Towards a Robust Characterization of Material Damage Evolution via Linear and Nonlinear Ultrasonic Guided Wave Features

Open Access
Author:
Choi, Gloria W
Graduate Program:
Engineering Science and Mechanics
Degree:
Doctor of Philosophy
Document Type:
Dissertation
Date of Defense:
May 30, 2017
Committee Members:
  • Clifford Jesse Lissenden III, Dissertation Advisor
  • Clifford Jesse Lissenden III, Committee Chair
  • Joseph Lawrence Rose, Committee Member
  • Bernhard R Tittmann, Committee Member
  • Parisa Shokouhi, Outside Member
Keywords:
  • guided waves
  • nonlinear guided waves
  • frequency domain finite element
  • composite
  • metals
  • pipes
  • plates
  • semianalytical finite element method
  • nonlinear generation within finite width plates
  • nonlinear guided wave generation
  • third harmonic
  • second harmonic
  • higher harmonic
  • mutual interaction
  • self interaction
  • wave mixing
  • CFRP
  • kink
  • marcelling
  • out of plane ply waviness
  • fatigue
  • creep-fatigue ratcheting
  • microstructure
  • inhomogeneous damage
Abstract:
Guided wave mode selection, which considers the application, structure, material properties and geometry, is crucial for defect dectection and characterization. This requires understanding of linear and nonlinear elastic guided wave propagation within a waveguide and the interaction with inhomogeneous features or localized discontinuities within the waveguide. Some aspects towards characterization of defects and material damage evolution via linear and nonlinear ultrasonic guided wave features are presented. Nondestructive quality assurance testing methods are limited for thick carbon fiber reinforced polymer (CFRP) structures and have poor resolution for detects such as out-of-plane wavy plies. As one example of a linear guided wave method, a portion of my work involved the numerical investigation, via Frequency Domain Finite Element Method (FDFEM), on the response of a few ultrasonic guided wave modes after interaction with out of plane wavy defects in thick CFRP. The analysis identified a guided wave mode and frequency combination that exhibited greater sensitivity than lower order modes and frequency pairs to interaction with the inhomogeneous or localized discontinuity of geometry and material properties. While linear elastic guided waves are suitable for detection and characterization of inhomogeneous macroscale features, we are also interested in techniques that can provide earlier detection. Nonlinear ultrasonics has the potential to be used to characterize microstructural evolution, which can ultimately enable earlier remaining life prediction and improve condition-based maintenance of structures. The goal of the conducted work was to improve understanding of the interactions between nonlinear ultrasonic guided waves and evolving microstructure features, and to determine an experimental technique sensitive to damage states prior to when macroscale damage is visible. Experiments have been conducted to investigate the sensitivity of the 3rd harmonic, resulting from self interaction of one primary wave or two-wave mixing to localized monotonic tensile deformation and fatigue damage of aluminum plates, using magnetostrictive transducers to excite shear horizontal waves in plates and axisymmetric torsional T(0,1) mode in pipes. Theoretical investigations provide experimental guidelines and offer some insights for interpreting results from experiments using those nonlinear ultrasonic techniques. Damage of interest are the following: ratcheting induced by creep-fatigue in Inconel 617 thin wall tubing and fatigue damage in aluminum alloy and Inconel 718 plates. Nonlinear guided wave theory was used with the Semi-Analytical Finite Element Method, to consider second and third harmonic generation within a finite width plate. With the additional geometric boundaries of a finite width, the dispersion analysis reveals wavestructure profiles dependence through the width direction and many additional modes can exist compared with planar guided wave propagation. Calculation of power flux of mode combinations that exhibited phase matching, was able to determine that additional cumulative higher harmonic modes can be generated compared with that of planar wave guides.