Research On Bolt Crack Detection Technology Of Brake Disc For High-speed Train

With the improvement of train speed, the kinetic energy of trains increase sharply. So the importance of train brake disc is increasing and bolt, as a kind of fastening device connecting axle and brake disc, is particularly important. But the domestic research on the Non-destructive Testing of bolt in brake disc of high-speed train is not enough, so it is very important to develop a set of automatic crack detection system.In this thesis, based on a large number of documents, a kind of automatic crack detection system based on the principle of ultrasonic is proposed. The hardware platform based on FPGA is designed for ultrasonic excitation and receiving. And a software is written for ultrasonic signal processing, so as to realize the detection of the bolt crack.Thesis firstly compares the advantages and disadvantages of the various ultrasonic detecting method, and scheme based on ultrasonic pulse reflection method is proposed. Meanwhile, the overall system design, including hardware platform and system software, is proposed as well. Then the design of ultrasonic detection hardware platform is completed. And the composition and modules of ultrasonic hardware system, including selection of ultrasonic probe, design and optimization of ultrasonic transmitting and receiving circuit, data transmission module and special mechanism of data transmission, are introduced. And the FPGA peripheral circuit and working mechanism is described in detail. Each module of the system software is completed. The user interface is written and the wavelet threshold denoising algorithm, removing noise while keeping the time domain information of the original signal, is completed. Crack identification and positioning module for the detection and location of cracks have carried out effective judgment. And a kind of recognition algorithm based on frequency domain features is proposed for solving micro-cracks problem.Thesis already implements the crack detection of brake disc bolt. Experiment environment in the laboratory is set up, and bolts with a pre-existing cracks and bolts with suspected crack from the field are used to verify the accuracy and reliability of the system.