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Crack propagation in a commercial steel
lnm ~¢tr4v~,. ~ ~men~ Cel~Tm..Ihe.l~l~e, w,~= be I ;rim ~ edl~ning ~eronm~nl INNImgOff a OeIIc~or W~Itl ~ 13tOpoe4KIte~lnoIo~v a ra(lsst,on die(actOr WOClO Oe C~OeloleO~ CIMllctlng the pl'eeenca of COWO~,on=n e~ooloo Crllc,Jr..llthat Isenatrate I~evO~d a p,eoetl'~n,neC~ Ct,~cal daI~1and thus w w r ~ t rsoe,r 13 refS
Aqoeatto
ondoll~
from
Methadon. P A ItS Diss Abe. I~t S e p t 1 ~ , 4 I .
f a t I D e ~ CrlM~W i n s t e e l s . ( D i m r t a t i o n ) . (3)
The investigation of the relationships between acoustic emission beheviour and fatigue orecks in a r~teel and the findings of the successful monitoring of the corrosion fatigue of • fult-eca~e welded Y-jo~m ire related'Small-scale fatigue tests were used to investigate the acoustic emissions (AE) beheviour of fatigue crack growth through a steel to BS 4360 50D, The effects of variations in sample microstructure obtained by heat treatment and welding were considered, as were the effects of crack growth at different stress ratios, Corrosion fatigue testing at cathodic protection potentials ranging from open circuit to - 1200 mV (SCE) were used to investigate the effects of environment on the AE Primary emissions, which occur close to peak load, were found to be generated by the advance of the crack tip plastic zone into previously undefonmed material. Secondary emissions were found to be mostly generated by crack closure processes during in-air fatigue, and the crushing of corrosion products within the crack during corrosion fatigue testing. These results show that crack growth rate characterization is only possible using primsry AE. Secondary AE can only be used to indicate the presence and location of a crack, and the best method for sepmating primary from secondary AE ia to filter on the basis of load. The small-scale results were related to AE detected while monitoring the fatigue of a full-sized welded Y-joint in seawater. The results of this were very promising, with the initiation and propagetion of a crack being detectt~l; locations of the extremities of the crack using onlv primary emi~ons gave a crack size in excellent agreement with other NDT techniques. A second crack wse shown by the AE to be non-propagating and this was subsequently confirmed. Based on these findings, a system outline for offshore use is proposed.
Froeturo imalylll of an air g e n i i v a l v e d k m . Dhar, S. PrMct. MetBIIogr. Oct. 1988, 25, (10), 5 0 2 - 6 1 2 The valve components are considered as the mcst critically loaded compressor parts. The demand for more reliable functions of the whole compressor system is steadily rising. The fatigue performance is influenced by various factors such as valve design, valve material and treatment, geometric factors and operating conditions. The air compressor runs at 24 Hz and at 8 bar pressure. Wave propagation approach has been used to find mechanical stresses causing a typical impact fatigue failure. Frectographic analysis was carried out to understand the fatigue fracture beheviour at the crack tip. Physical tests carried out in the failed component and construction of a theoretical model explaining crack initiation and propagation under a typical impact failure loading are also covered. 2 refs. E f f e c t o f i n t e r n a l hydrogen on t h e f a t i g u e crack growth of a 12Cr1 M e steel. Rodkey, G.F. and J o n ~ R.H. J. Nucl. Mater. J u l y (11) 1988, lrdS-lb'TB, 7 6 0 - 7 6 5 Internal hydrogen concentrations of 4 appm were found to have a significant effect on the fatigue crack growth rate of 12Cr-1Mo steel tested at 25"C This effect was most pronounced at values ~<1 MPA~m for tests conducted at a load ratio of 0.5. Hydrogen induced an intergranular fracture mode that increased in percentage of the total fracture with decreasing crack velocities at decreasing AK values. Hydrogen has been shown to induce intergranular fracture in this steel in precharged and dynamic tensile tests and in subcriticai crack growth tests at cathodic potentials. The fatigue crack growth rate of both the H-charged and uncharged material was a function of the cyclic frequency between frequencies of 0.2 and 5 Hz: the fatigue crack growth rate increased with decreasing frequencies or increasing period, There is some evidence that the as-received H concentration of 1 appm affected the crack growth rate. 5 refs.
