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Low cycle fatigue fracture behaviours of steel beam-columns with wide flange and box cross sections
Mechanical properties Surface engineering of titanium. Morton, P.H. and Bell, T. Mem. Etud. Sci. Rev. Metall. 86, (10), 639-646, Oct. 1989 Surface technological processes applied to Ti improve its resistance to various types of wear: adherence, abrasion, fatigue, and corrosion wear. Review is given of the surface techniques used: anodizetion, ion implantation, physical deposit in vapour phase, thermomechanical treatment, thermal projection, addition to the molten metal, etc. Future fields of application are suggested. 12 refs. C r e e p - f a t i g u e life prediction of turbine r o t o r 1 C r - M o - V forged steels under simulated cyclic thermal stresses. Yamaguchi, K., Ijima, K.,
Kobayashi, K. and Nishijima, S. Teteu-to-Hagane (J. Iron Steel Inst. Jpn.) 75, (12), 2242-2249, Dec. 1989 (in Japanese) Isothermal long term creep-fatigue and combined temperature-strsin cycling tests under simulated thermal stresses of high temperature components were carried out with newly developed testing machines suitable for long running. Materials examined were three heats of turbine rotor 1Cr-Mo-V forged steel with different impurity contents. The results obtained were evaluated by a life prediction method proposed by the authors which was based on the linear damage rule looking st the creep rupture ductility of materials after long exposure at high temperatures. Graphs, photomicrographs. 20 refs. Effect of g e o m e t r y on fatigue crack g r o w t h in plane strain. Shercliff,
H.R. and Fleck, N.A. University of Cambridge Report No PB89-193098/XAB Jan 1989, 68 pp
Fatigue tests were conducted in plane strain in two specimen geometries, using 6082-T6 AI alloy and BS4360 50B steel. Crack growth rate and crack closure responses were monitored for constant amplitude tests and following a single overload. The results agree with finite element predictions and the effect of geometry is explained by the difference in T-stress between the geometries. Biaxiai overload tests were conducted which supported the conclusions from the uniaxial experiments.
Fundamentals of muWaxlal behaviour of components at high temperatures: I. Multiexlal creeping. Penkalla, H.-J., Rodig, M. and Nickel, H. Materialprufung 31, (10), 304-310, Oct. 1989 (in German) The testing of components at high temperatures and under multiaxial loads has the function to investigate deformation and yielding, and to verify the transfer of materials parameters and meterials-constitutive equations to real loading cases. The fundamentals for transferring constitutive equations are presented with regard to creep, low cycle fatigue and the development of damage at high temperatures. Apart from a general definition of the prerequisites, the rules applying to materials of the von Misse type are explained and discussed in the example of pipe geometries. The materials mentioned include Fe and Ni base alloys and austenitic stainless steel. 20 refs. Predicting crack g r o w t h under thermo-mechanical cycling. Nicholas, T.,
Hell, M.L. and Haritos, G.K. Int. J. Frsct. 41, (3), 157-176, Nov. 1989
Load-controlled tests were conducted on Inconel ~18 under thermo-mechanical fatigue (TMF) to evaluate crack growth rate as a function of phase angle between load and temperature. A model is developed to predict TMF crack growth rates based solely on isothermal data. The model uses a linear summation concept based on contributions to crack growth of the two dominant mechanisms which are active at the minimum and maximum temperature of the cycle: mechanical fatigue and environmentally assisted crack growth. It was found that damage, which contributes significantly to crack growth, occurs only during the increasing load portion of a TMF cycle and only while the time-dependent contribution is an increasing function. A discussion of the dominant mechanisms and a comprehensive review of the literature in TMF crack growth is presented. Applicability of the modeling concepts to other materials is discussed. 46 refs. Temperature and rate dependence of saturation stress f o r l o w amplitude fatigue of copper crystals b e t w e e n 4.2-350 K. Basinski, Z.S. and Basinski,
S.J. Acta Metall. 37, (12), 3255-3262, Dec. 1989 Copper single crystals oriented for single glide were fatigued at temperatures from 4.2-350 K in an inert atmosphere. The fatigue behaviour was similar at all temperatures. Saturation stress decreased smoothly with increasing fatigue temperature from approx 85 MPs at 4.2 K to approx 27 MPa st 350 K. The effect of cycling rate on saturation stress was also measured. The observations suggest that the same fundamental mechanism, which must be mechanical in nature, operates throughout the temperature interval studied. The activation energy of the operating mechanism, calculated from the observed temperature and rate dependence of the saturation stress, increases linearly with temperature, from approx 0.175 eVF at 77.4 K to approx 0.7 eV at room temperature. At 77.4 K (as at room temperature) fatigue life is shorter in reactive than in inert environment. 32 refs.
