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Variable amplitude loading test of transverse stiffener joints for fatigue design of steel highway bridges
Fatigue Abstracts O. US. Since the increase in liti? did not appear to be related to any observable difference in microstmcture as a function of silica content, it was speculated that the change in life was due to differences in sintering or time dependent deformation of the coatings during thermal exposure. The sintering rates were exantmed for coatings containing 0.1 and 1.OC/c silica. The measurements indicate an increase in sintering with increasing silica content. Sintering of thermal barrier coatings has been related to increases in elastic modulus and strength in palsma sprayed zirconia. These properties will affect the stress levels in the ceramic layer of the TBC and are therefore expected to influence the thermal fatigue life of the coating. Preliminary deformation studies included in the current program suggest that the 0.1 and 1.0% silica coatings exhibil different dependence of deformation on the strain rate. However. the effect of the difference m deformation on TBC lit) is unclear since the failure mechanisms during thermal fatigue are not well understood Graphs. 13 rcf.
Communication: microstructural stability of the ( o~ + 13 ) solution-treated and quenched near-a titanium alloy Ti-5.8al-4Sn-3.5Zr-0.70Nh-0.50Mo0.35Si-0.06C Ghosal. P., Pra~ad, R. aml Ramaclumdra, C. Metall. Mater. lropls. A (19¢)5) 26A (10). 2751-2755
The lower the solution treatment temperature (in the range studied) in the (a + 13) phase lield lollowed by oil quenching, the lower is the stability ol the resulting microstructure when subjected to aging at 973 K, even for a v e r } short time of 2 h. 'fhe term stability is understood in terms of increasing size of the silicide particles that were precipitated and also the ~ 2 phase caused by the partitioning of alloying elements. Thus, the observed insensitivity and slower fatigue crack rates in the stabilized condition with the embrittling phases (silicides and c~ 2) in the bimodal microstructures, as opposed to the other investigation,,, needs further detailed study. Photomicrographs, diffractkm patterns, 34 rel.
Variable amplitude loading test of transverse stiffener joints for fatigue design of steel highway bridges. Sakam~, M., Mikami, I., Kano, K. and Yonemnto, E. J. Soc. Mater. Sci. Jim. (1995) 44 (5(10), 557 561 A long-life variable amplitude fatigue test is performed using plate girder specimens with four types of transverse stiffener connections under highway traffic loading. Fatigue cracks are initiated from the fillet weld toe at the stiffener end on both the tension side and compression side, form blow holes contained in web to-flange longitudinal fillet welds, and from the transverse fillet weld toe of the patch plate on the compression flange. The fatigue fidlurc life of all four details of the transverse stiffener connections satisfies the condition of JSSC category D. JIS SM490A and SS400 steels are discussed. Graphs, 4 ref.
Effect of aging on fatigue crack growth at Sn-Pb/Cu interfaces. Yao, D. and Shang, J.K. Metall. Mater. Tr+m.v A (October 1995) 26A (10), 2677-2685 The effect of isothermal aging on fatigue crack growth behavior at the Sn-Pb solder/Ca interface was examined, with emphasis on the role of interracial microstructure. Flexural peel interface-crack specimens were made from the joints of cutectic Sn-Pb solder and Cu and were further aged at 443 K lor 7 and 30 days. The kinetics of fatigue crack growth along the solder/Cu interfaces were measured from flexural peel specimens as a function of strain energy release rate. Aging was found to induce not only microstructural changes in the solder and at the interface, but also degradation in fatigue crack growth resisiance of the interface from the fatigue threshold to the fast fracture. The fatigue threshold decreased from 25 to 20 J m -' after aging for 7 days and to 10 J m -~ following aging for 30 days. The degradation in the fatigue crack growth resistance is related to the formation of a Pb-rich layer at the interface. Graphs, photomicrographs, 45 ref.
Effect of welding technology upon the fatigue strength of welded joints under biaxial stress state. D:iubinski, J. Proc. 4th Ira. C
An investigation into fatigue of fillet welded plate joints under rotating principal stress direction. Reza Razmjoo, (2. Proc. 4th bzt. Cot~fi on Biaxial/Multiaxial Fatigue 1I, St. Germain en Layc, France, 31 May-3 June 1994. pp. 205 219 The current recommendations in BS5400 and BS5500 for the fatigue life prediction of a series of welded joints under rotating principal stress direction are assessed. Experiments are discussed with a simple loading arrangement capable of producing the condition of the rotating principal stress directioo, The experimental work consisted of a series of endurance tests on fillet welded joints in steel plate Graphs, 3 ref.
