HOW LOAD MEASUREMENT WORKS AND HOW WE IMPROVE IT
Direct determination of preload with the intellifast system
How can preload be measured?
The measured variable âultrasonic time-of-flightâ changes by increasing elongation and reduced ultrasonic traveling speed at growing axial stress.
Permanently-mounted transducers are deposited on every single bolt and provide more accurate, objectively reproducible measurements and documentation. Two types are distinguished:
- Thin film plasma transducers are the most advanced transducer technology as they are certifiable, environmental durability, have the biggest temperature range and are robust. Moreover, plasma transducers build the only technology to comply with DIN EN 4859.
- Glued on ceramics transducers are advantageous in the lead-time and are often used in R&D and process capability studies.
Hand held contact probes are low cost but suffer from high tolerances and non-repeatable measurements leading to higher measurement inaccuracy (reattachment error).
With STRAIN GAUGES
- Strain gauges area used to measure the stress inside or aside of the bolt.
- Strain gauges are accurate but expensive in preparation, lead-time and installation.
- Strain gauges usually require mechanical preparation and therefore modification of the bolt.
- The length of the bolt before and after tightening is measured while considering temperature, material and geometry.
- Mechanical or optical tools are used with limited accuracy and notably effort.