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Creep fatigue failure of a secondary reformer burner tube
422
Fatigue Abstracts
of fatigue crack initiation and propagation in the two Ni3AI(B) alloys are different. Graphs, photomicrographs, 7 ref.
surface of the flange rim. A fatigue crack extended 120mm before final fracture occurred. Photomicrographs, 3 ref.
Application of FEM for crack propagation analysis Ohkubo, T. and Nakajima, T. Tokyo Konye Kaisuz Centa, Kenkyu Hoko (Rep. Tokyo Metrop. Ind. Technol. Cent.) (1995) 24, 1-4 (in Japanese)
Creep fatigue failure of a secondary reformer burner tube Monem, A., Batahgy, E. and Zaghloul, B. Mater. Perform. (June 1995) 34 (6), 49 51
The fatigue crack propagation for injection machine parts 'hot-runner" made of AMS5355C (SUS630) steel was described by ANSYS, FEM analysis and by techniques of fracture mechanics. The analytical model consists of crosssection of right angle to its axis. The stress distribution around the initial minute crack in the surface of the parts was calculated from thermal road and injection pressure connectively. Then its stress was used as a calculating value of stress intensity factor. As a result, the fatigue life of parts with complex load can be estimated with high accuracy. Graphs, 6 ref.
After three years of service, the outer tube of a secondary reformer burner at a fertilizer plant fractured at a circumferential weld. Creep fatigue was identified as the failure mechanism. The creep damage was accelerated by coarsening of grain boundary carbides, which was caused by overheating. Fatigue damage was promoted by both internal and external welding defects, which were exacerbated by thermal cycles in shut-down/start-up operations. Tube material was Alloy 800H (UNS N0ggl0). Photomicrographs, 3 ref.
Fatigue strength of deelg-draw steel structural parts: transferability of
Generating material strength standards of aluminium alloys for research reactors. II. Design fatigue curve under non-effective creep condition Tsuji, H. and Miya, K. Nucl. Eng. Des. (1995) 155 (3), 547-557
uniaxial test results (Zur Ubertragbarkeit der Schwingfestigkeit aus einachsigen Begleitprebenversuchen auf Bauteile aus Tiefziehstahlen) Hund, R. Ertelt, H.-J. and Kroplin, B. Mater. wiss. Werkst.tech. (1995) 26 (5), 269-275 (in German) In the course of further reducing the weight of structural parts, constantly growing importance is being attributed to the analysis of fatigue strength. Owing to the possibilities of numerical stress analysis, the so-called local stress concept has become popular in addition to the nominal approach. The article illustrates the difficulties occurring with fatigue life predictions according to the local stress concept for hot-rolled deep-draw steel structural parts. The fatigue life of the structural parts has been predicted through elaste-plastic finite element calculations using uniaxial fatigue tests of smooth specimens. An important prerequisite for the local stress approach is the transferability of the uniaxial fatigue strength to the structural parts. Therefore, a highly ductile, hot-rolled deep-draw steel has been used to show in what respect transferability of fatigue strength is given from uniaxial tests to structural components. Thereby, the notch root strain has been proved to be insufficient for the transferability. Graphs, 17 ref.
Long-term high-cycle fatigue behaviour at temperatures in the creep range (Langzeitschwingfestigkeitsverhalten bei Temperaturen im Kriechgebiet) Kussmaul, K., Maile, K. and Bothe, K. Mater. wiss. Werst.tech. (1995) 26 (5), 241 250 (in German) The long-term high-cycle fatigue behaviour of the martensitic steel X22CrMoVI2 1 and the Ni-base superalloy IN792 has been investigated. For that purpose, the influence of the ratio of static mean stress to HCF stress amplitude was examined. In addition, the influence of notches on the longterm HCF endurance has been determined. The HCF data can be correlated with creep rupture data by a combination of the method of Keil and Maier and of the Moore-Kommers-Jasper diagram; additionally, interpolations for any ratio of static mean stress to HCF stress amplitude can be performed. This means that it will be possible in certain cases to replace costly long-term HCF tests by short-term tests at higher temperature. The superposition of HCF and LCF loading leads to lifetime reductions, which can be explained by simple drainage accumulation rules only for small HCF stress amplitudes. Graphs, 4 ref.
