Special Section Papers

Accuracy of Conventional Finite Element Models in Bulk-Forming of Micropins From Sheet Metal

[+] Author and Article Information
M. Kraus, T. Hufnagel, M. Merklein

Department Mechanical Engineering,
Institute of Manufacturing Technology,
Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU),
Egerlandstr. 13,
Erlangen 91058, Germany

Contributed by the Manufacturing Engineering Division of ASME for publication in the JOURNAL OF MICRO-AND NANO-MANUFACTURING. Manuscript received November 12, 2018; final manuscript received February 13, 2019; published online April 11, 2019. Assoc. Editor: Martin Jun.

J. Micro Nano-Manuf 7(1), 010902 (Apr 11, 2019) (5 pages) Paper No: JMNM-18-1047; doi: 10.1115/1.4042965 History: Received November 12, 2018; Revised February 13, 2019

The ongoing miniaturization trend in combination with increasing production and functional volume leads to a rising demand for metallic microparts. Bulk forming of microparts from sheet metal provides the potential for mass production of those components by an extensive simplification of the handling. The advantage of a high production rate contrasts with the disadvantage of a low utilization of material. In this context, it is necessary to investigate suitable measures to increase the material utilization. To save cost intensive trial and error tests, numerical analysis could be an appropriate method for a basic process investigation. In this work, a validation with experimental results in the macro- and microscale was used to investigate the eligibility of the finite element method (FEM) for a basic process analysis. For a high transferability, the finite element (FE) models were validated for various tribological conditions and material states. The results reveal that there is a high agreement of the experimental and numerical results in the macroscale. In microscale, conventional FEM shows inaccuracies due to the negligence of size effects in the discretization of the process. This fact limits the application of conventional FE-programs. Furthermore, the results show that lubricated and dry formed blanks lead to the same friction force and process result in the microscale. In addition, the basic formability of the prestrengthened pins in further forming stages was experimentally demonstrated.

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Fig. 1

Procedure for this study

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Fig. 2

Grain size of Cu-OFE blanks

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Fig. 3

Numerical and experimental determined force–displacement curves by forming annealed Cu-OFE for (a) macroscale and (b) microscale

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Fig. 4

Validation of the pin height

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Fig. 5

Experimental determined hardness distribution of the deformed workpiece compared with the strain hardening of the simulation for annealed Cu-OFE

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Fig. 6

Micrographs of the specimens (Cu-OFE; annealed)

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Fig. 7

Exemplary process chain for multistage forming of small metallic components from the sheet metal (Cu-OFE; as-rolled)



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