Comments on the p r i n t practice of fatigue analysis of nuclear power plant components. Jansky, J. and Schulz, H. Int. J. Pressure Vessels Piping1988, 34, ( 1 - 6 ) , 1 4 3 - 1 5 4
Mechanical properties Lubdoatiott of m crumbed-pin beedmg in m two-strelke cycle marina ditl a n g i n a . WBkun, Y., Hamr, mke, T. and Soejkna. M. Bull Mar Eng Soc Jpw. Mar. 1 2 . I ( L (1). 1-11 The lubr,c41t,on Of a crosshead.p,n bear,ng in a two.stress cycJe d,esel eng,ne ,s Quire ~o s,nce the t~rnng ,S abbeys ~JDlected TO the Io4~lng nn S Snnlle dure(.lnon w,th small arnpl,tude of oscollabon The theoret,cal snIF~gel on the fu~r,cat,On cnarl¢~erlstic~ for the conve~tlonsl and the offset type~ bear,ng$ ate made The o,).hlm behlwour between the fWO ~3eS of bearings is comD4q~ and the des~n cr,rer=a for each tvped ~ r = n g are invesl=~lt~ ~xp~'.me~tal s~Jcl~ ate also cattle(J Out tO exsm=ne the influences Of Dea,,ng t~De and OQanng n~ltw,a= on ant, sa,zlJre and ant,.fat=gue From the tt~ecrat~cal and the exl3~mental works rt ,S fo~r~l that the Oear,ng performance of the off,el 1vised Oeat,~ IS SuI~I*~Or10 thai Of the Convant:oni] rVl3e~ i;)elr,ng and AI silOv :S su,table maret,al as the Deal.ng metal 19 refs
I;le~mt ampents of orack prep~tgatico aetalymm under variable amplitude loading condition= an¢f p r e d i c t i o n . m e t h o d s . Nowack, H. and • 4ar/uen, R. Int. J. A4ater. Prod. Technol. t 9 8 8 , 3 , (1), 1 0 4 - 1 1 9 A state-of-the-art survey is given of the field of fatigue crack propagation. After a brief description of essential macroscopic and microscopic crack phenomena, mechanics tools for the representation of crack data are outlined. A survey of crack propagation prediction methods for variable amplitude loading is given, and it is shown how far they explicitly account for the non-Iinearity in the damage accumulation due to Ioad-history-depandent sequence effects. The viewpoint of the practical application of the crack propagation prediction methods in engineering design is specially considered. Some aspects regarding the further development of crack propagation analyses (consideration of compression loads. dK/da, short cracks and microstructural processes) are given. Materials considered include AI alloys 7475 and 2024.25 refs.
B.,r~t/ckUeand fracture behaviour of the P M AI-Li a l l o y t N - ~ 6 X L . We/ss, I~, R. and ~cha~r, R. Met. PowdBrRep. Oct. 1 1 , 43, (10), 668-671 Fatigue life and fatigue crack growth properties of the commercial mechanically alloyed AI-Mg-Li alloy AI-905X1 were studied. Its microstructure consisted of predominantly uniform and equiaKed fine grains of high dislocation density and a large number of fine ditpersoids containing occasional bands of larger grains virtually devoid of dislocations end particles. LCF and HCF data were' determined at room and elevated temperature up to II~P loading cycles for stress Patios R = - 1 and 0, Fracture toughness was measured and particular emphasis was placed on the observation of near-threshold fatigue crack growth behaviour in the range of 10 -s m/cycle > da/dN > 10 -12 m/cycle over the R-value range - 3 < R < 0.8. It was concluded that the high tensile strength of AI-905XL was due to its extremely fine grain size compared with standard ingot-metallurgy alloys. Ductility end fracture toughness are lower than for 70000-series alloys. High-cycle fatigue strength is higher than that of ingot-metaflu~gy AI 7075-T6. Combined evaluation of endurance and effective threshold data enable prediction of the critical defect size affecting fatigue strength. 18 refs.
