Etapas del proyecto 1. Etapa 1

At the Chair of Forming Technologies at the University of Siegen vibrations damping composite sheets were investigated regarding their forming limits.

During forming, failure modes like delamination, displacement and buckling of the cover sheets occur. The mechanical properties of the metal layers are determined by uniaxial

Metal Forming – Process, Tools, Design 106

tensile tests. Tensile shear tests are carried out under variation of the shear velocity. The numerical calculations are calibrated with the tensile shear test. To verify the adhesive description, maximal tension and displacement in normal direction will be proved.

A plastomechanical preliminary design has been developed for sandwich sheets with a viscoelastic and shear transmitting interlayer. Especially displacement and delamination are described with preliminary design and verified with numerical calculations. But this plastomechanical preliminary design shows improvable deliverables. Especially the inaccuracies of the strain distribution over thickness and bending angle should be improved. Therefore many experimental forming tests with different materials are planned. Instead of symmetrical sandwiches, significant improvements can be achieved by e.g. reducing the thickness of the outer metal layer. With increasing the number of sheets the total thickness of the composite can be achieved. On the other hand thin inner layers tend to buckling. The buckling tendency should be investigated further.

Author details

Bernd Engel and Johannes Buhl*

University of Siegen, Chair of Forming Technology, Siegen, Germany

Acknowledgement

A part of this present Investigation has been financially supported of Bundesministerium für Wirtschaft und Technologie (BMWi).

8. References

[1] Roos E, Maile K. Werkstoffkunde für Ingenieure Berlin Heidelberg: Springer; 2005. [2] Lange K. Umformtechnik: Blechbearbeitung, Handbuch für die Industrie und

Wissenschaft Berlin Heidelberg: Springer-Verlag; 1990.

[3] Jandel B, Meuthen AS. Coil Coating Wiesbaden: Vieweg & Sohn Verlag; 2008.

[4] Antiphon. antiphon® MPMTM - vibration damping sandwich material. [Online].; 2010 [cited 2010 04 21. Available from: www.antiphon.se.

[5] ThyssenKrupp Steel. Bondal® Körperschalldämpfender Verbundwerkstoff. [Online].; 2009 [cited 2010 04 21. Available from: www.thyssenkrupp-steel.com.

[6] Engel B, Buhl J. Metal Forming of Vibration-Damping Composite Sheets. steel research international. 2011;(DOI: 10.1002/srin.201000205).

[7] Hellinger V. New Possibilities for Improved Bending of Vibration Damping Laminated Sheets. CIRP annals: manufacturing technology. 1999.

[8] Habenicht G. Kleben Heidelberg: Springer-Verlag; 2009.

formability of brittle sheet metal in multilayer metallic sheets. CIRP Annals - Manufacturing Technology 59. 2010: p. 287–290.

[14] Ohashi Y, Wolfenstine J, Koch R, Sherby O. Fracture Behavior of a Laminated Steel– Brass Composite in Bed Tests. Materials Science and Engineering. 1992.

[15] Köhler M. Plattiertes Stahlblech Düsseldorf: Stahl-Informations-Zentrum; 2006.

[16] Deutsches Institut für Normung. DIN 50125 Prüfung metallischer Werkstoffe - Zugproben. In. Berlin: Beuth Verlag GmbH; 2004.

[17] Swift HW. Plastic Instability under Plane Stress. Journal of the Mechanics and Physics of Solids 1, Department of Engineering, University of Sheffield UK. 1952: p. 1–18. [18] Groche P, von Breitenbach G, Steinheimer R. Properties of Tubular Semi-finished

Products for Hydroforming. steel research international 76, No. 2/3, Stahleisen GmbH, Düsseldorf. 2005.

[19] Normenausschuss Materialprüfung (NMP), Materials Testing Standards Committee. Prüfung von Klebverbindungen- Probenherstellung Berlin: Beuth Verlag GmbH; 2006. [20] Normenausschuss Materialprüfung (NMP) MTSC. Strukturklebstoffe - Bestimmung des

Scherverhaltens struktureller Klebungen - Teil 2: Scherprüfung für dicke Fügeteile (ISO 11003-2:2001, modifiziert); Deutsche Fassung EN 14869-2:201 Berlin: Beuth Verlag GmbH; 2011.

[21] Nutzmann M. Umformung von Mehrschichtverbundblechen für Leichtbauteile im Fahrzeugbau Aachen: Shaker Verlag; 2008.

[22] Alfano G, Crisfield MA. Finite element interface models for the delamination analysis of laminated composites: mechanical and computational issues. International Journal for Numerical Methods in Engineering. 2001.

