Design of functionally graded compliant mechanisms using topology optimization

Conlan-Smith, Cian James

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https://hdl.handle.net/2142/97500 Copy

Description

Title

Design of functionally graded compliant mechanisms using topology optimization

Author(s)

Conlan-Smith, Cian James

Issue Date

2017-04-27

Director of Research (if dissertation) or Advisor (if thesis)

James, Kai A.

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)

• Topology optimization
• Compliant mechanism design
• Functionally graded materials
• Bio-inspired design
• Geometric non-linearity
• Stress constrained design

Abstract

This research applies topology optimization to create feasible functionally graded complaint mechanism designs with the aim of improving structural performance compared to traditional homogeneous compliant mechanism designs. Structural performance is assessed with respect to mechanical/geometric advantage and stress distributions. A novel modified solid isotropic material with penalization (SIMP) method is adopted for representing local element material properties in FGM structures. The method of moving asymptotes (MMA) is used in conjunction with adjoint sensitivity analysis to find the optimal distribution of material properties. Functionally graded materials (FGMs) have material properties that vary based on spatial position. Here, FGMs are implemented using two different resource constraints \textendash \ one on the mechanism's volume and the other on the integral of the Young's modulus distribution throughout the design domain. Two sets of results are presented \textendash \ polymeric and metallic designs. Geometric non-linear analysis based on the Neo-Hookean model for hyperelastic materials is used to solve the mechanics problem for polymeric designs, whereas analysis of metallic materials is solved using conventional linear finite element analysis (FEA). Tensile tests are performed to obtain the material properties used in the analysis. To ensure an accurate representation when using linear FEA, metallic designs are subject to stress constraints. A novel method of stress-based design for FGM structures is presented where local yield strength is a function of local Young's modulus. Results suggest that FGMs can achieve the desired improvements in structural performance for certain designs and can also have a favorable effect on the von Mises stress distribution.

Graduation Semester

2017-05

Type of Resource

text

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http://hdl.handle.net/2142/97500

Copyright and License Information

Copyright 2017 Cian Conlan-Smith

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