Comparison of the L cr wave TOF and shear‐wave spectrum methods for the uniaxial absolute stress evaluation of steel members

Abstract

The absolute stress of steel members is a key parameter for determining the performance of steel structures. Compared with other nondestructive evaluation methods, ultrasonic methods, which correlate material stress with ultrasonic velocity, have received the greatest amount of research attention. In this study, we investigated the measurement of the absolute stress distribution of steel members using two ultrasonic methods: a longitudinal critically refracted (Lcr) wave method and a shear wave method. The Lcr wave is generated from the longitudinal wave mode conversion and exhibits the greatest sensitivity to stress. The shear waves are generated by the birefringence effect, and their synthesis signal spectrum exhibits a minimum that varies with stress. A comparison of the two absolute stress evaluation methods is performed. Specifically, four steel members with identical dimensions and materials are used to investigate the discreteness of the calibrated parameters. The uniaxial absolute stress distributions of two steel members with variable cross sections are measured using the two methods and verified using the traditional strain gauge method. The results show that the uniaxial stress distributions of the two steel members can be evaluated by both the Lcr wave time-of-flight method and the shear-wave spectrum method, although the latter is more accurate for the measurement of stress distribution. Furthermore, the measurement principles, parametric calibrations, sensitivity, accuracy, and repeatability of the two methods are compared, and their applicability is discussed. KEYWORDS acoustoelastic effect, birefringence effect, Lcr wave TOF method, nondestructive stress measurement, shear-wave spectrum method, steel members, uniaxial absolute stress

Measurement of the stress of steel members using the ultrasonic phase spectrum

“…31 Current research has shown that a change in stress of 100 MPa causes a change in the Lcr wave TOF of 17.5 ns, and the corresponding change rate is 1.19‰. 25 To verify this, an experiment is carried out on a set of steel members to obtain the change in the Lcr wave TOF due to stress per 100 MPa. Results are given in Table 6.…”

“…According to the above discussion, Equation (25) indicates that the phase spectrum can be used to capture the first RF. A loading test is carried out on a sample for verification.…”

“…However, the change of the Lcr wave TOF is at the nanosecond level, which requires a higher sampling rate and is easily affected by the environmental high-frequency noise. 25 Meanwhile, the acoustic time for an unstressed state is required, 26 which limits the application of the TOF method. Spectral analysis provides a possibility for the further development of ultrasonic nondestructive testing.…”

“…In this case, characteristic quantities in the echo spectrum are more sensitive to stress. 25,28,29 In addition, data of the unstressed state are no longer special. The combination of the spectrum analysis technique and ultrasonic method provides a possibility to improve the sensitivity of the stress measurement of steel members.…”

A method for long-term on-line monitoring of temperature stress of continuously welded rail

“…The influence factors such as temperature, material structure, component curvature, surface roughness, and transducer frequency on the detection results and signal strength were analyzed briefly. Li et al, 22 He et al, 23,24 Wei et al, 25,26 and Haibo et al 27 established a critical refraction P-wave stress detection system with a generator and two receivers. The change of critical refraction longitudinal wave velocity caused by stress was calculated with the cross-correlation algorithm and digital image correlation, which improved the accuracy of the detection results.…”