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Determination of high-temperature cyclic strength of welded joints by loading at room temperature
230
Abstracts
Isothermal shear low-cycle fatigue behaviour of 62Sn-36Pb-2Ag surface mount solder Joints. Li, Y.Q., Tang, X:Y., Ma, J.S. and Huang, L. Acta Metall. Sin. (China) (18 Apr. 1994) 30 (4), A164-A169 (in Chinese)
Method and device for the determination of fatigue limit of sheet metal. Geshelin, V.G. and Osipov, A.F. Ind, Lab. (Russia) (May 1994) 59 (11), 1053-1056
The isothermal low-cycle fatigue bchaviour of 62Sn-36Pb-2Ag surface mount solder joint of copper or Kovar alloy under shear stress has been discussed; meanwhile, the curve of shear fatigue life vs. cyclic shear stress amplitude has been obtained, and the failure mechanism under different shear stress amplitude at different temperatures is analysed. The results show that there is obvious cyclic creep behaviour during constant stress amplitude low-cycle fatigue in 62Sn-36Pb-2Ag surface mount solder joints. The failure of the solder joint is due to the interaction of fatigue and creep. At 25 *C, under low shear stress amplitude, the failure is controlled mainly by fatigue mechanism; in contrast, under high shear stress amplitude, it is controlled mainly by creep mechansism. The failure mechanism at 100 *C is similar to that at 25 *(2, only the transfer stress "r+ from fatigue mechanism to creep mechanism is lower than that at 25 *C. Under similar relative shear stress amplitude (x+/% and "r+lx'b), the fatigue crack propagation rate da/dN at 100 *C is similar to that at 25 *C. Graphs, photomicrographs, 7 ref.
A method for the determination of fatigue limit of sheet metals, which allowed one to take into account the influence of plate stress, deformed state and different levels of previous plastic deformations, was developed. The method was used for the investigation of tensile deformations and strain hardening of sheet and channel samples of 08GSYuF and 08Yu steels. Graphs.
Bonded composite repair of cracked load-bearing holes. Paul, J., Bartholomeusz, R.A., Jones, R. and Ekstrom, M. Eng. Fract. Mech. (June 1994) 48 (3), 455-461 Externally bonded composite repairs have recently been shown to be an effective technique for repairing a range of structural problems associated with cracked or damaged aircraft components, including multi-site damage in cracked fuselage lap-joints. This paper attempts to clarify further the mechanisms by which these repairs work. The results are presented of a combined numerical and experimental investigation into the use of bonded repairs for a load-bearing 7075 hole containing a single 'through-thickness' crack. The specimen was repaired with bonded boron/epoxy doublers and a steel sleeve insert. Constant-amplitude fatigue tests were performed, on both the repaired and unrepaired specimens, and the resultant fatigue crack growth data are presented. These crack growth data are then correlated with the stress intensity factors obtained from a three-dimensional finite element analysis. Graphs, 13 ref. Design and testing of bonded GLARE patches in the repair of fuselage fatigue cracks in large transport aircraft. Fredell, R. van Barneveld, W. and Vogelesang, L.B. Proc. Conf. Moving Forward With 50 Years of Leadership in Advanced Materials, Anaheim, California, USA. (11-14 Apr. 1994) 624-638. Advanced composite patch repairs of cracked aluminium structures have proven themselves in service since the late 1960s, primarily involving the application of high modulus boron-epoxy or carbon-epoxy composites to thick wing structures. The present paper describes the design, analysis and testing of the relatively low-cost, moderate elastic modulus fibre metal laminate G L A R E 2 in the bonded patch repair of cracked AI 7075-T6 coupons and stiffened fuselage panels. G L A R E 2, a glass-fibre-reinforced AI laminate, has a coefficient of thermal expansion slightly less than monolithic AI. Its use as a relatively low-cost bonded crack patching material is compared with traditional advanced composite materials and monolithic metals. The results show that in the bonded patch repair of cracked stiffened fuselage panels, GLARE 2 shows excellent crack-stopping characteristics. G L A R E provides a high-performance, low-cost, user-friendly material alternative to the high-modulus composites B and C. Graphs, 4 ref. Corrosion-mechanical fatigue: direct and reverse effects Sosnovskff, L.A. and Makhutov, N.A. Ind. Lab. (Russia) (Jan. 1994) 59 (7), 678-695 Processes of influence of corrosion environment on the decrease in fatigue resistance and reverse effect - mechanical activation of corrosion reactions - are reviewed. Relationships between corrosion rate, chemical composition, microstructure, external stresses, and mechanical properties are illustrated with examples of investigation of 45 and Khl7N2 steels, aluminium and nickel alloys, 60-40 brass and some others. Graphs. Temperature effect on the corrosion-fatigue behaviour in aqueous medium, in the case of AFNOR Z40 CSD 10-1 Steel. [Influence de la temperature sur la fatigue-corrosion en milieu aqueux de racier ZA0 CSD 10-1.]. Katundi, G., Stasi. M., Stasi. J. and Lieurade, H.-P. Mec. lndust. Mater. (Mar. 1994) 47 (1), 241-244 (in French)
