Manufacturing of artificial sub-surface cracks to investigate non-linear features of electro-mechanical impedance measurements

The electro-mechanical impedance method is a standard SHM approach. The method evaluates the dynamic frequency response of a structure to harmonic excitation. Both excitation and measurement are done by a piezoelectric element. This contribution presents a manufacturing process to generate sub-surface cracks in metallic beams with an opening small enough to create non-linear response to harmonic excitation. The generated simple beam with sub-surface crack is analyzed by means of vibration measurements by a piezoelectric element and a Laser-Scanning-Vibrometer, linear and non-linear FE analysis and microscopic images. Challenges in the measurement of non-linear response signals are revealed and needed further enhancement of the manufacturing process is presented. The non-linear dynamic response signal calculated by the non-linear FE analysis is presented and discussed regarding the detection and parameter identification of sub-surface cracks typical for composite delamination or sandwich debonding by the electro-mechanical impedance method.

[1]  Wen Wu,et al.  Investigation of contact acoustic nonlinearity at solid interface , 1998, 1998 IEEE Ultrasonics Symposium. Proceedings (Cat. No. 98CH36102).

[2]  Peter Cawley,et al.  The impedance method of non-destructive inspection , 1984 .

[3]  C. Rogers,et al.  Modeling of the Electro-Mechanical (E/M) Impedance Response of a Damaged Composite Beam , 1999, Adaptive Structures and Material Systems.

[4]  C. M. Scala,et al.  The Development of Acoustic Emission for Structural Integrity Monitoring of Aircraft , 1992 .

[5]  Marc Rébillat,et al.  Laser shock a novel way to generate calibrated delamination in composites: concept and first results , 2015 .

[6]  Victor Giurgiutiu,et al.  Damage Detection in Thin Plates and Aerospace Structures with the Electro-Mechanical Impedance Method , 2005 .

[7]  Rune Brincker,et al.  Vibration Based Inspection of Civil Engineering Structures , 1993 .

[8]  Chun H. Wang,et al.  Higher harmonic generation of guided waves at delaminations in laminated composite beams , 2017 .

[9]  Christoph Kralovec,et al.  Electro-Mechanical Impedance Measurements as a Possible SHM Method for Sandwich Debonding Detection , 2017 .

[10]  I. Solodov,et al.  Nonlinear NDE using contact acoustic nonlinearity (CAN) , 1994, 1994 Proceedings of IEEE Ultrasonics Symposium.

[11]  Sandra GSCHOßMANN,et al.  Lamb wave excitation and detection with piezoelectric elements : Essential aspects for a reliable numerical simulation , 2016 .

[12]  C. Viechtbauer,et al.  Enhancing the Strain Sensitivity of Carbon Nanotube-Polymer Thin Films For Damage Detection and Structural Monitoring , 2015 .

[13]  Christoph Kralovec,et al.  Model-based Evaluation of Electro-mechanical Impedance Measurements for Detection and Size Identification of Face Layer Debondings in Sandwich Panels , 2017 .