Three-dimensional quantitative in situ study of crack initiation and propagation in AA6061 aluminum alloy sheets via synchrotron laminography and finite-element simulations

Ductile crack initiation and propagation in AA6061 aluminum alloy for a fatigue precrack have been studied in situ via synchrotron radiation computed laminography, a technique specifically developed for three-dimensional imaging of laterally extended sheet specimens with micrometer resolution. The influence of the microstructure, i.e. due to the presence of coarse Mg2Si precipitates and iron-rich intermetallics, on the void nucleation process is investigated. Coarse Mg2Si precipitates are found to play a preponderant role in the void nucleation and ductile fracture process. Void growth and void coalescence are then observed and quantified by three-dimensional image analysis during crack initiation and propagation. Parameters for a Gurson–Tvergaard–Needleman micromechanical damage model are identified experimentally and validated by finite-element simulations.

[1]  Eric Maire,et al.  In situ observation of ductile fracture using X-ray tomography technique , 2011 .

[2]  Mark F. Horstemeyer,et al.  A void–crack nucleation model for ductile metals , 1999 .

[3]  J. Leblond,et al.  A criterion for the onset of void coalescence under combined tension and shear , 2012 .

[4]  D. M. Tracey,et al.  On the ductile enlargement of voids in triaxial stress fields , 1969 .

[5]  T. Morgeneyer,et al.  Flat to slant ductile fracture transition: Tomography examination and simulations using shear-controlled void nucleation , 2011 .

[6]  I. Sinclair,et al.  Experimental and numerical analysis of toughness anisotropy in AA2139 Al-alloy sheet , 2009 .

[7]  Mark F. Horstemeyer,et al.  Quantification of damage evolution in a 7075 aluminum alloy using an acoustic emission technique , 2011 .

[8]  James C. Newman,et al.  Fracture mechanics testing on specimens with low constraint––standardisation activities within ISO and ASTM , 2005 .

[9]  J. Devaux,et al.  Bifurcation Effects in Ductile Metals With Nonlocal Damage , 1994 .

[10]  Yang Shen,et al.  Experimental and numerical characterization of anisotropic damage evolution of forged Al6061-T6 alloy , 2011 .

[11]  A. Needleman,et al.  Analysis of the cup-cone fracture in a round tensile bar , 1984 .

[12]  Françoise Peyrin,et al.  Observation of microstructure and damage in materials by phase sensitive radiography and tomography , 1997 .

[13]  F. M. Beremin.  Cavity formation from inclusions in ductile fracture of A508 steel , 1981 .

[14]  A. Pineau,et al.  Ductile rupture in thin sheets of two grades of 2024 aluminum alloy , 2004 .

[15]  Thomas Pardoen,et al.  Thickness dependence of cracking resistance in thin aluminium plates , 1999 .

[16]  C. Donne,et al.  Fracture and damage mechanics modelling of thin-walled structures – An overview , 2009 .

[17]  R. H. Stone,et al.  Discussion of “metallurgical factors affecting fracture toughness of aluminum alloys” , 1975 .

[18]  F. Delannay,et al.  Micromechanics of room and high temperature fracture in 6xxx Al alloys , 2007 .

[19]  Tony Warwick,et al.  Synchrotron radiation instrumentation : Eighth international conference on synchrotron radiation instrumentation, San Francisco, California, 25-29 August 2003 , 2004 .

[20]  François Hild,et al.  3D Digital Volume Correlation of Synchrotron Radiation Laminography Images of Ductile Crack Initiation: An Initial Feasibility Study , 2013 .

[21]  I. Sinclair,et al.  Synchrotron radiation computed laminography for polymer composite failure studies , 2010, Journal of synchrotron radiation.

[22]  John W. Hutchinson,et al.  A computational approach to ductile crack growth under large scale yielding conditions , 1995 .

[23]  J. Baruchel,et al.  On the implementation of computed laminography using synchrotron radiation. , 2011, The Review of scientific instruments.

[24]  Stephen T. Newman,et al.  State of the art electrical discharge machining (EDM) , 2003 .