Optimum balance between strength and ductility for fatigue properties. Hu, Z.-Z. Eng. Fract. Mech. (June 1994) 48 (3); 445-453 By means of the fatigue crack equivalent stress-strain model indicated with macro-strength and micro-ductility, the relations between the fatigue behaviour and strength of ductility are derived. The results show that a condition of optimum balance between strength and ductility is the product maximum of macro-strength and micro-ductility, which is applicable for the determination of the fatigue threshold, fatigue crack propagation rate, fatigue limit of a notched specimen, as well as the number of stress cycles to initiate a fatigue crack. 300M and 45Cr are mentioned. Graphs, 13 ref. Estimation of fatigue crack propagation rate In steel. Li, Z. Eng. Fract. Mach. (June 1994) 48 (3), 339-345 Based on the fatigue crack propagation (FCP) expression developed by X. Zheng and M.A. Hirt, a new method for the estimation of FCP rate is suggested. It is pointed out that when AKth (the FCP threshold) and the mechanism in the intermediate region of FCP are known, the FCP rates can be predicted from tensile properties. In this paper, the FCP rate curves of low-alloy steels SM50 B, HT80, SP42, SPV50 and their welded joints are predicted. It is shown that the predicted lines agree fairly well with the test results. It is also shown that FCP threshold AKIn is sensitive to stress ratio R but not to weld technology. Graphs, 15 ref. Thermographic examination of fatigue exercise on high strength pressure vessel. Huang, Y., Lin, X.R., Xu, J., Li, S.X. and Li, W. Acta Metall. Sin. (China) (18 May 1994) 30 (5), A225-A231 (in Chinese) An infrared thermographic system was used to monitor the process of fatigue compression of a high-strength steel (D6AC) pressure vessel under working pressure. The IRCE effect obtained by thermography at the beginning of fatigue testing can determine the stress-concentrated areas. The leaks in the vessel under compression may testify that the examination of the stressconcentrated area by thermography is available. The fatigue softening and hardening effect was found in the tests. The thermographic results for the stress distribution of cylindrical thin-wall pressure vessel are in agreement with those computed by the Global coordinate system. It is believed that the fatigue exercise effact under working pressure may prolong the working life of the pressure vessel. Graphs, 6 ref. Creep-fatigue interaction in alloys GH30 and GH34. Wang, X., Zhou, H. and Kong, Q.P. Acta Metall. Sine. (China) (18 May 1994) 30 (5), AI95-A199 Two different negative interactions in alloys GH30 and GH34 were observed under prior creep followed by fatigue and under continuous cyclic creep, respectively. The exponent of the fatigue damage, for the former, in the interaction term is much larger than that of the creep damage, and hence the negative interaction is mainly as a result of the sequential fatigue damage being restrained by the prior creep. The exponent of the creep damage, for the latter, in the interaction term is much larger than that of the fatigue damage, and hence as a result of creep damage being partly recovered by the fatigue (cyclic loading and unloading). The microscopic origin of the two different negative interactions has been explained in the light of microscopic observations. Graphs, photomicrographs, 11 ref. A reliability assessment of reactor pressure vessels. Wu, W.F., Shin, C.S. and Tsai, C.H. Int. J. Pressure Vessels Piping (1994) 57 (1), 77-84
The goal of this study was to evaluate the influence of the cooling water on the fatigue strength of a chromium, silicon and molybdenum alloy steel used for marine engine valves. The results show a high reduction of the fatigue strength in comparison with those obtained in air, more pronounced by temperature increase. This study shows that the use of a corrosion inhibitor eliminates the detrimental effect of the medium and the temperature on the fatigue life. Graphs, photomicrographs, 7 ref.
