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HANNOVER MESSE 2019, 01 - 05 April
R&D-Project

Smart Bolts

Measurement of pre-tensioning forces in screw connections

Logo CiS Forschungsinstitut für Mikrosensorik

Exhibitor

CiS Forschungsinstitut für Mikrosensorik

Exhibitor details
Exhibitor details
Logo Smart Bolts
Development status
Under development
Market introduction
01.2018
Degree of documentation
Very well documented
Market orientation
Niche market

Product description

CiS Research Institute is currently developing a new silicon-based MEMS sensor to verify safety-related screw connections. Such special screws are used in mechanical engineering, conveyor technology and wind turbines, e.g.
The new sensor is applied to the screw head and measures its deformation caused by the screw pre-tensioning force. Not to be confused with the torque, the screw pre-tensioning force affects the parts to be connected between the thread and the screw head. It causes an elastic deformation in all parts of the screw. At the screw head, this deformation is quite easy to measure. Up to now the strain on the screw could only be determined by measuring its length or attaching strain gauges at the screw shaft. These solutions lend themselves specifically to the evaluation of single screws. The MEMS sensor developed by CiS Research Institute consists of four piezo-resistive, strain-sensitive measurement resistors which are switched to a Wheatstone bridge. The active surface without the electrical connections amounts to no more than (200 x 200) µm² with a thickness of 10 µm (fig. 1). The sensor is joined to the screw head using glass solder. A FEM-analysis determined the most suitable position on the screw head (fig. 2).

Hall 4, Stand F34

German Pavilion - Thuringia

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