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The interdependence of plastic behaviour and final properties of steel wire, analysed by the finite element method
Örebro University, Department of Technology.
2004 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The finite element method (FEM) has been used in order to study the interdependence of plastic behaviour and final properties in steel wire. Three processes metal forming have been studied: billet forging, wire rod rolling, and cold drawing.

The forging study focuses on the possibilities to eliminate voids, pores and pipes by altering the bite ratio in open die forging. Forging is used in wire manufacturing when dealing with materials that are difficult or impossible to roll, e.g. tool steels like high-speed steels, and powder metallurgically manufactured materials like tungsten-molybdenum filament wire. The elimination of inner defects by forging were successfully simulated by the FEM.

The rolling study focuses on the problems due of the extreme finish rolling velocities in modern wire rod mills and modern technologies such as thermo-mechanical rolling and sizing. A design for a high-speed laboratory mill for studies of material behaviour at extreme strain rates was made. With a combination of two-high stands and three-roll units is it possible to obtain a smoother temperature distribution in the bar cross section.

Two studies of the cold drawing process were made. The first describes the distribution of the plastic deformation due to the die geometry. It was found that the influence of the die angle on the amount of inhomogeneous deformation decreases with increasing area reduction. The frictional behaviour was also studied.

The second study describes how the bearing geometry affects the residual stress-state in the wire. It was found that a small taper could change the residual stress state in the surface immensely. This was shown with FE simulations and verified by X-ray diffraction measurements. The results in this paper gives a tool for control of the residual stress-state in the wire. This gives a possibility to increase e.g. the fatigue strength in the final product.

Place, publisher, year, edition, pages
Örebro: Örebro universitetsbibliotek , 2004. , p. 22
Series
Örebro Studies in Technology, ISSN 1650-8580 ; 12
Keywords [en]
Technology, FEM, defects, steel wire, wire drawing, rolling, forging
Keywords [sv]
Teknikvetenskap
National Category
Engineering and Technology
Research subject
Mechanical Engineering
Identifiers
URN: urn:nbn:se:oru:diva-86ISBN: 91-7668-421-0 (print)OAI: oai:DiVA.org:oru-86DiVA, id: diva2:137366
Public defence
2004-12-10, Hörsal T, Teknikhuset, Örebro universitet, Örebro, 10:00 (English)
Opponent
Supervisors
Available from: 2004-11-18 Created: 2004-11-18 Last updated: 2017-10-18Bibliographically approved
List of papers
1. FEM-simulation of drawing out in open die forging
Open this publication in new window or tab >>FEM-simulation of drawing out in open die forging
2004 (English)In: Steel Research International, ISSN 1611-3683, Vol. 75, no 12, p. 812-817Article in journal (Refereed) Published
Abstract [en]

Experiments and finite element simulations were performed in order to study how the bite ratio influences the closing of inner flaws such as voids and pipes in the open die forging process. Square rolled blooms of carbon steel with a transversal hole in the centre were forged with a constant height reduction but with different bites in order to study the closing of voids during the process. Corresponding finite element simulations were performed in full 3D with full thermo-mechanical coupling. Also the influence of the friction and of the temperature gradient in the workpiece were studied. The elimination of an artificial defect by forging was successfully simulated by the finite element method. It is established that the closure of voids is highly dependent on the bite ratio. The closure of voids under the edge of the tool is however not improved by a higher bite ratio. There is a slight tendency that the situation under the tool edge is worse when the bite ratio is increased.

Place, publisher, year, edition, pages
Düsseldorf: Verlag Stahleisen, 2004
Research subject
maskinteknik
Identifiers
urn:nbn:se:oru:diva-3208 (URN)
Available from: 2004-11-18 Created: 2004-11-18 Last updated: 2017-10-18Bibliographically approved
2. Finite element modelling and laboratory simulation of high speed wire rod rolling in 3-roll stands
Open this publication in new window or tab >>Finite element modelling and laboratory simulation of high speed wire rod rolling in 3-roll stands
2003 (English)In: Steel Research International, ISSN 1611-3683, Vol. 74, no 7, p. 431-443Article in journal (Refereed) Published
Abstract [en]

Modern wire rod rolling is characterized by high finish rolling speed and requirements on close tolerances and well defined mechanical properties of the rolled product. In some senses the technological development has run in advance of the scientific knowledge of the phenomena involved in the process. Thus at present no laboratory mill is in operation for rolling speeds above 40 m/s. The modern technologies on thermomechanical rolling and sizing give certain phenomena difficult to handle for the mills, and especially finish rolling at low reductions and temperatures performed in three-roll units sometimes give surprises on grain size distribution and allied properties of the wire rod. Traditional plastic analysis has proven not to be sufficient to analyse the processes involved in high speed rolling of close tolerance wire rod with well-defined properties. Simulations by means of the Finite Element Method on the other hand have proven to be a powerful tool for this kind of analysis, even if the initial difficulties in creating a suitable model require certain care. Also the calculation capacity must be sufficient for making relevant three-dimensional thermomechanically coupled studies. The high speed rolling of wire rod can be simulated under full-scale conditions, and with correct boundary condition in the high-speed laboratory wire rod mill at Orebro University. By utilizing both conventional two-high stands and three-roll units it has been possible to design a laboratory rolling mill for any rolling condition that can occur in wire rod mills. Rolling speeds up to 80 m/s can be combined with thermo-mechanical rolling in any interesting temperature range, and with total flexibility of reductions. Further, fundamental studies of high-speed deformations can be performed in full-scale and with correct frictional conditions and geometries. Thanks to the flexibility in layout and combinations with other equipment in the laboratory also other processes can be simulated.

Place, publisher, year, edition, pages
Düsseldorf: Verlag Stahleisen, 2003
Research subject
Mechanical Engineering
Identifiers
urn:nbn:se:oru:diva-4062 (URN)
Available from: 2007-06-21 Created: 2007-06-21 Last updated: 2017-10-18Bibliographically approved
3. Development and validation of FEM models for wiredrawing
Open this publication in new window or tab >>Development and validation of FEM models for wiredrawing
2004 (English)In: Wire Journal International, ISSN 0277-4275, Vol. 37, no 5, p. 73-76Article in journal (Refereed) Published
National Category
Engineering and Technology
Research subject
Mechanical Engineering
Identifiers
urn:nbn:se:oru:diva-3210 (URN)
Available from: 2004-11-18 Created: 2004-11-18 Last updated: 2017-10-18Bibliographically approved
4. The influence of bearing geometry on the residual stress state in cold drawn wire, analyzed by the FEM
Open this publication in new window or tab >>The influence of bearing geometry on the residual stress state in cold drawn wire, analyzed by the FEM
(English)Manuscript (preprint) (Other academic)
Research subject
Mechanical Engineering
Identifiers
urn:nbn:se:oru:diva-3211 (URN)
Available from: 2004-11-18 Created: 2004-11-18 Last updated: 2017-10-18Bibliographically approved

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