A theoretical investigation is presented on the reliability assessment of nuclear reactor pressure vessels. In the analysis, a Poisson-type random walk model is assumed to represent the randomly occurred transients, which have randomly distributed stresses. These transient stresses cause a predominant initial crack size to grow and, therefore, degrade the reliability of a pressure vessel. Following the probabilistic fracture mechanics approach, the variability of the material properties is considered. A numerical calculation is carried out based on available empirical data. It is found that for a typical BWR pressure vessel, the failure probability lies in the order of i0 -~ and the failure rate is approximately in the order of 10 -8 vessel/year. The result is in agreement with other published results. Graphs, 14 ref.
Determination of high-temperature cyclic strength of welded joints by loading at room temperature. Filatov, V.M. and Evropin, S.V. Ind. Lab. (Russia) (Feb. 1994) 59 (8), 808-811.
The influence of crack closure on the positive load ratio (R) dependence of fatigue threshold stress intensity factor range (AKth) of AISI 316 stainless steel in air at room temperature. Packiaraj, C.C., Ray, S.K. and Mannan, S L. Int. J. Pressure Vessels Piping (1994) 57 (1), 65-70
A method of fatigue testing of samples that modelled parts of high-temperature constructions was developed. Testing proceeded at room temperature. The method was applied for the investigation of tensile strength of a sample of edge joint weld of coaxial shells of 08Khl8NIOT chromium nickel steel.
Near-threshold fatigue crack growth (FCG) behaviour of 316 SS at positivc R-ratios in air at room temperature is influenced by crack closure. Empirical modifications of McEvily-Groeger and Zhao Xiaopeng equations are proposed to incorporate crack closure effects; the modified equations are found to
Abstracts
Isothermal shear low-cycle fatigue behaviour of 62Sn-36Pb-2Ag surface mount solder Joints. Li, Y.Q., Tang, X:Y., Ma, J.S. and Huang, L. Acta Metall. Sin. (China) (18 Apr. 1994) 30 (4), A164-A169 (in Chinese)
Method and device for the determination of fatigue limit of sheet metal. Geshelin, V.G. and Osipov, A.F. Ind, Lab. (Russia) (May 1994) 59 (11), 1053-1056
The isothermal low-cycle fatigue bchaviour of 62Sn-36Pb-2Ag surface mount solder joint of copper or Kovar alloy under shear stress has been discussed; meanwhile, the curve of shear fatigue life vs. cyclic shear stress amplitude has been obtained, and the failure mechanism under different shear stress amplitude at different temperatures is analysed. The results show that there is obvious cyclic creep behaviour during constant stress amplitude low-cycle fatigue in 62Sn-36Pb-2Ag surface mount solder joints. The failure of the solder joint is due to the interaction of fatigue and creep. At 25 *C, under low shear stress amplitude, the failure is controlled mainly by fatigue mechanism; in contrast, under high shear stress amplitude, it is controlled mainly by creep mechansism. The failure mechanism at 100 *C is similar to that at 25 *(2, only the transfer stress "r+ from fatigue mechanism to creep mechanism is lower than that at 25 *C. Under similar relative shear stress amplitude (x+/% and "r+lx'b), the fatigue crack propagation rate da/dN at 100 *C is similar to that at 25 *C. Graphs, photomicrographs, 7 ref.
A method for the determination of fatigue limit of sheet metals, which allowed one to take into account the influence of plate stress, deformed state and different levels of previous plastic deformations, was developed. The method was used for the investigation of tensile deformations and strain hardening of sheet and channel samples of 08GSYuF and 08Yu steels. Graphs.
