On 15.06 and 16.06.2020, top-class speakers will shed light on current issues in the process industry at the virtual event ACHEMA Pulse. In the session “Safety First! Pt.1”, Dr. Klaus Ettrich will present the topic “Innovative sensors for monitoring mechanical connections” at 14:20.
At the CiS Research Institute, novel silicon-based MEMS sensors are being developed to check safety-relevant bolted joints. Until now, the strain of the bolt has been measured, for example, by a length measurement of the bolt, an ultrasonic method, by strain gauges (DMS) attached to the bolt shaft or in the bolt.
The MEMS sensor developed consists of four piezoresistive strain-sensitive measuring resistors connected to form a Wheatstone bridge. This is placed on the bolt head and measures its deformation when a corresponding bolt preload force is applied. This causes elastic deformation in all parts of the bolt. The measurement on the bolt head is easily accessible.
The advantages of silicon as a bulk material in terms of signal modulation, reproducibility and long-term stability are explained. Innovative joining techniques can connect the silicon strain gauges to the elastic deformation body. These include glass-frit bonding, silver sintering or joining based on reactive multilayer systems.
Application examples for the industrial use of these microsensors are also presented and experimental data are explained. Investigations at the IAB in Weimar show the effects of tightening torque and internal pressure of bolted joints. The new measuring sensors for bolt load testing record the pretension of bolts and can help to continuously improve safety in plant engineering.
We would like to thank the Federal Ministry for Economic Affairs and Energy (BMWi) for the financial support of the projects: BAVI (49MF180012) and MIKADO (49MF180163).