[25]  James C. Newman,et al.  The effect of crack tunneling on crack growth: experiments and CTOA analyses , 2003 .

[26]  Arnaud Weck,et al.  Visualization by X-ray tomography of void growth and coalescence leading to fracture in model materials , 2008 .

[27]  J. Martin,et al.  The effect of dispersoids on the ductile fracture toughness of AlMgSi alloys , 1983 .

[28]  A. J. Moffat,et al.  In situ synchrotron computed laminography of damage in carbon fibre-epoxy [90/0](s) laminates , 2010 .

[29]  A. Gurson.  Plastic flow and fracture behavior of ductile materials incorporating void nucleation, growth and interaction , 1988 .

[30]  A. Gokhale,et al.  Void growth in 6061-aluminum alloy under triaxial stress state , 2003 .

[31]  Thomas Pardoen,et al.  Anisotropic ductile fracture of Al 2024 alloys , 2008 .

[32]  Jacques Besson,et al.  Anisotropic ductile fracture: Part I: experiments , 2004 .

[33]  M. Sutton,et al.  Three-Dimensional Crack Growth in Ductile Materials: Effect of Stress Constraint on Crack Tunneling , 2008 .

[34]  H. Wafai,et al.  Interaction between anisotropic plastic deformation and damage evolution in Al 2198 sheet metal , 2010 .

[35]  A. Needleman,et al.  Void Nucleation Effects in Biaxially Stretched Sheets , 1980 .

[36]  P. Houizot,et al.  Use of the mark-tracking method for optical fiber characterization , 2011 .

[37]  K. Jata,et al.  The influence of Mn dispersoid content and stress state on ductile fracture of 2134 type Al alloys , 1989 .

[38]  A. Pineau,et al.  Crack initiation and stable crack growth resistance in A508 steels in relation to inclusion distribution , 1981 .

[39]  C. Nan,et al.  Experiment and multiscale modeling of the coupled influence of constituents and precipitates on the ductile fracture of heat-treatable aluminum alloys , 2005 .

[40]  Jacques Besson,et al.  Ductile tearing of pipeline-steel wide plates: II. Modeling of in-plane crack propagation , 2001 .

[41]  E. Maire,et al.  Damage studies in heterogeneous aluminium alloys using X-ray tomography , 2005 .

[42]  R. A. Jeniski.  Effects of Cr addition on the microstructure and mechanical behavior of 6061-T6 continuously cast and rolled redraw rod , 1997 .

[43]  Jacques Besson,et al.  Simulation of the ductile tearing for two grades of 2024 aluminum alloy thin sheets , 2006 .

[44]  J. Rice,et al.  CONDITIONS FOR THE LOCALIZATION OF DEFORMATION IN PRESSURE-SENSITIVE DILATANT MATERIALS , 1975 .

[45]  Jacques Besson,et al.  Anisotropic ductile fracture: Part II: theory , 2004 .

[46]  J. Martin,et al.  The effects of dispersoids upon the micromechanisms of crack propagation in AlMgSi alloys , 1979 .

[47]  A. Weck,et al.  Experimental investigation of void coalescence in metallic sheets containing laser drilled holes , 2008 .

[48]  I. Sinclair,et al.  Ductile crack initiation and propagation assessed via in situ synchrotron radiation-computed laminography , 2011 .

[49]  Thomas Pardoen,et al.  Micromechanics-based model for trends in toughness of ductile metals , 2003 .

[50]  Michael A. Sutton,et al.  Investigation of crack tunneling in ductile materials , 2010 .

[51]  E. Maire,et al.  Damage quantification in aluminium alloys using in situ tensile tests in X-ray tomography , 2011 .

[52]  Lukas Helfen,et al.  Efficient Volume Reconstruction for Parallel-Beam Computed Laminography by Filtered Backprojection on Multi-Core Clusters , 2013, IEEE Transactions on Image Processing.

[53]  P. W. Bridgman.  Studies in large plastic flow and fracture : with special emphasis on the effects of hydrostatic pressure , 1964 .