605
Fatigue design data and concepts of aluminium structures. IV. Takeuchi, K. Kei Kinzoku Y~etxtt (.I. Light Met. Weld ('onst~) il9951 33 i4). 34 42 Factors influencing the design of welded joints for 5000 and 7000 series A[ alloys are studied. Factors include size and thickness of the specimens and plates. S N diagrams are provided for different thickness of plates and stress levels to give details on design of welded ioints. Residual stress for different design with different thickness of H type joints is given for 7020 and 5083 AI alloys. Graphs, 12 rcf.
Corrosion fatigue testing of eight different steels in an Icelandic geothermal environment. Thort?]orn.sson, I. Mater. De~. (1995) 16 (2), 97-102 Rotating bending tests were carried out on eight different steels in geothermal steam from three different geothermal environments. The steels ranged from high-strength turbine blade to low-strength steels, and from high- to low-alloy steels. The testing environments were geothermal steam froth three different sites containing different amounts and compositkms of non-condensable gases (CO_,. H2S and H:) and other impurities. Fatigue testing in air was carried out for reference. This paper describes the final results from the [celandic part of the Nordic Industrial fired project "Fatigue under spectrum loading and in corrosive environments'. Graphs. photomicrographs. 7 ref.
Directional dependence of corrosion fatigue of iron-silicon bicrystals. Wang. ,I.-S. am/ Mesarovic. S.D. Acta Metall. Mater. (1995) 43 (10), 3837 3849 A directional dependence of the corrosion fatigue behavior of Fe-2.7 wt.~ Si alloy Sigma 51100]/021) bicrystals was observed in a film forming solution. To understand this directional dependence, dislocation nucleation analyses at the opposite crack tips based on the Rice Thomson concept and continuum elastic-plastic analyses, within single crystal theory, of the near tip fields by finite element method were performed. Explanations of brittle/ductile fatigue crack growth under corrosive conditions and the local crack tip rotation within the interface are offered based on these analyses. Graphs+ photomicrographs+ 42 ref.
Effect of temperature on small fatigue crack growth in nickel-base superalloys. Okazaki, M.. Nohmi. S. and Yamada, H. J. Soc. Mater. Sci., Jpn. (1995) 44 I498), 348 354 Based on the measurement of crack opening-closing behavior, the effect of temperature on small fatigue crack growth behavior was investigated in three kinds of nickel-base superalloys at the temperature range of 873-1123 K, in comparison with the physically king crack properties; a polycrystalline alloy (CM247LC+CC), a directionally-solidified alloy (CM247LC-DS), and a single crystal alloy ICMSX-2) at temperatures of 873, 1023 and 1123 K. It was found that the propagation resistance and the fatigue threshold ot a long crack increased with temperature in all the materials on an appearance, However, the long crack growth rates at three different temperatures were approximately represented by a unique curve, by taking account of temperature dependences, not only of crack closure level, but also of elastic modulus. On the other hand, the small fatigue crack growth resistance decreased with temperature even when the crack closure phenomenon was taken into account. In addition+ the small fatigue crack exhibited considerably higher growth rate than the long crack at a given effective stress intensity factor range, and grew even at the lower effective stress intensity range than the hmg crack threshold. Based on the results thns obtained and the chemical analysis near crack propagation plane, the factors which lead to the lack of similitude in propagation law between small and hmg cracks were also discussed. Graphs. photomicrographs. 11 ref.
Fatigue strength of bolts tightened in plastic region-fatigue strength assurance in reusing. Yamada, H., Saruki, K., Hotta, S. and Kanoh, T. J. Soc. Mater. Sci.. Jpn. (1995) 44 (498), 338 342 In reusing, a bolt is repeatedly tightened and loosened. The reusing properties of a shank-ekmgation bolt and a thread-elongation holt tightened in a plastic region were investigated from a viewpoint of fatigue strength, The fatigue tests were carried out on both types of bolts which were subjected to 10-cycle tightening in a plastic region. As a result, the 10-cycle tightening had little influence on the fatigue limit of the bolts. However, on the thread-elongation bolt, the microcracks (approximately 7 IX m in length) appeared at the thread root after repeated tightening in the plastic region. Then, the fatigue limit of a cracked bolt was predicted by using the fracture mechanics method. The threshold stress intensity factor range (AKml of the bolt material (SCM440) was determined from the fatigue crack propagation tests with pre-strained smooth specimens under a high stress ratio. The stress intensity factor range (AK) of the thread root was calctdated by using the equation for a single edged crack without considering a stress concentration. In this equation, the crack length made of the actual and latent crack length was used as the effective crack length. The fatigue limit predicted from the above mentioned AK,, and AK agreed approximately with the fatigue limit of a crack bolt. This prediction clarified that the microcracks of approximately 7 ix m length had little influence on the fatigue limit of bolts, but that the fatigue limit decreased with increasing the crack length > 7 is m. Graphs. photomicrographs, 12 ref.
