Study On Tightening Torque Detection Of Light-Rail's In-service Screw Anchors Based On Vibration Test Technology

Those screw anchors assembled on Light-Rail of Chongqing are the key research objects of this paper. Since they are the most important part to connect piers and girders of Light-Rail, their health to the safe operation of Light-Rail plays the vital function.The Light-Rail screw anchors were tightened at the same tightening torque when they were assembled. However, due to machining defects, rust caused by climate factors, long-term service's influence and complicated effect of time-varying load, the tightening-torque of those screw anchors will change. Therefore, a monitoring operation must be taken to make sure that all those screw anchors works in normal.According to the characteristics of this special structure, cross-seat track traffic, and needs of those screw anchors'detection, we worked out an auto data acquisition system to collect those screw anchors'vibration signals. On the hardware aspect of this system, following the scheme of impulse-impact vibration test, we designed a practical impact device based on pneumatic technology and a kind of improved accelerometer which could properly collect acceleration signal of those in-service screw anchors under that special environment. On the software aspect of this system, relevant software was also programmed using C/C++ language in Visual Studio.Net development environment.After this acquisition action was completed, in order to avoid using fault signals to analyze its vibration characteristics, I studied those vibration signals and figured out a functionary method to decide its validity of those signals.Analysis about those in-service screw anchors'tightening torque is the major research in this paper, so, I referenced to the current vibration signal analysis methods, and in-depth studied wavelet analysis and its application on vibration signal and advantage of information entropy. Finally, based on the assumption that the impulse response of the screw anchors represented the tightening torque, and wavelet packet transform and energy entropy technology were used, the function relationship between tightening torque and entropy became obvious enough to identify the tightening torque of these screw anchors.