Moein Abdi
Moein Abdi recently completed his Ph.D. in mechanical engineering at the University of Auckland, where his research focused on the free and forced vibration analysis of waveguides with nonlinear boundaries using a wave approach. He has worked on various topics in both linear and nonlinear vibration domains, encompassing the linear vibration of microcantilevers in Atomic Force Microscopy (AFM), nonlinear vibrations of continuous structures through wave propagation and reflection, and vibrations of metamaterial beams with grading piezoelectric elements. He is now working as a teaching technician at the University of Auckland and supporting multidisciplinary teaching spaces and overseeing laboratories for mechanical, civil, and structural engineering courses.
His PhD project concerned the free and forced vibrations of waveguides with nonlinear boundaries analytically, numerically and experimentally. The study investigates the reflection of time-harmonic waves in a waveguide featuring a nonlinear boundary stiffness, focusing on applications to rods and beams. Numerical examples illustrate energy leakage into higher harmonics, determining the minimum magnitudes of reflection coefficients for axial and flexural waves at the fundamental frequency. An experimental method for the measurement of reflection coefficients featuring a nonlinear boundary is studied and a nonlinear boundary configuration introduced characterized by cubic stiffness, representing essential nonlinearity. The results show that with multiple incident waves and for flexural vibration in the presence of nearfield waves the maximum energy that can leak into higher harmonics increases.
Experiment Set up:
The experimental arrangement consisted of a beam with a tip mass and a nonlinear boundary configuration. Wave decomposition and estimation of scattering coefficients should be used to measure the waves reflection coefficients. A shaker is used to excite the beam, and the strength of the force can be changed using a power supply. Three accelerometers are used to make the measurements at different points. The accelerometers should be equally spaced. A signal analyzer is used to collect the data and then the signals are processed, and the wavenumber and reflection coefficients are obtained using the wave decomposition method.
The experiment set-up for estimation of reflection coefficients of a beam with nonlinear boundary