- Email: [email protected]
High temperature fatigue damage in three austenitic alloys
F’afis-Erdogan law by a change d variable in the law. end Wang and Zakai’s theorem. By using the solution of tba stodmstic diii equation and its pmbaMii dansity, asampbpmceaaandlfLdiibutionotfatigwcmck~areobtained.rsrpcrtivdy Thesethec&xlmauttsamcompamdwiththesllpsrimsmddatafwhiitensibsbu& steel APFH 60. Through the comoadaon. an immwement inthe&nwamodalismede. 6mfs.
forthwmml-nychdal~~ Afmctutmmochaniacritdon amwtfn of am turbine mmtarib. Afmdmd N.J.. Mkwx. Gig. F/&z. Me&
1988,
n,
RM.
fofinveat@ionoftheb&sviourofsdii*d~~.tltebnMti~of inclusions and intemmnular oheses. ths content and diibutfon of bvdro~en etc. The o*ofimportana,of~abo;a-mentionedfactaswhichinR-~mech~nical properties of the ste& espacially its ductilii. was detetminsd. The faoiaue and fracture CharacteriS(& AK,,,. daldN. 0-v -?Yc) tics of the castings were stcdii and relevant p”4wR WMWXI. investigation was also made on the cav~lon bdwiir of the steel and i*l dependence on microstructure and on mechanical pmpanias. 25 rah.
and
EffectofkW
(3). 535-w
The application of several fracture mechanics data correlation parameters to predIctIn the crack propagation life of turbine engine hot section materials was evaluated. A survey was conducted to determine the conditions where conventional fracturemechanics approahces may not be adquate to characterize cracking behavior. Both conventional linear and non-linear fracture mechanics analyses were considered. Isothermal and thefmaC mechanical (variable temoemtwe) crack propagation tests were performed in hastellwx. and B-1900 + Hf n&ids. The crack’growth data reduced using the stress intensity factor. the strain intensitv factor and the J-integral. None of these three parameters successf&y correlated the c&k grmvth data. All tt& parameters showed strain range effects and significant scatter betwaen the various testinQ condiis (in-phase. out-of-phase. in cormlatin~ hiQh temperlsodwmel).tipammeterwhichshowedthemosteffe*ii ature and variable temperature crack amwth was a modiied stress intensitv factor (AL) computed using the &wed load. the closing bending moment caused & the in&&e compliance with crack length and with the effective opening stress. The A& was shown to rationalize the effect of mode of testing (stress vs strain controlled) and the mode of fracture. Furthermore. the isothermal data at T,,, and T_ wm shown to provide an upper and lower bounds for the therm&mechanical fatigue data if plotted in terms of AK_. 47 refs.
Influenceof multipk overked on fetiiue credo reterdetion in high
The influence of muttiple overloads at various stress intensity levels (A0 in the linear regime of the Paris plot was studied in the high strength low alloy structural steel SANl+55. It was observed that crack retardation increases by increasing the overload ratio and the number of overloads. Saturation effect was &sewed for overload peak ratio -z 1.6 and crack arrest for overload peak ratio > 1.3. An attempt is also made in explaining the crack acceleration and retardation process by using crack closure model proposed by Newman. The increase in SIN life due to crack closure effect of multiple overloads. for fail safe damage tolerant design. is also discussed 14 refs.
ker.
Sci. E&J.A Sept. 1988,Alas. (2). 233-239
Theeffectoftemperatureonmeoldicsnescs(rain~.onmehigh~faigue for Cu life and on the near-sudaos and interior diion sbuctum. was dewmined -1s in tbs tempammnmnge296-83K.Amductionintampemtureleadstoa -in aewd and of the SN curved to hiQtmr stmes vetoes. while shii of the cyclic indspendart. These msults am discussed on the the CoffiMansw plot is wre basis of the corresponding changes in the clwacteristic spacings of dislocation stmctute. 22refs.
the
Hiph tempereturefetiiue w
A series of &ic strain wntrdled t&s has bsen canfed out at B[xTC on three high temperature auatedtic Fe-based alloys. These alloys wem AlSl type 316 stainleas steel, Allov 600 H and Sandvik 263 MA. The te8ts wem canfed out under constant total strain con&l using a constant strain rate of 0.006s-‘. Damege mechanics was applied to the results to follow the accumulation of demege. By caaidainp the chmges in modulus fully &d&d as a function of plastic strain ranga. de& the fact that each alloy had bean chosen because of a diit stress response at 6OOY. namely cyclic saturation. hardening, and softening followed by hardening for the AISI 316. 253 MA and Alloy 800 H. respsctively. Although each alloy accumulated fatigue damage in a similar manner. the longs lives of Sandvik 253 MA and Alloy @JO H at a given total strain range were due to a smaller dastic strain component and a reducad stale I crack propagation rate. In the 253 MA al&, slip was predominantly plensr with some cells occasionally forming at high strain ranges. Slip was localized in Alloy 800 H due to the shearing of small y’ precipitates. In the AISI 316 stainless steel, didocation cells formed at all strain ranges it is concluded that all these alloys accumulate damge similarly. independent of their deformation behaviour. 26 refs.
