Thesis
Numerical investigation on fatigue and corrosion behaviour of 3-D printed structures
- Creator
- Rights statement
- Awarding institution
- University of Strathclyde
- Date of award
- 2022
- Thesis identifier
- T16388
- Person Identifier (Local)
- 201879508
- Qualification Level
- Qualification Name
- Department, School or Faculty
- Abstract
- Structural failure can be a challenging and unpredictable phenomenon to detect, especially under the combination of mechanical loads and environmental conditions. Additive manufacturing has recently gained interest because of its capability of producing complex metal geometries directly from a digital model. However, despite its high potential, the process induced imperfections, like pores, microstructural changes due to the layer-by-layer manufacturing, and residual stresses could significantly reduce the material resistance and impact the crack growth behaviour. Therefore, the combinations of those manufacturing factors add another complexity layer that needs further investigation with advanced and sophisticated numerical techniques. The numerical techniques commonly used to investigate the structural behaviour are primarily based on classical continuum mechanics with the governing equations in the form of partial differential equations. However, such methods become inadequate in the presence of the field’s discontinuities, such as cracks, especially when dealing with additively manufactured materials. To overcome these limitations, in this dissertation, a new continuum mechanics theory (i.e., Peridynamics) based on integro-differential equations is utilised. Peridynamics already proved its applicability and effectiveness in modelling discontinuities such as crack nucleation and propagation, micro-cracks interaction problems, polycrystalline fracture, stress-corrosion cracking and simulations of fracture phenomena under different loading conditions, accounting for potential failure due to corrosion. Nonetheless, its applicability and accuracy for the investigation of additively manufactured materials still remain to be assessed. For this reason, this work focused on the application of Peridynamics on fatigue and corrosion fatigue problems in additively manufactured materials utilized in marine environment. The developed methodology showed its capability of evaluating the effects of porosity on fatigue nucleation and propagation process. Additionally, the application of the columnar granularity and residual stresses in the structure proved the anisotropy in the material response and their substantial impact on fatigue crack growth rates. Lastly, a numerical framework for corrosion fatigue problems, which combines the Peridynamics fatigue crack growth model and Peridynamics diffusion model is proposed in order to couple the mechanical and diffusion fields existing in the material due to the impact of environmental fatigue. The developed numerical corrosion fatigue model showed the capability of the framework to predict the corrosion fatigue crack growth rates by capturing the effects of the loading frequency on the fatigue performance. The numerical results have been validated against the experimental data available in the literature and verified with the commonly used commercial Finite Element Analysis numerical solutions.
- Advisor / supervisor
- Oterkus, Selda
- Oterkus, Erkan
- Resource Type
- DOI
Relations
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