Fatigue propagation of long cracks in metastable austenitic stainless steels

Fatigue crack growth of a metastable austenitic stainless steel was investigated in thin specimen under positive stress ratio. Annealed and Co l d rolled conditions were used to test the influence of the microstructure. The influence of load ratio and load history on propagation behavior was analyzed using the Elber`s closure approach, the Donald and Paris partial crack closure and the empirical Kujawski (∆K•Kmax) α parameter. Results show that load ratio effects could be explained by two parameters concepts . It see ms that the amount of martensite transformation is responsible for the observed differences in fatigue crack growth resistance.Postprint (published version

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Fatigue crack growth of a metastable austenitic stainless steel

The fatigue crack growth behavior of an austenitic metastable stainless steel AISI 301LN in the Paris region is investigated in this work. The fatigue crack growth rate curves are evaluated in terms of different parameters such as the range of stress intensity factor Delta K, the effective stress intensity factor Delta K-eff, and the two driving force parameter proposed by Kujawski K*.; The finite element method is used to calculate the stress intensity factor of the specimens used in this investigation. The new stress intensity factor solution has been proved to be an alternative to explain contradictory results found in the literature.; Fatigue crack propagation tests have been carried out on thin sheets with two different microstructural conditions and different load ratios. The influence of microstructural and mechanical variables has been analyzed using different mechanisms proposed in the literature. The influence of the compressive residual stress induced by the martensitic transformation is determined by using a model based on the proposal of McMeeking et al. The analyses demonstrate the necessity of including K-max as a true driving force for the fatigue crack growth. A combined parameter is proposed to explain the effects of different variables on the fatigue crack growth rate curves. It is found that along with residual stresses, the microcracks and microvoids are other factor affecting the fatigue crack growth rate in the steel studied. (C) 2015 Elsevier Ltd. All rights reserved.Peer Reviewe

Crack closure and fatigue crack growth near threshold of a metastable austenitic stainless steel

In this paper R-ratio effects on fatigue crack growth near threshold region of a metastable austenitic stainless steel (MASS) in two different conditions, i.e. annealed and cold rolled, is investigated. The authors present two approaches to correlate FCGR data for R = 0.1, 0.3, 0.5, 0.7 and K-max = 23 MPa root m using a two-parameters approach (Delta K, K-max and alpha in Kujawski's model) and crack closure model (using Elber's K-op, and in Donald's ACRn2 approaches). The K-op and ACRn2 were experimentally measured on a single edge tension specimens. The K-op measurements were performed using a modified method and based on ASTM standards. While the two driving force approaches correlate data well in the Paris region, they fail to correlate them in the threshold region. However, this correlation can be improved in the threshold region when a different alpha value from the Paris region is used. The authors indicated that two different mechanisms operate; one in the Paris region and another in the near threshold. Hence, they proposed to combine the two-parameter and crack closure approaches where Delta K is replaced by Delta K-eff (estimated by a new method proposed in this paper), which is shown to correlate the FCGR data for different stress ratios for annealed steel. The correlation for cold rolled condition shows improvement with the new approach but is not as good as for the annealed one. The author further suggests to modify K-max in the two-parameter approach. (C) 2015 Elsevier Ltd. All rights reserved.Peer Reviewe

Fatigue crack growth of a metastable austenitic stainless steel

The fatigue crack growth behavior of an austenitic metastable stainless steel AISI 301LN in the Paris region is investigated in this work. The fatigue crack growth rate curves are evaluated in terms of different parameters such as the range of stress intensity factor Delta K, the effective stress intensity factor Delta K-eff, and the two driving force parameter proposed by Kujawski K*.; The finite element method is used to calculate the stress intensity factor of the specimens used in this investigation. The new stress intensity factor solution has been proved to be an alternative to explain contradictory results found in the literature.; Fatigue crack propagation tests have been carried out on thin sheets with two different microstructural conditions and different load ratios. The influence of microstructural and mechanical variables has been analyzed using different mechanisms proposed in the literature. The influence of the compressive residual stress induced by the martensitic transformation is determined by using a model based on the proposal of McMeeking et al. The analyses demonstrate the necessity of including K-max as a true driving force for the fatigue crack growth. A combined parameter is proposed to explain the effects of different variables on the fatigue crack growth rate curves. It is found that along with residual stresses, the microcracks and microvoids are other factor affecting the fatigue crack growth rate in the steel studied. (C) 2015 Elsevier Ltd. All rights reserved.Peer Reviewe

Fatigue propagation of long cracks in metastable austenitic stainless steels

Fatigue crack growth of a metastable austenitic stainless steel was investigated in thin specimen under positive stress ratio. Annealed and Co l d rolled conditions were used to test the influence of the microstructure. The influence of load ratio and load history on propagation behavior was analyzed using the Elber`s closure approach, the Donald and Paris partial crack closure and the empirical Kujawski (∆K•Kmax) α parameter. Results show that load ratio effects could be explained by two parameters concepts . It see ms that the amount of martensite transformation is responsible for the observed differences in fatigue crack growth resistance

Estimation of the Plain High-Cycle Fatigue Propagation Resistance in Steels

In this work a method to estimate the high cyclic fatigue propagation life of steel specimens under constant loading is presented. This method is based in experimental evidence that the fatigue limit represents the threshold stress for the propagation of nucleated cracks, so that both the fatigue limit and the fatigue resistance depend on the effective resistance of the microstructural barriers that have to be overcome by the nucleated cracks. It is proposed also, that in those cases where the number of cycles that is necessary for the nucleation of the cracks can be neglected, the fatigue crack propagation life can be taken as an estimation of the total fatigue life. The high cycle fatigue propagation life of a structural steel of the type JIS 10C is estimated

Fatigue propagation of long cracks in metastable austenitic stainless steels

Fatigue crack growth of a metastable austenitic stainless steel was investigated in thin specimen under positive stress ratio. Annealed and Co l d rolled conditions were used to test the influence of the microstructure. The influence of load ratio and load history on propagation behavior was analyzed using the Elber`s closure approach, the Donald and Paris partial crack closure and the empirical Kujawski (∆K•Kmax) α parameter. Results show that load ratio effects could be explained by two parameters concepts . It see ms that the amount of martensite transformation is responsible for the observed differences in fatigue crack growth resistance