Research Papers

Investigating Discrepancies in Vibration Bending Fatigue Behavior of Additively Manufactured Titanium 6Al-4V

[+] Author and Article Information
Onome Scott-Emuakpor

Air Force Research Laboratory,
Aerospace Systems Directorate,
Wright-Patterson AFB, OH 45433
e-mails: onomese@hotmail.com; onome.scott-emuakpor.1@us.af.mil

Casey Holycross

Air Force Research Laboratory,
Aerospace Systems Directorate,
Wright-Patterson AFB, OH 45433
e-mail: caseyholycross@gmail.com

Tommy George

Air Force Research Laboratory,
Aerospace Systems Directorate,
Wright-Patterson AFB, OH 45433
e-mail: tommy.george@us.af.mil

Luke Sheridan

Air Force Research Laboratory,
Aerospace Systems Directorate,
Wright-Patterson AFB, OH 45433
e-mail: luke.sheridan.1@us.af.mil

Emily Carper

Air Force Research Laboratory,
Aerospace Systems Directorate,
Wright-Patterson AFB, OH 45433
e-mail: emily.carper@us.af.mil

Joseph Beck

Perceptive Engineering Analytics, LLC,
Minneapolis, MN 55418
e-mail: Joseph.A.Beck@peanalyticsllc.com

1Corresponding author.

Contributed by the Materials Division of ASME for publication in the Journal of Engineering Materials and Technology. Manuscript received July 13, 2018; final manuscript received February 12, 2019; published online March 12, 2019. Assoc. Editor: Anastasia Muliana. The work was authored in part by a U.S. Government employee in the scope of his/her employment. ASME disclaims all interest in the U.S. Government’s contribution.

J. Eng. Mater. Technol 141(4), 041002 (Mar 12, 2019) (9 pages) Paper No: MATS-18-1208; doi: 10.1115/1.4042955 History: Received July 13, 2018; Accepted February 12, 2019

The vibration bending fatigue life uncertainty of additively manufactured titanium (Ti) 6Al-4V specimens is studied. In this investigation, an analysis of microscopic discrepancies between ten fatigued specimens paired by stress amplitude is correlated with the bending fatigue life scatter. Through scanning electron microscope (SEM) analysis of fracture surfaces and grain structures, anomalies and distinctions such as voids and grain geometries are identified in each specimen. These data along with previously published results are used to support assessments regarding bending fatigue uncertainty. The understanding gained from this study is important for the future development of a predictive vibration bending fatigue life model.

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Fig. 1

Insert specimen for vibration bending fatigue test (mm) [9]

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Fig. 2

Vibration bending fatigue test setup [15]

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Fig. 3

Hybrid specimen with instrumentation location [15]

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Fig. 4

Build types with maximum normal strain directions experienced during fatigue and tensile testing [9]

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Fig. 5

Vibration bending fatigue life comparisons of LPBF Ti 6Al-4V builds [9]

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Fig. 6

PCA z-score versus stress amplitude: horizontal specimen [9]

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Fig. 7

PCA z-score versus stress amplitude: vertical specimen [9]

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Fig. 8

PCA z-score versus stress amplitude: thick specimens [9]

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Fig. 9

Fracture surface images: (a) H-INS-2 and (b) H-INS-8

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Fig. 10

Fracture surface images: (a) V-INS-2 and (b) V-INS-11

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Fig. 11

Fracture surface images: (a) TH-INS-2 and (b) TH-INS-4

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Fig. 12

Fracture surface images: (a) H-INS-4 and (b) H-INS-6

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Fig. 13

Fracture surface images: (a) V-INS-4 and (b) V-INS-6

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Fig. 14

Keyence contour plot of void on specimen V-INS-2 fracture surface

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Fig. 15

Elliptical hole in the flat plate

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Fig. 16

Notch sensitivity factors for alpha–beta titanium alloys

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Fig. 17

Ti 6Al-4V fatigue data with stress concentration factor correction

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Fig. 18

Micrographs of Ti 6Al-4V: (a) cold-rolled, (b) thick, (c) vertical, and (d) horizontal

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Fig. 19

Ti 6Al-4V fatigue data with lamellae variation error bars

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Fig. 20

Fracture surface and void of fatigue specimen V-INS-6

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Fig. 21

Crack growth plot comparing LPBF data with cast Ti 6Al-4V properties

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Fig. 22

Ti 6Al-4V energy release rate comparisons between LPBF data in earlier sections and previously published data from Nalla et al. [45]



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