Research On Numerical Analysis And Visualization Of Ultrasonic Longitudinal Waves Scattering In Defected Solids

Ultrasonic nondestructive testing technology is widely used in fields of railway, petroleum chemical industry, machinery manufacturing, aerospace and medical. However, ultrasonic is a stress wave that can't be observed directly. People mainly study the propagation and scattering of ultrasonic wave in solid through the transducer that receives echo waves. Thus the visualization of ultrasonic transmission can be realized and used to provide experimental basis for the research and application of ultrasonic nondestructive testing technology.First this thesis simulates the propagation and scattering of ultrasonic longitudinal waves in models with different defects by ANSYS. Then a dynamic photoelastic observation device is designed and some photoelastic photographs of ultrasonic longitudinal waves propagating in the transparent solids with the same sizes and defects are obtained. And the experimental results are consistent with the finite element simulation results basically. Therefore people can use finite element simulation to study the propagation and scattering of ultrasonic waves in opaque solids with complex defects.In the visual experiment part, a dynamic photoelastic observation device is designed successfully. And the device includes ultrasonic transmitting module, acousto-optic delay module, amplifying module and photoelastic system module. The ultrasonic transmitting module can emit sync signal of the ultrasonic longitudinal waves. The acousto-optic delay module controls delay time of the sync signal by Verilog programming language. The output of the acousto-optic delay module can trigger the amplifying module to export rectangular wave signal with narrow width and high current, which can drive directly the supper-bright light emitting diodes(LED). Finally the device shows the size of stress during the propagation in the form of light strength, and demonstrates the propagation by light and dark stripes. The photoelastic photographs clearly show the mode conversion, creeping waves, grazing incidence and angle scattering. Compared the photoelastic photographs with the snapshots of wave field, this thesis finds the experimental results are consistent with the finite element simulation results basically. This thesis discusses the future research in this field, such as quantitative research of ultrasonic propagation and scattering with image processing technology.