Corrosion fatigue behaviour of duplex stainless steel X2CrNiMoN2253 under heat transfer conditions. (Schwingungsrisskorrosionsverhalten des Duplexstahles X2CrNiMoN2253 unter definierten Wttrmeiibergangsbedingungen) Vollmar, J. and Roeder, E. Mater. wiss. Werkst.tech. (1995) 26 (5), 223-240 (in German) The corrosion behaviour of metallic components is affected not only by the temperature of the corrosive environment but also by the heat transfer conditions between the heated material and the cooling agent. Therefore the corrosion fatigue behaviour of the anstenitic-ferritic stainless steel X2CrNiMoN22 5 3 (German material-number 1.4462) in 3% NaC1 solution was investigated for isothermal conditions and three different heat transfer conditions. The specimens were tested under cyclic tension load (R = o-u/oL = 0) with a frequency o f f = 25 Hz up to 107 cycles. The isothermal fatigue strengths were 380 N mm 2 for room temperature and 340 N mm -2 for a temperature of 70°C. For heat transfer conditions between the sinusoidal-loaded specimens and the corrosive agent a newly developed testing equipment is presented. The corrosion fatigue strength for a heat flux of 45 kW m 2 reached a value of 410 N mm -2, while the improvement relative to the isothermal room temperature strength is lower for higher heat flux values (100 and 150 kW m 2). The better corrosion fatigue behaviour for heat transfer conditions is based on the favourable conditions for the formation of the passive layer. The thickness of the layer is nearly twice as high as for isothermal room temperature corrosion and therefore the crack initiation is delayed. For higher values of heat flux, local corrosion attack was found. With that the positive effect on corrosion fatigue strength was diminished. Graphs, photomicrographs, 24 ref.
Fatigue failure of an aircraft wheel flange Elshawesh, F., Abusowa, K. and Elhoud, A. Mater. Perform. (1995) 34 (6), 53-54 The main wheel flange of a transport aircraft failed during taxiing, immediately after workover service. The wheel flange was forged from a 2014-T6 (UNS A92014) aluminium alloy. Visual and microscopic examination of the failed part revealed that the fracture was due to fatigue initiated from pits at the
Aluminium alloys are frequently used as structural materials for reactors. The material strength standards, however, such as the yield strength values (S~), tensile strength values (S,) and design fatigue curve needed to use AI alloys as structural materials in design by analysis have not been determined yet. Hence, a series of material tests was performed and the results were statistically analysed. Materials tested were A5052P-O, A5052BE O, A6061P-T651, A6061BE-T6 and A6063BE-T6. The procedures used to generate the design fatigue curve are described. Creep effects on the design fatigue curve were evaluated, and a negligible creep region was determined by restrictions of the temperature and stress. The mean stress effect was evaluated using a modified Goodman line. The design fatigue curve presented has already been adopted in the Science and Technology Agency regulatory guide (standards for structural design of nuclear research plants). Graphs, 11 ref.
Advanced creep-fatigue evaluation rule for fast breeder reactor components: generalization of elastic follow-up model Kasahara, N., Nagata, T., lwata, K. and Negishi. H. Nucl. Eng. Des. (1995) 155 (3), 499-518 High-temperature operative conditions of fast breeder reactors (FBRs) cause plastic and creep deformations of structures, which lead to the magnification of the creep-fatigue damage of the materials. To take these effects into account, a structural design code for the Japanese prototype FBR Monju has adopted an elastic follow-up model. The elastic follow-up model shows a potential for expressing both the plastic and creep behaviours of structures. However, this model has weaknesses, which means that it cannot be used to treat material properties quantitatively, and also cannot be adaptive to the existence of stress redistributions. Consequently, the elastic follow-up model was generalized, by introducing the concepts of: an elastic follow-up model using a power law, for the purpose of the quantitative evaluation of material properties: combined elastic follow-up models, for consideration of stress redistributions: and an equivalent elastic follow-up model of Neuber's rule. By applying the generalized elastic follow-up model to structural discontinuity portions, an advanced creep-fatigue evaluation rule based on elastic analysis was proposed. The proposed method was verified through structural strength tests and inelastic finite element calculations for 304L anstenitic stainless steel. As a result, the design stresses are raised significantly compared with those of the structural design code for Monju. Graphs, 34 ref.
