New Softmagnetic Sensor at IEM
For the extended characterization of the magneto-mechanical coupling, a new type of magnetic sensor was developed and procured as part of the DFG priority program "Targeted use of residual stress in electrical steel sheets to increase energy efficiency".
Conventional magneto-mechanical sensors allow either scalar measurements under exclusively parallel magnetic field variables and mechanical stress or vectorial measurements of the magnetic field variables with freely adjustable plane stress states, which are usually limited to a maximum of 30 MPa. The novel approach allows a vectorial measurement of the magnetic field quantities under the influence of mechanical loads up to the plastic deformation range at different angles between magnetization and the mechanical stress σ.
A rotatable magnetization yoke is attached to one side of the sensor. This magnetization yoke is extended by two needles to measure the magnetic flux density generated in the sample and an H-coil to determine the magnetic field strength. The scalar field values can thus be determined for each set angle of the magnetization yoke and the controller can set sinusoidal flux densities.
A vector hysteresis sensor is located on the opposite side of the magnetization yoke. This sensor is attached statically and enables the measurement of the vector field magnitudes for all specified combinations of mechanical stress, magnetic modulation and the angle of the magnetization yoke.
Another special feature of the sensor is the support frame to prevent the sample from bending under pressure loads. The sample can be clamped using three adjusting screws in such a way that the sheet metal can just slide in the support frame. Thus, the mechanical stress state of the sheet remains unaffected, while the two faces of the frame are as close as possible to the sample. The range of measurable compressive stresses can be significantly expanded as a result.
A universal testing machine with a maximum force of 2 kN serves as the mechanical loading unit, which allows loading up to the point of mechanical failure of the sample for all conventional sheet metal thicknesses.