Formability of Micro-Tubes in Hydroforming

Journal Article · Wed May 04 00:00:00 EDT 2011 · AIP Conference Proceedings

DOI:https://doi.org/10.1063/1.3589569· OSTI ID:21516766

Hartl, Christoph; Anyasodor, Gerald ^[1]; Lungershausen, Joern ^[2]

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1. Institute of Production, Cologne University of Applied Sciences, Betzdorfer Str. 2, 50679 Cologne (Germany)
2. Institute of Product and Production Engineering, University of Northwestern Switzerland, Klosterzelgstr. 2, 5210 Windisch (Switzerland)

Micro-hydroforming is a down-scaled metal forming process, based on the expansion of micro-tubes by internal pressurization within a die cavity. The objective of micro-hydroforming is to provide a technology for the economic mass production of complex shaped hollow micro-components. Influence of size effects in metal forming processes increases with scaling down of metal parts. Investigations into the change in formability of micro-tubes due to metal part scaling down constituted an important subject within the conducted fundamental research work. Experimental results are presented, concerning the analysis of the formability of micro-tubes made from stainless steel AISI 304 with an outer diameter of 800 {mu}m and a wall thickness of 40 {mu}m. An average ratio of tube wall thickness to grain size of 1.54 of up to 2.56 was analyzed. Miniaturised mechanical standard methods as well as bulge tests with internal hydrostatic pressurization of the tubular specimens were applied to analyze the influence of size-dependent effects. A test device was developed for the bulge experiments which enabled the pressurization of micro-tubes with internal pressures up to 4000 bar. To determine the attainable maximum achievable expansion ratio the tubes were pressurized in the bulge tests with increasing internal pressure until instability due to necking and subsequent bursting occurred. Comparisons with corresponding tests of macro-tubes, made from the here investigated material, showed a change in formability of micro-tubes which was attributed to the scaling down of the hydroforming process. In addition, a restricted applicability of existing theoretical correlations for the determination of the maximum pressure at bursting was observed for down-scaled micro-hydroforming.

• OSTI ID: 21516766
• Journal Information: AIP Conference Proceedings, Vol. 1353, Issue 1; Conference: ESAFORM 2011: 14. international ESAFORM conference on material forming, Belfast, Northern Ireland (United Kingdom), 27-29 Apr 2011; Other Information: DOI: 10.1063/1.3589569; (c) 2011 American Institute of Physics; ISSN 0094-243X
• Country of Publication: United States
• Language: English

Related Subjects

42 ENGINEERING
ANNEALING
CAVITIES
COMPARATIVE EVALUATIONS
CORRELATIONS
DIES
EQUIPMENT
EXPANSION
GRAIN SIZE
INSTABILITY
MASS
METALS
PLASTICITY
PRESSURIZATION
SCALING
STAINLESS STEELS
THICKNESS
TUBES
ALLOYS
CARBON ADDITIONS
DIMENSIONS
ELEMENTS
EVALUATION
HEAT TREATMENTS
HIGH ALLOY STEELS
IRON ALLOYS
IRON BASE ALLOYS
MECHANICAL PROPERTIES
MICROSTRUCTURE
SIZE
STEELS
TRANSITION ELEMENT ALLOYS