Ultrasonic measurement of the residual stresses in patch welded steel plates
Abstract
This study begins with a review of the nature and origins of residual stresses and the techniques currently used to measure these stresses, both destructive and nondestructive. The theory of ultrasonic stress measurement, acoustoelasticity, is discussed in detail, with special emphasis on the use of critically refracted longitudinal (LCR) waves. The ultrasonic stress measurement technique used in this study utilizes LCR waves that are transmitted and received on the same surface and travel just beneath the surface of the plate. The stresses within the plate affect the travel time of these waves in accordance with the acoustoelastic relationship. Considerable attention has been directed toward the use of high angle, longitudinal waves for both nondestructive inspection and stress evaluation. To further longitudinal and shear wave the understanding of the characteristics of these waves, longitudinal and shear wave beam profiles are presented for the LCR wave transducer used in this study and for a commercial creeping wave transducer. The results show that both probes do indeed produce a critically refracted longitudinal wave as well as a trailing shear wave that is refracted into the material at a much lower angle, approximately 33'. Furthermore, the simple and accurate method developed to measure the radiation patterns from these transducers also is presented. Differences in the ultrasonic travel times of the LCR wave were obtained in a stress relieved and a non-stress relieved 13 mm (1/2 in.) thick, structural steel plates. The two 1.2 in (48 in.) square plates were patch welded in the center to create a residual stress field; and subsequently, one of the plates was stress relieved. The LCR travel-time measurements on the plates not only differentiated between the residual stress states but also gave some indication of their distribution and magnitude. Neither texture nor the localized residual stresses significantly affected the results. These findings verify that they LCR ultrasonic technique can indeed measure weld induced residual stresses and demonstrate the potential of this technique for evaluating the state of post-weld heat treatment in common structural steel.
Description
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Citation
Junghans, Paul Gerard (1994). Ultrasonic measurement of the residual stresses in patch welded steel plates. Master's thesis, Texas A&M University. Available electronically from https : / /hdl .handle .net /1969 .1 /ETD -TAMU -1994 -THESIS -J955.