Communication: microstructural stability of the ( o~ + 13 ) solution-treated and quenched near-a titanium alloy Ti-5.8al-4Sn-3.5Zr-0.70Nh-0.50Mo0.35Si-0.06C Ghosal. P., Pra~ad, R. aml Ramaclumdra, C. Metall. Mater. lropls. A (19¢)5) 26A (10). 2751-2755
The lower the solution treatment temperature (in the range studied) in the (a + 13) phase lield lollowed by oil quenching, the lower is the stability ol the resulting microstructure when subjected to aging at 973 K, even for a v e r } short time of 2 h. 'fhe term stability is understood in terms of increasing size of the silicide particles that were precipitated and also the ~ 2 phase caused by the partitioning of alloying elements. Thus, the observed insensitivity and slower fatigue crack rates in the stabilized condition with the embrittling phases (silicides and c~ 2) in the bimodal microstructures, as opposed to the other investigation,,, needs further detailed study. Photomicrographs, diffractkm patterns, 34 rel.
Variable amplitude loading test of transverse stiffener joints for fatigue design of steel highway bridges. Sakam~, M., Mikami, I., Kano, K. and Yonemnto, E. J. Soc. Mater. Sci. Jim. (1995) 44 (5(10), 557 561 A long-life variable amplitude fatigue test is performed using plate girder specimens with four types of transverse stiffener connections under highway traffic loading. Fatigue cracks are initiated from the fillet weld toe at the stiffener end on both the tension side and compression side, form blow holes contained in web to-flange longitudinal fillet welds, and from the transverse fillet weld toe of the patch plate on the compression flange. The fatigue fidlurc life of all four details of the transverse stiffener connections satisfies the condition of JSSC category D. JIS SM490A and SS400 steels are discussed. Graphs, 4 ref.
Effect of aging on fatigue crack growth at Sn-Pb/Cu interfaces. Yao, D. and Shang, J.K. Metall. Mater. Tr+m.v A (October 1995) 26A (10), 2677-2685 The effect of isothermal aging on fatigue crack growth behavior at the Sn-Pb solder/Ca interface was examined, with emphasis on the role of interracial microstructure. Flexural peel interface-crack specimens were made from the joints of cutectic Sn-Pb solder and Cu and were further aged at 443 K lor 7 and 30 days. The kinetics of fatigue crack growth along the solder/Cu interfaces were measured from flexural peel specimens as a function of strain energy release rate. Aging was found to induce not only microstructural changes in the solder and at the interface, but also degradation in fatigue crack growth resisiance of the interface from the fatigue threshold to the fast fracture. The fatigue threshold decreased from 25 to 20 J m -' after aging for 7 days and to 10 J m -~ following aging for 30 days. The degradation in the fatigue crack growth resistance is related to the formation of a Pb-rich layer at the interface. Graphs, photomicrographs, 45 ref.
Effect of welding technology upon the fatigue strength of welded joints under biaxial stress state. D:iubinski, J. Proc. 4th Ira. C
An investigation into fatigue of fillet welded plate joints under rotating principal stress direction. Reza Razmjoo, (2. Proc. 4th bzt. Cot~fi on Biaxial/Multiaxial Fatigue 1I, St. Germain en Layc, France, 31 May-3 June 1994. pp. 205 219 The current recommendations in BS5400 and BS5500 for the fatigue life prediction of a series of welded joints under rotating principal stress direction are assessed. Experiments are discussed with a simple loading arrangement capable of producing the condition of the rotating principal stress directioo, The experimental work consisted of a series of endurance tests on fillet welded joints in steel plate Graphs, 3 ref.
605
Fatigue design data and concepts of aluminium structures. IV. Takeuchi, K. Kei Kinzoku Y~etxtt (.I. Light Met. Weld ('onst~) il9951 33 i4). 34 42 Factors influencing the design of welded joints for 5000 and 7000 series A[ alloys are studied. Factors include size and thickness of the specimens and plates. S N diagrams are provided for different thickness of plates and stress levels to give details on design of welded ioints. Residual stress for different design with different thickness of H type joints is given for 7020 and 5083 AI alloys. Graphs, 12 rcf.
