Ultrasonic Testing for Transverse Discontinuities in Dissimilar Welds: Theoretical and Experimental Results

摘要

In a typical reactor pressure vessel, weld joints between dissimilar metals such as Ni-Cr alloy, austenite and ferrite, exist. These welds are very vulnerable to stress corrosion cracking. Experimental and theoretical investigations have been made to determine the relevant test parameters necessary for crack detection. The experiments were done using two types of probe arrangements: two separate probes, one acting as a transmitter and the other one as a receiver arranged in a "V" form; and a phased array twin crystal probe.Characteristic differences in the crack detection procedure were investigated by measurements with respect to a representative reference specimen with a circumferential dissimilar weld. Measurements show ways and means for reliable detection of transverse discontinuities. Accompanying theoretical calculations using the ray tracing model confirm the influence of some test parameters on ultrasonic propagation behavior in anisotropic regions of a dissimilar weld.