Quantitative Fracture Surface Analysis of Fatigue Crack Propagation Under Variable Amplitude Loading

The crack propagation behavior in a 2024 T351 Aluminum Alloy under constant amplitude loading has been studied. This study is complemented by quantitative microfractographic observations and energetic analysis. The obtained results under constant amplitude fatigue tests show that different crack propagation stages can be identified and correlated with the evolution of the characteristic features. In another hand, the energetic analysis shows that there is a discontinuous crack growth at low growth rates as against a cycle by cycle growth mechanism at high growth rates.

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“…A method for quantitative analysis of fatigue fracture surfaces is proposed, the following technique method presented in 14,15 is used.…”

Section: Methodsmentioning

confidence: 99%

Crack propagation under constant amplitude loading based on an energetic parameters and fractographic analysis

et al. 2012

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“…The change in behaviour from low to high growth rates was associated with a change in To determine the ECA loading a critical analysis of the global fracture surface appearance was carried out [15]. It was shown that the global fracture surface evolution characterized by the percentage area covered by striations, pseudo cleavage facets, and dimples depends upon the K, , value and the R ratio for CA conditions.…”

Section: Energy Based Eca Determinationmentioning

confidence: 99%

Equivalent Constant Amplitude Concepts Examined Under Fatigue Crack Propagation by Block Loading

Ranganathan

Desforges

1996

Fatigue Fract Eng Mat Struct

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Abstrad-Fatigue crack growth behaviour under block loading sequences has been studied on the aluminium alloy 2024 T351, using four different equivalent constant amplitude concepts. The root mean squared method gives acceptable results only for relatively long blocks. The equivalent method based on the Pans law (modified to take into account crack closure) gives good predictions for the observed growth rates as does Elbers' method. Finally, a new method based on energy considerations gives excellent results for the studied test conditions. NOMENCLATURE a = crack length BL = block loading da/dN =crack growth rate i = cycle number ECA =equivalent constant amplitude K = stress intensity factor KO = stress intensity factor at crack opening Kmus = maximum stress intensity factor in a block K,, K-= maximum and minimum K levels in a cycle m, rn' = slopes of Pans' law and Elbers' relation respectively N = number of cycles P = load Nq = number of equivalent cycles P , , = maximum load in a block P , , Pd =maximum and minimum loads at cycle i P = crack opening load B = effective mean level Q = energy dissipated per cycle Qi =energy dissipated at cycle i in a block Q,-, = enclosed energy RMS = root mean squared R = load ratio %p = equivalent R ratio R, = load ratio corresponding to cycle i in a block LIE = Elbers' efficiency factor VA = variable amplitude a = specimen compliance AK = stress intensity factor range Qm, = total energy dissipated per block AKem = effective AK 6 =crack mouth opening displacement 998 N. RANGANATHAN AND J. R. DESFORGES

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“…Ranganathan and coworkers [18] identified facets, striations, and dimples as salient features on fracture surfaces of three aluminum alloys and developed a grid technique to quantify their spatial distributions. Plots of percent area of the feature versus load parameters showed that peak to peak load ratio and maximum stress intensity factor are most important in determining fracture surface appearance.…”

Section: Introductionmentioning

confidence: 99%

Microstructural Failure Physics for Structural Failure Prognosis and Diagnosis

Shockey¹,

Simons²,

Kobayashi³

et al. 2003

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The public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, to Department of Defense, Washington Headquarters Services, Directorate for Information , 1215 Jefferson Davis Highway, Suite 1204, Arlington, VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to any penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number. PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ADDRESS. REPORT DATE (DD-MM-YY)2. REPORT TYPE 3. DATES COVERED (From -To) SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES) 10. SPONSORING/MONITORING AGENCY ACRONYM(S)AFRL SPONSORING/MONITORING AGENCY REPORT NUMBER(S) AFRL-ML-WP-TR-2004-4232 DISTRIBUTION/AVAILABILITY STATEMENTApproved for public release; release is unlimited. SUPPLEMENTARY NOTESReport contains color. ABSTRACTThe physics of microstructural deformation and failure in IN100 was investigated to improve existing tools for predicting and analyzing turbine disc failure. A finite element failure model of damage evolution under cyclic loads was developed and applied to simulate fatigue cracking in a compact tension specimen. A procedure was developed for determining from a fracture surface whether a failed component had experienced overloads and for estimating the overload magnitude and crack delay. A method for extracting and categorizing fracture surface features was developed to assist microstructure-based prognosis models and enable a data base approach for failure analysis. SUBJECT TERMS I. EXECUTIVE SUMMARYFracture physics based tools for predicting and diagnosing structural failure are needed to improve the readiness of DoD assets. The research effort reported here is aimed at improving understanding of the evolution of deformation and failure of material microstructure-an underlying component of practical tools for predicting the fitness of a structural system for the next mission and determining the cause and reconstructing the history of structural failure.In this project we performed the following:(1) Extended the development of a finite element microstructural failure model to simulate damage development in the microstructure of a nickel superalloy. The algorithm can be used in conjunction with continuum/empirical procedures in seeking more accurate predictions of crack growth.(2) Developed and demonstrated a procedure for determining from the fracture surface whether a failed component had experienced overloads, and for estimating the overload magnitude and crack delay. This procedure can be used to help determine the cause and history of a fa...

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Quantitative Fracture Surface Analysis of Fatigue Crack Propagation Under Variable Amplitude Loading

Cited by 6 publications

References 7 publications

Crack propagation under constant amplitude loading based on an energetic parameters and fractographic analysis

Crack propagation under constant amplitude loading based on an energetic parameters and fractographic analysis

Equivalent Constant Amplitude Concepts Examined Under Fatigue Crack Propagation by Block Loading

Microstructural Failure Physics for Structural Failure Prognosis and Diagnosis

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