A micmetructurellym A. and de has Rim, E.R. Fatigue Ftact. Eng. Ma&. The effect of variation of stress frequency on fatigue Crack propagation in 99.5% pure Ti. which has remarkable strain rate dependanca in the plastic mgion and anisotropy. was studied. Fatigue crack propwetion tests were carried out under four stress frequencies: two constant m&s frequmcbs (f = 20 Hz. 0.02 Hz) and two stress frequencies changed steo-wiss if = [email protected] Hz 0.02-M Hz). The tast soecimans were cut out from rollino dir&ion and transverse direction to rollinb of the plate. An orthotropic elasto/visco-plastic analysis of fatiQue crack popagation was performad by the use of the orthotropic viscoplastic model. and the comparison between the change of crack propagation rate due to variation of stress frequencies and ths visco-plastic strain bshaviwr at the crack tip calculated by the anaMs was made. The results obtained are summarized as follows: it was found from the experiments that the crack propagation rate changed characteristically depending on cutting out direction of the specimen caused by anisotropy of Ti plate and on the variation of stress fmqwncy. A parameter closely related to the fatigue crack propagation rate is the visco-plastic strain range at the crack tip. The effect of variation of stress frequency on the fatigue crack propapetion rate may be explained by the variation of the visco-plastic strain range at the crack tip based on an anisotropic visco-plasticity of the materials. 9 refs.
A etetietkel model for the p_+ktiop of fetigue cmck growth under ;,$kck type spectrum Ioedmg. sslrvw.G.C. Yang,J.N. and Schwwtz
in three euetenitii elkye. numbme,
A.indNikmJ.4 FefiBue Fmct En@. Maa9c S@wx 19B0.11,(6). 397-407
fetigue creek growth equetion. Nmwrc, S?mct. 1988.11,(5). 383-396
A brief outline of a recently dwelopsd model which dez&bes the microstructurallv short and the physic&-y short crack periods of fatigue crack growth is prenented. A single equ.atiMl todescribebomragimasisdiscusssdsnd~moddapplmdtodasonamsdiumcarbon steel. Good pmdictiMlS &tinQ t0 the actual ex pedmwnal lifetime were ad+& The results are compared with the prediction of fatigue life based on a previously mpofted two-equation approach. 25 mfs.
Aductiliiexhe+knmketknofecmekng~creepfetigue t$e on euetembc eteel. Wed D.S., M J., Auafm, C. and Gmm ~~~FrsctEng.~l1988,11,(5),J71-3B1 A limited number of long tem~ cmep/fafii tests perfomwd on twc batches of type 316 steel and one batch of asaockxted 17CrBNi2Mo vwld metal are mpotted. Tast durstions range from 5000-32 000 h and temparatums from 550-62FC. Subsequent metallographic examination shows the failures to be wholly or pmdominently intergranular. The resuhs are analysed using a ductility exhaustion approach. and it is shown that the endurances obtained are within * factor of two of predicted valuss. Tha -Its confirm that the dedign aoproach to creep/fatigue currenttv baii developed in the UK and baaed on ductility exhaustion is like& to be satisfactorv. 16 I&.
Eng Fmct Mech. lSBB,3l, (3). 371-380 A log normal statistical model has been developed for the prediction of crack Qrcwth damage accumulation under conditions of a block type spectrum loading in high temperatures. Both the distribution of crack lemath at anv given life and the distribution of load cycles to reach any riven crack length &?a p&&d. An experimental test programma was conducted for the verification pwpose. The theoretical predictions based on the statistcal model were cornoared to test data from 12 so&men tests for INlOO. a Ni-base suoemllay. generated und& a Mock type spectrum. A good correlation was obtained between the predicted distributions and the test results. 21 refs
Effect of cyclic frequency on the fetigue life of ABME BA-106B
piping eteelin PWR environments.T&l, J. Mater. Eng. Sept. 1988.10,(3), 193-203
J.B.
