The Simulating And Research Of Nondestructive Testing Based On Synthetic Aperture Ultrasonic

With the development of NDT (Nondestructive Testing), the application field also steps into a flourish times especially in the interface weld of ship. In recent years, the boat with the bubble in the interface weld will result in shipwreck at the terrible situation in sailing. So the NDT has been the primary technology in the boatbuilding industry. This is the background of the thesis. But it's contradictive between the detective depth and high resolution when we take use of Ultrasonic to detective object. In other words, it will get lower detective depth with high frequency Ultrasonic system and it also will get lower resolution with low frequency Ultrasonic system. The thesis present a new way—apply the SAR theory in NDT system to dispose the contradiction between the detective depth and high resolution.Through the discussion in SAR imaging principle, imaging algorithm and orientation distinguish etc., we get a theoretic result that imaging resolution is just related with aperture and no related with pulse frequency. It's also tells us the feasibility of applying the SAR theory in NDT system. We added detecting and date rearranging into the traditional Doppler structure. That makes it from the traditional serial structure which may cause the data pile to the parallel structure which may make system to be a real time system. In the simulating phase, we proved that imaging resolution is just related with aperture and no related with pulse frequency from the simulating image. To sum up, it's quiet suitable way to solve the contradictive between the detective depth and high resolution through the application of SAR technique in NDT.