Meche~mal
prollZe~ia0 ef m~lkeIJllm
i m p e r e l l o y d i l c a produced by
p o w d e r mwtaNOrgy, l a w K, FunJ~ S. ~ Yokomaku, T Met. PowderRep. Oct 1 I , . 4 3 , (10), 6 6 4 - 8 6 6
A powder metallurgy Ni-bese superalioy. AF115, for turbine discs, was studied using sampies either ss-HIPed or produced by H IP plus isothermal forging. Properties studied included microstructure, tensile strength, stress-rupture strength, tow-cycle fatigue life. and fatigue crack propagation rate. MicrOstructure of as-HIPed material was partly the same as before compaction while that of forged material was completely recrystailized. AF115 HIPed discs had markedly improved tensile, stress-rupture, and fatigue strengths compared with conventions; wrought and and IN718. Low-cycle fatigue life at 673 and 908 K was also superior, and discs produced by isothermal forging of fine powder had the longest life. Fatigue crack propagation rate was influenced by grain size, but in the region AK ~ 20 MPa~/m was smaller than that of IN718.9 refs.
Int J Fatigue May 1989
In the evaluation of present operating experience with respect to the safew assessment of nuclear power plant (NPP) components, the following conclusions can be drawn. (1) Thermally induced loads such as local temperature stratification (large temperature differences in pipe cross-sections under laminar flow conditions) and fluctuations have been underestimated in the former thermal-hydraulic analysis. (2) Environmental influences are not covered adequately in the design codes. (3) The freedom of the stress analyst in grouping the specified cyclic Ioadings. and the degree of conservatism in calculating the stresses, results in a large variation of the calculated usage factor; the estimated life usage fractions for the different local regions are conservative but not necessarily representative. The goal of the fatigue analyses for NPPs should be (a) to identify local areas where significant fatigue Ioadings are expected to occur, and (b) to show that the component is protected against fatigue failure. At present, the emphasis in performing and reviewing fatigue analysis is on the licensing steps before the NPP is put into operation. The designer must evaluate the fatigue loading pattern at an early stage to optimize the design. With respect to the lifetime assessment of the plant, it is the opinion of the authors that only a simplified procedure should be required for the operating license. To assess the residual fatigue life at any time during operation, it makes much more sense to follow the plant operational history as it develops. To follow this approach, it is necessary to manage and process the plant operating data in such a way that it can be used for a detailed fatigue evaluation. Computerized systems which can meet these requirements are commercially available and used for viable parts in conventional power plants. The advantages of this procedure are (i) a more representative number to account for the actual fatigue load and life fraction used; (iS) a better selection of local areas for recurring in-service inspection; (iii) a more reliable data base for the application of sophisticated fatigue analyses to assess damage mechanisms, including environmental and load-history effects. As a result, i n increase in plant performance and safety is expected. Examples of carbon steel are given. 9 refs. Effect of deformation-nitroearburizing treatrnent Sour o f I ( D 0 s t e e l . Meng, X.C. and Liu, ZR. Ind. Heat. Sept. 1988, r~, (9), 23 ISSN: 0 0 1 9 - 8 3 7 4
on f a t i g u e b e h a v .
The effect of a combined deformation-nitrocarburizing treatment on fatigue crack initiation and propagation in 1020 steel is described. The larger the deformation, the longer the time required to initiate a crack and the lower the crack propagation rate. The reason for lower crack propagation rate is refined substructure of specimens treated by deformationnitrocarburizing. 5 refs.
Rare earths and the mechanical properties of steel. Yu, J., Yu, Z and Wu, C. J. Met. M a y 1968, 40, (5), 26-31 While the western steel industry's interest in rare-earth metals (eg Ce) has waned since the 1970s, additions of this resource can nonetheless be used to improve the fatigue and creep properties of steel (eg 16Mn, 35CrNiMoV, 18Cr2Ni4WA. W18Cr4VMn, 00Si2Mn, 2.25Cr-1 Me) and depress temper embrittlement. With the largest rare-earth resources in the world, the People's Republic of China has maintained a significant research commitment in this area, determining that several mechanical properties of steel may be enhanced, aside from the traditional movements in toughness characteristics, In desulphurization processing, for example, rare-earth injection favourebly complements the Ca injection technology which is currently prevalent in the West Further. rare earths react quite efficiently with the hydrogen in steels to lower the H diffusion coefficient, 50 refs,
crack growth r a t e a t low &K in a s i n g l e c r y s t a l superalIoy. Telesman. J and Ghosh. L. /nt. J. Fract. M a y 1988, 37, (1), R 1 9 - R 2 2
Accelerated
To obtain a better understanding of the effect of the microstructural processes on fatigue crack growth (FCG) behaviour, a programme has been undertaken to determine the low &Kcrack growth behaviour of a single crystal Ni-based PVVA-1480 superalloy. A singlecrystal alloy was chosen as the best modelling material, since the deformation mechanisms can be more thoroughly examined, and the effect of grain orientation on FCG can be evbluated. 7 refs.
