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Research Papers

Study of Dimensional Repeatability and Fatigue Life for Deformation Machining Bending Mode

[+] Author and Article Information
J. Ziegert

e-mail: jziegert@uncc.edu
International Center for Automotive Research,
Clemson University, Greenville, SC 29607

B. Woody

Department of Mechanical Engineering,
University of North Carolina at Charlotte,
Charlotte, NC 28078

Department of Mechanical Engineering,
Northwestern University,
Evanston, IL 60208

1Present address: Assistant Professor, Indian Institute of Technology Ropar, Rupnagar, India.

2Corresponding author.

Contributed by the Manufacturing Engineering Division of ASME for publication in the JOURNAL OF MANUFACTURING SCIENCE AND ENGINEERING. Manuscript received July 1, 2011; final manuscript received May 13, 2012; published online November 12, 2012. Assoc. Editor: Jyhwen Wang.

J. Manuf. Sci. Eng 134(6), 061009 (Nov 01, 2012) (11 pages) doi:10.1115/1.4007716 History: Received July 01, 2011; Revised May 13, 2012

Deformation machining (DM) is a hybrid process which combines two emerging manufacturing processes, machining of thin structures and single-point incremental forming (SPIF). This hybrid process enables the creation of structures that have geometries that would be difficult or impossible to create using any either process alone. A comprehensive study of DM bending mode components has been carried out in this paper by studying their dimensional repeatability and fatigue life and comparing these with similar components fabricated with sheet metal. Experimental studies have been performed for part features created by the DM “bending mode” process, in which a thin vertical wall is machined on the part, and then incrementally bent with a single-point forming tool. The dimensional repeatability of DM components is compared with sheet metal components made by single-point incremental forming and conventional bending in a press brake [Agrawal et al., 2010, “Comparison of Dimensional Repeatability of Deformation Machined Components With Sheet Metal Components,” North American Manufacturing Research Conference, NAMRC 38, Transactions of NAMRI/SME, Vol. 38, pp. 571–576]. The results of this study indicate that the DM process is not capable of holding tolerances as tight as a standard milling process. This may be due to local variations in material properties that influence the yield strength and resulting springback. However, thin components created by DM are more repeatable than similar components created from sheet metal using SPIF, but less repeatable than components created by conventional bending of sheet metal. The second objective of the present work is to investigate whether components fabricated using the DM process can be considered for fatigue critical applications [Megahed et al., 1996, “Low-Cycle Fatigue in Rotating Cantilever Under Bending I: Theoretical Analysis,” Int. J. Fatigue, 18(6), pp. 401–412; Khalid et al., 2007, “Bending Fatigue Behavior of Hybrid Aluminum/Composite Drive Shafts,” Mater. Des., 28, pp. 329–334]. Studies were performed to experimentally compare the fatigue life of components fabricated by DM process with sheet metal components made by single-point incremental forming and conventional bending. Results of the study indicate that sheet metal SPIF components under the present loading conditions have significantly longer fatigue life of approximately 3900–5500 cycles, compared to DM and sheet metal conventionally bent components with approximately equal fatigue life of 2200–3900 cycles.

Copyright © 2012 by ASME
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References

Smith, S., Woody, B., Ziegert, J., and Huang, Y., 2007, “Deformation Machining—A New Hybrid Process,” CIRP Ann., 56(1), pp. 281–284. [CrossRef]
Agrawal, A., Ziegert, J., Smith, S., Woody, B., and Cao, J., 2010, “Comparison of Dimensional Repeatability of Deformation Machined Components With Sheet Metal Components,” North American Manufacturing Research Conference, NAMRC 38, Transactions of NAMRI/SME, Vol. 38, pp. 571–576.
Megahed, M. M., Eleiche, A. M., and Abd-Allah, N. M., 1996, “Low-Cycle Fatigue in Rotating Cantilever Under Bending I: Theoretical Analysis,” Int. J. Fatigue, 18(6), pp. 401–412. [CrossRef]
Khalid, Y. A., Mutasher, S. A., Sahari, B. B., and Hamouda, A. M. S., 2007, “Bending Fatigue Behavior of Hybrid Aluminum/Composite Drive Shafts,” Mater. Des., 28, pp. 329–334. [CrossRef]
Tlusty, J., Smith, S., and Winfough, W. R., 1996, “Techniques for the Use of Long Slender End Mills in High-Speed Milling,” CIRP Ann., 45(1), pp. 393–396. [CrossRef]
Smith, S., Winfough, W. R., and Halley, J., 1998, “The Effect of Tool Length on Stable Metal Removal Rate in High Speed Milling,” CIRP Ann., 47(1), pp. 307–310. [CrossRef]
Jeswiet, J., Micari, F., Hirt, G., Bramley, A., Duflou, J., and Allwood, J., 2005, “Asymmetric Single Point Incremental Forming of Sheet Metal,” CIRP Ann., 54(2), pp. 88–114. [CrossRef]

Figures

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Fig. 1

Deformation machining and its advantages

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Fig. 2

(a) and (b) Photographs of the component, (c) drawing of the component

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Fig. 3

Tool path adapted to create the component shown in Fig. 2

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Fig. 4

Setup for sheet metal SPIF components

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Fig. 13

Perpendicular distance of each point on side surface from the reference plane for sheet metal conventionally bent components

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Fig. 12

Perpendicular distance of each point on side surface from the reference plane for sheet metal SPIF components

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Fig. 11

Perpendicular distance of each point on side surface from the reference plane for deformation machined components

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Fig. 10

Angle of the top surface from the horizontal plane

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Fig. 9

Standard deviation of perpendicular distances, on top surface, from the reference plane for all three classes of components

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Fig. 8

Perpendicular distance of each point on top surface from the reference plane for sheet metal conventionally bent components

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Fig. 7

Perpendicular distance of each point on top surface from the reference plane for sheet metal SPIF components

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Fig. 6

Perpendicular distance of each point on top surface from the reference plane for deformation machined components

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Fig. 5

(a) Sheet metal SPIF component, (b) sheet metal conventional bending component

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Fig. 14

Standard deviation of perpendicular distances, on side surface, from the reference plane for all three classes of components

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Fig. 23

Number of cycles versus load (N) for sheet metal SPIF components

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Fig. 24

Photograph of a typical component (a) before and (b) after the fracture

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Fig. 15

Experimental setup on Instron model 1332

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Fig. 16

Photograph of the fixture used to hold the specimen

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Fig. 17

Displacement model used in fatigue testing

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Fig. 18

Stress state in the specimen at amplitude X = 1 mm

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Fig. 19

Stress state in the specimen at amplitude X = 0.65 mm

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Fig. 20

Number of cycles versus load (N) for deformation machined components

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Fig. 21

Initiation of fracture in a component during fatigue testing

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Fig. 22

Number of cycles versus load (N) for sheet metal conventionally bent components

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