Bonded composite repair of cracked load-bearing holes. Paul, J., Bartholomeusz, R.A., Jones, R. and Ekstrom, M. Eng. Fract. Mech. (June 1994) 48 (3), 455-461 Externally bonded composite repairs have recently been shown to be an effective technique for repairing a range of structural problems associated with cracked or damaged aircraft components, including multi-site damage in cracked fuselage lap-joints. This paper attempts to clarify further the mechanisms by which these repairs work. The results are presented of a combined numerical and experimental investigation into the use of bonded repairs for a load-bearing 7075 hole containing a single 'through-thickness' crack. The specimen was repaired with bonded boron/epoxy doublers and a steel sleeve insert. Constant-amplitude fatigue tests were performed, on both the repaired and unrepaired specimens, and the resultant fatigue crack growth data are presented. These crack growth data are then correlated with the stress intensity factors obtained from a three-dimensional finite element analysis. Graphs, 13 ref. Design and testing of bonded GLARE patches in the repair of fuselage fatigue cracks in large transport aircraft. Fredell, R. van Barneveld, W. and Vogelesang, L.B. Proc. Conf. Moving Forward With 50 Years of Leadership in Advanced Materials, Anaheim, California, USA. (11-14 Apr. 1994) 624-638. Advanced composite patch repairs of cracked aluminium structures have proven themselves in service since the late 1960s, primarily involving the application of high modulus boron-epoxy or carbon-epoxy composites to thick wing structures. The present paper describes the design, analysis and testing of the relatively low-cost, moderate elastic modulus fibre metal laminate G L A R E 2 in the bonded patch repair of cracked AI 7075-T6 coupons and stiffened fuselage panels. G L A R E 2, a glass-fibre-reinforced AI laminate, has a coefficient of thermal expansion slightly less than monolithic AI. Its use as a relatively low-cost bonded crack patching material is compared with traditional advanced composite materials and monolithic metals. The results show that in the bonded patch repair of cracked stiffened fuselage panels, GLARE 2 shows excellent crack-stopping characteristics. G L A R E provides a high-performance, low-cost, user-friendly material alternative to the high-modulus composites B and C. Graphs, 4 ref. Corrosion-mechanical fatigue: direct and reverse effects Sosnovskff, L.A. and Makhutov, N.A. Ind. Lab. (Russia) (Jan. 1994) 59 (7), 678-695 Processes of influence of corrosion environment on the decrease in fatigue resistance and reverse effect - mechanical activation of corrosion reactions - are reviewed. Relationships between corrosion rate, chemical composition, microstructure, external stresses, and mechanical properties are illustrated with examples of investigation of 45 and Khl7N2 steels, aluminium and nickel alloys, 60-40 brass and some others. Graphs. Temperature effect on the corrosion-fatigue behaviour in aqueous medium, in the case of AFNOR Z40 CSD 10-1 Steel. [Influence de la temperature sur la fatigue-corrosion en milieu aqueux de racier ZA0 CSD 10-1.]. Katundi, G., Stasi. M., Stasi. J. and Lieurade, H.-P. Mec. lndust. Mater. (Mar. 1994) 47 (1), 241-244 (in French)
Optimum balance between strength and ductility for fatigue properties. Hu, Z.-Z. Eng. Fract. Mech. (June 1994) 48 (3); 445-453 By means of the fatigue crack equivalent stress-strain model indicated with macro-strength and micro-ductility, the relations between the fatigue behaviour and strength of ductility are derived. The results show that a condition of optimum balance between strength and ductility is the product maximum of macro-strength and micro-ductility, which is applicable for the determination of the fatigue threshold, fatigue crack propagation rate, fatigue limit of a notched specimen, as well as the number of stress cycles to initiate a fatigue crack. 