，
Metric screwed tightening-pulling relation test method standard
Introduction
The metric screwed tightening-pulling relation test method standard is used to determine the external friction generated by the thread screw connection, and the clamping force-pulling force law as a reference to determine the clamping force of the two-way bolt joint. The standard test procedure includes three parts: test rig, test sample preparation and test.
Test Rig
The test rig used in the standard test consists of a self-aligning pendulum fixture and a main pull frame. The self-aligning pendulum fixture is fixed to the main pull frame, and a clamping nut whose purpose is to hold the fastening sample is installed at the top of the main pull frame. The axis of the self-aligning pendulum frame is mounted with a high precision load cell, and anti-wobble springs are installed between the bearing support block and the main pull frame to reduce the influence of friction caused by the elastic deformation of the bearing support block.
Test Sample Preparation
The standard test sample should include two parts: the fastener and the test part. The thickness and size of the test part should be determined according to the size of the screw used in the test. The fastener is screwed into the test part, and each sample should be tested at three different torque levels, low, medium and high. The bolts are tightened to the torque levels of 0.7N·m, 1.4N·m and 2.1 N·m respectively, and the torque is measured using a torque wrench.
Test
In the standard test, the clamping force-pulling force relationship is determined. After the sample is tightened to the specified torque, the pulling force is applied to the sample at a speed of 0.5mm/min. A recorder is used to record the clamping force and the pulling force at the same time, and the clamping force-pulling force relationship is determined. In addition, the clamping force-pulling force transition point (opening point) is determined, which is the point at which the two curves intersect.
Conclusion
In summary, the metric screwed tightening-pulling relation test method standard is used to determine the external friction generated by the thread screw connection, and the clamping force-pulling force law as a reference to determine the clamping force of the two-way bolt joint. The standard test procedure includes three parts: test rig, test sample preparation and test. The test fixture consists of a self-aligning pendulum fixture and a main pull frame. The sample preparation involves using a torque wrench to tighten the bolts to three different torque levels. The pulling force is applied to the sample at a speed of 0.5 mm/min to determine the clamping force-pulling force relationship, and the transition point (opening point) is determined.
