Proc. SPIE. 9799, Active and Passive Smart Structures and Integrated Systems 2016
KEYWORDS: Rockets, Ferroelectric materials, Sensors, Composites, Interfaces, Manufacturing, Nondestructive evaluation, Solids, Structural health monitoring, Finite element methods, Software development, Microsoft Foundation Class Library, Electromagnetic coupling
Various damages might occur during the solid rocket motor (SRM) manufacturing/operational phase, and the debonding of propellant/insulator/composite case interfaces is one of damage types which determine the life of a motor. The detection of such interface debonding damage will be beneficial for developing techniques for reliable nondestructive evaluation (NDE) and structural health monitoring (SHM). Piezoelectric sensors are widely used for structural health monitoring technique. In particular, electromechanical impedance (EMI) techniques give simple and low-cost solutions for detecting damage in various structures. In this work, piezoelectric EMI structural health monitoring technique is applied to identify the debonding condition of propellant/insulator interface structure using finite element method and experimental investigation. A three-dimensional coupled field finite element model is developed using the software ANSYS and the harmonic analysis is conducted for high-frequency impedance analysis procedure. In the experimental study, the impedance signals were measured from PZT and MFC sensors outside attached to composite case monitoring the different debonding conditions between the propellant and insulator. Root mean square deviation (RMSD) based damage index is conducted to quantify the changes i n impedance for different de bonding conditions and frequency range. Simulation and experimental results confirmed that the EMI technique can be used effectively for detecting the debonding damage in SRM and is expected to be useful for future application of real SRM’s SHM.
Among structural health monitoring techniques, nonlinear ultrasonic spectroscopy methods are found to be effective
diagnostic approach to detecting nonlinear damage such as fatigue crack, due to their sensitivity to incipient structural
changes. In this paper, a nonlinear ultrasonic modulation method was developed to detect and locate a fatigue crack on
an aluminum plate. The method is different with nonlinear wave modulation method which recognizes the modulation of
low-frequency vibration and high-frequency ultrasonic wave; it recognizes the modulation of tone burst and high-frequency
ultrasonic wave. In the experiment, a Hanning window modulated sinusoidal tone burst and a continuous
sinusoidal excitation were simultaneously imposed on the PZT array which was bonded on the surface of an aluminum
plate. The modulations of tone burst and continuous sinusoidal excitation was observed in different actuator-sensor paths,
indicating the presence and location of fatigue crack. The results of experiments show that the proposed method is
capable of detecting and locating the fatigue crack successfully.
Most of the members of modern structures operate under loading conditions, which may cause damages or cracks. Interest
in detecting structural damage, at the earliest possible stage (i.e. breathing crack), has always been a major issue in the
structural health monitoring community. Among structural health monitoring techniques, Lamb waves is frequently used
as diagnostic tools to detect damage in plate-like structures. The decomposition of the time reversal operator (DORT)
method is a selective detection and focusing technique using an array of transmit-receive transducers. But there is little
research on locating breathing crack on the plate using Lamb wave DORT method. In this paper, a proposed approach
based on the DORT method is developed to locate a simulated breathing crack on the aluminum plate using Lamb wave
through finite element simulation on the commercial finite element code ANSYS platform. The nonlinear superharmonic,
generated by a breathing crack under the effect of an external Lamb wave interrogation signal, was related to the location
of the crack. This method, which uses PZT array and operates under multi-modes pulse-echo mode, can estimate the
position of the breathing crack in 2D image by numerically backpropagating selective eigenvector using the S0 Lamb wave
propagation analytical solution. The numerical simulation results illustrate the proposed method.
An actual structure including connections and interfaces may exist nonlinear. Because of many complicated problems
about nonlinear structural health monitoring (SHM), relatively little progress have been made in this aspect. Statistical
pattern recognition techniques have been demonstrated to be competitive with other methods when applied to real
engineering datasets. When a structure existing 'breathing' cracks that open and close under operational loading may
cause a linear structural system to respond to its operational and environmental loads in a nonlinear manner nonlinear. In
this paper, a vibration-based structural health monitoring when the structure exists cracks is investigated with
autoregressive support vector machine (AR-SVM). Vibration experiments are carried out with a model frame. Time-series
data in different cases such as: initial linear structure; linear structure with mass changed; nonlinear structure; nonlinear
structure with mass changed are acquired.AR model of acceleration time-series is established, and different kernel
function types and corresponding parameters are chosen and compared, which can more accurate, more effectively locate
the damage. Different cases damaged states and different damage positions have been recognized successfully. AR-SVM
method for the insufficient training samples is proved to be practical and efficient on structure nonlinear damage detection.
Taking use of VR, GIS and WWW technique, this paper discusses how to develop a software system, combining with theories of urban planning. This system could provide a platform for urban pkmning, on which the effect of design, environment and layout can be examined before construction. At the same time, the system could provide designing thta and special analysis. So the superintending departments and experts could evaluate the design in the system, and the infoimation of evaluation could be feed back to the system to redesign, till the result is satisfying.