Driving forces for localized corrosion‐to‐fatigue crack transition in Al–Zn–Mg–Cu

Research on fatigue crack formation from a corroded 7075-T651 surface provides insight into the governing mechanical driving forces at microstructure-scale lengths that are intermediate between safe life and damage tolerant feature sizes. Crack surface marker-bands accurately quantify cycles (Ni) to form a 10–20 μm fatigue crack emanating from both an isolated pit perimeter and EXCO corroded surface. The Ni decreases with increasing-applied stress. Fatigue crack formation involves a complex interaction of elastic stress concentration due to three-dimensional pit macro-topography coupled with local micro-topographic plastic strain concentration, further enhanced by microstructure (particularly sub-surface constituents). These driving force interactions lead to high variability in cycles to form a fatigue crack, but from an engineering perspective, a broadly corroded surface should contain an extreme group of features that are likely to drive the portion of life to form a crack to near 0. At low-applied stresses, crack formation can constitute a significant portion of life, which is predicted by coupling macro-pit and micro-feature elastic–plastic stress/strain concentrations from finite element analysis with empirical low-cycle fatigue life models. The presented experimental results provide a foundation to validate next-generation crack formation models and prognosis methods.

[1]  Robert P. Wei,et al.  Statistical analysis of constituent particles in 7075-T6 aluminum alloy , 2006 .

[2]  J. E. Ritter,et al.  Stress Intensity Factor for a Peripherally Cracked Spherical Cap , 2005 .

[3]  M. Cerit,et al.  Numerical investigation on stress concentration of corrosion pit , 2009 .

[4]  Ian M. Robertson,et al.  The effect of hydrogen on dislocation dynamics , 1999 .

[5]  O. Ostash,et al.  Local Strain Measurement for Prediction of Fatigue Macrocrack Initiation in Notched Specimens , 2003 .

[6]  T. C. Lindley,et al.  The effect of porosity on the fatigue life of cast aluminium-silicon alloys , 2004 .

[7]  C. Laird,et al.  Fatigue crack nucleation based on a random slip process—I. Computer model , 1993 .

[8]  Gerd Heber,et al.  A geometric approach to modeling microstructurally small fatigue crack formation: I. Probabilistic simulation of constituent particle cracking in AA 7075-T651 , 2008 .

[9]  J. Toribio,et al.  K‐DOMINANCE CONDITION IN HYDROGEN ASSISTED CRACKING: THE ROLE OF THE FAR FIELD , 1997 .

[10]  R. Buchheit,et al.  Electrochemical behavior and localized corrosion associated with Al7Cu2Fe particles in aluminum alloy 7075-T651 , 2006 .

[11]  Alan Turnbull,et al.  Challenges in modelling the evolution of stress corrosion cracks from pits , 2009 .

[12]  J. Papazian,et al.  Observations of fatigue crack initiation in 7075-T651 , 2010 .

[13]  J. Scully,et al.  Hydrogen Solubility, Diffusion and Trapping in High Purity Aluminum and Selected Al-Base Alloys , 2000 .

[14]  Margery Hoffman,et al.  Corrosion and fatigue research — structural issues and relevance to naval aviation , 2001 .

[15]  J. Toribio,et al.  Fractographic and numerical study of hydrogen–plasticity interactions near a crack tip , 2006 .

[16]  Kumar V. Jata,et al.  Effects of pitting corrosion on the fatigue behavior of aluminum alloy 7075-T6: modeling and experimental studies , 2001 .

[17]  I. Papadopoulos.  A HIGH‐CYCLE FATIGUE CRITERION APPLIED IN BIAXIAL AND TRIAXIAL OUT‐OF‐PHASE STRESS CONDITIONS , 1995 .

[18]  Gerd Heber,et al.  DDSim: A hierarchical, probabilistic, multiscale damage and durability simulation system – Part I: Methodology and Level I , 2009 .

[19]  V. Ozoliņš,et al.  Hydrogen in aluminum: First-principles calculations of structure and thermodynamics , 2004 .

[20]  D. Knowles,et al.  Predicting fatigue crack initiation through image-based micromechanical modeling , 2007 .

[21]  S. Spence,et al.  The EIFS distribution for anodized and pre-corroded 7010-T7651 under constant amplitude loading , 2005 .

[22]  G. K. Cole,et al.  The Implications of Corrosion with respect to Aircraft Structural Integrity. , 1997 .

[23]  Richard P. Gangloff,et al.  Fatigue crack formation and growth from localized corrosion in Al–Zn–Mg–Cu , 2009 .

