1 Calibration method Nowadays, what is commonly referre […]
1 Calibration method
Nowadays, what is commonly referred to as a tension calibrator is an axial force meter. In order to ensure the installation quality of the high-strength bolt connection pair, the mobile axial force meter used to detect the axial force at the installation site is composed of a spoke-type pressure sensor and a digital display instrument matched with it.
The mobile axial force meter is mainly applicable to the installation site, and the pre-tightening force after the tightening is compared with the torque application tool of the on-site construction in order to correct the on-site tightening torque in time. The calibration and verification of the on-site screwing tools through the mobile axial force meter provides a certain quality guarantee for the on-site construction quality.
2 strain method
Attach the strain gauge to the object to be measured and make it expand and contract with the strain of the object to be measured, so that the metal foil inside will expand or contract with the strain. Many metals change their electrical resistance when they are mechanically stretched or contracted. Strain gauges use this principle to measure the strain by measuring the change in resistance.
The strain method uses strain gauges to form the working principle of a Wheatstone bridge, then encapsulates it to form a bolt axial force sensor device, and then installs the sensor between the bolt and the connected part, and places a gasket between the bolt and the sensor. The force of the sensor is uniform. Because the sensor is squeezed by the pre-tightening force of the bolt, the strain gauge inside the sensor changes, resulting in displacement and strain. The strain is measured by the above-mentioned principle method, and the pre-tightening force is calculated from the relationship between strain and stress.
3 Ultrasonic measurement method
People have studied and explored the relationship between sound wave and stress in theory for many years. In the 21st century, there are already bolt stress ultrasonic measuring instruments on the market. Because the ultrasonic stress measurement method can be directly measured, has high accuracy and simple measurement, especially the bolts in service can be tracked and tested regularly, so the development is relatively fast.
The calculation principle of the ultrasonic stress detection method is to first measure the sound required for ultrasonic conduction back and forth under the stress state and the unstressed state; then use the torque machine and the tensile machine to compare with the ultrasonic stress meter, and the results obtained by the measuring instrument are very good. , The error is extremely small.
Ultrasonic stress measuring instrument can detect the bolt installation process, detect the axial force of the existing bolts in service, and detect the bolts in service. It can monitor the bolt pre-tightening force of the machine at any time, which plays an important role in protecting the safe operation of equipment or vehicles.