Structural Health Monitoring ,
Structural Dynamics ,
Elastic Wave Propagation in Solids ,
Mechanics of Composite Materials
I would like to develop myself as a Physician of Structures and it is in that respect, my research focus is centered around structural health monitoring (SHM) and advanced non-destructive testing (NDT) techniques.
This will count as one of your downloads.
You will have access to both the presentation and article (if available).
During the last couple of decades, ultrasonic guided waves have been shown to be increasingly capable of interrogating long bones in the human skeleton in order to characterize osteoporosis. Their diagnostic role is promising as the established gold-standard diagnostic techniques of dual-energy x-ray absorptiometry (DXA) and quantitative computed tomography (QCT) do not provide information about the material properties. Ultrasonic guided waves can provide information about the material properties as well as the geometry (i.e., cortical bone thickness) and cracks. Wave propagation in cortical bone is much different than in soft tissue. Likewise, there are similarities and differences between wave propagation in bone and mechanical components such as pipes and plates. While steel pipes and plates typically are homogeneous, prismatic, isotropic, uniform thickness, and essentially lossless; long bones are heterogeneous, non-prismatic, anisotropic, variable thickness, and very lossy. Thus, guided wave propagation in long bones is quite complicated, and yet it is not uncommon to use Lamb wave propagation as a surrogate for wave propagation in long bones. The aim of this work is to compare and contrast wave propagation in a long bone with that in a plate to point out where the surrogate Lamb wave analog is useful and where it is not. The semi-analytical finite element (SAFE) method is used to obtain dispersion curves for a cross-section of the plate, and mid-diaphyseal cross-section of the tibial cortex. The frequency domain finite element (FDFE) method is used to account for the non-prismatic nature of the bone and damping.
Non-cumulative higher and sub-harmonic Lamb wave mode generation as a result of partial-debond of piezoelectric wafer transducers (PWT) bonded onto an Aluminium plate, is numerically investigated and experimentally validated. The influence of excitation frequency on the extent of nonlinearity due to clapping mechanism of the partially-debonded PWTs is discussed. A set of specific frequency range is arrived at based on the Eigen-value and Harmonic analyses of PWTs used in the model. It is found that, at these frequencies, which are integral multiple of the first width-direction mode of a PWT, significantly higher amplitudes of higher-harmonics are observed. It is also seen that at specific debond-positions and lengths, sharp sub-harmonics in addition to higher-harmonics are present. Signal processing is carried out using Fast Fourier transform, which is normalized for comparisons.