Research And Development Of Ultrasonic TOFD Weld Testing System

TOFD (Time of flight diffraction) is one of the most advanced technologies in the field of ultrasonic nondestructive testing. It can get the sizes and locations of flaws according to the difference between the time of return diffraction signals from the tips of flaw. It has been widely used in weld testing currently as a hot aspect at home and abroad. This method has many remarkable advantages such as highly testing speed, highly precision, highly detecting rate, accurately locating flaws and convenience etc. when combined with computer, it can achieve automatic real-time detecting.Based on the principle of TOFD, this thesis gives the flaws'qualitative analysis in detail and contrasts different modes of scanning and displaying. To eliminate the blind area, we bring the additional scanning and three integrated detecting means. An acquisition system has been designed according to peculiarity of TOFD, the software codes of core chips has also been compiled. Finally, some experiments are made.The following are main achievements of this thesis:1.Main concern of TOFD is the principle, detecting method, signal characteristics, math analysis model and basic system structure. To deal with blind area, additional scanning and integrated means are brought out.2.Designed a data acquisition card together with USB interface circuit, main modules of it contain USB interface, programmable gain amplifier circuit, band-pass filter circuit, A/D converter acquisition circuit, MCU and FPGA.3.Designed and compiled the codes of XC2S100 with Verilog HDL, which implemented four phase offset clocks, sequential controlling module, data storage module, channel choice module, parameters'writing and reading etc.4.C8051F121 that Designed with assemble language, mainly used to control the gain of amplifier circuit, the operation of read and write, the storage of acquisition data, the communication interface, and the pre-analysis of data etc.5.Used Labview to programme the user controlling interface, which supported man-machine conversation, disposing and analyzing of data, displaying of return waveform etc.6.Debugged the whole software codes of system, and did the acquisition experiments of signals.