AN ARRAY-BASED SYSTEM FOR MONITORING CRACKS IN INDUSTRIAL-PLANT AT HIGH-TEMPERATURES

We have designed ultrasonic arrays to monitor fatigue cracks in steel components of industrial plant operating at temperatures up to 400 deg rees C, and developed an imaging algorithm to process the data. The cr ack monitoring system uses two monolithic arrays based on lithium niob ate, a piezoelectric material which works at high temperatures. The tr ansmitting array fires a steered beam and diffracted signals from flaw s in the test subject are collected on individual elements of the rece iver. Real fatigue cracks have been imaged at room temperature and the tips located to within 0.5 mm of their known positions. Side-drilled holes simulating flaws have been successfully identified from data col lected at high temperatures.