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Study of the influence of contact geometry and contact pressure on sliding distance to galling in the Slider-On-Flat-Surface wear tester
Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.ORCID iD: 0000-0002-1225-0598
Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.ORCID iD: 0000-0002-9441-2502
Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.ORCID iD: 0000-0001-6029-2613
2013 (English)In: Tribology Transactions, ISSN 1040-2004, E-ISSN 1547-397X, Vol. 56, no 6, p. 1137-1145Article in journal (Refereed) Published
Abstract [en]

One of the major causes of tool failure in sheet metal forming is wear in the form of galling. Galling is gradual buildup of adhered sheet material on the tool and leads to unacceptable scratches on the sheet surface and to components that fail to meet tolerances. Because it is difficult to reproduce operational and interactional conditions in laboratory test equipments it is hard to test, model, and predict galling initiation.Here the authors examine how changes from elliptical to line contact geometry influenced galling initiation under dry sliding by using a slider-on-flat surface (SOFS) wear tester. A micro clean tool steel was tested against ferritic low-strength and martensitic high-strength steel sheets.The sliding distance to galling initiation was extracted from friction data and verified by scanning electron microscopy (SEM) observations. The presence of adhesive wear on worn tools after completed tests was used as a criterion. Experimental results showed that the elliptical contact causes galling quicker than the line contact.Applicability of experimental results depends on the relevance of test conditions, so contact pressures calculated for the described tests were compared to calculated contact pressures in a semi-industrial U-bending test and to literature data relevant to industrial applications. Good agreement between values observed for SOFS and for most selected industrial applications was found, which assume that contact pressures typical for most common industrial applications can be successfully simulated by selection of tool geometry and normal load in the SOFS tester.

Place, publisher, year, edition, pages
London: Taylor & Francis, 2013. Vol. 56, no 6, p. 1137-1145
Keywords [en]
galling, wear, sheet metal forming, friction
National Category
Materials Engineering
Research subject
Materials Engineering
Identifiers
URN: urn:nbn:se:kau:diva-8970DOI: 10.1080/10402004.2013.827766ISI: 000324614500023OAI: oai:DiVA.org:kau-8970DiVA, id: diva2:467769
Available from: 2011-12-19 Created: 2011-12-19 Last updated: 2017-12-08Bibliographically approved
In thesis
1. On tool steel, surface preparation, contact geometry and wear in sheet metal forming
Open this publication in new window or tab >>On tool steel, surface preparation, contact geometry and wear in sheet metal forming
2011 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

In sheet metal forming operations the life length of the production equipment islargely dependent on the wear of the tools that are in direct contact with the sheet.One form of adhesive wear where some sheet material gets transferred to the tool, alsoknown as galling, is the most common cause of tool failure. The transferred materialsticks firmly to the tool and will scratch subsequent sheets and increase friction, renderingthem anywhere from aesthetically unsightly to completely ripped apart. Withcareful combination of several parameters the tools production life can be significantlyextended. The surface preparation of the tools has a large influence on the tool life, thesurface has to be smooth and yet not without texture. It was shown in strip reductiontesting that the orientation as well as the depth of the surface texture left by polishinginfluenced the tool life and that a texture perpendicular to the sliding direction was toprefer. The geometry of the forming tool is also a parameter to take into account as itinfluences the tool life not only by changing the contact pressure but also in itself. Ina sliding against flat sheet test rig a lower contact pressure increased the sliding distanceto galling. When two different geometries were compared at the same contactpressure it was found that there was a difference in tool life. As to the tool itself thematerial it’s made of influences the wear rate and tool life. Different tool steels wasinvestigated in sliding wear against metal sheets; Vancron 40 performed better thanVanadis 6 and S290PM performed better than a AISI M2 grade steel.

Place, publisher, year, edition, pages
Karlstad: Karlstads universitet, 2011. p. 47
Series
Karlstad University Studies, ISSN 1403-8099 ; 2011:64
Keywords
Wear, Galling, sheet metal, deep drawing, Tool steel, surface preparation, Friction
National Category
Materials Engineering
Research subject
Materials Engineering
Identifiers
urn:nbn:se:kau:diva-8883 (URN)978-91-7063-403-1 (ISBN)
Presentation
2012-01-13, 21A342, Karlstads universitet, Karlstad, 09:12 (English)
Opponent
Supervisors
Available from: 2011-12-20 Created: 2011-12-08 Last updated: 2014-09-04Bibliographically approved
2. Adhesive wear testing and modelling of tool steels sliding against sheet metals
Open this publication in new window or tab >>Adhesive wear testing and modelling of tool steels sliding against sheet metals
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Sheet metal forming is a manufacturing method used because of its versatility. Sheets are plastically deformed by a tool to create a product. A tool is expected to last for several 100,000 forming operations and efforts are made to optimize the tools. A common type of wear referred to as galling is the adhesion of sheet material to the tools. This problem has become more prevalent as new high strength sheet materials have been developed at the same time as lubricants have become heavily regulated. This has forced the development of new tool steels with improved resistance to galling. There are many parameters influencing the response to galling. In this work the influence of surface preparation, contact geometry, material selection and lubrication has been investigated. The surface of the forming tools has a large influence on the tools effective life. To refurbish a forming tool is expensive and often requires special shops and hand polishing. The influence on galling of different surface preparations suited for sheet metal forming was investigated using a strip-reduction equipment. The contact conditions of a tool sliding against metal sheets were investigated using FE models. The contact conditions were calculated for a U-bending test and for a sliding-on-flat-surface wear tester. The results were compared to those found in literature. One model incorporated the surface roughness of a sheet as measured by optical profilometry. The strength of the interface between the tool and the sheet material determine if material can be transferred onto the tool. The interface between the tool and adhered sheet material was closely studied using transmission electron microscopy of thin lamellas produced by focused ion beam milling. This showed sheet material adhering to the tool without the formation of an interlayer. Finally, several different combinations of tool steels and sheet materials were tested with regards to their ability to withstand galling.

Abstract [en]

Baksidestext:

Sheet metal forming can be used to produce a wide range of products but the initial costs are high as the forming tools are expensive. Wear of the tools in the form of galling i.e. the adhesion of tiny pieces of sheet material to the tools has become more prevalent as high strength sheet materials have been developed and lubricants have become heavily regulated.

In this work the influence on galling of surface preparation, contact geometry, material selection and lubrication has been investigated. It was found that tool surfaces should be polished as rougher surfaces quickly picked up material that adhered to the tools and subsequently scratched the sheets. The strength of the interface between the tool and the sheet material determine if material can be transferred onto the tool. The interface was studied using bright field transmission electron microscopy and the sheet material was found to adhere to the tool without the formation of an interlayer. The conditions under which galling occurs were studied using a slider on flat surface wear tester and several different material combinations were tested with regards to their galling resistance. The contact conditions of the test equipment were also modeled using FE models to better understand the strains of the materials involved.

Place, publisher, year, edition, pages
Karlstad: Karlstads universitet, 2014. p. 64
Series
Karlstad University Studies, ISSN 1403-8099 ; 2014:25
Keywords
Adhesive wear
National Category
Materials Engineering
Research subject
Materials Engineering
Identifiers
urn:nbn:se:kau:diva-31793 (URN)978-91-7063-556-4 (ISBN)
Public defence
2014-05-09, 21A342, Eva Erikssonsalen, Karlstad, 10:15 (English)
Opponent
Supervisors
Available from: 2014-05-05 Created: 2014-03-30 Last updated: 2014-05-05Bibliographically approved

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Lindvall, Fredrik W.Gåård, AndersKrakhmalev, PavelBergström, Jens

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