The Experts below are selected from a list of 4410 Experts worldwide ranked by ideXlab platform
Fred Nilsson - One of the best experts on this subject based on the ideXlab platform.
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High temperature fatigue crack growth in two metals under constant and Variable Amplitude loading
International Journal of Fatigue, 2002Co-Authors: Tomas Månsson, Jan Skantz, Fred NilssonAbstract:Abstract Results are presented for fatigue crack growth at elevated temperatures during both constant Amplitude and Variable Amplitude loading. A careful experimental investigation is presented to show that the concept of the effective stress-intensity factor range ΔKIeff can be used to eliminate the load ratio effect on fatigue data and produce one single set of crack growth data. The fatigue crack propagation data corrected for crack closure is then used for comparison of mean crack propagation rates for Variable Amplitude Loads with simple time histories. It is concluded that measured crack closure can not fully explain the discrepancies between measured and predicted propagation rates. A reduction factor fitted to the experimental data could be used to successfully correlate the results.
Simon Barter - One of the best experts on this subject based on the ideXlab platform.
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a comparison of crack growth behaviour in several full scale airframe fatigue tests
International Journal of Fatigue, 2007Co-Authors: L Molent, Simon BarterAbstract:Abstract Metal fatigue plays a major role in the design of optimised flight vehicles. Economics dictate that modern air vehicles be optimised for weight to maximise performance, therefore an ability to accurately design against the possibility of fatigue failures is paramount. An essential element of the airframe design and certification process is the full-scale fatigue test, where an airframe is subjected to realistic Variable Amplitude Loads which are representative of those predicted to occur over the life-of-type. Generally these fatigue tests are cycled until the equivalent of several lifetimes is achieved or an unrepairable failure occurs. The results of the full-scale fatigue testing of aircraft structures are generally considered to be the foundation for confirming and managing continuing structural airworthiness. This paper reviews fatigue crack growth data from a significant number of fatigue tests on several different military aircraft types. The data analysed generally include the primary crack(s) leading to failure of the test article. The aircraft considered include the F/A-18, F-16, F-111, A4, A7, Mirage III-0, P3C, T37B and the PC-9. It was instructive to compare the crack growth histories from these tests as in general these airframes were designed for different requirements, using different metallic materials, manufacturing processes and analysis tools, and generally were the result of different design regulations or requirements. As a result of this review of the cracking found in these tests it was concluded that a relatively simple crack growth model adequately represents typical crack growth and that this model can be used to aid in the optimisation of fatigue design such that an airframe will just survive the certification fatigue test requirements. The results of this investigation should assist in the development of future optimised structures and allow a better understanding of the limitations caused by fatigue crack growth in airframes.
Rui Calçada - One of the best experts on this subject based on the ideXlab platform.
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Fatigue crack growth modelling of fão bridge puddle iron under Variable Amplitude loading
International Journal of Fatigue, 2020Co-Authors: José A.f.o. Correia, Hermes Carvalho, Grzegorz Lesiuk, António Mourão, Lucas Figueiredo Grilo, Abílio De Jesus, Rui CalçadaAbstract:Abstract This study addresses the fatigue crack growth behaviour of a material from an old riveted steel bridge, the Portuguese Fao Bridge, based on an experimental program of constant and Variable Amplitude loading tests. The material under consideration is a centenary puddle iron, for which information on fatigue crack growth under Variable Amplitude Loads is not available in the literature. Additionally, the experimental program aimed at analysing the fracture surfaces of the specimens through observations under Scanning Electron Microscopy (SEM), and correlate their characteristics with macroscopic fatigue crack growth behaviour. Furthermore, a crack closure analysis was performed using electrical strain gauges applied on the back face of the CT specimens. The fatigue crack propagation along the parallel to the rolling direction (L) revealed to be higher when compared with the transverse direction (T). The experimental data obtained in this study were compared with existing fatigue crack propagation models, such as the Paris model with linear damage accumulation, according to Miner’s rule, as well as with more complex crack propagation models, with capacity for modelling retardation effects of single overLoads. The Paris model with linear damage accumulation, despite its simplicity, led to the best predictions for the generality of Variable Amplitude random block loading. The original Wheeler model is enough to correlate the crack propagation data under overLoads, since the application of more sophisticated models would not be justified by the extremely high scatter observed in these old materials.
Tomas Månsson - One of the best experts on this subject based on the ideXlab platform.
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High temperature fatigue crack growth in two metals under constant and Variable Amplitude loading
International Journal of Fatigue, 2002Co-Authors: Tomas Månsson, Jan Skantz, Fred NilssonAbstract:Abstract Results are presented for fatigue crack growth at elevated temperatures during both constant Amplitude and Variable Amplitude loading. A careful experimental investigation is presented to show that the concept of the effective stress-intensity factor range ΔKIeff can be used to eliminate the load ratio effect on fatigue data and produce one single set of crack growth data. The fatigue crack propagation data corrected for crack closure is then used for comparison of mean crack propagation rates for Variable Amplitude Loads with simple time histories. It is concluded that measured crack closure can not fully explain the discrepancies between measured and predicted propagation rates. A reduction factor fitted to the experimental data could be used to successfully correlate the results.
L Molent - One of the best experts on this subject based on the ideXlab platform.
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a comparison of crack growth behaviour in several full scale airframe fatigue tests
International Journal of Fatigue, 2007Co-Authors: L Molent, Simon BarterAbstract:Abstract Metal fatigue plays a major role in the design of optimised flight vehicles. Economics dictate that modern air vehicles be optimised for weight to maximise performance, therefore an ability to accurately design against the possibility of fatigue failures is paramount. An essential element of the airframe design and certification process is the full-scale fatigue test, where an airframe is subjected to realistic Variable Amplitude Loads which are representative of those predicted to occur over the life-of-type. Generally these fatigue tests are cycled until the equivalent of several lifetimes is achieved or an unrepairable failure occurs. The results of the full-scale fatigue testing of aircraft structures are generally considered to be the foundation for confirming and managing continuing structural airworthiness. This paper reviews fatigue crack growth data from a significant number of fatigue tests on several different military aircraft types. The data analysed generally include the primary crack(s) leading to failure of the test article. The aircraft considered include the F/A-18, F-16, F-111, A4, A7, Mirage III-0, P3C, T37B and the PC-9. It was instructive to compare the crack growth histories from these tests as in general these airframes were designed for different requirements, using different metallic materials, manufacturing processes and analysis tools, and generally were the result of different design regulations or requirements. As a result of this review of the cracking found in these tests it was concluded that a relatively simple crack growth model adequately represents typical crack growth and that this model can be used to aid in the optimisation of fatigue design such that an airframe will just survive the certification fatigue test requirements. The results of this investigation should assist in the development of future optimised structures and allow a better understanding of the limitations caused by fatigue crack growth in airframes.
