Krishnan Balasubramanian

This paper presents the development of a testing technique for measuring the angle of inclination and depth of surface-breaking inclined cracks in simple geometry components using a manual ultrasonic time of flight diffraction system. The testing technique in this work can be useful in risk based test planning for simple geometry components such as pipelines and boiler headers.

This paper proposes a technique for automatic discontinuity location and sizing using the ultrasonic time of flight diffraction technique. Here, the crack tips are modeled as point sources of diffracted waves in a homogenous, isotropic medium. The diffraction arcs are modeled using a ray based approach and the modeled arcs are correlated with the experimental B-scan data. The points of high correlation provide information about the location of the crack tips. A statistical echo separation procedure to isolate the diffraction arcs in the B-scan image is discussed. This paper also addresses the issue of application of this time of flight diffraction technique to a thin section (less than 12 mm [0.47 in.]), wherein the echoes from the various sources (lateral wave, back surface reflection, diffraction from crack tips and so on) interfere with each other, making it difficult to identify diffracted signals from the discontinuity tips.

This paper presents the reliability analysis of a manual ultrasonic time of flight diffraction test system for characterization of surface breaking inclined cracks. Probability of detection (POD) and probability of sizing (POS) curves for the detection and sizing of such cracks have been developed from experimental data. In the development of POD and POS curves, it has been assumed and subsequently verified that the signal responses (a values for an angle of inclination of the crack 0) have a normal distribution. The effects of probe angle and probe center spacing on both POD and POS have been investigated. The curves obtained in this work can be useful in risk based test planning for simple geometry components, such as pipelines and boiler headers, using a manual/automated time of flight diffraction system.