[23] Hashimoto K, Ohwue T, Takita M. Formability of steel-plastic laminated sheets. In Group 1bcotIDDR. Controlling sheet metal forming processes. Metals Park, Ohio: ASM International; 1988.

[24] Takiguchi M, Yoshida F. Effect of Forming Speed on Plastic Bending of Adhesively Bonded Sheet Metals. JSME International Journal Series A. 2004.

[25] Engel B, Buhl J. Roll Forming of Vibration-Damping Composite Sheets. In The 8th international Conference and Workshop on numerical simulation of 3d sheet metal forming processes.: AIP Conference Proceedings, Volume 1383, pp. 733-741; 2011.

Metal Forming – Process, Tools, Design 108

[26] Banks J. AutoSimulations, Inc., Atlanta, GA 30067, U.S.A. Introduction to simulation. In P. A. Farrington HBNDTSaGWEe. Proceedings of the 1999 Winter Simulation Conference. Atlanta,: Print ISBN: 0-7803-5780-9; 1999.

[27] M. Weiss, B. F. Rolfe, M. Dingle, J. L. Duncan. Elastic Bending of Steel-Polymer-Steel (SPS) Laminates to a Constant Curvature. Journal of Applied MechANICS. 2006. [28] Takiguchi M, Yoshida F. Deformation Characteristics and Delamination Strength of

Adhesively Bonded Aluminium Alloy Sheet under Plastic Bending. JSME International Journal. 2003.

[29] Hudayari Ġ. Theoretische und experimentelle Untersuchungen zum Walzrunden von plattierten und nicht-plattierten Grobblechen Siegen : Höpner und Göttert; 2001. [30] Fritzen CP. Technische Mechanik II (Elastomechanik) Siegen: UNI SIEGEN; 2006. [31] Kreulitsch, H. Voest-Alpine Stahl Linz GmbH. Formgebung von Blechen und Bändern

durch Biegen Wien: Springer; 1995.

[32] Lerch R, Sessler G, Wolf D. Technische Akustik: Grundlagen Und Anwendungen Heidelberg: Springer; 2008.

[33] Möser M, Heckl M, Kropp W, Cremer L. Körperschall: Physikalische Grundlagen und Technische Anwendung Heidelberg: Springer; 2010.

[34] Pflüger M, Brandl F, Bernhard U, Feitzelmayer K. Fahrzeugakustik Wien New York: Springer; 2010.

[35] Knaebel M, Jäger H, Mastel R. Technische Schwingungslehre Wiesbaden: Vieweg+Teubner | GWV Fachverlage GmbH; 2009.

[36] Ross D, Ungar E, Kerwin E.. Damping of Flexural Vibrations by Means of Viscoelastic Laminate. Structural Damping. 1959.

[37] Mead DJ, Markus S. The forced vibration of a three-layer, damped sandwich beam with arbitrary boundary conditions. Journal of Sound and Vibration. 1969.

[38] Sadasiva Rao YVK, Nakra BC. Vibrations of Unsymmetrical Sandwich Beams and Plates With Viscoelastic Cores. Journal Sound Vibrations. 1974.

[39] Mead DJ. A comparison of some equations for the flexural vibration of damped sandwich beams. Journal Sound Vibration. 1982.

[40] Dewangan P. Passive viscoelastic conatrained layer damping for structural application. National Institude of Technology Rourkela. 2009.

© 2012 Shimizu et al., licensee InTech. This is an open access chapter distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/48296

1. Introduction

Microforming technology has been receiving much attention as one of the most economical mass production methods for micro components (Geiger et al., 2001). Especially, metal foils have the great advantage to produce high-aspect three-dimensional shapes by miniaturizing the process dimensions of sheet metal forming technologies.

Since the relative ratio of the surface area to the volume of metal foils becomes significantly larger with miniaturization, tribological behaviour is of great significance for the micro- sheet formability. Over the last decade, basic researches of the size effect of tribology in microforming have been performed worldwide (Vollertsen et al., 2009). One of the representative reports of scale effect in bulk metal forming is the double-cup-extrusion (DCE) test (Engel, 2006). By scaling the diameter of CuZn15 specimen from 4mm to 0.5mm, the scaled DCE test was conducted. Identified with a FE analysis, the significant increase of the friction factor m with decreasing the scale was confirmed. Another reports regard to the size effect of coefficient of friction in bulk metal forming was done by Putten et al. (Putten et al., 2007). The scaled plane strain compression tests were conducted with the aim of application on flat rolling. As similar tendency as DCE test, the friction coefficient increased with decreasing scale dimension.

