Date of Award
5-28-2025
Publication Type
Thesis
Degree Name
M.A.Sc.
Department
Mechanical, Automotive, and Materials Engineering
Keywords
Aluminum; Blowforming; Oscillations frequenices; Superplastic; Fine Element Analysis
Supervisor
Daniel Green
Rights
info:eu-repo/semantics/embargoedAccess
Creative Commons License
This work is licensed under a Creative Commons Attribution-NonCommercial-No Derivative Works 4.0 International License.
Abstract
The superplastic deformation behaviour of AA5083 aluminium alloy sheets was examined through uniaxial tensile testing conducted to failure at 450°C, with a minor oscillating load superimposed on the monotonically increasing tensile load. Tensile tests were performed across a range of constant strain rates, from 0.001 to 0.3 s⁻¹, with the oscillatory load introduced as a sinusoidal function of fixed amplitude and frequency. Results demonstrated that the application of a minor oscillating load led to a relative enhancement in strain at fracture of approximately 20% to 50% across the strain rate spectrum investigated. Further studies assessed the influence of oscillation amplitude and frequency. Amplitudes varied from 0 N to 2 N, with a logarithmic increase in fracture strain observed as amplitude increased. Oscillation frequencies ranged from 5 Hz to 80 Hz, yielding a general improvement in elongation; however, no consistent trend was identified between frequency and elongation. The alloy’s inherent strain rate sensitivity at 450°C was also evident, characterized by a logarithmic decrease in fracture strain and a corresponding logarithmic increase in ultimate tensile strength with increasing strain rate. Notably, the presence of an oscillatory load did not alter this strain rate dependency. Scanning electron microscopy (SEM) was employed to evaluate the microstructural evolution before and after deformation. Observations confirmed grain boundary sliding as the dominant superplastic deformation mechanism in both conventional and oscillation-assisted tests. Finite Element Analysis (FEA) was conducted to simulate the tensile tests at their respective strain rates. The model demonstrated strong agreement with experimental results, exhibiting an average cumulative error of 4.8% and a validation metric of 95.2%, indicating high fidelity between the simulated and experimental data. Three material models were evaluated: the Johnson-Cook model, the conventional PowerLaw Model, and a modified PowerLaw Model incorporating strain-dependent material parameters. Among these, the modified PowerLaw Model yielded the most accurate predictions of tensile behavior across all strain rates. Subsequently, blow forming of a part was simulated using the modified PowerLaw Model. The predicted thickness distribution along the center line of the formed part was compared to experimental measurements, resulting in a cumulative error of approximately 6%, further validating the model. This model represents a valuable tool for simulating diverse test conditions and optimizing superplastic forming operations, thereby contributing to more efficient and accurate manufacturing of complex aluminum components.
Recommended Citation
Kiawi, Leo, "Experimental and Numerical Investigation of Oscillation-Enhanced Superplastic Forming of AA5083 Parts" (2025). Electronic Theses and Dissertations. 9735.
https://scholar.uwindsor.ca/etd/9735