Fatigue life tests in pressurized water reactor (FWR) environments were performed on smooth and sharply notched specimens of ASME SA-106-B piping steel at cyc6c frequenties of 1.0. 0.1. and 0.017 Hz. On the basis of these tests, it was concluded that no effect of cyclic frequenw existed for smooth specimens. whereas a frequency of 0.17 Hz proved to have the most datrimental effect on the cyziic Iii of the notched specimens. However. a reduction in fatigue stwgth in the low cycle fatigue regime and a fatigue strength enhancemant in hiQh cycle regime was observed in both 288’C air environment tests and FWR environment tests. This is believed to be due to dynamic strain ageing pmcesses As a result. the unrent ASME Section Ill design cww for carbon steels is non-conservative in its positioning. which may decrease the prasumed safety ftior against fatigue failures in C steel piping components having !xnxturaI discontinuities. 22 mfs.
Int
J Fatigue May 1989
G.J. andRkC R.H. FatigueFmct. Eng. Matw. Stnnz& lSRB.11,(5),366370 fatigue-and cme~fatigue tent and from at& bad-c&trolled aad; growth tests on aged 321 stainless steeJ (parent and simulated HAZ) at 650%. In the cmw-f&we tests. constant disolaoemeo t tensile hold oeriods of 12-192 h were used. Cmck Qrowth rates compfised b&h qdii and dwell p&d contributions. Cyclic QmwIh connibutins are described by a Paris-w law and ~iw? fastaf crack ~mwlh rates than those asxdated with pure fatigue tBw. Dwell period contrikrtnns am desuibed by tlw e parameter. The total ~Clic crack QrcV”?hrates am give bv summing the c@fi and &all p&d conaibutiofls. Estimates of C using a mfmwcestmssappmech.togmherwkhtheapprwMtesttws relaxation creep data, are shown to conefete we6 witf~ expedn~tallv measured C values. Crack growth ratir) during static load-contmllad tests cormlate well with C. Good agreement is obtained batwaen crack growth m during the atadc tests and those pmducsd during the hold period of the c-fatigue tests. 10 mfs.
Pmpegetionmdckeureof#hc&fotIgueemkeetnotahaundu mtraam.~K.T~K.andT~N. wme=l Fat&m Fmct Eng. Matw. sbuer 19BB, 11, (6). 343-364 Single-edge-notched specimens of a larr-carbon amel (so UIS SM41B) wme f&Quad under cyclic in-plans bendin with capa*vemeanstlaems.Thedweiopmentofcmck closure with crack growth was studii both w and theoretically. The dMiOn
forthwmml-nychdal~~ Afmctutmmochaniacritdon amwtfn of am turbine mmtarib. Afmdmd N.J.. Mkwx. Gig. F/&z. Me&
1988,
n,
RM.
fofinveat@ionoftheb&sviourofsdii*d~~.tltebnMti~of inclusions and intemmnular oheses. ths content and diibutfon of bvdro~en etc. The o*ofimportana,of~abo;a-mentionedfactaswhichinR-~mech~nical properties of the ste& espacially its ductilii. was detetminsd. The faoiaue and fracture CharacteriS(& AK,,,. daldN. 0-v -?Yc) tics of the castings were stcdii and relevant p”4wR WMWXI. investigation was also made on the cav~lon bdwiir of the steel and i*l dependence on microstructure and on mechanical pmpanias. 25 rah.
and
EffectofkW
(3). 535-w
The application of several fracture mechanics data correlation parameters to predIctIn the crack propagation life of turbine engine hot section materials was evaluated. A survey was conducted to determine the conditions where conventional fracturemechanics approahces may not be adquate to characterize cracking behavior. Both conventional linear and non-linear fracture mechanics analyses were considered. Isothermal and thefmaC mechanical (variable temoemtwe) crack propagation tests were performed in hastellwx. and B-1900 + Hf n&ids. The crack’growth data reduced using the stress intensity factor. the strain intensitv factor and the J-integral. None of these three parameters successf&y correlated the c&k grmvth data. All tt& parameters showed strain range effects and significant scatter betwaen the various testinQ condiis (in-phase. out-of-phase. in cormlatin~ hiQh temperlsodwmel).tipammeterwhichshowedthemosteffe*ii ature and variable temperature crack amwth was a modiied stress intensitv factor (AL) computed using the &wed load. the closing bending moment caused & the in&&e compliance with crack length and with the effective opening stress. The A& was shown to rationalize the effect of mode of testing (stress vs strain controlled) and the mode of fracture. Furthermore. the isothermal data at T,,, and T_ wm shown to provide an upper and lower bounds for the therm&mechanical fatigue data if plotted in terms of AK_. 47 refs.
