TY - JOUR
T1 - Low-frequency acoustoelastic-based stress state characterization
T2 - Theory and experimental validation
AU - Albakri, Mohammad I.
AU - Malladi, V. V.N.Sriram
AU - Tarazaga, Pablo A.
N1 - Publisher Copyright:
© 2018 Elsevier Ltd
PY - 2018/11
Y1 - 2018/11
N2 - The acoustoelastic theory has been widely utilized for nondestructive stress measurements in structural components. Most of the currently available techniques operate at the high-frequency, weakly-dispersive portions of the dispersion curves and rely on time-of-flight measurements to quantify the effects of stress state on wave speed. High-frequency elastic waves are known to be less sensitive to the state-of-stress of the structure. As a result of such low sensitivity, calibration at a known stress state is required to compensate for material uncertainties, texture effects, and geometry variations of the structure under test. In this work, a new model-based stress measurement technique is developed. The technique integrates the acoustoelastic theory with numerical optimization and allows the utilization of the highly-stress-sensitive, strongly-dispersive, low-frequency flexural waves for reference-free stress measurements. The technique is experimentally validated on a long, rectangular aluminum beam, where accurate stress measurements have been achieved at low excitation frequencies. For instance, with a 500 Hz excitation signal, the error in the measured state-of-stress is found to be in the order of 1 MPa for the different loading scenarios considered in this study. Experimental results show that the developed technique is capable of measuring the state-of-stress without the need for calibration at a known stress state, which makes it ideal for in-service structures.
AB - The acoustoelastic theory has been widely utilized for nondestructive stress measurements in structural components. Most of the currently available techniques operate at the high-frequency, weakly-dispersive portions of the dispersion curves and rely on time-of-flight measurements to quantify the effects of stress state on wave speed. High-frequency elastic waves are known to be less sensitive to the state-of-stress of the structure. As a result of such low sensitivity, calibration at a known stress state is required to compensate for material uncertainties, texture effects, and geometry variations of the structure under test. In this work, a new model-based stress measurement technique is developed. The technique integrates the acoustoelastic theory with numerical optimization and allows the utilization of the highly-stress-sensitive, strongly-dispersive, low-frequency flexural waves for reference-free stress measurements. The technique is experimentally validated on a long, rectangular aluminum beam, where accurate stress measurements have been achieved at low excitation frequencies. For instance, with a 500 Hz excitation signal, the error in the measured state-of-stress is found to be in the order of 1 MPa for the different loading scenarios considered in this study. Experimental results show that the developed technique is capable of measuring the state-of-stress without the need for calibration at a known stress state, which makes it ideal for in-service structures.
KW - Acoustoelasticity
KW - Dispersion
KW - Nondestructive evaluation
KW - Optimization
KW - Reference-free stress measurement
UR - http://www.scopus.com/inward/record.url?scp=85047269581&partnerID=8YFLogxK
U2 - 10.1016/j.ymssp.2018.04.011
DO - 10.1016/j.ymssp.2018.04.011
M3 - Article
AN - SCOPUS:85047269581
SN - 0888-3270
VL - 112
SP - 417
EP - 429
JO - Mechanical Systems and Signal Processing
JF - Mechanical Systems and Signal Processing
ER -