Endurance calculation of wire ropes running over sheaves Feyrer, K. Wire (1995) 2, 99-103 At the OIPEEC Round Table in East Kilbride in 1985 the author presented a method of calculating the life of wire ropes and rope drives. Since then the method has been improved in some points, especially as regards the influence of fluctuating tensile force, reverse bending and wire strength. Symbols for the loading elements of wire ropes were introduced with which the loading sequence in a rope drive can be graphically described. The actual form of the calculation method is presented. With this method it is possible to evaluate the probable number of working cycles to rope disposal and rope breakage, the maximum rope tension allowed, and the optimal rope diameter. A first investigation has shown that the calculated numbers of working cycles correspond very well with those reached by wire ropes in practical usage. Meanwhile the comparison between real and calculated wire rope endurance has been made in several cranes, lifts, ropeways, etc. This comparison shows a very good correspondence. 28 ref.
Thermomechanical fatigue life prediction in gas turbine superanoys: a fracture mechanics approach Nissley, D.M. AIAA J. (1995) 33 (6), 1114-1120 A model is presented that was developed to predict thermomechanical fatigue crack initiation and estimate mode I crack growth of gas turbine hot-section gas-path superalloys. The model is based on a strain density fracture mechanics approach modified to account for thermal exposure and single-crystal anisotropy. Thermomechanical fatigue crack initiation and small crack growth are modelled by employing an initial material defect size. Model capability was quantified by applying the model to two hot-section gas-path superalloys:
Fatigue Abstracts
of fatigue crack initiation and propagation in the two Ni3AI(B) alloys are different. Graphs, photomicrographs, 7 ref.
surface of the flange rim. A fatigue crack extended 120mm before final fracture occurred. Photomicrographs, 3 ref.
Application of FEM for crack propagation analysis Ohkubo, T. and Nakajima, T. Tokyo Konye Kaisuz Centa, Kenkyu Hoko (Rep. Tokyo Metrop. Ind. Technol. Cent.) (1995) 24, 1-4 (in Japanese)
Creep fatigue failure of a secondary reformer burner tube Monem, A., Batahgy, E. and Zaghloul, B. Mater. Perform. (June 1995) 34 (6), 49 51
The fatigue crack propagation for injection machine parts 'hot-runner" made of AMS5355C (SUS630) steel was described by ANSYS, FEM analysis and by techniques of fracture mechanics. The analytical model consists of crosssection of right angle to its axis. The stress distribution around the initial minute crack in the surface of the parts was calculated from thermal road and injection pressure connectively. Then its stress was used as a calculating value of stress intensity factor. As a result, the fatigue life of parts with complex load can be estimated with high accuracy. Graphs, 6 ref.
After three years of service, the outer tube of a secondary reformer burner at a fertilizer plant fractured at a circumferential weld. Creep fatigue was identified as the failure mechanism. The creep damage was accelerated by coarsening of grain boundary carbides, which was caused by overheating. Fatigue damage was promoted by both internal and external welding defects, which were exacerbated by thermal cycles in shut-down/start-up operations. Tube material was Alloy 800H (UNS N0ggl0). Photomicrographs, 3 ref.
