Texture Evolution in Rolling of Electric Steel Copyright: © IBF

Energy technology is an important research area in terms of sustainability. Products manufactured by forming technology also play a decisive role in this.
The production of electrical steel sheet and coil windings for electric motors, for example, have a major influence on their efficiency.
But also in the field of turbomachinery and wind turbines, large metallic components contribute significantly to their function and efficiency.

The research topics embedded in this cross-sectional area are assigned to different research groups and are presented below.


Cold Rolling Strategies for Producing Magnetic-Optimized Electrical Steel Sheet in Energy-Efficient Electrical Drives

Multiskalen-Modell zur Berechnung der Texturentwicklung beim Kaltwalzen

One way to increase the efficiency of electric drives is to optimize the magnetic properties of the electrical steel used in the magnetic core. In order to quantify the influence of process parameters on these final properties and to create a scientific-theoretical basis for the development of low-loss electrical steel, an interdisciplinary DFG research group, FOR 1897, is working on the integrated process chain modeling. The main task of the IBF is to investigate and simulate the cold rolling process. Experimentally, the IBF will test different rolling strategies on the cold and hot rolling mill. A multi-scale model that includes a macroscopic finite element model and a microscopic crystal plasticity finite element model is created to compute the texture evolution, which makes it possible to determine the influence of different rolling strategies and initial states on the local texture development during cold rolling. By linking the sub-models, it enables model-based process design of low-loss electrical sheets for highly efficient electric drives.

For further information, please contact Jannik Gerlach.

Image: Multi-scale model for simulating texture evolution during cold rolling, Copyright: IBF, IMM

Specific Shaped Copper Windings Manufactured by Forming Technique

Laborwerkzeug der mehrstufigen Stauchumformung

Although distributed windings have electromagnetic advantages in electric traction drives with a central motor, the electric wheel hub motor represents an application in traction drives where concentrated windings are to be preferred. Due to the compact design of concentrated windings in the axial direction in combination with the highly limited installation space, the maximum torque density of the electric wheel hub motor can be increased by using variable cross-section single tooth coils. At IBF, various forming approaches for the production of variable cross-section single-tooth coils were investigated on a laboratory scale. The most effective approach of multi-stage upsetting, in which the coil is formed in several strokes to target geometry with variable cross-sectional shape, starting from a CNC-bent single-tooth coil of rectangular wire, was optimised for series production in an industrial environment, in close cooperation with the project partners.

For further information, please contact Michel Henze.

Image: Laboratory tool of multi-stage upsetting, Copyright: IBF

Profile Ring Rolling

Axialwalzspalt während des Axialprofilierprozesses

Profiling of ring rolled components is an important step for the near net shape production, which leads to material savings as well as time saving regarding the machining. Based on the area of application, all four sides of the cross section can be profiled. Dependent on the type of the profile and the geometry of the ring different challenges during the process occur. Examples for these challenges are the reaching of the desired profile filling and conicity in the cross section.
At the Institute of Metal forming strategies for a stable process, which leads to the desired final geometry are developed and investigated numerically as well as experimentally using the IBF ring rolling mill. Therefore, tool and preform design as well as modifications of the actual process strategy are subject of the research.

For further information, please contact Mirko Gröper.

Image: Axial roll gap during the axial profiling process, Copyright: IBF
  Ring rolling of a profiled cross section

Open-Die Forging of Hollow Shafts

Freiformschmieden einer innenkonturierten Hohlwelle am IBF

During the last years, the importance of alternative energy sources as wind energy has risen constantly. A higher energy production by wind power plants cannot only be achieved by setting up additional wind parks, but also by an increase in the performance and by this the size of newly built plants. The electric capacity of up to 6 MW requires larger generators which transform the mechanical to electrical energy. This leads to an increased weight of the whole tower construction. One possible approach to realize lightweight construction is to replace the commonly casted hollow generator shaft by a forged shaft with significantly better mechanical properties. Compared to casted hollow shaft, a weight reduction of 50-60% can be realized. For this purpose, the IBF has successfully developed a forging method performed on the open-die forging center, which allows the open-die forging of hollow shafts with an outer and inner contour with respect to an optimized microstructure to ensure good mechanical properties.

For further information, please contact Niklas Reinisch.

Image: Open-die forging of an inner-contoured hollow shaft at IBF, Copyright: IBF
Forging of a Hollow Shaft
Forging of a hollow shaft

FE Simulation of Multi-Stage Bending Processes

Biegezentrum eines Stanzbiegeautomaten

The stamping and bending technology is used for the production of complex bending parts, for example for the electric industry. The process design is mainly based on expert knowledge and experimental testing. Aim of the cooperation project with Phoenix Feinbau GmbH & Co. KG is the development of precise FE models to describe multi-stage bending processes and the springback behavior of the produced parts. One key aspect is the identification of material data of high-strength spring steels by means of an inverse modeling approach under bending conditions. Experimental investigations are further carried out to implement the FE boundary conditions correctly. The validated FE models are then applied to examine and evaluate different influencing factors on the final parts in stamping and bending processes.

For further information, please contact Thomas Bremen.

Image: Bending center of a stamping and bending machine, Copyright: Phoenix Feinbau GmbH & Co. KG
Manufacturing of an Outer Skin Component of a Shelby Daytona Cobra Coupé
Springback simulation of multi-stage bending processes