Improving the fatigue strength of specimens similar to components by an optimized airless blast cleaning treatment: II. Kloos, K.H., Kaiser, B. and Oppermann T. Automob. Ind. 34, (5), 601-605, Sept. 1989 (in German) Part 1 of this publication presented the influence of different airless blast cleaning conditions on the surface roughness, the surface hardness and the fatigue behaviour worked out on the material Ck45V. The highest fatigue strength was obtained by using smaller shot size, independent of the shot. Taking into account that the compensation of the decrease in hardness is responsible for the high fatigue limits due to peening, the compressive residual stresses and their stability at the tensile stressed surface (pulsating bending load) has to be considered as well. It is now obvious why peening treatments with smaller shot size gave the best results in fatigue behaviour. All fatigue fractures started at the surface of the specimens and therefore the value of the compressive residual stress is also of high importance for the fatigue behaviour. With the optimization of the peening conditions it was obtained that the maximum of the compressive residual stresses moves towards the surface with decreasing shot size. The fatigue behaviour of all drop-forged
Int J Fatigue September 1990
materials (e.g. Ck45V, Ck45SV, Ck45BY, 49MnVS3BY, 37Cr4V, 42CrMo4V) examined can be summarized as follows. With regard to the fatigue behaviour an optimized airless blast cleaning of the examined heat treatable steels on surface with oxide scales leads to higher fatigue limits than those which can be expected from polished specimens. On the other hand this defined sidees blast cleaning treatment reduces the scatter bends to value less than standardized Wohler curves cell for. As fatigue strengths caused by an airless blast cleaning treatment cannot be transferred to the finite life region it is intended to investigate the fatigue life of random loaded peened specimens. 6 refs. Fatigue-crack g r o w t h in 2090 A I - U alloy. Pao, P.S., Cooley, L.A., Imam,
M.A. and Yoder, G.R. Scr. Metall. 23, (8), 1455-1460, Aug. 1989 The fatigue-crack growth kinetics of the 12.7 mm thick 2090-T8E41 alloy plate varies significantly with plate thickness location. The apparent fetigue-crack growth rates in the midthickness location are substantially lower than those in the surface region at intermediate and high applied stress intensity ranges. The lower crack growth rates are related to the extraordinarily tortuous fatigue profile which induces high crack closure levels. Such a tortuous crack profile appears to be primarily a consequence of the alloy's intense crystallographic texture and its great propensity for planar slip. 20 refs. The continuous l o w cycle fatigue beheviour of commerical and phosphorus-doped stainless steel. Kim, J.J. and Nam, S.W. Scr. Metal/. 23, (8), 1437-1442, Aug. 1989 The low cycle fatigue (LCF) behaviour of type 304L stainless steel and the effect of phosphorus level on this behaviour has been investigated. Lower fatigue life, higher tensile strength, and reduced ductiliW are observed for the P-doped material (0.2 vs. 0.03% P). It is believed that the propagating critical crack size becomes short in the P-doped material as a result of the higher strength and lower ductility. Density of cracks is higher for doped material and sharpness of cracks is regular. Low-P material tends to have fewer cracks with an irregular texture. 12 refs.
Muiticycle fatigue damage at 1000 °C in an Fe--Ni-Cr alloy. Gerland, M. and de Fouquet, J. Scr. Metall. 23, (8), 1255-1260, Aug. 1989 (in French) Nicral C35 (Z40NCNb35-25) was tested in the cast and wrought conditions in Ar and air atmospheres. At 1000 °C precipitates do not block dislocation movement or cause cyclic fatigue hardening. In wrought material dislocation movement induces cavitation followed by intergrenular cracking, but in cast material the dendritic morphology favours transgranular crack propagation. Consequently cast specimens offer greater fatigue resistance. 10 refs. L o w cycle fatigue fracture behaviours of steel beem-columns w i t h w i d e flange and box cross sections. Yamada, M., Kawabata, T. and Yamanaka,
K. Stahlbau 58, (12), 361-364, Dec. 1980 (in German) Tests are carried out on these beam columns loaded by cyclic bending under constant axial compression. The influences of b/tvalues of flange and web elements and the values of displacement angle amplitudes on the deformation and fatigue fracture behaviour are clarified. Lots of trsnverse resistances are initiated through the local buckling of web elements and not through that of flange elements. There are two types in the low cycle fatigue of such beam-columns and such fracture types are decided by the values of their deflection angle amplitudes. Under smaller deflection angle amplitudes, fatigue fracture occurs through the unrestricted axial shortening of columns with transverase resistances, i.e. cross-sectional fracture. Under larger deflection angle amplitudes, fatigue fracture occurs through the loss of lateral resistances, Le. structural failure. 9 refs.
