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Special Section: Micromanufacturing

# Effects of Crystallographic Anistropy on Orthogonal Micromachining of Single-Crystal Aluminum

[+] Author and Article Information
Benjamin L. Lawson, Nithyanand Kota

Department of Mechanical Engineering, Carnegie Mellon University, Pittsburgh, PA 15213

O. Burak Ozdoganlar1

Department of Mechanical Engineering, Carnegie Mellon University, Pittsburgh, PA 15213ozdoganlar@cmu.edu

1

Corresponding author.

J. Manuf. Sci. Eng 130(3), 031116 (Jun 03, 2008) (11 pages) doi:10.1115/1.2917268 History: Received May 30, 2006; Revised December 17, 2007; Published June 03, 2008

## Abstract

Anisotropy of workpiece crystals has a significant effect in micromachining since the uncut chip thickness values used in micromachining are commensurate with characteristic dimensions of crystals in crystalline materials. This paper presents an experimental investigation on orthogonal micromachining of single-crystal aluminum at different crystallographic orientations for varying uncut chip thicknesses and cutting speeds using a diamond tool. Micromachining forces, specific energies, effective coefficient of friction, shear angles, shear stresses, and chip morphology were examined for six crystallographic orientations at uncut chip thicknesses ranging from $5μmto20μm$ and cutting speeds ranging from $5mm∕sto15mm∕s$. Three distinct types of forces were observed, including steady (Type-I), bistable (Type-II), and fluctuating (Type-III) force signatures. The forces were seen to vary by as much as threefold with crystallographic orientation. Although the effect of cutting speed was small, the uncut chip thickness was seen to have a significant orientation-dependent effect on average forces. Chip morphology, analyzed under scanning electron microscopy, showed shear-front lamella, the periodicity of which was seen to vary with crystallographic orientations and uncut chip thicknesses.

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## Figures

Figure 1

(a) Diagram of the single-crystal cutting process and (b) projection of the crystallographic orientations onto the standard stereographic triangle

Figure 2

Diagram of the cutting planes and cutting directions used during the experimentation

Figure 3

The experimental testbed

Figure 4

Cutting (C), thrust (T), and lateral (L) forces for (a) (12 5 0) facet for 5mm∕s and 20μm, (b) (6 7 0) facet with 10mm∕s and 20μm, (c) (3 2 0) facet with 5mm∕s and 5μm, and (d) (2 7 0) facet with 5mm∕s and 5μm

Figure 5

Forces from three repetitions on (2 7 0) facet for 5mm∕s speed and 5μm prescribed uncut chip thickness

Figure 6

The specific cutting energies for (a) 5mm∕s, (b) 10mm∕s, and (c) 15mm∕s; and the specific thrust energies for (d) 5mm∕s, (e) 10mm∕s, and (f) 15mm∕s

Figure 7

The effective coefficient of friction for (a) 5mm∕s, (b) 10mm∕s, and (c) 15mm∕s

Figure 8

Shear angles for (a) 5mm∕s, (b) 10mm∕s, and (c) 15mm∕s.

Figure 9

Shear stresses for (a) 5mm∕s, (b) 10mm∕s, and (c) 15mm∕s

Figure 10

SEM images of chips from the (2 7 0) orientation illustrating the perspectives and magnifications used in analysis

Figure 11

SEM image of the face of the chips produced on the (2 7 0) orientation

Figure 12

Shear-front lamella at 20μm prescribed uncut chip thickness and 15mm∕s speed for (a) (2 9 0), (b) (2 7 0), (c) (4 11 0), (d) (12 5 0), (e) (3 2 0), and (f) (6 7 0) crystallographic orientations

Figure 13

450× magnification SEM image illustrating the difference between the apparent thickness of the lamella from the face and the profile views for the (2 9 0) orientation at 10mm∕s and 20μm prescribed uncut chip thickness

Figure 14

SEM image comparing lamellae and chip thicknesses before (top) and after (bottom) the transition for the bistable case of the (6 7 0) orientation with v=10mm∕s and hcp=20μm

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