Boosting the application of ultrasonic arrays

Single- or dual-element angle beam transducers exhibit operating characteristics suitable for a large range of practical field applications. These capabilities can be improved by operating such transducers as phased arrays, where each of the array elements can be pulsed with appropriate time delays, thus controlling the shape and the sound beam direction on a large scale. However, the usually complicated handling of the available array systems - together with their high costs - have been an obstacle to a wider application of this technique. Our contribution describes the strategy currently pursued at IZFP to improve this situation and to simultaneously optimize the performance of ultrasonic arrays. The first part of this strategy is aiming at the improvement of piezoelectric composite materials, which are characterized by a high electromechanical coupling coefficient, broad bandwidth and mechanical flexibility. The piezo-composites are at present fabricated using the dice-and-fill technique, which will in the near-future be replaced by a sol-gel technique leading to a considerable reduction of costs. The second part of our strategy is pursued within a close corporation of three Fraunhofer-Institutes, where phased array components are designed and developed on the basis of highly integrated electronic units. Finally, appropriate software has been elaborated for delay time calculation with respect to a large variety of inspection problems. Appropriate models are used to simulate and optimize the generated beam fields and the detected flaw signals, where curved surfaces and interfaces as well as specific material properties such as anisotropy and viscoelasticity can be accounted for. This bundle of measures is intended to open a wider field of applications by reducing the costs and at the same time improving the capabilities and the reliability of ultrasonic array systems. Illustrative examples and results will be presented.