300M and 45Cr are mentioned. Graphs, 13 ref. Estimation of fatigue crack propagation rate In steel. Li, Z. Eng. Fract. Mach. (June 1994) 48 (3), 339-345 Based on the fatigue crack propagation (FCP) expression developed by X. Zheng and M.A. Hirt, a new method for the estimation of FCP rate is suggested. It is pointed out that when AKth (the FCP threshold) and the mechanism in the intermediate region of FCP are known, the FCP rates can be predicted from tensile properties. In this paper, the FCP rate curves of low-alloy steels SM50 B, HT80, SP42, SPV50 and their welded joints are predicted. It is shown that the predicted lines agree fairly well with the test results. It is also shown that FCP threshold AKIn is sensitive to stress ratio R but not to weld technology. Graphs, 15 ref. Thermographic examination of fatigue exercise on high strength pressure vessel. Huang, Y., Lin, X.R., Xu, J., Li, S.X. and Li, W. Acta Metall. Sin. (China) (18 May 1994) 30 (5), A225-A231 (in Chinese) An infrared thermographic system was used to monitor the process of fatigue compression of a high-strength steel (D6AC) pressure vessel under working pressure. The IRCE effect obtained by thermography at the beginning of fatigue testing can determine the stress-concentrated areas. The leaks in the vessel under compression may testify that the examination of the stressconcentrated area by thermography is available. The fatigue softening and hardening effect was found in the tests. The thermographic results for the stress distribution of cylindrical thin-wall pressure vessel are in agreement with those computed by the Global coordinate system. It is believed that the fatigue exercise effact under working pressure may prolong the working life of the pressure vessel. Graphs, 6 ref. Creep-fatigue interaction in alloys GH30 and GH34. Wang, X., Zhou, H. and Kong, Q.P. Acta Metall. Sine. (China) (18 May 1994) 30 (5), AI95-A199 Two different negative interactions in alloys GH30 and GH34 were observed under prior creep followed by fatigue and under continuous cyclic creep, respectively. The exponent of the fatigue damage, for the former, in the interaction term is much larger than that of the creep damage, and hence the negative interaction is mainly as a result of the sequential fatigue damage being restrained by the prior creep. The exponent of the creep damage, for the latter, in the interaction term is much larger than that of the fatigue damage, and hence as a result of creep damage being partly recovered by the fatigue (cyclic loading and unloading). The microscopic origin of the two different negative interactions has been explained in the light of microscopic observations. Graphs, photomicrographs, 11 ref. A reliability assessment of reactor pressure vessels. Wu, W.F., Shin, C.S. and Tsai, C.H. Int. J. Pressure Vessels Piping (1994) 57 (1), 77-84
The goal of this study was to evaluate the influence of the cooling water on the fatigue strength of a chromium, silicon and molybdenum alloy steel used for marine engine valves. The results show a high reduction of the fatigue strength in comparison with those obtained in air, more pronounced by temperature increase. This study shows that the use of a corrosion inhibitor eliminates the detrimental effect of the medium and the temperature on the fatigue life. Graphs, photomicrographs, 7 ref.
A theoretical investigation is presented on the reliability assessment of nuclear reactor pressure vessels. In the analysis, a Poisson-type random walk model is assumed to represent the randomly occurred transients, which have randomly distributed stresses. These transient stresses cause a predominant initial crack size to grow and, therefore, degrade the reliability of a pressure vessel. Following the probabilistic fracture mechanics approach, the variability of the material properties is considered. A numerical calculation is carried out based on available empirical data. It is found that for a typical BWR pressure vessel, the failure probability lies in the order of i0 -~ and the failure rate is approximately in the order of 10 -8 vessel/year. The result is in agreement with other published results. Graphs, 14 ref.
Determination of high-temperature cyclic strength of welded joints by loading at room temperature. Filatov, V.M. and Evropin, S.V. Ind. Lab. (Russia) (Feb. 1994) 59 (8), 808-811.
The influence of crack closure on the positive load ratio (R) dependence of fatigue threshold stress intensity factor range (AKth) of AISI 316 stainless steel in air at room temperature. Packiaraj, C.C., Ray, S.K. and Mannan, S L. Int. J. Pressure Vessels Piping (1994) 57 (1), 65-70
A method of fatigue testing of samples that modelled parts of high-temperature constructions was developed. Testing proceeded at room temperature. The method was applied for the investigation of tensile strength of a sample of edge joint weld of coaxial shells of 08Khl8NIOT chromium nickel steel.
Near-threshold fatigue crack growth (FCG) behaviour of 316 SS at positivc R-ratios in air at room temperature is influenced by crack closure. Empirical modifications of McEvily-Groeger and Zhao Xiaopeng equations are proposed to incorporate crack closure effects; the modified equations are found to