Crack propagation in a commercial Int. J. Fract. M a y 1988, 37, (1), 7 3 - 8 0
s t e e l . Bilir, O.G. and Haznedar, F.
207
Aqoeatto
ondoll~
from
Methadon. P A ItS Diss Abe. I~t S e p t 1 ~ , 4 I .
f a t I D e ~ CrlM~W i n s t e e l s . ( D i m r t a t i o n ) . (3)
The investigation of the relationships between acoustic emission beheviour and fatigue orecks in a r~teel and the findings of the successful monitoring of the corrosion fatigue of • fult-eca~e welded Y-jo~m ire related'Small-scale fatigue tests were used to investigate the acoustic emissions (AE) beheviour of fatigue crack growth through a steel to BS 4360 50D, The effects of variations in sample microstructure obtained by heat treatment and welding were considered, as were the effects of crack growth at different stress ratios, Corrosion fatigue testing at cathodic protection potentials ranging from open circuit to - 1200 mV (SCE) were used to investigate the effects of environment on the AE Primary emissions, which occur close to peak load, were found to be generated by the advance of the crack tip plastic zone into previously undefonmed material. Secondary emissions were found to be mostly generated by crack closure processes during in-air fatigue, and the crushing of corrosion products within the crack during corrosion fatigue testing. These results show that crack growth rate characterization is only possible using primsry AE. Secondary AE can only be used to indicate the presence and location of a crack, and the best method for sepmating primary from secondary AE ia to filter on the basis of load. The small-scale results were related to AE detected while monitoring the fatigue of a full-sized welded Y-joint in seawater. The results of this were very promising, with the initiation and propagetion of a crack being detectt~l; locations of the extremities of the crack using onlv primary emi~ons gave a crack size in excellent agreement with other NDT techniques. A second crack wse shown by the AE to be non-propagating and this was subsequently confirmed. Based on these findings, a system outline for offshore use is proposed.
Froeturo imalylll of an air g e n i i v a l v e d k m . Dhar, S. PrMct. MetBIIogr. Oct. 1988, 25, (10), 5 0 2 - 6 1 2 The valve components are considered as the mcst critically loaded compressor parts. The demand for more reliable functions of the whole compressor system is steadily rising. The fatigue performance is influenced by various factors such as valve design, valve material and treatment, geometric factors and operating conditions. The air compressor runs at 24 Hz and at 8 bar pressure. Wave propagation approach has been used to find mechanical stresses causing a typical impact fatigue failure. Frectographic analysis was carried out to understand the fatigue fracture beheviour at the crack tip. Physical tests carried out in the failed component and construction of a theoretical model explaining crack initiation and propagation under a typical impact failure loading are also covered. 2 refs. E f f e c t o f i n t e r n a l hydrogen on t h e f a t i g u e crack growth of a 12Cr1 M e steel. Rodkey, G.F. and J o n ~ R.H. J. Nucl. Mater. J u l y (11) 1988, lrdS-lb'TB, 7 6 0 - 7 6 5 Internal hydrogen concentrations of 4 appm were found to have a significant effect on the fatigue crack growth rate of 12Cr-1Mo steel tested at 25"C This effect was most pronounced at values ~<1 MPA~m for tests conducted at a load ratio of 0.5. Hydrogen induced an intergranular fracture mode that increased in percentage of the total fracture with decreasing crack velocities at decreasing AK values. Hydrogen has been shown to induce intergranular fracture in this steel in precharged and dynamic tensile tests and in subcriticai crack growth tests at cathodic potentials. The fatigue crack growth rate of both the H-charged and uncharged material was a function of the cyclic frequency between frequencies of 0.2 and 5 Hz: the fatigue crack growth rate increased with decreasing frequencies or increasing period, There is some evidence that the as-received H concentration of 1 appm affected the crack growth rate. 5 refs.