[24]  Robert P. Wei,et al.  Fracture mechanics and surface chemistry studies of fatigue crack growth in an aluminum alloy , 1980 .

[25]  P. Papanikos,et al.  Corrosion-induced hydrogen embrittlement of 2024 and 6013 aluminum alloys , 2004 .

[26]  D. McDowell,et al.  A δJ-BASED APPROACH TO BIAXIAL FATIGUE , 1992 .

[27]  J. Lankford,et al.  THE EFFECT OF WATER VAPOR ON FATIGUE CRACK TIP MECHANICS IN 7075-T651 ALUMINUM ALLOY , 1983 .

[28]  C. Sarrazin-Baudoux,et al.  Some critical aspects of low rate fatigue crack propagation in metallic materials , 2010 .

[29]  Mark F. Horstemeyer,et al.  Three-dimensional finite element analysis using crystal plasticity for a parameter study of microstructurally small fatigue crack growth in a AA7075 aluminum alloy , 2009 .

[30]  S. Pantelakis,et al.  Fatigue and damage tolerance behaviour of corroded 2024 T351 aircraft aluminum alloy , 2005 .

[31]  S. Agnew,et al.  Fatigue crack surface crystallography near crack initiating particle clusters in precipitation hardened legacy and modern Al–Zn–Mg–Cu alloys , 2011 .

[32]  Ne Ashbaugh,et al.  The role of air in fatigue load interaction , 2003 .

[33]  A. Fatemi,et al.  A CRITICAL PLANE APPROACH TO MULTIAXIAL FATIGUE DAMAGE INCLUDING OUT‐OF‐PHASE LOADING , 1988 .

[34]  D. McDowell,et al.  Microstructure-sensitive computational modeling of fatigue crack formation , 2010 .

[35]  William A. Herman,et al.  A SIMPLIFIED LABORATORY APPROACH FOR THE PREDICTION OF SHORT CRACK BEHAVIOR IN ENGINEERING STRUCTURES , 1988 .

[36]  Ming Gao,et al.  Chemical and metallurgical aspects of environmentally assisted fatigue crack growth in 7075-T651 aluminum alloy , 1988 .

[37]  Robert S. Piascik,et al.  Environmental fatigue of an Al-Li-Cu alloy: Part II. Microscopic hydrogen cracking processes , 1993, Metallurgical and Materials Transactions A.

[38]  David L. McDowell,et al.  Simulation-based strategies for microstructure-sensitive fatigue modeling , 2007 .

[39]  K. Lam,et al.  Multiple crack interaction and its effect on stress intensity factor , 1991 .

[40]  Phil E. Irving,et al.  Corrosion pit size distributions and fatigue lives: a study of the EIFS technique for fatigue design in the presence of corrosion , 2004 .

[41]  Ming Gao,et al.  A transmission electron microscopy study of constituent-particle-induced corrosion in 7075-T6 and 2024-T3 aluminum alloys , 1998 .

[42]  Dierk Raabe,et al.  Microstructural aspects of crack nucleation during cyclic loading of AA7075-T651 , 2009 .

[43]  Richard P. Gangloff,et al.  Environmental Fatigue-Crack Surface Crystallography for Al-Zn-Cu-Mg-Mn/Zr , 2008 .

[44]  M. Liao,et al.  Fatigue modeling for aircraft structures containing natural exfoliation corrosion , 2007 .

[45]  R. Gangloff,et al.  Environment and microstructure effects on fatigue crack facet orientation in an AlLiCuZr alloy , 1996 .

[46]  Michael Ortiz,et al.  A micromechanical model of cyclic deformation and fatigue-crack nucleation in f.c.c. single crystals , 1997 .

[47]  S. Suresh,et al.  Influence of corrosion deposits on near-threshold fatigue crack growth behavior in 2xxx and 7xxx series aluminum alloys , 1982 .

[48]  N. Noda,et al.  Stress Concentration Factor Formulas Useful for All Notch Shapes in a Flat Test Specimen Under Tension and Bending , 2002 .

[49]  J. Hirth,et al.  Effects of hydrogen on the properties of iron and steel , 1980 .

[50]  L. Kunz,et al.  Small cracks: nucleation, growth and implication to fatigue life , 2003 .

[51]  Robert P. Wei,et al.  A probability model for the growth of corrosion pits in aluminum alloys induced by constituent particles , 1998 .

[52]  L. Keer,et al.  The effect of plastic deformation on crack initiation in fatigue , 1991 .

