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Research Papers

Minimizing Defects Between Adjacent Foils in Ultrasonically Consolidated Parts

[+] Author and Article Information
J. O. Obielodan, G. D. Janaki Ram

Department of Mechanical and Aerospace Engineering, Utah State University, Logan, UT 84322-4130

B. E. Stucker1

Department of Mechanical and Aerospace Engineering, Utah State University, Logan, UT 84322-4130brent.stucker@usu.edu

D. G. Taggart

Department of Mechanical Engineering, University of Rhode Island, Kingston, RI 02881

1

Corresponding author.

J. Eng. Mater. Technol 132(1), 011006 (Nov 03, 2009) (8 pages) doi:10.1115/1.3184033 History: Received December 01, 2008; Revised April 20, 2009; Published November 03, 2009; Online November 03, 2009

Two types of defects normally occur in ultrasonically consolidated parts: (i) Defects that occur between mating foils in successive layers (“type 1” defects) and (ii) defects that occur within a layer between two foils laid side-by-side (“type 2” defects). While some success has been achieved in minimizing type 1 defects, type 2 defects, however, have been given very little attention. Both types of defects are undesirable and should be minimized if ultrasonically consolidated parts are to be used in structural applications. This work describes an investigation of how to minimize type 2 defects in ultrasonically consolidated parts. According to our hypothesis, a foil being deposited must overlap the adjacent deposited foil by an optimum amount to ensure a defect-free joint between the two foils. Transverse tensile specimens were fabricated with various amounts of foil overlap (by changing the foil width setting) to test this hypothesis. Metallographic and fractographic studies showed a clear correlation between foil overlap, defect incidence, and tensile strength. It was found that a foil width setting of 23.81 mm helps minimize type 2 defects in ultrasonically consolidated Al 3003 parts using standard foils of 23.88 mm (equivalent to 0.94 in.) nominal width.

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Figures

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Figure 1

Micrograph showing type 1 interlayer bonding defects (arrowed)

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Figure 2

A micrograph with arrows showing type 2 defects between adjacent foils

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Figure 3

(a) Solidica Formation™ UC machine, (b) close-up view of ultrasonic sonotrode from below, and (c) schematic of the UC process

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Figure 4

End view of (a) gap and (b) overlap between two adjacent foils

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Figure 5

End view patterns of (a) 50% overlap and (b) random overlap foil arrangements

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Figure 6

Picture showing a layer with a popped foil, which was corrected by repeating the weld

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Figure 7

Ultrasonically consolidated tensile test specimens

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Figure 8

Representative micrographs for each set of tensile specimens: (a) longitudinal sample, (b) 2396 sample, (c) R2396 sample, (d) 2393 sample, (e) 2390 sample, (f) 2387 sample, (g) 2384 sample, (h) 2381 sample, and (i) 2378 sample

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Figure 9

Bar chart with error bars showing strength comparison for samples fabricated with different width settings

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Figure 10

Fractured surfaces of selected sample specimens: (a) view of the fractured surface of a longitudinal sample, (b) higher magnification view of the longitudinal sample, (c) view of the fractured surface of an R2396 sample, (d) view of the fractured surface of a 2390 sample, (e) view of the fractured surface of a 2384 sample, and (f) view of the fractured surface of a 2381 sample

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Figure 11

Fracture paths of some of the specimens: (a) side view of the fracture surface of a longitudinal sample, (b) side view of the fracture surface a 2390 sample, (c) side view of the fracture surface a 2384 sample, and (d) fracture line of a polished R2396 sample

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