For how to evaluate the anti-loosening performance of fasteners, two standard test methods are commonly used at home and abroad. The first is the accelerated vibration test method for fasteners (ISO standard or GJB715.3-89), and the second is the transverse vibration test method for fasteners (GB/T10431-1989). Both are test methods for accelerating the loosening of fastener connections. They have their own characteristics. The first method is currently mainly used in aerospace systems in China, while the second method is mostly used in other systems.
Fastener accelerated vibration test method (ISO standard or GJB715.3-89). The loading method and vibration and impact conditions of this method are closer to the actual use state of various fasteners. The second method cannot evaluate the anti-loosening performance of the loose connection of fasteners, while the first method can provide comparable evaluation results for the anti-loosening performance of various fastener loose connections. The threaded fastener connection in the working state may lose the pre-tightening force due to various reasons such as the wear of the supporting surface, the compression of the connected part, the overload yield of the bolt or the action of external load, and it may be tightened. The tight connection in the state becomes a loose connection with no pretension (or insufficient pretension). At this time, keeping the fastener itself locked so that it can be loosened within a certain period of time is very important to prevent the connected parts from failing due to separation.
Fastener transverse vibration test method (GB/T10431-1989). This method is to directly apply force to the bolt (or screw), so it can make the fastener connection loose in a shorter time, and the test efficiency is higher. Another feature of the second method is that it can accurately measure the variable of the pre-tightening force of the fastener connection during the vibration test, describe the change process of the pre-tightening force in the test, and give the pre-tightening force and the number of vibrations (or time) The relationship curve diagram, and the variable of the expected tightening force is used as the criterion to measure the looseness of the fastener connection. This is more intuitive and accurate than the first method, and easier to operate.