Fatigue strength of deelg-draw steel structural parts: transferability of
Generating material strength standards of aluminium alloys for research reactors. II. Design fatigue curve under non-effective creep condition Tsuji, H. and Miya, K. Nucl. Eng. Des. (1995) 155 (3), 547-557
uniaxial test results (Zur Ubertragbarkeit der Schwingfestigkeit aus einachsigen Begleitprebenversuchen auf Bauteile aus Tiefziehstahlen) Hund, R. Ertelt, H.-J. and Kroplin, B. Mater. wiss. Werkst.tech. (1995) 26 (5), 269-275 (in German) In the course of further reducing the weight of structural parts, constantly growing importance is being attributed to the analysis of fatigue strength. Owing to the possibilities of numerical stress analysis, the so-called local stress concept has become popular in addition to the nominal approach. The article illustrates the difficulties occurring with fatigue life predictions according to the local stress concept for hot-rolled deep-draw steel structural parts. The fatigue life of the structural parts has been predicted through elaste-plastic finite element calculations using uniaxial fatigue tests of smooth specimens. An important prerequisite for the local stress approach is the transferability of the uniaxial fatigue strength to the structural parts. Therefore, a highly ductile, hot-rolled deep-draw steel has been used to show in what respect transferability of fatigue strength is given from uniaxial tests to structural components. Thereby, the notch root strain has been proved to be insufficient for the transferability. Graphs, 17 ref.
Long-term high-cycle fatigue behaviour at temperatures in the creep range (Langzeitschwingfestigkeitsverhalten bei Temperaturen im Kriechgebiet) Kussmaul, K., Maile, K. and Bothe, K. Mater. wiss. Werst.tech. (1995) 26 (5), 241 250 (in German) The long-term high-cycle fatigue behaviour of the martensitic steel X22CrMoVI2 1 and the Ni-base superalloy IN792 has been investigated. For that purpose, the influence of the ratio of static mean stress to HCF stress amplitude was examined. In addition, the influence of notches on the longterm HCF endurance has been determined. The HCF data can be correlated with creep rupture data by a combination of the method of Keil and Maier and of the Moore-Kommers-Jasper diagram; additionally, interpolations for any ratio of static mean stress to HCF stress amplitude can be performed. This means that it will be possible in certain cases to replace costly long-term HCF tests by short-term tests at higher temperature. The superposition of HCF and LCF loading leads to lifetime reductions, which can be explained by simple drainage accumulation rules only for small HCF stress amplitudes. Graphs, 4 ref.
Corrosion fatigue behaviour of duplex stainless steel X2CrNiMoN2253 under heat transfer conditions. (Schwingungsrisskorrosionsverhalten des Duplexstahles X2CrNiMoN2253 unter definierten Wttrmeiibergangsbedingungen) Vollmar, J. and Roeder, E. Mater. wiss. Werkst.tech. (1995) 26 (5), 223-240 (in German) The corrosion behaviour of metallic components is affected not only by the temperature of the corrosive environment but also by the heat transfer conditions between the heated material and the cooling agent. Therefore the corrosion fatigue behaviour of the anstenitic-ferritic stainless steel X2CrNiMoN22 5 3 (German material-number 1.4462) in 3% NaC1 solution was investigated for isothermal conditions and three different heat transfer conditions. The specimens were tested under cyclic tension load (R = o-u/oL = 0) with a frequency o f f = 25 Hz up to 107 cycles. The isothermal fatigue strengths were 380 N mm 2 for room temperature and 340 N mm -2 for a temperature of 70°C. For heat transfer conditions between the sinusoidal-loaded specimens and the corrosive agent a newly developed testing equipment is presented. The corrosion fatigue strength for a heat flux of 45 kW m 2 reached a value of 410 N mm -2, while the improvement relative to the isothermal room temperature strength is lower for higher heat flux values (100 and 150 kW m 2). The better corrosion fatigue behaviour for heat transfer conditions is based on the favourable conditions for the formation of the passive layer. The thickness of the layer is nearly twice as high as for isothermal room temperature corrosion and therefore the crack initiation is delayed. For higher values of heat flux, local corrosion attack was found. With that the positive effect on corrosion fatigue strength was diminished. Graphs, photomicrographs, 24 ref.
