TY - GEN
T1 - Nonlinear acoustic structural health monitoring
AU - Zagrai, Andrei
AU - Donskoy, Dimitri
AU - Chudnovsky, Alexander
AU - Golovin, Edward
PY - 2006
Y1 - 2006
N2 - Structural health monitoring (SHM) is an essential technology for maintaining the safety, high performance and operational readiness of civilian and military aircraft. Passive and active SEM methodologies incorporating fiber optic, piezoelectric, dielectric and other types of sensors have been explored for the detection of structural damage resulting from excessive mechanical and/or environmental (e.g. corrosion) loads. One of the promising SHM techniques is embedded ultrasonics in which information on structural health is inferred from records of the elastic waves scattered by structural inhomogeneities or cracks. This approach works well when the damage size exceeds a wavelength of the interrogation signal. As a result, small-scale incipient damage may be difficult to detect using conventional embedded ultrasonics practices. In addition, in complex structures such as the aircraft skin, a large number of structural features (e.g. holes, ribs, etc) opens the possibility of misclassification if features and damage scattered signals exhibit comparable characteristics. To address these limitations of the ultrasonic SHM, we propose to utilize the damage-induced nonlinearity of structural material for discriminating different stages of material deterioration and damage development. A concept of a nonlinear acoustic SHM is introduced that is based on the effect of the nonlinear interaction of elastic waves at the damage interface. This nonlinear interaction results in additional spectral components at the combination frequencies noticeable in the spectrum of the received signal Amplitudes of the additional spectral components indicate the presence and severity of structural damage. We demonstrate the applicability of the nonlinear acoustic SHM for the detection of material degradation at various scales: from micro/meso damage accumulation to macro scale cracks. Examples of macro-scale damage detection are presented and damage characterization capabilities of the method are highlighted. To determine the sensitivity of the method to the micro/meso scale damage accumulation before the material fracture, we conducted a series of strain-controlled fatigue tests in which deterioration of structural material (aluminum) was monitored simultaneously by assessing the sample's mechanical characteristics and by measuring the nonlinear acoustic manifestation of structural damage at the combination frequencies. A stable increase of the material nonlinearity was observed during the test, which correlated with the respective decrease of the specimen's stiffness. Scanning acoustic microscopy and SEM analyses of the experimental samples further support the feasibility of nonlinear acoustic SUM for monitoring material degradation at extremely early stages before the onset of macro-scale disintegration and fracture.
AB - Structural health monitoring (SHM) is an essential technology for maintaining the safety, high performance and operational readiness of civilian and military aircraft. Passive and active SEM methodologies incorporating fiber optic, piezoelectric, dielectric and other types of sensors have been explored for the detection of structural damage resulting from excessive mechanical and/or environmental (e.g. corrosion) loads. One of the promising SHM techniques is embedded ultrasonics in which information on structural health is inferred from records of the elastic waves scattered by structural inhomogeneities or cracks. This approach works well when the damage size exceeds a wavelength of the interrogation signal. As a result, small-scale incipient damage may be difficult to detect using conventional embedded ultrasonics practices. In addition, in complex structures such as the aircraft skin, a large number of structural features (e.g. holes, ribs, etc) opens the possibility of misclassification if features and damage scattered signals exhibit comparable characteristics. To address these limitations of the ultrasonic SHM, we propose to utilize the damage-induced nonlinearity of structural material for discriminating different stages of material deterioration and damage development. A concept of a nonlinear acoustic SHM is introduced that is based on the effect of the nonlinear interaction of elastic waves at the damage interface. This nonlinear interaction results in additional spectral components at the combination frequencies noticeable in the spectrum of the received signal Amplitudes of the additional spectral components indicate the presence and severity of structural damage. We demonstrate the applicability of the nonlinear acoustic SHM for the detection of material degradation at various scales: from micro/meso damage accumulation to macro scale cracks. Examples of macro-scale damage detection are presented and damage characterization capabilities of the method are highlighted. To determine the sensitivity of the method to the micro/meso scale damage accumulation before the material fracture, we conducted a series of strain-controlled fatigue tests in which deterioration of structural material (aluminum) was monitored simultaneously by assessing the sample's mechanical characteristics and by measuring the nonlinear acoustic manifestation of structural damage at the combination frequencies. A stable increase of the material nonlinearity was observed during the test, which correlated with the respective decrease of the specimen's stiffness. Scanning acoustic microscopy and SEM analyses of the experimental samples further support the feasibility of nonlinear acoustic SUM for monitoring material degradation at extremely early stages before the onset of macro-scale disintegration and fracture.
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U2 - 10.2514/6.2006-2260
DO - 10.2514/6.2006-2260
M3 - Conference contribution
AN - SCOPUS:34247117790
SN - 1563478080
SN - 9781563478086
T3 - Collection of Technical Papers - AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics and Materials Conference
SP - 7897
EP - 7913
BT - Collection of Technical Papers - 47th AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics and Materials Conference
T2 - 47th AIAA/ASME/ASCE/AHS/ASC Structures, Structural Dynamics and Materials Conference
Y2 - 1 May 2006 through 4 May 2006
ER -