The electrical contact resistance between two fastener components is a key quality parameter, especially when the bolted joints carry electrical current. If the resistance is too high, heat is generated between the elements. In response to this problem, Kistler has introduced the OhmBox to its ANALYSE friction coefficient test stand to measure electrical resistance while fastening is actually in progress.
With the help of the Kelvin method, users of the new OhmBox can precisely record the electrical contact resistance during the fastening process and correlate it with other parameters, such as applied torque.
To do this, the user connects two measurement tips as close as possible to the bolted joint. The OhmBox then constantly emits current, and the highly sensitive measuring system registers the voltage loss through the electrical contact resistance – even down to the microohm range. In this way, the user can accurately determine the level of electrical resistance during tightening and slackening. To prevent distortion of measured values by external influences, the bolted joint under test can be fully isolated in the test set-up.
Evaluation software delivers optimal quality parameters
The testXpert® software from Kistler records the entire testing procedure, with online user defined data visualisation. In the software, the electrical contact resistance can then be displayed together with other measured values, such as the applied torque over the angle or time axis. This enables developers to determine and verify the optimum combination of parameters quickly and reliably – giving them a valid basis for meeting quality requirements and comparing different materials.
Kistler points out the OhmBox can supplement an ANALYSE system that is already in operation, or can be combined with a new system with additional, individually selectable modules for friction coefficient, tightening torque or preloading force. Following a straightforward set-up procedure carried out by Kistler experts, manufacturers can then design and implement a diverse range of test scenarios – thus ensuring that their bolted joints remain safe and reliable, even when carrying electrical current.
www.kistler.com/GB/en
Having spent a decade in the fastener industry experiencing every facet – from steel mills, fastener manufacturers, wholesalers, distributors, as well as machinery builders and plating + coating companies, Claire has developed an in-depth knowledge of all things fasteners.
Alongside visiting numerous companies, exhibitions and conferences around the world, Claire has also interviewed high profile figures – focusing on key topics impacting the sector and making sure readers stay up to date with the latest developments within the industry.
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