Corrosion end compatibility. Berry, W.E. CAB Curr. Aware. Bull. (194), 6 Oct. 1989 A practical description of stress corrosion cracking and materials selection to avoid the problem has been prepared by Lockheed. The alloy systems covered are steel, AI alloys, Fe-Ni-Cr, Cu alloys, and Ti alloys. Environmentally assisted aerospace fatigue problems encountered over the past 30 years in the Netherlands have been described by the Netherlands National Aerospace Laboratory NLR. The affect of 0.1 at.% Zr (0.2 wt.%) addition to hot isostatically pressed I~-NiAI on long term cyclic oxidation has been investigated by NASA. The 0.1 at.% Zr additon maintained the protective oxide scale throughout 3000 1 h cycles (cz AI 2 03 on Ni-48.3AI-0.1Zr and NiAI204 on Ni-38.1AI-0.1Zr). Ultrasonic methods for detecting hydrogen damage in steel components have been studied at Southwest Research Institute. Of three methods studied, the ultrasonic backscatter technique was the most effective. 4 refs. Interpretation of fatigue softening at r o o m temperature in a superalloy.
Sundarsraman, M., Chen, W. and Wahl, R.P. Scr. Metal/. 23, (10), 1795-1800, Oct. 1989
The nature of stress response after intermediate anneal in Nimonic PE16 is due to the renucleetion of fine ~/' particle dissolved during cyclic (LCF) loading. Button head type LCF specimens were machined from heat treated Nimonic PE16. Fatigue tests were conducted in total axial strain controlled mode under fully reversed push-pull loading at constant nominal strain rate. The nature of fatigue induced slip bands was studied by optical and transmission electron microscopy. 17 refs. Fatigue c r a c k g r o w t h transitions in T i - 6 A I - 4 V alloy. Ravichandran, K.S.
and Dwarakadasa, E.S. Scr. Metall. 23, (10), 1685-1690, Oct. 1989
There are two transitions during fatigue crack growth in s Ti alloy, caused by cyclic and monotonic plastic zones when their respective sizes become equal to the ~ lath size. To produce a Widmanstattan colony structure, a Ti-6AI-4V alloy was bets annealed at 1040 °C and cooled. Fatigue crack propagation testing was performed on 10 mm thick compact tension specimens by a manual load shedding procedure to generate data on near threshold fatigue crack growth behaviour and crack closure for this microstructure. Fractogrsphy and crack path profile examination were performed in a scanning electron microscope. 12 refs.
451
Kobayashi, K. and Nishijima, S. Teteu-to-Hagane (J. Iron Steel Inst. Jpn.) 75, (12), 2242-2249, Dec. 1989 (in Japanese) Isothermal long term creep-fatigue and combined temperature-strsin cycling tests under simulated thermal stresses of high temperature components were carried out with newly developed testing machines suitable for long running. Materials examined were three heats of turbine rotor 1Cr-Mo-V forged steel with different impurity contents. The results obtained were evaluated by a life prediction method proposed by the authors which was based on the linear damage rule looking st the creep rupture ductility of materials after long exposure at high temperatures. Graphs, photomicrographs. 20 refs. Effect of g e o m e t r y on fatigue crack g r o w t h in plane strain. Shercliff,
H.R. and Fleck, N.A. University of Cambridge Report No PB89-193098/XAB Jan 1989, 68 pp
Fatigue tests were conducted in plane strain in two specimen geometries, using 6082-T6 AI alloy and BS4360 50B steel. Crack growth rate and crack closure responses were monitored for constant amplitude tests and following a single overload. The results agree with finite element predictions and the effect of geometry is explained by the difference in T-stress between the geometries. Biaxiai overload tests were conducted which supported the conclusions from the uniaxial experiments.