The work focused on the sheet metal forming has been done by Vollertsen and Hu (Vollertsen & Hu, 2006, 2007). The strip drawing method allowing the determination of friction parameters for micro-deep drawing was developed. It was shown that the friction coefficient again increased with decreasing the size. Additionally, the scale dependent friction coefficient was determined by strip drawing test and the calculated value was introduced to the FEM simulation. Especially if the non-uniform pressure distribution was

Metal Forming – Process, Tools, Design 112

taken into account in the deep drawing simulation, relative good results were derived for different dimensions (Vollertsen et al., 2008).

These tendencies of the increasing friction coefficient with decreasing dimension in many experiment of forming process have been mainly explained by the “lubricant pocket model” (Engel, 2006). The lubricant pocket model is the only one available model for the description of size effects in lubricated friction (Vollertsen et al., 2009). The basic feature of describing the size effect based on this model is that the increasing relative ratio of OLPs (Open lubricant pockets), which cannot keep the lubricant. With decreasing the scale dimension, the relative ratio of OLPs increases and it results in the increase of friction resistance (Engel, 2006). As overviewed above, the overall investigation suggests the low effect of lubricant in micro-scale region.

From the other point of view of:

1. Dirt handling of the tiny work pieces, 2. Contamination of fine products,

3. Lubricant clogging between the micro scale clearance, and

4. Unstable formability due to the high sensitivity of the variation of lubricant quantity or the effects of meniscus and viscous forces,

the microforming process would be preferred not to use a lubricant (Aizawa et al., 2010). In response to these findings, the activity of the application of the coating treatment on the die substrate, targeting the microforming, is gradually increasing. Hanada et al. fabricated a micro-die utilizing chemical vapour deposition (CVD) diamond coating (Hanada et al, 2003). The surface roughness of the diamond dies was approximately 10 nm, and the diamond dies showed good lubricating ability in the microcoining of polymethylmethacrylate (PMMA). Fuentes et al. investigated the tribological properties of Al thin foils (0.2mm nominal thickness) in sliding contact with PVD-coated carbide forming- tools for microforming (Fuentes et al., 2006). Uncoated, CrN-coated and WC-C-coated tools were tested, using a pin-on-disk configuration. They have shown that the sticking of Al was retarded using low friction magnetron sputtered WC-C-coated carbides. Fujimoto et al. proposed a novel surface treatment process for micro-dies (Fujimoto et al., 2006). They developed a high-energy ion beam irradiation for finishing die-surfaces and a CVD diamond-like carbon (DLC) was coated on the die surface after finished. They have succeeded to reduce the surface roughness by ion beam irradiation process and the high wear resistance of the DLC coating was demonstrated with the 50,000 shots of the microbending tests. In the recent work on the coating treatment for micro die, an impressive coating technology was proposed by Aizawa et al. (Aizawa et al., 2010). The nano-laminated DLC coating was invented and applied to improve the coated tool life, where delamination of coated layers was significantly retarded or saved by optimum interlayer and nano-scopic lamination of DLC sublayers. Micro stamping system, which included the severe wearing condition of ironing and bending step, was employed in the 10,000 shots progressive dry micro-stamping, where SKD-11 punches underwent severe wear in stamping of AISI-304 stainless sheets or pure titanium sheets.

is contributed by:

• Adhesion of the sliding surface,

• Deformation of surface asperities in contact, • Plowing by wear particles and hard asperities, and

• So called, ratchet mechanism, which is due to a lateral force required for the contact asperities to climb against each other.

μa:Adhesion component

μp:Plowing component

μd: Deformation component

μr: Ratchet component

Deformation

of surface

asperities in

contact

Adhesion of the

sliding surface

Plowing by wear

particles and

hard asperities

Hard

Soft

Hard

Soft

Hard

Soft

Hard

Soft

Climbing of

contact

asperities

against each

other

As illustrated in Fig.1, the geometry of surface asperities would contribute to the real area of contact and sliding resistance, and it is a dominant factor over the dry friction behaviour. However, basic research on the meso-scale tribological behaviour of dry friction, such as the contact interaction of the surface asperities, is not well discussed, especially for micro-sheet metal forming (Vollertsen et al. 2009). In view of the surface functionalization and the structural optimisation, construction of the surface design guide based on the

Metal Forming – Process, Tools, Design 114

characterization of tribological behaviour under dry friction is a pressing need for the further high precision forming process design.

In view of the significant importance of tribology in micro-sheet metal forming, this chapter creates an overview of the effect of surface topography of tools and workpieces on micro- sheet formability. Starting with an introduction of the newly developed micro-deep drawing experimental system and that of a finite element simulation model with surface asperities, the impact of surface topography on the tiny micro-scale forming behaviour is discussed.