Tailored TestingCopyright: IBF
The development of new materials and processes may also require the use and further development of innovative testing technologies. The institute offers a wide range of possibilities for this.
The research topics embedded in this cross-sectional area are assigned to different research groups and are presented below.
Testing Under Bending Load
Various forming processes apply an alternating bending load to the workpiece. Such changes in the load direction make the consideration of the material behavior under low cyclic loading necessary. In order to test materials under alternating loads, a test rig has been designed at the Institute of Metal Forming. The test rig offers the possibility to apply unidirectional bending as well as cyclic bending. A flexible tool enables a fast variation of bending radii and distance of the bending dies. The material data can be derived from an inverse simulation using the measured machine data of bending force and displacement.
For further information, please contact Pavlo Pavliuchenko.
Image: Test stand for bending loads, Copyright: IBF
Investigation of Bond Formation and Failure of Metallic Alloys
Roll bonding enables the targeted combination of different materials and thus their mechanical and thermal properties in a single material composite. However, the connection created under pressure load can tear up again due to shear stress at the end of the roll gap. Thus, industrial production requires very long process chains, which are often determined by trial and error. In order to allow for a knowledge based design of such process chains, a basic experiment, using the torsion plastometer TA STD 812, was developed at the Institute of Metal Forming to characterize bond formation and failure. In this test, the connecting partners are heated inductively and joined under combined pressure and shear stress. After bond formation, the strength can be tested at deformation temperature under a combination of tensile, compressive and shear stress. The procedure thus enables testing under near-process conditions.
For further information, please contact Jürgen Nietsch.
Image: Hot glowing steel specimens during bond investigation, Copyright: IBF
Friction Determination With Extended Conical Tube-Upsetting Test
The conical tube-upsetting test is used to determine the friction coefficients for different friction models. Similar to the ring compression test, which is also available at the institute, the geometric change of the specimen is measured and evaluated by means of nomograms. The conical contact surface suppresses the occurrence of static friction and thus enables more homogeneous test conditions, even under high prevailing friction. In addition, a blue line laser has been added to the test setup in order to record the contour change during forming. These measured values can be used on the one hand for the inverse determination of the prevailing friction and on the other hand for the examination of the change in friction during the compression process. The test setup allows the testing of workpiece temperatures up to approx. 1200 °C. In addition, the tools can be preheated to temperatures of up to 300 °C.
For further information, please contact Michel Henze.
Image: Glowing conical tube specimen before and after upsetting, Copyright: IBF
The goal of the hot-gas-bulge test project is to deliver accurate material data for the virtual testing and design of hot stamping processes. Hot-stamping is a quite new process, which is mostly used by the automotive industry for the production of high strength components. The high strength levels are achieved by simultaneous forming and quenching of hot steel sheets with initial temperatures up to 950 °C.
For further information, please contact Alexander Braun.
Image: Annealed steel sheet in hot gas bulge test, Copyright: IBF
Determination of Wear Characteristics With Compression-Torsion-Tribometer
For the determination of wear parameters, a self-constructed compression-torsion-tribometer is used. The steel specimen, which is optionally coated and / or lubricated, can be pressed onto a counter body under a maximum axial load of 18 kN. An engine realizes a relative movement between the two specimens. By measuring the transmitted torque and controlling the axial force, rotational speed and number of rotations, the wear behavior, for example with regard to adhesion and abrasion, can be investigated under a controlled load spectrum. In addition, an encapsulation of the specimens allows higher contact pressures and thus the approximation of load collectives during extrusion of aluminum. The tribometer is used, for example, for examining dry extrusion of pure aluminum.
For further information, please contact Marco Teller.
Image: Compression-torsion-tribometer, Copyright: IBF
Thermal Characterization of Surface Contacts
For the simulation of hot forming processes, the knowledge of the heat transfer between the tool and the work piece is of importance. Currently the determination of the interfacial heat transfer coefficient is carried out via inverse methods in transient condition, which sometimes provides only insufficient results. Therefore, a test stand for the steady state heat conduction is being developed at the IBF in cooperation with the Department for Industrial Furnaces and Heat Engineering. Thereby, various influencing variables such as atmosphere, contact pressure, temperature and surface roughness may be varied in order to model the corresponding processes as application-orientated as possible. Particular focus is placed on lower contact pressures at higher temperatures, which allows the modeling of processes such as annealing of coiled metal strips or the slab transport on the roller conveyors.
For further information, please contact Jürgen Nietsch.
Image: Test rig for determining the steady state heat conduction, Copyright: IBF