Comments on the p r i n t practice of fatigue analysis of nuclear power plant components. Jansky, J. and Schulz, H. Int. J. Pressure Vessels Piping1988, 34, ( 1 - 6 ) , 1 4 3 - 1 5 4
Mechanical properties Lubdoatiott of m crumbed-pin beedmg in m two-strelke cycle marina ditl a n g i n a . WBkun, Y., Hamr, mke, T. and Soejkna. M. Bull Mar Eng Soc Jpw. Mar. 1 2 . I ( L (1). 1-11 The lubr,c41t,on Of a crosshead.p,n bear,ng in a two.stress cycJe d,esel eng,ne ,s Quire ~o s,nce the t~rnng ,S abbeys ~JDlected TO the Io4~lng nn S Snnlle dure(.lnon w,th small arnpl,tude of oscollabon The theoret,cal snIF~gel on the fu~r,cat,On cnarl¢~erlstic~ for the conve~tlonsl and the offset type~ bear,ng$ ate made The o,).hlm behlwour between the fWO ~3eS of bearings is comD4q~ and the des~n cr,rer=a for each tvped ~ r = n g are invesl=~lt~ ~xp~'.me~tal s~Jcl~ ate also cattle(J Out tO exsm=ne the influences Of Dea,,ng t~De and OQanng n~ltw,a= on ant, sa,zlJre and ant,.fat=gue From the tt~ecrat~cal and the exl3~mental works rt ,S fo~r~l that the Oear,ng performance of the off,el 1vised Oeat,~ IS SuI~I*~Or10 thai Of the Convant:oni] rVl3e~ i;)elr,ng and AI silOv :S su,table maret,al as the Deal.ng metal 19 refs
I;le~mt ampents of orack prep~tgatico aetalymm under variable amplitude loading condition= an¢f p r e d i c t i o n . m e t h o d s . Nowack, H. and • 4ar/uen, R. Int. J. A4ater. Prod. Technol. t 9 8 8 , 3 , (1), 1 0 4 - 1 1 9 A state-of-the-art survey is given of the field of fatigue crack propagation. After a brief description of essential macroscopic and microscopic crack phenomena, mechanics tools for the representation of crack data are outlined. A survey of crack propagation prediction methods for variable amplitude loading is given, and it is shown how far they explicitly account for the non-Iinearity in the damage accumulation due to Ioad-history-depandent sequence effects. The viewpoint of the practical application of the crack propagation prediction methods in engineering design is specially considered. Some aspects regarding the further development of crack propagation analyses (consideration of compression loads. dK/da, short cracks and microstructural processes) are given. Materials considered include AI alloys 7475 and 2024.25 refs.
B.,r~t/ckUeand fracture behaviour of the P M AI-Li a l l o y t N - ~ 6 X L . We/ss, I~, R. and ~cha~r, R. Met. PowdBrRep. Oct. 1 1 , 43, (10), 668-671 Fatigue life and fatigue crack growth properties of the commercial mechanically alloyed AI-Mg-Li alloy AI-905X1 were studied. Its microstructure consisted of predominantly uniform and equiaKed fine grains of high dislocation density and a large number of fine ditpersoids containing occasional bands of larger grains virtually devoid of dislocations end particles. LCF and HCF data were' determined at room and elevated temperature up to II~P loading cycles for stress Patios R = - 1 and 0, Fracture toughness was measured and particular emphasis was placed on the observation of near-threshold fatigue crack growth behaviour in the range of 10 -s m/cycle > da/dN > 10 -12 m/cycle over the R-value range - 3 < R < 0.8. It was concluded that the high tensile strength of AI-905XL was due to its extremely fine grain size compared with standard ingot-metallurgy alloys. Ductility end fracture toughness are lower than for 70000-series alloys. High-cycle fatigue strength is higher than that of ingot-metaflu~gy AI 7075-T6. Combined evaluation of endurance and effective threshold data enable prediction of the critical defect size affecting fatigue strength. 18 refs.
Meche~mal
prollZe~ia0 ef m~lkeIJllm
i m p e r e l l o y d i l c a produced by
p o w d e r mwtaNOrgy, l a w K, FunJ~ S. ~ Yokomaku, T Met. PowderRep. Oct 1 I , . 4 3 , (10), 6 6 4 - 8 6 6
A powder metallurgy Ni-bese superalioy. AF115, for turbine discs, was studied using sampies either ss-HIPed or produced by H IP plus isothermal forging. Properties studied included microstructure, tensile strength, stress-rupture strength, tow-cycle fatigue life. and fatigue crack propagation rate. MicrOstructure of as-HIPed material was partly the same as before compaction while that of forged material was completely recrystailized. AF115 HIPed discs had markedly improved tensile, stress-rupture, and fatigue strengths compared with conventions; wrought and and IN718. Low-cycle fatigue life at 673 and 908 K was also superior, and discs produced by isothermal forging of fine powder had the longest life. Fatigue crack propagation rate was influenced by grain size, but in the region AK ~ 20 MPa~/m was smaller than that of IN718.9 refs.
