Sets of Piezoelectric Probeheads for Stress Evaluation with Subsurface Waves

Abstract

This paper discusses the development of piezoelectric ultrasonic probeheads for measurements of time of flight of subsurface or surface wave ultrasonic pulses. Sets of such probes found application in ultrasonic stress evaluation. In precise measurements of time of flight using piezoelectric transducers, the main source of time scatter proved to be variation in the condition of liquid couplant layers. The thickness of this couplant layer depends on surface roughness of the sample being evaluated. Paper describes a new configuration of probes, composed of two transmitting and four receiving probes arranged along one line, designed to reduce coupling influence on readings. Presented is comparison of readings obtained with known sets of probes and with a new one. Also presented are results of residual stress evaluation performed with various 6-transducer sets of probes on railroad rails, monoblock railroad wheels and pillars of hydraulic press. All measurements were performed in industrial conditions, without any special surface preparation.

Ultrasonic Evaluation of Residual Hoop Stress in Forged and Cast Railroads Wheels—Differences

“…Evaluations of hoop stresses in wheels using subsurface waves, described in [12,13,15,16,25,32], were performed with special, multitransducer sets of ultrasonic probes minimizing the influence of surface roughness on readings and equipped with temperature sensor for automatic temperature correction [39]. For this set of probes the distance on which TOF was measured was L = 180 mm.…”