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Research Papers: Other (Seals, Manufacturing)

Effect of Low-Frequency Modulation on Deformation and Material Flow in Cutting of Metals

[+] Author and Article Information
Ho Yeung

Center for Materials Processing
and Tribology,
School of Industrial Engineering,
Purdue University,
315 N. Grant Street,
West Lafayette, IN 47907
e-mail: hyeung@purdue.edu

Yang Guo

M4 Sciences LLC,
1201 Cumberland Avenue, Suite A,
West Lafayette, IN 47906
e-mail: yguo@m4sciences.com

James B. Mann

M4 Sciences LLC,
1201 Cumberland Avenue, Suite A,
West Lafayette, IN 47906
e-mail: jbmann@m4sciences.com

W. Dale Compton

Center for Materials Processing and Tribology,
School of Industrial Engineering,
Purdue University,
315 N. Grant Street,
West Lafayette, IN 47907
e-mail: dcompton@purdue.edu

Srinivasan Chandrasekar

Center for Materials Processing and Tribology,
School of Industrial Engineering,
Purdue University,
315 N. Grant Street,
West Lafayette, IN 47907
e-mail: chandy@purdue.edu

1Corresponding author.

Contributed by the Tribology Division of ASME for publication in the JOURNAL OF TRIBOLOGY. Manuscript received April 22, 2015; final manuscript received July 1, 2015; published online August 31, 2015. Assoc. Editor: George K. Nikas.

J. Tribol 138(1), 012201 (Aug 31, 2015) (9 pages) Paper No: TRIB-15-1131; doi: 10.1115/1.4031140 History: Received April 22, 2015; Revised July 01, 2015

The deformation field, material flow, and mechanics of chip separation in cutting of metals with superimposed low-frequency modulation (<1000 Hz) are characterized at the mesoscale using high-speed imaging and particle image velocimetry (PIV). The two-dimensional (2D) system studied involves a sharp-wedge sliding against the workpiece to remove material, also reminiscent of asperity contacts in sliding. A unique feature of the study is in situ mapping of material flow at high resolution using strain fields and streaklines and simultaneous measurements of tool motions and forces, such that instantaneous forces and kinematics can be overlaid onto the chip formation process. The significant reductions in specific energy obtained when cutting with modulation are shown to be a consequence of discrete chip formation with reduced strain levels. This strain reduction is established by direct measurements of deformation fields. The results have implications for enhancing sustainability of machining processes and understanding surface deformation and material removal in wear processes.

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References

Figures

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Fig. 1

Cylindrical (face) turning with feed modulation at phase angle φ showing formation of discrete chips: (a) schematic and (b) 2D model of (a) showing three successive traverses of the tool on the unfolded cylinder surface. The shaded region is the undeformed chip geometry. The actual TP has an inclination of ho/πd, which is ignored in the model as hoπd. For MAM with φ = π, the maximum h(t) = 2ho and R = Lo/2ho.

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Fig. 2

Discrete and continuous cutting regimes in φ − A/ho space. The pictures in the figure show successive TPs on the unfolded cylinder surface for the modulation conditions marked by diamond shapes. Undeformed chip shapes (shaded gray) are also shown for specific conditions.

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Fig. 3

Experimental setup for characterization of force, displacement, chip thickness, and material flow (by imaging). Seven signals are monitored and recorded simultaneously during the machining: modulation amplitude z(t), forces in three-directions (Fx, Fy, Fz), modulation actuator voltage (V) and current (I) inputs, and encoder pulse input. In addition, images of the chip formation and machining zone are obtained using the high-speed camera and analyzed by PIV.

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Fig. 4

TP, WP, and chip thickness (h(t)), as measured over a modulation cycle. TP and WP are derived from real-time measurements of the spindle speed/position and z(t); h(t) = WP − TP. Various points (1–8) of interest in the TP are marked for reference. The region h(t) = 0 corresponds to the noncutting part of the MAM cycle. Material: Al 6061-T6.

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Fig. 5

Forces and z(t) in MAM. This modulation cycle is the same as in Fig. 4 with corresponding labeling of the points. The CM force levels are shown as dotted lines for comparison.

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Fig. 6

High-speed images of chip formation in Al 6061-T6. Frames 1–8 are selected from an image sequence in the experiments of Figs. 4 and 5. The arrows attached to the tool show instantaneous tool velocity relative to the workpiece.

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Fig. 7

Effect of R on (left) specific energy (U, J/mm3) and (right) strain (〈ε〉) in cutting of Cu

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Fig. 8

Streaklines (top) and effective strain fields (bottom) in machining of Cu

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Fig. 9

Image of fully developed chip in CM showing uniform flow structure. Note the much larger chip thickness compared to those in Fig. 8 for same ho. This is indicative of larger strain in the CM chip.

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Fig. 10

Tool engagement with workpiece at different φ illustrating local rake angle effect; and corresponding values of U (J/mm3), 〈ε〉, and peak Fc (N). The boundary of the two shaded areas outlines the current TP while the two dotted lines show previous TPs. The dark shaded area is the chip cross section. (a) φ = 90 deg—peak Fc = 200, U = 1.8, and 〈ε〉  = 1.5, (b) φ = 180 deg—peak Fc = 240, U = 2.1, and 〈ε〉  = 1.55, and (c) φ = 270 deg—peak Fc = 280, U = 2.5, and 〈ε〉  = 1.7.

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Fig. 11

Streakline patterns (top) and strain fields (bottom) in machining of Cu

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