Int J Fatigue May 1989
In the evaluation of present operating experience with respect to the safew assessment of nuclear power plant (NPP) components, the following conclusions can be drawn. (1) Thermally induced loads such as local temperature stratification (large temperature differences in pipe cross-sections under laminar flow conditions) and fluctuations have been underestimated in the former thermal-hydraulic analysis. (2) Environmental influences are not covered adequately in the design codes. (3) The freedom of the stress analyst in grouping the specified cyclic Ioadings. and the degree of conservatism in calculating the stresses, results in a large variation of the calculated usage factor; the estimated life usage fractions for the different local regions are conservative but not necessarily representative. The goal of the fatigue analyses for NPPs should be (a) to identify local areas where significant fatigue Ioadings are expected to occur, and (b) to show that the component is protected against fatigue failure. At present, the emphasis in performing and reviewing fatigue analysis is on the licensing steps before the NPP is put into operation. The designer must evaluate the fatigue loading pattern at an early stage to optimize the design. With respect to the lifetime assessment of the plant, it is the opinion of the authors that only a simplified procedure should be required for the operating license. To assess the residual fatigue life at any time during operation, it makes much more sense to follow the plant operational history as it develops. To follow this approach, it is necessary to manage and process the plant operating data in such a way that it can be used for a detailed fatigue evaluation. Computerized systems which can meet these requirements are commercially available and used for viable parts in conventional power plants. The advantages of this procedure are (i) a more representative number to account for the actual fatigue load and life fraction used; (iS) a better selection of local areas for recurring in-service inspection; (iii) a more reliable data base for the application of sophisticated fatigue analyses to assess damage mechanisms, including environmental and load-history effects. As a result, i n increase in plant performance and safety is expected. Examples of carbon steel are given. 9 refs. Effect of deformation-nitroearburizing treatrnent Sour o f I ( D 0 s t e e l . Meng, X.C. and Liu, ZR. Ind. Heat. Sept. 1988, r~, (9), 23 ISSN: 0 0 1 9 - 8 3 7 4
on f a t i g u e b e h a v .
The effect of a combined deformation-nitrocarburizing treatment on fatigue crack initiation and propagation in 1020 steel is described. The larger the deformation, the longer the time required to initiate a crack and the lower the crack propagation rate. The reason for lower crack propagation rate is refined substructure of specimens treated by deformationnitrocarburizing. 5 refs.
Rare earths and the mechanical properties of steel. Yu, J., Yu, Z and Wu, C. J. Met. M a y 1968, 40, (5), 26-31 While the western steel industry's interest in rare-earth metals (eg Ce) has waned since the 1970s, additions of this resource can nonetheless be used to improve the fatigue and creep properties of steel (eg 16Mn, 35CrNiMoV, 18Cr2Ni4WA. W18Cr4VMn, 00Si2Mn, 2.25Cr-1 Me) and depress temper embrittlement. With the largest rare-earth resources in the world, the People's Republic of China has maintained a significant research commitment in this area, determining that several mechanical properties of steel may be enhanced, aside from the traditional movements in toughness characteristics, In desulphurization processing, for example, rare-earth injection favourebly complements the Ca injection technology which is currently prevalent in the West Further. rare earths react quite efficiently with the hydrogen in steels to lower the H diffusion coefficient, 50 refs,
crack growth r a t e a t low &K in a s i n g l e c r y s t a l superalIoy. Telesman. J and Ghosh. L. /nt. J. Fract. M a y 1988, 37, (1), R 1 9 - R 2 2
Accelerated
To obtain a better understanding of the effect of the microstructural processes on fatigue crack growth (FCG) behaviour, a programme has been undertaken to determine the low &Kcrack growth behaviour of a single crystal Ni-based PVVA-1480 superalloy. A singlecrystal alloy was chosen as the best modelling material, since the deformation mechanisms can be more thoroughly examined, and the effect of grain orientation on FCG can be evbluated. 7 refs.
Crack propagation in a commercial Int. J. Fract. M a y 1988, 37, (1), 7 3 - 8 0
s t e e l . Bilir, O.G. and Haznedar, F.
207