[53]  F. Dunne,et al.  High– and low–cycle fatigue crack initiation using polycrystal plasticity , 2004, Proceedings of the Royal Society of London. Series A: Mathematical, Physical and Engineering Sciences.

[54]  D. McDowell,et al.  Polycrystal orientation distribution effects on microslip in high cycle fatigue , 2003 .

[55]  P. Prevéy,et al.  Restoring Fatigue Performance of Corrosion Damaged Aa7075-T6 and Fretting in 4340 Steel with Low Plasticity Burnishing , 2002 .

[56]  Bård Wathne Tveiten,et al.  Surface roughness characterization for fatigue life predictions using finite element analysis , 2008 .

[57]  Nao-Aki Noda,et al.  Variation of the stress intensity factor along the crack front of interacting semi-elliptical surface cracks , 2001 .

[58]  P. Swann,et al.  Pre-exposure embrittlement and stress corrosion failure in AlZnMg Alloys , 1976 .

[59]  A. K. Vasudevan,et al.  Classification of environmentally assisted fatigue crack growth behavior , 2009 .

[60]  R. A. Oriani.  Whitney Award Lecture—1987: Hydrogen—The Versatile Embrittler , 1987 .

[61]  Fatigue-life calculations on pristine and corroded open-hole specimens using small-crack theory , 2009 .

[62]  R. N. Parkins,et al.  Reduced ductility of high-strength aluminium alloy during or after exposure to water , 1979 .

[63]  E. Lee,et al.  The effect of microstructure and environment on fatigue crack closure of 7475 aluminum alloy , 1984 .

[64]  Rj Bucci,et al.  Predicting fatigue life of pre-corroded 2024-T3 aluminum from breaking load tests , 2004 .

[65]  S. Lynch.  Mechanisms of environmentally assisted cracking in AlZnMg single crystals , 1982 .

[66]  R. Reed,et al.  Stress concentration due to a hyperboloid cavity in a thin plate , 1970 .

[67]  Y. Bréchet,et al.  Study of fatigue damage in 7010 aluminum alloy , 1998 .

[68]  C.J.E. Smith.  Management of Corrosion of Aircraft , 2010 .

[69]  P. R. Underhill,et al.  Fatigue crack growth from corrosion damage in 7075-T6511 aluminium alloy under aircraft loading , 2003 .

[70]  S. A. Fawaz.  Equivalent initial flaw size testing and analysis of transport aircraft skin splices , 2003 .

[71]  Ted Belytschko,et al.  Crack shielding and amplification due to multiple microcracks interacting with a macrocrack , 2007 .

[72]  C. Buckley,et al.  Hydrogen in aluminum , 1997 .

[73]  R. Buchheit,et al.  Evaluation of a simple microstructural-electrochemical model for corrosion damage accumulation in microstructurally complex aluminum alloys , 2009 .

[74]  B. Hillberry,et al.  A model of initial flaw sizes in aluminum alloys , 2001 .

[75]  R. P. Gangloff,et al.  6.02 – Hydrogen-assisted Cracking , 2003 .

[76]  R. Sunder.  Fatigue as a process of cyclic brittle microfracture , 2005 .

[77]  James M. Larsen,et al.  Effect of initiation feature on microstructure-scale fatigue crack propagation in Al–Zn–Mg–Cu , 2012 .

[78]  Richard P. Gangloff,et al.  Effect of corrosion severity on fatigue evolution in Al–Zn–Mg–Cu , 2010 .

[79]  D. G. Harlow,et al.  The effect of constituent particles in aluminum alloys on fatigue damage evolution: Statistical observations , 2010 .

[80]  Richard P. Gangloff,et al.  Environment-exposure-dependent fatigue crack growth kinetics for Al–Cu–Mg/Li , 2007 .

[81]  B. M. Hillberry,et al.  Initiation and shape development of corrosion-nucleated fatigue cracking , 2007 .

[82]  H. Neuber.  Theory of Stress Concentration for Shear-Strained Prismatical Bodies With Arbitrary Nonlinear Stress-Strain Law , 1961 .

[83]  G. Pressouyre,et al.  Trap theory of Hydrogen embrittlement , 1980 .

[84]  William Braisted,et al.  Fatigue life prediction of corrosion-damaged high-strength steel using an equivalent stress riser (ESR) model. Part II: Model development and results , 2009 .

[85]  B. Craig,et al.  Multiple fatigue crack growth in pre-corroded 2024-T3 aluminum , 2005 .