Theses and Dissertations
Issuing Body
Mississippi State University
Advisor
Jha, Ratneshwar
Committee Member
Leckey, A.C. Cara
Committee Member
Rais-Rohani, Masoud
Committee Member
Sullivan, Rani Warsi
Committee Member
Lacy, Thomas E.
Other Advisors or Committee Members
Hammi, Youssef
Date of Degree
5-6-2017
Document Type
Dissertation - Open Access
Major
Aerospace Engineering
Degree Name
Doctor of Philosophy
College
James Worth Bagley College of Engineering
Department
Department of Aerospace Engineering
Abstract
Wave propagation analysis in 1-D and 2-D composite structures is performed efficiently and accurately through the formulation of a User-Defined Element (UEL) based on the wavelet spectral finite element (WSFE) method. The WSFE method is based on the first order shear deformation theory which yields accurate results for wave motion at high frequencies. The wave equations are reduced to ordinary differential equations using Daubechies compactly supported, orthonormal, wavelet scaling functions for approximations in time and one spatial dimension. The 1-D and 2-D WSFE models are highly efficient computationally and provide a direct relationship between system input and output in the frequency domain. The UEL is formulated and implemented in Abaqus for wave propagation analysis in composite structures with complexities. Frequency domain formulation of WSFE leads to complex valued parameters, which are decoupled into real and imaginary parts and presented to Abaqus as real values. The final solution is obtained by forming a complex value using the real number solutions given by Abaqus. Several numerical examples are presented here for 1-D and 2-D composite waveguides. Wave motions predicted by the developed UEL correlate very well with Abaqus simulations using shear flexible elements. The results also show that the UEL largely retains computational efficiency of the WSFE method and extends its ability to model complex features. An enhanced cross-correlation method (ECCM) is developed in order to accurately predict damage location in plates. Three major modifications are proposed to the widely used cross-correlation method (CCM) to improve damage localization capabilities, namely actuator-sensor configuration, signal pre-processing method, and signal post-processing method. The ECCM is investigated numerically (FEM simulation) and experimentally. Experimental investigations for damage detection employ a PZT transducer as actuator and laser Doppler vibrometer as sensor. Both numerical and experimental results show that the developed method is capable of damage localization with high precision. Further, ECCM is used to detect and localize debonding in a composite material skin-stiffener joint. The UEL is used to represent the healthy case whereas the damaged case is simulated using Abaqus. It is shown that the ECCM successfully detects the location of the debond in the skin-stiffener joint.
URI
https://hdl.handle.net/11668/17586
Recommended Citation
Khalili, Ashkan, "Spectrally Formulated User-Defined Element in Abaqus for Wave Motion Analysis and Health Monitoring of Composite Structures" (2017). Theses and Dissertations. 4026.
https://scholarsjunction.msstate.edu/td/4026
Comments
SHM||Lamb Wave||Wave Propagation||UEL||Abaqus||FEM||Spectral Finite Element||Cross-Correlation||Structural Health Monitoring