Influenceof multipk overked on fetiiue credo reterdetion in high
The influence of muttiple overloads at various stress intensity levels (A0 in the linear regime of the Paris plot was studied in the high strength low alloy structural steel SANl+55. It was observed that crack retardation increases by increasing the overload ratio and the number of overloads. Saturation effect was &sewed for overload peak ratio -z 1.6 and crack arrest for overload peak ratio > 1.3. An attempt is also made in explaining the crack acceleration and retardation process by using crack closure model proposed by Newman. The increase in SIN life due to crack closure effect of multiple overloads. for fail safe damage tolerant design. is also discussed 14 refs.
ker.
Sci. E&J.A Sept. 1988,Alas. (2). 233-239
Theeffectoftemperatureonmeoldicsnescs(rain~.onmehigh~faigue for Cu life and on the near-sudaos and interior diion sbuctum. was dewmined -1s in tbs tempammnmnge296-83K.Amductionintampemtureleadstoa -in aewd and of the SN curved to hiQtmr stmes vetoes. while shii of the cyclic indspendart. These msults am discussed on the the CoffiMansw plot is wre basis of the corresponding changes in the clwacteristic spacings of dislocation stmctute. 22refs.
the
Hiph tempereturefetiiue w
A series of &ic strain wntrdled t&s has bsen canfed out at B[xTC on three high temperature auatedtic Fe-based alloys. These alloys wem AlSl type 316 stainleas steel, Allov 600 H and Sandvik 263 MA. The te8ts wem canfed out under constant total strain con&l using a constant strain rate of 0.006s-‘. Damege mechanics was applied to the results to follow the accumulation of demege. By caaidainp the chmges in modulus fully &d&d as a function of plastic strain ranga. de& the fact that each alloy had bean chosen because of a diit stress response at 6OOY. namely cyclic saturation. hardening, and softening followed by hardening for the AISI 316. 253 MA and Alloy 800 H. respsctively. Although each alloy accumulated fatigue damage in a similar manner. the longs lives of Sandvik 253 MA and Alloy @JO H at a given total strain range were due to a smaller dastic strain component and a reducad stale I crack propagation rate. In the 253 MA al&, slip was predominantly plensr with some cells occasionally forming at high strain ranges. Slip was localized in Alloy 800 H due to the shearing of small y’ precipitates. In the AISI 316 stainless steel, didocation cells formed at all strain ranges it is concluded that all these alloys accumulate damge similarly. independent of their deformation behaviour. 26 refs.
A micmetructurellym A. and de has Rim, E.R. Fatigue Ftact. Eng. Ma&. The effect of variation of stress frequency on fatigue Crack propagation in 99.5% pure Ti. which has remarkable strain rate dependanca in the plastic mgion and anisotropy. was studied. Fatigue crack propwetion tests were carried out under four stress frequencies: two constant m&s frequmcbs (f = 20 Hz. 0.02 Hz) and two stress frequencies changed steo-wiss if = [email protected] Hz 0.02-M Hz). The tast soecimans were cut out from rollino dir&ion and transverse direction to rollinb of the plate. An orthotropic elasto/visco-plastic analysis of fatiQue crack popagation was performad by the use of the orthotropic viscoplastic model. and the comparison between the change of crack propagation rate due to variation of stress frequencies and ths visco-plastic strain bshaviwr at the crack tip calculated by the anaMs was made. The results obtained are summarized as follows: it was found from the experiments that the crack propagation rate changed characteristically depending on cutting out direction of the specimen caused by anisotropy of Ti plate and on the variation of stress fmqwncy. A parameter closely related to the fatigue crack propagation rate is the visco-plastic strain range at the crack tip. The effect of variation of stress frequency on the fatigue crack propapetion rate may be explained by the variation of the visco-plastic strain range at the crack tip based on an anisotropic visco-plasticity of the materials. 9 refs.
A etetietkel model for the p_+ktiop of fetigue cmck growth under ;,$kck type spectrum Ioedmg. sslrvw.G.C. Yang,J.N. and Schwwtz
in three euetenitii elkye. numbme,
A.indNikmJ.4 FefiBue Fmct En@. Maa9c S@wx 19B0.11,(6). 397-407
fetigue creek growth equetion. Nmwrc, S?mct. 1988.11,(5). 383-396
A brief outline of a recently dwelopsd model which dez&bes the microstructurallv short and the physic&-y short crack periods of fatigue crack growth is prenented. A single equ.atiMl todescribebomragimasisdiscusssdsnd~moddapplmdtodasonamsdiumcarbon steel. Good pmdictiMlS &tinQ t0 the actual ex pedmwnal lifetime were ad+& The results are compared with the prediction of fatigue life based on a previously mpofted two-equation approach. 25 mfs.
