We investigated the theoretical formulation and initial experimental investigation of static and dynamic strain sensing using the Composite Long-range Variable-direction Emitting Radar (CLoVER) transducers. CLoVER Transducers are manufactured using the piezoelectric fibers integrated with the interdigitated electrodes with wedge-shaped sectors arranged in a circular way. A coupled-field analytical model was developed based on the piezoelectricity constitutive equations with the consideration of the anisotropic material properties of CLoVER transducers. The analytical formulation was derived under a cylindrical coordinate system for a single CLoVER sector.
The work presents a damage characterization framework based on a simulation library and matching pursuit algorithm to estimate damage features in typical aerospace structures. The large damage database is generated by numeric simulation. The recent development of the University of Michigan’s Local Interaction Simulation Approach (UM/LISA) is an ideal tool for generating such a damage database in a very efficient manner. It includes capability for piezoelectric coupled field simulation, non-reflective boundary techniques, and contact penalty method for nonlinear guided wave simulation, and can execute on multiple-GPU platform for fast computation.
To verify and evaluate the performance of a space robot controller, kinematics and dynamics of the system have to be formed beforehand for computer simulation. The work is devoted to develop a new kinematic notation for space robots and to come up with an open source of Matlab subroutines for the propose of obtaining the proper dynamics equations of space robots in symbolic forms automatically. For the new kinematic notation, we will present the general form and two special cases.
Non-reflective boundary techniques are typically used in simulation to reduce boundary reflections and reduce model size. The non-reflective boundary conditions and boundary layer methods are developed and implemented in UM-LISA to faciliate simulation so that users can focus on the area of interest while avoiding boundary interferences.
The current implementation of NRB techniques implemented in UM-LISA are illustrated below
The following picture shows the performance of different NRB techniques.
For more information about the algorithm and features, please check the following references.
Phased array methods are a promising approach to damage detection by enabling guided wave steering and beam focusing leading to improved localization and sizing of structural damage. Due to the costs and challenges to addressing piezoelectric arrays in parallel, most phased array methods actuate piezoelectric elements one at a time in round-robin fashion with postprocessing algorithms used to synthetically steer and focus the guided waves. Here we investigated true parallel excitation and sensing of ceramic piezoelectric actuators in a standard structural health monitoring data acquisition system without requiring highly specialized and expensive ultrasonic data acquisition equipment.
One field of research in Structural Health Monitoring (SHM) is relevant to guided wave modeling and simulation. An in-house code has been developed at the University of Michigan, with abundant features for wave simulation such as non-reflective boundary (NRB) techniques, piezoelectric coupled, contact dynamics, multiple GPU parallelization, etc. The code is running on a multiple-GPU platform and is demonstrated to be much more efficient than commericial Finite Element software.
The algorihtm we adopted is Local Interacation Simulation Approach (LISA), a finite difference solver proposed by P.
The acoustic black hole (ABH) effect produces drastic wave compression and energy trapping in thin-walled structures. Recent research has shown that the reflected wave in realistic ABH structures can be reduced by attaching specific wave concentration areas with thin absorbing layer.
In this work, the novel design and implementation of one-dimensional (1D) functionally graded acoustic black hole (FGABH) are studied, as an alternative to achieve low reflection effect. Two kinds of the FG-ABHs are demonstrated, i.
