Material Characterization using Ultrasonic Testing

Aim and objectives of project: 

The main aim of this EngD project is to use diffuse ultrasound to reconstruct texture (i.e., orientation distribution of crystallites in a polycrystalline material) in an inspected metal component with complex geometry. This entails investigating the physical evolution of the diffuse ultrasonic field in arbitrary inspection directions, to enable reliable measurements of longitudinal and shear wave speeds. The texture could then be obtained from the measured polycrystal speeds by using a texture-inversion mathematical formula. 

What NDT problem I am working to solve: 

Up till today, ultrasound is still primarily used to inspect regular shapes or flat surfaces early in the manufacturing process. During fabrication of any component, processes like mechanical working and heat treatment alters crystal structure, and thereby material properties. Thus, I am working on expanding the capability of ultrasound to inspect components (that tend to have complex geometry) across many stages the manufacturing process, to enhance the performance and ensure safety of the components. This is crucial to verify that the material properties do not worsen during the process. 

Progress so far: 

So far, experiments were designed and conducted to understand the parameters (such as sufficient gain, optimal time delay and window length) needed to achieve useful diffuse field for wave measurements. A parametric study was also conducted to investigate the effectiveness of different noise-removal methods. There is also work in progress to measure wave speed, at different inspection angles, from diffuse fields and to improve the measurement’s accuracy. A simulation model is also being built to verify the theoretical understandings of diffuse field and the experimental results gathered till now.