Aductiliiexhe+knmketknofecmekng~creepfetigue t$e on euetembc eteel. Wed D.S., M J., Auafm, C. and Gmm ~~~FrsctEng.~l1988,11,(5),J71-3B1 A limited number of long tem~ cmep/fafii tests perfomwd on twc batches of type 316 steel and one batch of asaockxted 17CrBNi2Mo vwld metal are mpotted. Tast durstions range from 5000-32 000 h and temparatums from 550-62FC. Subsequent metallographic examination shows the failures to be wholly or pmdominently intergranular. The resuhs are analysed using a ductility exhaustion approach. and it is shown that the endurances obtained are within * factor of two of predicted valuss. Tha -Its confirm that the dedign aoproach to creep/fatigue currenttv baii developed in the UK and baaed on ductility exhaustion is like& to be satisfactorv. 16 I&.
Eng Fmct Mech. lSBB,3l, (3). 371-380 A log normal statistical model has been developed for the prediction of crack Qrcwth damage accumulation under conditions of a block type spectrum loading in high temperatures. Both the distribution of crack lemath at anv given life and the distribution of load cycles to reach any riven crack length &?a p&&d. An experimental test programma was conducted for the verification pwpose. The theoretical predictions based on the statistcal model were cornoared to test data from 12 so&men tests for INlOO. a Ni-base suoemllay. generated und& a Mock type spectrum. A good correlation was obtained between the predicted distributions and the test results. 21 refs
Effect of cyclic frequency on the fetigue life of ABME BA-106B
piping eteelin PWR environments.T&l, J. Mater. Eng. Sept. 1988.10,(3), 193-203
J.B.
Fatigue life tests in pressurized water reactor (FWR) environments were performed on smooth and sharply notched specimens of ASME SA-106-B piping steel at cyc6c frequenties of 1.0. 0.1. and 0.017 Hz. On the basis of these tests, it was concluded that no effect of cyclic frequenw existed for smooth specimens. whereas a frequency of 0.17 Hz proved to have the most datrimental effect on the cyziic Iii of the notched specimens. However. a reduction in fatigue stwgth in the low cycle fatigue regime and a fatigue strength enhancemant in hiQh cycle regime was observed in both 288’C air environment tests and FWR environment tests. This is believed to be due to dynamic strain ageing pmcesses As a result. the unrent ASME Section Ill design cww for carbon steels is non-conservative in its positioning. which may decrease the prasumed safety ftior against fatigue failures in C steel piping components having !xnxturaI discontinuities. 22 mfs.
Int
J Fatigue May 1989
G.J. andRkC R.H. FatigueFmct. Eng. Matw. Stnnz& lSRB.11,(5),366370 fatigue-and cme~fatigue tent and from at& bad-c&trolled aad; growth tests on aged 321 stainless steeJ (parent and simulated HAZ) at 650%. In the cmw-f&we tests. constant disolaoemeo t tensile hold oeriods of 12-192 h were used. Cmck Qrowth rates compfised b&h qdii and dwell p&d contributions. Cyclic QmwIh connibutins are described by a Paris-w law and ~iw? fastaf crack ~mwlh rates than those asxdated with pure fatigue tBw. Dwell period contrikrtnns am desuibed by tlw e parameter. The total ~Clic crack QrcV”?hrates am give bv summing the c@fi and &all p&d conaibutiofls. Estimates of C using a mfmwcestmssappmech.togmherwkhtheapprwMtesttws relaxation creep data, are shown to conefete we6 witf~ expedn~tallv measured C values. Crack growth ratir) during static load-contmllad tests cormlate well with C. Good agreement is obtained batwaen crack growth m during the atadc tests and those pmducsd during the hold period of the c-fatigue tests. 10 mfs.
Pmpegetionmdckeureof#hc&fotIgueemkeetnotahaundu mtraam.~K.T~K.andT~N. wme=l Fat&m Fmct Eng. Matw. sbuer 19BB, 11, (6). 343-364 Single-edge-notched specimens of a larr-carbon amel (so UIS SM41B) wme f&Quad under cyclic in-plans bendin with capa*vemeanstlaems.Thedweiopmentofcmck closure with crack growth was studii both w and theoretically. The dMiOn