Strain and damage interactions under plane strain conditions: 3D in situ measurements for different microstructures

The link between microstructure, strain heterogeneity, strain localization and damage under plane strain conditions is very complex. Yet, it is important to understand as forming limit diagrams exhibit the lowest strain level under plane strain conditions. Here, the interactions of strain and damage are assessed ahead of notches of thin sheet specimens where a plane strain condition is found, with no strain in crack propagation direction [1,2]. This region is investigated via in situ synchrotron laminography and digital volume correlation (DVC). Synchrotron laminography is a technique specifically developed for three-dimensional (3D) imaging of regions of interest inside laterally extended sheet specimens with micrometre resolution. DVC is carried out using the natural image contrast caused by iron rich intermetallic particles present in the alloy [3]. The study is carried out for different 2XXX series alloys with different tempers and associated work hardening, grain shapes and sizes as well as textures [4-6]. The development of early slant strain concentration bands is found for the majority of these conditions and further discussed using FE simulations. [1] A. Buljac, T. Taillandier-Thomas, T.F. Morgeneyer, L. Helfen, S. Roux, F. Hild, Slant strained band development during flat to slant crack transition in AA 2198 T8 sheet: in situ measurements, International Journal of Fracture, 200 (1) (2016) 49–62 [2] F. Bron, J. Besson, Simulation of the ductile tearing for two grades of 2024 aluminum alloy thin sheets”, Engineering Fracture Mechanics, 73 (2006) 1531-1552 [3] T.F. Morgeneyer, L. Helfen, H. Mubarak, F. Hild, 3D Digital Volume Correlation of Synchrotron Radiation Laminography images of ductile crack initiation: an initial feasibility study, Experimental Mechanics, 53 (2013) 543-556 [4] T.F. Morgeneyer, T. Taillandier-Thomas, L. Helfen, T. Baumbach, I. Sinclair, S. Roux, F. Hild, In situ observation of early strain localisation during failure of thin Al alloy (2198) sheet, Acta Materialia, 69 (2014) 78-91 [5] T.F. Morgeneyer, T. Taillandier-Thomas, A. Buljac, L. Helfen, F. Hild, On strain and damage interactions during tearing: in situ measurements and simulations for a ductile alloy (AA2139-T3), Journal of the Mechanics and Physics of Solids, 96 (2016) 550–571 [6] A. Buljac, F. Hild, L. Helfen, T.F. Morgeneyer, On deformation and damage micromechanisms in strong work hardening 2198 T3 aluminium alloy, Acta Materialia, 149 (2018) 29-45