Abstract
Critically refracted longitudinal (Lcr) waves have been investigated with a computerized data acquisition and analysis technique to evaluate residual stresses present in a residual stress reference standard. This measurement system has an ability to detect travel-times with a precision of 0. l nanoseconds and an accuracy of less than 2.5 nanoseconds. A residual stress reference standard developed for previous research was used as the sample to measure travel-times. The sample was designed and developed so as to create large areas of uniaxial compressive and tensile stresses. Travel-time measurements were made across the breadth of the sample on both sides in increments of 0. 127 m (0.5 inches). This provided data for mapping travel-time variations across both sides of the sample. The zero stress travel-time was determined by averaging the travel-times across the sample. From the travel-time data, stress changes and strain across the sample were also mapped. Strain gage data from a previous study on the same sample was used to compare the residual stress patterns with the ones obtained with the Lcr travel-time data. The strain gage data were found to generally support the Lcr travel-time mapping. However, in addition the Lcr travel-time data indicated bending in the sample. The results showed that Lcr technique presented travel-time data accurately and precisely and represented the true state existing in the sample.
Kypa, Jagan Mohan (1999). Computer aided analysis for residual stress measurement using ultrasonic techniques. Master's thesis, Texas A&M University. Available electronically from
https : / /hdl .handle .net /1969 .1 /ETD -TAMU -1999 -THESIS -K97.