A defect detection technique based on time-reversal concept is proposed to detect and locate the defects in a plate
structure. Time-reversal imaging method is widely use as an advanced, robust data processing and imaging technique in
structure health monitoring to detect the defects. Physically, the time reversed signal will retrace its original path
precisely, which means that the signals will be refocused back on the source and defects after we record, time reverse
and back propagate the wave signal experimentally or numerically. In this paper, a distributed actuator/sensor network is
placed on a square homogeneous plate to generate and collect the wave signals in the plate. The time-reversal technique
is then used to interpret the physical meaning of the recorded data and image the defects in the plate. Computer
simulations are presented to illustrate the feasibility of the technique in this paper.
Materials State Awareness (MSA) goes beyond traditional NDE and SHM in its challenge to characterize the current
state of material damage before the onset of macro-damage such as cracks. A highly reliable, minimally invasive system
for MSA of Aerospace Structures, Naval structures as well as next generation space systems is critically needed.
Development of such a system will require a reliable SHM system that can detect the onset of damage well before the
flaw grows to a critical size. Therefore, it is important to develop an integrated SHM system that not only detects macroscale
damages in the structures but also provides an early indication of flaw precursors and microdamages. The early
warning for flaw precursors and their evolution provided by an SHM system can then be used to define remedial
strategies before the structural damage leads to failure, and significantly improve the safety and reliability of the
structures. Thus, in this article a preliminary concept of developing the Hybrid Distributed Sensor Network Integrated
with Self-learning Symbiotic Diagnostic Algorithms and Models to accurately and reliably detect the precursors to
damages that occur to the structure are discussed. Experiments conducted in a laboratory environment shows potential of
the proposed technique.
As wireless sensor has emerged as a promising technology in recent years, active sensing which integrates actuation capability in a wireless sensor unit for detecting localized damage has been brought into sight in structural health monitoring. However, the inefficiency of conventional energy conversion system is a major constraint for the utilization of reactive actuator, such as piezoelectric, in the wireless sensor unit since power source is limited. This paper proposes a highly efficient low power switching amplifier to drive piezoelectric disc in the high frequency for wireless sensor applications.
Conventional wireless sensors for structural health monitoring do not accommodate the need of high frequency data acquisition. Lack of development of this type of wireless smart sensors will without doubt hinder the applications of active diagnostic methods, normally used in local damage interrogation. In this paper, a novel wireless smart sensor design, using FPGA as co-controller with ultra sensing capability, is presented. The development and some outstanding issues of the sensor are discussed in detail, and a preliminary experimental result is given to verify the effectiveness of this wireless smart sensor design.