Fatigue failure of an aircraft wheel flange Elshawesh, F., Abusowa, K. and Elhoud, A. Mater. Perform. (1995) 34 (6), 53-54 The main wheel flange of a transport aircraft failed during taxiing, immediately after workover service. The wheel flange was forged from a 2014-T6 (UNS A92014) aluminium alloy. Visual and microscopic examination of the failed part revealed that the fracture was due to fatigue initiated from pits at the
Aluminium alloys are frequently used as structural materials for reactors. The material strength standards, however, such as the yield strength values (S~), tensile strength values (S,) and design fatigue curve needed to use AI alloys as structural materials in design by analysis have not been determined yet. Hence, a series of material tests was performed and the results were statistically analysed. Materials tested were A5052P-O, A5052BE O, A6061P-T651, A6061BE-T6 and A6063BE-T6. The procedures used to generate the design fatigue curve are described. Creep effects on the design fatigue curve were evaluated, and a negligible creep region was determined by restrictions of the temperature and stress. The mean stress effect was evaluated using a modified Goodman line. The design fatigue curve presented has already been adopted in the Science and Technology Agency regulatory guide (standards for structural design of nuclear research plants). Graphs, 11 ref.
Advanced creep-fatigue evaluation rule for fast breeder reactor components: generalization of elastic follow-up model Kasahara, N., Nagata, T., lwata, K. and Negishi. H. Nucl. Eng. Des. (1995) 155 (3), 499-518 High-temperature operative conditions of fast breeder reactors (FBRs) cause plastic and creep deformations of structures, which lead to the magnification of the creep-fatigue damage of the materials. To take these effects into account, a structural design code for the Japanese prototype FBR Monju has adopted an elastic follow-up model. The elastic follow-up model shows a potential for expressing both the plastic and creep behaviours of structures. However, this model has weaknesses, which means that it cannot be used to treat material properties quantitatively, and also cannot be adaptive to the existence of stress redistributions. Consequently, the elastic follow-up model was generalized, by introducing the concepts of: an elastic follow-up model using a power law, for the purpose of the quantitative evaluation of material properties: combined elastic follow-up models, for consideration of stress redistributions: and an equivalent elastic follow-up model of Neuber's rule. By applying the generalized elastic follow-up model to structural discontinuity portions, an advanced creep-fatigue evaluation rule based on elastic analysis was proposed. The proposed method was verified through structural strength tests and inelastic finite element calculations for 304L anstenitic stainless steel. As a result, the design stresses are raised significantly compared with those of the structural design code for Monju. Graphs, 34 ref.
Endurance calculation of wire ropes running over sheaves Feyrer, K. Wire (1995) 2, 99-103 At the OIPEEC Round Table in East Kilbride in 1985 the author presented a method of calculating the life of wire ropes and rope drives. Since then the method has been improved in some points, especially as regards the influence of fluctuating tensile force, reverse bending and wire strength. Symbols for the loading elements of wire ropes were introduced with which the loading sequence in a rope drive can be graphically described. The actual form of the calculation method is presented. With this method it is possible to evaluate the probable number of working cycles to rope disposal and rope breakage, the maximum rope tension allowed, and the optimal rope diameter. A first investigation has shown that the calculated numbers of working cycles correspond very well with those reached by wire ropes in practical usage. Meanwhile the comparison between real and calculated wire rope endurance has been made in several cranes, lifts, ropeways, etc. This comparison shows a very good correspondence. 28 ref.
Thermomechanical fatigue life prediction in gas turbine superanoys: a fracture mechanics approach Nissley, D.M. AIAA J. (1995) 33 (6), 1114-1120 A model is presented that was developed to predict thermomechanical fatigue crack initiation and estimate mode I crack growth of gas turbine hot-section gas-path superalloys. The model is based on a strain density fracture mechanics approach modified to account for thermal exposure and single-crystal anisotropy. Thermomechanical fatigue crack initiation and small crack growth are modelled by employing an initial material defect size. Model capability was quantified by applying the model to two hot-section gas-path superalloys: