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Title: A microstructure based multiscale computational framework for metal forming
Author: Asim, Umair Bin
ISNI:       0000 0004 7967 6731
Awarding Body: University of Aberdeen
Current Institution: University of Aberdeen
Date of Award: 2019
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The aerospace industry is relying on the lightweight and high-strength metallic alloys for a very long time. The two types of alloys that take the precedence are the aluminium and titanium alloys. The aluminium and titanium alloys which are used in the airframe applications, are ductile in nature and they are characterized by their ability to undergo considerable plastic deformation before failure because of which they can be formed into required shapes. The failure of such materials are of a cone-and-cup type and the fracture surface is wavy because of the mechanisms of void nucleation, growth and coalescence, signifying ductile failure. A rigorous representative volume element (RVE) based void growth study of voids of known porosity, size, shape and orientation was carried out in single crystals and bicrystals of aluminium and titanium alloys at different stress triaxialities using fully validated crystal plasticity finite element method. It has been reported that the voids tend to nucleate on the phase boundaries in the titanium alloys. The RVE study of void growth in hexagonal close-packed single crystal -phase and on the interface of the bicrystal of and (body centred cubic) phases were carried out in case of titanium alloys. The effects of the Burger orientation relation and phase boundary inclination on void growth were also investigated in the bicrystals. It was found that all these parameters govern the void growth. The results obtained from the RVE study were quantified and a model is proposed to predict the void growth depending on the equivalent strain, stress triaxiality and PBI in case of bicrystals. A constitutive model is developed, implemented and validated in a commercially available finite element analysis software which extends current crystal plasticity theory to account for the effects of void growth and coalescence in single and bicrystals.
Supervisor: Siddiq, Amir ; Kartal, Mehmet Sponsor: University of Aberdeen
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Aerospace engineering ; Alloys ; Elastic analysis (Engineering) ; Plasticity