University of Illinois Urbana-Champaign

Design of lightweight fracture-resilient structures

Dabbara, Raghavendra Rohit

Content Files
DABBARA-THESIS-2024.pdf

Permalink

https://hdl.handle.net/2142/124468

Description

Title
Design of lightweight fracture-resilient structures
Author(s)
Dabbara, Raghavendra Rohit
Issue Date
2024-05-03
Director of Research (if dissertation) or Advisor (if thesis)
Geubelle, Philippe H
Department of Study
Aerospace Engineering
Discipline
Aerospace Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
M.S.
Degree Level
Thesis
Keyword(s)
Fracture, Topological Derivative, Ansys Mechanical, Optimization
Abstract
This thesis discusses the applications of the Topological Derivative (TD) method in the design of lightweight fracture-resilient structures and as a tool to identify the crack initiation parameters. The topological derivative describes the variation of a response functional to infinitesimal changes in topology, such as the introduction of an infinitesimal crack or hole. In previous work, Alidoost et al. developed an approximation of the energy release rate field in a three-dimensional domain associated with a small surface crack of any boundary location, direction, and orientation combination using the topological derivative which requires only one analysis of the non-cracked domain. The current work integrates the TD formulation into Ansys Mechanical to identify the crack initiation parameters of a half-penny-shaped crack on the surface of a three-dimensional body. First, comparisons have been made between the values calculated using the TD method, those available in the literature, and those computed using Ansys to demonstrate the accuracy of TD-based calculations. Later, a gradient-based optimization scheme is developed, which takes the stress state of a crack-free domain to calculate the energy release rate of a surface crack of any arbitrary rotation and creates an energy contour to locate the crack initiation coordinates and crack orientation. In the second part of this thesis, we developed a gradient-based shape optimization scheme built upon the topological derivative method. This work is a continuation to where a similar scheme to design fracture-resilient structures is developed. However, a fundamental limitation of formulation in was that it employed super ellipses to define the hole boundaries, which restricts the optimizer regarding the shapes it can produce. The current work utilizes a boundary generated by the zero level-set of a B-surface controlled by a grid of design points that are free to create any arbitrary shape to optimize the objective function. Another advantage of B-surfaces is that they can move the hole boundary to the optimal location in the domain irrespective of the starting point. Novel concavity and curvature constraints have also been developed to keep the domain smooth and void-free. Multiple examples have been provided to demonstrate the effectiveness of this method in finding the optimum.
Graduation Semester
2024-05
Type of Resource
Thesis
Handle URL
https://hdl.handle.net/2142/124468
Copyright and License Information
Copyright 2024 Raghavendra Dabbara

Owning Collections

Graduate Dissertations and Theses at Illinois PRIMARY
Graduate Theses and Dissertations at Illinois