New Opportunities for NDT Using Non-Linear Interaction of Elastic Waves with Defects

作者：Solodov Igor; Doering Daniel; Busse Gerd^*

来源：Strojniski Vestnik-Journal of Mechanical Engineering, 2011, 57(3): 169-182.

DOI：10.5545/sv-jme.2010.168

• Nonlinear NDT
• defect-selective imaging
• nonlinear air-coupled emission

When material is subjected to an intense load, its stiffness changes due to elastic nonlinearity. This effect is especially pronounced in damaged materials, so that nonlinearity can be used as an indication of incipient damage. Under dynamic load, mechanical constraint between the fragments of planar defects provides gigantic nonlinearity in finite-amplitude contact vibrations. The local vibration spectra acquire a number of new frequency components which are used as signatures of damage. The experimental implementation of nonlinear NDT relies on the use of laser interferometers (Nonlinear Laser Vibrometry, NLV) to detect the nonlinear waves that are generated selectively by defects. In addition, the planar defects as localized sources of nonlinear vibrations efficiently radiate nonlinear airborne ultrasound (Nonlinear Air-Coupled Emission, NACE). The frequency conversion mechanism concerned with contact nonlinearity of the defect vibrations provides an efficient generation of air-coupled higher-order ultra-harmonics, ultra-subharmonics, and combination frequencies. Both the NLV and NACE are proposed for remote scanning and high contrast defect-selective imaging in nonlinear NDT.

• 出版日期2011-3