Fundamentals of muWaxlal behaviour of components at high temperatures: I. Multiexlal creeping. Penkalla, H.-J., Rodig, M. and Nickel, H. Materialprufung 31, (10), 304-310, Oct. 1989 (in German) The testing of components at high temperatures and under multiaxial loads has the function to investigate deformation and yielding, and to verify the transfer of materials parameters and meterials-constitutive equations to real loading cases. The fundamentals for transferring constitutive equations are presented with regard to creep, low cycle fatigue and the development of damage at high temperatures. Apart from a general definition of the prerequisites, the rules applying to materials of the von Misse type are explained and discussed in the example of pipe geometries. The materials mentioned include Fe and Ni base alloys and austenitic stainless steel. 20 refs. Predicting crack g r o w t h under thermo-mechanical cycling. Nicholas, T.,
Hell, M.L. and Haritos, G.K. Int. J. Frsct. 41, (3), 157-176, Nov. 1989
Load-controlled tests were conducted on Inconel ~18 under thermo-mechanical fatigue (TMF) to evaluate crack growth rate as a function of phase angle between load and temperature. A model is developed to predict TMF crack growth rates based solely on isothermal data. The model uses a linear summation concept based on contributions to crack growth of the two dominant mechanisms which are active at the minimum and maximum temperature of the cycle: mechanical fatigue and environmentally assisted crack growth. It was found that damage, which contributes significantly to crack growth, occurs only during the increasing load portion of a TMF cycle and only while the time-dependent contribution is an increasing function. A discussion of the dominant mechanisms and a comprehensive review of the literature in TMF crack growth is presented. Applicability of the modeling concepts to other materials is discussed. 46 refs. Temperature and rate dependence of saturation stress f o r l o w amplitude fatigue of copper crystals b e t w e e n 4.2-350 K. Basinski, Z.S. and Basinski,
S.J. Acta Metall. 37, (12), 3255-3262, Dec. 1989 Copper single crystals oriented for single glide were fatigued at temperatures from 4.2-350 K in an inert atmosphere. The fatigue behaviour was similar at all temperatures. Saturation stress decreased smoothly with increasing fatigue temperature from approx 85 MPs at 4.2 K to approx 27 MPa st 350 K. The effect of cycling rate on saturation stress was also measured. The observations suggest that the same fundamental mechanism, which must be mechanical in nature, operates throughout the temperature interval studied. The activation energy of the operating mechanism, calculated from the observed temperature and rate dependence of the saturation stress, increases linearly with temperature, from approx 0.175 eVF at 77.4 K to approx 0.7 eV at room temperature. At 77.4 K (as at room temperature) fatigue life is shorter in reactive than in inert environment. 32 refs.
Improving the fatigue strength of specimens similar to components by an optimized airless blast cleaning treatment: II. Kloos, K.H., Kaiser, B. and Oppermann T. Automob. Ind. 34, (5), 601-605, Sept. 1989 (in German) Part 1 of this publication presented the influence of different airless blast cleaning conditions on the surface roughness, the surface hardness and the fatigue behaviour worked out on the material Ck45V. The highest fatigue strength was obtained by using smaller shot size, independent of the shot. Taking into account that the compensation of the decrease in hardness is responsible for the high fatigue limits due to peening, the compressive residual stresses and their stability at the tensile stressed surface (pulsating bending load) has to be considered as well. It is now obvious why peening treatments with smaller shot size gave the best results in fatigue behaviour. All fatigue fractures started at the surface of the specimens and therefore the value of the compressive residual stress is also of high importance for the fatigue behaviour. With the optimization of the peening conditions it was obtained that the maximum of the compressive residual stresses moves towards the surface with decreasing shot size. The fatigue behaviour of all drop-forged
Int J Fatigue September 1990
materials (e.g. Ck45V, Ck45SV, Ck45BY, 49MnVS3BY, 37Cr4V, 42CrMo4V) examined can be summarized as follows. With regard to the fatigue behaviour an optimized airless blast cleaning of the examined heat treatable steels on surface with oxide scales leads to higher fatigue limits than those which can be expected from polished specimens. On the other hand this defined sidees blast cleaning treatment reduces the scatter bends to value less than standardized Wohler curves cell for. As fatigue strengths caused by an airless blast cleaning treatment cannot be transferred to the finite life region it is intended to investigate the fatigue life of random loaded peened specimens. 6 refs. Fatigue-crack g r o w t h in 2090 A I - U alloy. Pao, P.S., Cooley, L.A., Imam,
M.A. and Yoder, G.R. Scr. Metall. 23, (8), 1455-1460, Aug. 1989 The fatigue-crack growth kinetics of the 12.7 mm thick 2090-T8E41 alloy plate varies significantly with plate thickness location. The apparent fetigue-crack growth rates in the midthickness location are substantially lower than those in the surface region at intermediate and high applied stress intensity ranges. The lower crack growth rates are related to the extraordinarily tortuous fatigue profile which induces high crack closure levels. Such a tortuous crack profile appears to be primarily a consequence of the alloy's intense crystallographic texture and its great propensity for planar slip. 20 refs. The continuous l o w cycle fatigue beheviour of commerical and phosphorus-doped stainless steel. Kim, J.J. and Nam, S.W. Scr. Metal/. 23, (8), 1437-1442, Aug. 1989 The low cycle fatigue (LCF) behaviour of type 304L stainless steel and the effect of phosphorus level on this behaviour has been investigated. Lower fatigue life, higher tensile strength, and reduced ductiliW are observed for the P-doped material (0.2 vs. 0.03% P). It is believed that the propagating critical crack size becomes short in the P-doped material as a result of the higher strength and lower ductility. Density of cracks is higher for doped material and sharpness of cracks is regular. Low-P material tends to have fewer cracks with an irregular texture. 12 refs.
