Abstract
Characterization of cracks and crack propagation is of great importance in many industrial fields such as oil and gas, power generation or transportation industries. In particular, stress corrosion cracking (SCC) is a challenging issue in these industries. Conventionally, sample integrity is controlled by phased array ultrasonic testing because of its ease of use. In reality, this nondestructive testing (NDT) technique, considering linear acoustic assumptions, only reveals the opened parts of cracks. This leads to an underestimation of the crack depth because real cracks often contain closed parts and ramifications. Methods considering nonlinear effects or revealing these effects have shown to be appropriate to characterize closed parts of cracks. In this paper, we propose to use a nonlinear imaging method based on a fundamental wave amplitude difference approach. The purpose is to generate several conventional focused sequences with different power amplitudes. Then, the nonlinear image is obtained by subtracting images together, giving a nonlinear residue. This method is assessed with a fatigue crack obtained by mechanical fatigue cycles. It has been implemented in an open ultrasound platform that makes this inspection in real-time. It results that both linear and nonlinear images give complementary information. The linear images reveal opened parts of the cracks and nonlinear images gives information about the closed parts.
How to Cite:
Carcreff, E. ., Braconnier, D. ., Ohara, Y. ., Haupert, S. . & Renaud, G. ., (2019) “Nonlinear imaging of closed cracks by a fundamental wave amplitude difference approach”, Review of Progress in Quantitative Nondestructive Evaluation .
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