Modelling microstructural damage in AA7075 at large plastic strains (05/04/24)
Speaker and Affliation:
Dr. Abhishek Sarmah
McMaster University, Canada
When?
5th April, 2024 (Tuesday), 10.30 AM (India Standard Time)
Where
KPA Auditorium, Dept. of Materials Engineering, IISc, Bangalore
Abstract
Damage evolution in AA7075 is complex due to the presence of different second phase particles in the microstructure. Different particle stoichiometries, each with unique mechanical properties and geometrical features, can have a cumulative effect on damage with increasing applied loading.
A study of damage in such microstructures necessitates a hierarchical multiscale approach that effectively combines numerical modelling at different length scales with complementary experiments. Microscale finite element (FE) models created from actual microstructures using electron micrographs and tomography data, can capture real particle distribution along with key geometrical features of each particle stoichiometries. Additionally, nanoscale molecular dynamics (MD) simulations provide important cohesive properties describing interphases of various particles embedded in the matrix. Complementary experiments, such as in-situ scanning electron microscopy (SEM) and X-Ray computed tomography (XCT) tensile tests etc., yield important data necessary for both FE model calibration and validation.
Particle fracture marginally dominates particle decohesion. At low plastic strains, void nucleation is initiated by decohesion and fracture of coarse Fe-rich particles, which facilitate formation of localized deformation bands. At large plastic strains, elevated stresses within the localized bands facilitate decohesion and fracture of more resistant η and θ precipitates. The effect of particle morphology and size is significant. Void coalescence occurs along deformation bands driven by higher stresses due to accumulated plastic strain within the bands, in a process known as void sheeting.
About the Speaker
Abhishek Sarmah got his bachelor’s degree in Mechanical Engineering from Tezpur University, master’s degree in Materials Science and Engineering from IIT Gandhinagar and PhD from McMaster University. His research areas include numerical and experimental plasticity, damage mechanics, fracture mechanics, microstructure-property correlation, and material characterization. He was the 2021 recipient of The G.E. Orovas Memorial Scholarship. He has published his work in 6 international journals , 2 conferences and 1 book chapter.