Muiticycle fatigue damage at 1000 °C in an Fe--Ni-Cr alloy. Gerland, M. and de Fouquet, J. Scr. Metall. 23, (8), 1255-1260, Aug. 1989 (in French) Nicral C35 (Z40NCNb35-25) was tested in the cast and wrought conditions in Ar and air atmospheres. At 1000 °C precipitates do not block dislocation movement or cause cyclic fatigue hardening. In wrought material dislocation movement induces cavitation followed by intergrenular cracking, but in cast material the dendritic morphology favours transgranular crack propagation. Consequently cast specimens offer greater fatigue resistance. 10 refs. L o w cycle fatigue fracture behaviours of steel beem-columns w i t h w i d e flange and box cross sections. Yamada, M., Kawabata, T. and Yamanaka,
K. Stahlbau 58, (12), 361-364, Dec. 1980 (in German) Tests are carried out on these beam columns loaded by cyclic bending under constant axial compression. The influences of b/tvalues of flange and web elements and the values of displacement angle amplitudes on the deformation and fatigue fracture behaviour are clarified. Lots of trsnverse resistances are initiated through the local buckling of web elements and not through that of flange elements. There are two types in the low cycle fatigue of such beam-columns and such fracture types are decided by the values of their deflection angle amplitudes. Under smaller deflection angle amplitudes, fatigue fracture occurs through the unrestricted axial shortening of columns with transverase resistances, i.e. cross-sectional fracture. Under larger deflection angle amplitudes, fatigue fracture occurs through the loss of lateral resistances, Le. structural failure. 9 refs.
Corrosion end compatibility. Berry, W.E. CAB Curr. Aware. Bull. (194), 6 Oct. 1989 A practical description of stress corrosion cracking and materials selection to avoid the problem has been prepared by Lockheed. The alloy systems covered are steel, AI alloys, Fe-Ni-Cr, Cu alloys, and Ti alloys. Environmentally assisted aerospace fatigue problems encountered over the past 30 years in the Netherlands have been described by the Netherlands National Aerospace Laboratory NLR. The affect of 0.1 at.% Zr (0.2 wt.%) addition to hot isostatically pressed I~-NiAI on long term cyclic oxidation has been investigated by NASA. The 0.1 at.% Zr additon maintained the protective oxide scale throughout 3000 1 h cycles (cz AI 2 03 on Ni-48.3AI-0.1Zr and NiAI204 on Ni-38.1AI-0.1Zr). Ultrasonic methods for detecting hydrogen damage in steel components have been studied at Southwest Research Institute. Of three methods studied, the ultrasonic backscatter technique was the most effective. 4 refs. Interpretation of fatigue softening at r o o m temperature in a superalloy.
Sundarsraman, M., Chen, W. and Wahl, R.P. Scr. Metal/. 23, (10), 1795-1800, Oct. 1989
The nature of stress response after intermediate anneal in Nimonic PE16 is due to the renucleetion of fine ~/' particle dissolved during cyclic (LCF) loading. Button head type LCF specimens were machined from heat treated Nimonic PE16. Fatigue tests were conducted in total axial strain controlled mode under fully reversed push-pull loading at constant nominal strain rate. The nature of fatigue induced slip bands was studied by optical and transmission electron microscopy. 17 refs. Fatigue c r a c k g r o w t h transitions in T i - 6 A I - 4 V alloy. Ravichandran, K.S.
and Dwarakadasa, E.S. Scr. Metall. 23, (10), 1685-1690, Oct. 1989
There are two transitions during fatigue crack growth in s Ti alloy, caused by cyclic and monotonic plastic zones when their respective sizes become equal to the ~ lath size. To produce a Widmanstattan colony structure, a Ti-6AI-4V alloy was bets annealed at 1040 °C and cooled. Fatigue crack propagation testing was performed on 10 mm thick compact tension specimens by a manual load shedding procedure to generate data on near threshold fatigue crack growth behaviour and crack closure for this microstructure. Fractogrsphy and crack path profile examination were performed in a scanning electron microscope. 12 refs.
451