Application of electronic imaging for characterization of defects in nondestructive evaluation

Catastrophic failures of major engineering systems such as the space shuttle or nuclear reactor demands more reliable nondestructive evaluation(NDE) technology to maintain a high level of safety. Reliable defect characterization by NDE depends on its efficiency that eliminates the false confidence level in system performance. Also, the modern damage tolerant design based on fracture mechanics requires the reliability and accuracy of the NDE techniques used to detect and characterize flaws. Inspection codes for industrial components specify the sensitivity levels of an inspection method as well as the rejectable flaw size. For complete defect characterization the electronic imaging technique is widely used. In this work, imaging of defects was carried out on thick weldments of SA-229 pressure vessel steel. Generation of natural defects like cracks were realized by an innovative and reliable welding technique, and NDE techniques, conventional and advanced ones including acoustic holography were used for the crack characterization. Specimens after the test were machined to reveal the cracks and the actual crack morphology was measured and recorded. Through a computer model, the defect image was reconstructed and visualized at different sections. A comparative analysis on the reconstructed image in a computer, the actual one and the NDE result was carried out.