Ultrasonic testing is an important tool for assessing the structural integrity of pressurised components in nuclear power plants during in-service inspection. Consequently, the reliability of inspection is of high significance. In particular, it is important to determine the largest crack that could conceivably be missed during in-service inspection. This information is utilised in order to choose the most effective method for different situations. Probability of detection (POD) curves are used to quantify the effectiveness of the inspection. However, these POD curves require a lot of data points in order to provide reliable estimates of the lower limit performance. Traditionally, obtaining these curves has been relatively expensive and this is why different simulation tools have been used to reduce costs and the number of physical test-pieces needed. In the current study, a novel method based on limited test-pieces is explored to produce a POD curve from the measured data. The present data contains just three artificial cracks made with thermal fatigue. This is insufficient to produce a POD curve. However, the data was sufficient to evaluate the novel approach and to gain preliminary estimates of the expected POD and the most important influential parameters. In this study, the idea is to emulate the amplitude response from the measured crack in a way that represents an amplitude response from a certain crack size. This amplitude data is converted to a B-scan image from which the inspector will evaluate whether there is a crack or not. Then, a POD curve is generated from the achieved hit/miss data.
We combined noninvasive ultrasonic and optical measurements to estimate the mechanical properties of forming colloidal films. Light reflection measurements determined the stage of drying and film structure. A concurrent ultrasound measurement quantified the film stiffness. The main finding was that compressing capillary forces induced a temporal peak in film stiffness when air began to enter the pores in the film. We believe that empirically observing such a stiffening event has not been reported before. This finding advances the understanding of the physics of consolidating suspensions.
We develop an ultrasonic method for nondestructive structural quality analysis of Swiss-cheese. A phased array solution has been implemented to allow fast measurements, dynamic focusing and to alleviate shadowing problems. Initial results exploiting this setup are presented. The results show the potential of the method. However, high attenuation causes frequency downshift, which decreases the resolution as a function of probing depth. Structural inhomogeneity decreases the SNR of acquired signals. These issues lead to a high dynamic range demand for the system. Sophisticated imaging methods should be utilized to fully exploit the beam focusing and deflection capabilities of phased arrays, while maintaining rapid measurements. Compared to our earlier work with single transducer setup, a ten times decrease in measurement time was obtained.
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