Research Papers

Capitalizing on Heterogeneity and Anisotropy to Design Desirable Hardware That is Difficult to Reverse Engineer

[+] Author and Article Information
Stephen P. Harston

Department of Mechanical Engineering, Brigham Young University, Provo, UT 84602sharston@gmail.com

Christopher A. Mattson1

Department of Mechanical Engineering, Brigham Young University, Provo, UT 84602mattson@byu.edu

Brent L. Adams

Department of Mechanical Engineering, Brigham Young University, Provo, UT 84602b_l_adams@byu.edu


Corresponding author.

J. Mech. Des 132(8), 081001 (Jul 12, 2010) (11 pages) doi:10.1115/1.4001874 History: Received March 26, 2009; Revised May 24, 2010; Published July 12, 2010; Online July 12, 2010

This paper presents a method for treating material microstructure (crystallographic grain size, orientation, and distribution) as design variables that can be manipulated—for common or exotic materials—to identify the unusual material properties and to design devices that are difficult to reverse engineer. A practical approach, carefully tied to proven manufacturing strategies, is used to tailor the material microstructures by strategically orienting and laminating thin anisotropic metallic sheets. The approach, coupled with numerical optimization, manipulates the material microstructures to obtain the desired material properties at designer-specified locations (heterogeneously) or across the entire part (homogeneously). A comparative study is provided, which examines various microstructures for a simple fixed geometry. These cases show how the proposed approach can provide hardware with enhanced mechanical performance in a way that is disguised within the microscopic features of the material microstructure.

Copyright © 2010 by American Society of Mechanical Engineers
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Figure 1

Ultrasonic consolidation process with scanning electron microscope image of grains at the layer interface

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Figure 2

Reference frames defined for the part, lamina, and crystal

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Figure 3

Microstructure-to-material-properties flowchart

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Figure 4

Property closure of yield strength versus compliance for Ni 201. The outer loop is the property closure, the triangle represents an isotropic material with the same material properties in all directions, and the inner loop represents all material properties that can be obtained by applying the rotation and lamination theory to a material that starts with the microstructure shown as a star. The middle loop represents the material properties that can be obtained when the layer rotations are not constrained to a single plane.

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Figure 5

(a) Flowchart of a generic optimization framework to obtain improved performance with common materials; (b) an optimization framework specific to the structural stiffness

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Figure 6

Geometry and boundary conditions for the L-beam case study

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Figure 7

(a) Finite element mesh for the isotropic, single layer, and four layer L-beams; (b) finite element mesh for the heterogeneous L-beam

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Figure 8

Graphical representation of the feasible design space obtainable with rotations and laminations of the copper material used for substudies V and VI



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