Corrosion fatigue testing of eight different steels in an Icelandic geothermal environment. Thort?]orn.sson, I. Mater. De~. (1995) 16 (2), 97-102 Rotating bending tests were carried out on eight different steels in geothermal steam from three different geothermal environments. The steels ranged from high-strength turbine blade to low-strength steels, and from high- to low-alloy steels. The testing environments were geothermal steam froth three different sites containing different amounts and compositkms of non-condensable gases (CO_,. H2S and H:) and other impurities. Fatigue testing in air was carried out for reference. This paper describes the final results from the [celandic part of the Nordic Industrial fired project "Fatigue under spectrum loading and in corrosive environments'. Graphs. photomicrographs. 7 ref.
Directional dependence of corrosion fatigue of iron-silicon bicrystals. Wang. ,I.-S. am/ Mesarovic. S.D. Acta Metall. Mater. (1995) 43 (10), 3837 3849 A directional dependence of the corrosion fatigue behavior of Fe-2.7 wt.~ Si alloy Sigma 51100]/021) bicrystals was observed in a film forming solution. To understand this directional dependence, dislocation nucleation analyses at the opposite crack tips based on the Rice Thomson concept and continuum elastic-plastic analyses, within single crystal theory, of the near tip fields by finite element method were performed. Explanations of brittle/ductile fatigue crack growth under corrosive conditions and the local crack tip rotation within the interface are offered based on these analyses. Graphs+ photomicrographs+ 42 ref.
Effect of temperature on small fatigue crack growth in nickel-base superalloys. Okazaki, M.. Nohmi. S. and Yamada, H. J. Soc. Mater. Sci., Jpn. (1995) 44 I498), 348 354 Based on the measurement of crack opening-closing behavior, the effect of temperature on small fatigue crack growth behavior was investigated in three kinds of nickel-base superalloys at the temperature range of 873-1123 K, in comparison with the physically king crack properties; a polycrystalline alloy (CM247LC+CC), a directionally-solidified alloy (CM247LC-DS), and a single crystal alloy ICMSX-2) at temperatures of 873, 1023 and 1123 K. It was found that the propagation resistance and the fatigue threshold ot a long crack increased with temperature in all the materials on an appearance, However, the long crack growth rates at three different temperatures were approximately represented by a unique curve, by taking account of temperature dependences, not only of crack closure level, but also of elastic modulus. On the other hand, the small fatigue crack growth resistance decreased with temperature even when the crack closure phenomenon was taken into account. In addition+ the small fatigue crack exhibited considerably higher growth rate than the long crack at a given effective stress intensity factor range, and grew even at the lower effective stress intensity range than the hmg crack threshold. Based on the results thns obtained and the chemical analysis near crack propagation plane, the factors which lead to the lack of similitude in propagation law between small and hmg cracks were also discussed. Graphs. photomicrographs. 11 ref.
Fatigue strength of bolts tightened in plastic region-fatigue strength assurance in reusing. Yamada, H., Saruki, K., Hotta, S. and Kanoh, T. J. Soc. Mater. Sci.. Jpn. (1995) 44 (498), 338 342 In reusing, a bolt is repeatedly tightened and loosened. The reusing properties of a shank-ekmgation bolt and a thread-elongation holt tightened in a plastic region were investigated from a viewpoint of fatigue strength, The fatigue tests were carried out on both types of bolts which were subjected to 10-cycle tightening in a plastic region. As a result, the 10-cycle tightening had little influence on the fatigue limit of the bolts. However, on the thread-elongation bolt, the microcracks (approximately 7 IX m in length) appeared at the thread root after repeated tightening in the plastic region. Then, the fatigue limit of a cracked bolt was predicted by using the fracture mechanics method. The threshold stress intensity factor range (AKml of the bolt material (SCM440) was determined from the fatigue crack propagation tests with pre-strained smooth specimens under a high stress ratio. The stress intensity factor range (AK) of the thread root was calctdated by using the equation for a single edged crack without considering a stress concentration. In this equation, the crack length made of the actual and latent crack length was used as the effective crack length. The fatigue limit predicted from the above mentioned AK,, and AK agreed approximately with the fatigue limit of a crack bolt. This prediction clarified that the microcracks of approximately 7 ix m length had little influence on the fatigue limit of bolts, but that the fatigue limit decreased with increasing the crack length > 7 is m. Graphs. photomicrographs, 12 ref.