a g iven loading level. This approach is easy to use but it fails to g ive an adequate estim ation o f life in m any cases. There have been m any attempts to develop a m odel based on the nonlinear accum ulation o f fatigue dam age, but m ost o f them disregarded the com plex influence o f such factors as the stress state type, loading path, previous stress history in the process o f fatigue damage accumulation. Fatemi and Yang [1] have carried out a substantial survey o f the existing m odels, proposed a classification thereof, d iscussed advantages and disadvantages o f each m odel. In the paper, the influence o f sequential loading effects is studied on V T9 titanium alloys under tension-com pression , torsion and 90° out-of-phase non-proportional loading. The life estim ation m ethod is proposed both for regular and irregular m ultiaxial loading. A dam age m odel is put forward, w hich considers the nonproportional effects arising at a change o f the loading regim e. E xperim enta l Procedure. A high-temperature titanium alloy V T9 o f the T i-A l-M o - Z r-S i system b elongs to tw o-phase (a + /3) m artensitic alloys. The chem ical com position (in wt.% ) o f the material is g iven in Table 1. The microstructure o f the material o f the specim en billets consists o f (a + /3)-phases o f equiaxial structure and corresponds to the second type in the nine-type scale for bar materials according to Instruction N o. 1054-76 o f the A ll-U n ion Institute o f Aircraft Materials. © S. SH U K A EV , M. G LA D SK II, A . ZA K H O V A IK O , K. PA N A SO V SK II, 2008 56 ISSN 0556-171X. Проблемы прочности, 2008, № 1 mailto:shukayev@users.ntu-kpi.kiev.ua mailto:gladsky@gmail.com mailto:zakhov@users.ntu-kpi.kiev.ua A Method fo r Low-Cycle Fatigue Life Assessment T a b l e 1 Chemical Composition of VT9 Alloy Al Mo Si Fe Zr H2 n 2 C 6.50 3.40 0.30 0.081 1.58 0.006 0.018 0.06 Specim ens w ere m ade from as-delivered rolled bars 25 m m in diameter. The m echanical properties o f the material, w hich were determ ined by tensile testing o f 125-m m -long solid cylindrical specim ens at room temperature, have the fo llow ing mean values: proportional lim it 758 MPa, y ield strength 865 MPa, ultimate strength 973 MPa, elongation 17%, reduction o f the cross-sectional area 45%, and elastic m odulus 118 GPa. For the purpose o f providing a stress-strain state c lose to a hom ogeneous one, tubular specim ens w ith an outer diameter o f 11 m m , w all thickness o f 0.5 m m , gauge length o f 20 m m were used. The realized strain paths are show n in Fig. 1. / f 4 \ s " t f h Ar\1 \ \ 4 V \ \ \ *4 К N[> a t o Fig. 1. Schematics o f strain paths used. For the V T 9 titanium alloy the test program as g iven in Table 2 w as implemented. The basic m odes w ere as follow s: tension-com pression , alternating torsion, and 90° out-of-phase loading. The first stage o f the program w as the b lock axial loading and/or torsion m om ent test w ith g iven strain ranges. During this test the strain path remained constant. The second stage o f the program involved testing o f the specim ens w ith changing o f the strain path. A transition from one strain path to the other w as conducted w hen the D value reached 0.5 and then the specim en w as cycled to failure. A t the third stage the test w ith a m ultiple strain path change w as carried out. P ro p o sed M eth od . It w as prev iously m entioned that the application o f the Pisarenko-L ebedev m odified criterion for the fatigue life assessm ent o f the V T 1-0 titanium alloy under regular nonproportional loading show s a good agreem ent betw een the predicted and test data due to the com plex consideration o f the strain state type and nonproportionality o f loading [3]. Therefore it is recom m ended to apply the P isarenko- L ebedev m odified criterion as w ell as the chosen damage accum ulation hypothesis for assessing the V T9 titanium alloy fatigue life. In this study, the tw o damage accumulation hypotheses w ere analyzed: the linear hypothesis and the M anson approach w ith the Pisarenko-L ebedev equivalent strain in both cases, according to w hich the damage curve is a nonlinear function o f the relative fatigue life, D i = (n t / N fi ) q , where q = ( N f i / N f r )a ; a is the material constant to be calculated from the test data for sequential double-level loading, and N fr is the number o f load cycles to failure at a “reference” loading level. A nalyzing Figs. 2 and 3 one can see that during the application o f the P isarenko- L ebedev m odified criterion and the linear damage accum ulation hypothesis the best correlation betw een the predicted and test data is obtained for alternating torsion (paths t_01 and t_ 02 ). ISSN 0556-171X. Проблемыг прочности, 2008, № l 57 S. Shukaev, M. Gladskii, A. Zakhovaiko, and K. Panasovskii T a b l e 2 Strain Peak Values and Number o f Cycles to Failure for VT9 Titanium Alloy Test type £a y J V3 ni N f % cycle a_01 a 0.8 - 157 293 a 1.0 - 136 a_02 a 1.0 - 98 245 a 0.8 - 147 a 03 a 0 .6- 0 .8- 1.0- 0.8 - 50 519 a 04 a 1.0- 0 .8- 0 .6- 0.8 - 50 491 oatota — 0.8 1.0 50 475 oa o 1.0 1.0 77 218 a 1.0 - 141 atat 1/5 a 1.0 - 40 423 t - 1.0 130 atat 1/3 a 1.0 — 65 510 t - 1.0 219 t_01 t - 0 .8- 1.0- 1.2- 1.0 50 601 t_02 t - 1.2- 1.0- 0 .8- 1.0 50 528 at a 1.0 - 97 398 t - 1.0 301 ta t - 1.0 398 603 a 1.0 - 205 ao a 1.0 - 98 184 o 1.0 1.0 86 to t - 1.0 282 390 o 1.0 1.0 108 ot o 1.0 1.0 80 384 t - 1.0 304 A s a result, one can com e to a conclusion about the linearity o f damage accumulation process for a g iven loading type. The com bined application o f the P isarenko-Lebedev m odified criterion and o f the M anson’s approach show ed a h igh leve l o f correlation betw een the predicted data and test results for all the loading programs except the alternating torsion. So, the fo llow in g m odification o f the M anson approach is proposed: D i = ( n j N f i ) ß( m) ( 1) w here ß ( « ) = ( V a 2m + — 1- ( V a \ N fr> n \ N f r ) m is the strain path orientation angle, w hich determ ines the dom inating type o f the strain state, m = arctan / \ y a £ fs £ a y fs £ fs and y fs 58 ISSN 0556-171X. npoôëeMbi npounocmu, 2008, N9 1 A Method fo r Low-Cycle Fatigue Life Assessment ♦ a Q3; a 04 ■ i_ p i ; t_D2 ■ ADS o ao X Dt . x1o + a tat_1/3 -i- a tat 1/5 £>at ' D la / / / / , + *• / 4 A ' ♦a_Q3; a1_01 ; Aoa o an X Dt x lo + ata1_1 + ata1_1 • DStDta <-at . □ la U4 / / / / <2 / 1 / / p r A / / * A Nobservet Fig. 2 Fig. 3 Fig. 2. Comparison between the fatigue lives predicted by the modified linear damage rule and the experimental fatigue lives. Fig. 3. Comparison between the fatigue lives predicted by the modified damage curve approach and the experimental fatigue lives. are the fatigue strength coefficients for a finite life N f in the uniaxial and torsional loading cases. Thus, the damage accum ulation during the alternating torsion is linear, during the tension-com pression is calculated using the M anson approach, and during the biaxial proportional and non-proportional loading is assessed by their linear interpolation. The application o f formula (1) resulted in the best agreem ent betw een the predicted and experim ental data as show n in Fig. 4. C onclusion . The proposed m ethod o f fatigue life assessm ent under m ultiaxial low - cycle regular and irregular loading, w hich is based on the P isarenko-L ebedev m odified criterion, the linear damage accum ulation hypothesis, and the nonlinear M anson approach proved to be effective and to a llow for such factors as the strain state type, strain path type, and loading irregularity. ♦ a Ü3; a 04 ■ t_01 ; t_02 Aoa o a o XOt X t D + atat_1/3 + atat_1ß * oat ola Oat □ ta / / / Y / / / / / ^ ////̂/ A Fig. 4. Comparison between the fatigue lives predicted by the proposed approach and the experimental fatigue lives. 1. A. Fatemi and L. Yang, “Cumulative fatigue damage and life prediction theories: a survey of the state o f the art for homogeneous materials,” Int. J. Fatigue, 20, No. 1, 9-34 (1998). 2. T. Itoh, M. Sakane, M. Ohnami, et al., “Dislocation structure and non-proportional hardening of type 304 stainless steel,” in: Proc. o f the 5th Int. Conf. on Biaxial-Multiaxial Fatigue and Fracture, Cracow (1997), Vol. 1, pp. 189-206. 3. S. Shukaev, A. Zakhovaiko, M. Gladskii M., and K. Panasovskii, “Estimation o f low-cycle fatigue criteria under multiaxial loading,” Int. J. Reliab. Life Machin. Struct., 2, 127-135 (2004). Received 28. 06. 2007 ISSN 0556-171X. npoôneMU npoHHocmu, 2008, № 1 59