Research On Bolt Loosening Detection Technology Of Iron Tower

The high-speed rail communication tower is in the dynamic wind load for a long time,which induces the loosening of the bolts of each connection point easily and threatens the structural safety of tower.In view of the problems of complex detection work,high detection cost and low detection accuracy and low efficiency,a detection method based on the principle of impact elastic wave is proposed in this paper.The feasibility of the method is verified by the finite element simulation and the comparison test of the tower model.On this basis,a portable testing system for bolt loosening is designed,which can realize vibration excitation,signal receiving and processing,and automatic identification of bolt loosening.Firstly,the basic theory of vibration and the principle of impact elastic wave detection are introduced and the basic method of detecting tower bolt looseness based on impact elastic wave is put forward.Finite element modal analysis and transient simulation analysis are carried out by using the finite element model of the tower.Then,an experimental platform for tower verification is built,and the correctness of the finite element analysis is verified by electromagnetic vibration exciter and laser vibrometer.After that,a test method of tower bottom one-point excitation and the multi-point test of the tower body is proposed,and the optimum response frequency of the tower model is obtained,and the overall scheme of the detection system is designed.On this basis,this paper developed a portable detection device based on FPGA and STM32,and realized the functions of waveform transmitting,vibration signal receiving,data processing,human-computer interaction and storage.With the combination of Verilog HDL and Quartus ? IP kernel,the FPGA program designs the direct digital synthesis module(DDS),the data buffer module(FIFO)and the clock management module,which provides the desired excitation waveform,clock signal and caching ADC data.STM32 system software transplants the uC/OS-? operating system,which realizes the multitask management and priority arrangement of communication,SD card storage,LCD drive,FFT calculation and bolt loosening judgment.At the end of the paper,a series of laboratory and field testing experiments were carried out to test the automatic detection function of the detection system's launch,reception and bolt loosening.The experimental results show that the detection error of the system is less than 8%,and the system has the advantages of high efficiency,portability and high cost performance.