Application Of Differentiating Defect Signals Of Ultrasonic Testing Based On Independent Component Analysis Theory

The titanium alloy is general applied important part in aviation and spaceflight equipments. In the welding process of Ti allay needs to be proceeded to have nondestructive testing strictly. The laser welding is a kind of important Ti alloy welding methods. The signal of small defect will be submerged in surface wave signal and noise signal when we use ultrasonic testing system to inspecte the T-shape laser welding joint because of the joint dimension is small and so near to the surface, all of these can effect the ultrasonic testing result. Independent component analysis (ICA) is a new blind separation of sources testing technique. It deal with a group of mixed signal cobinated by some specialty source signals and purpose to separate these specialty source signals frome mixed signal.Through this way we can get rid of noise signals. The primary objective of this paper was to investigate the effect of ICA used in separating inspect signal and source signal.This paper summarizes the adverse effects of surface roughness on the reliability of an ultrasonic automatic inspection. It was primary discussed the adverse effects of the weld crown. Furthermore, the effect of some parameter such as frequency of transducer, water path, plus, and strobe have been investigated in this paper. After we set the water path 30mm, plus 6db and strobe 1mm far from the surface wave we got a best image. By the means of chose suitable frequency of transducer, we can limit the adverse effects of rough surface and thereby increase the reliability of ultrasonic automatic inspections. When the frequency of transducer is 10MHz, it is more suitable for the project. It will induct more noise signal when we set the plus too high and strobe too low. In addition, we will miss some little defect signals if we set the plus too low and strobe too high.At last, separating noise from observed signals was studied in this paper when the T-shape laser welding joint was inspected by ultrasonic testing system adopting independent component analysis theory to process the signals. The principle of automatic ultrasonic testing signals processing and negentropy law of ICA were introduced. The experimental data were processed using relative analysis tools. We picked the mixed figure signals up from the scan wave and separated the source signals and noise signals, after separation, we got a echo signal and noise signal clearly. Results showed that the ICA could separate defects signals from noise effectively in laboratory.