Real-time structural health monitoring (SHM) systems are applied many fields. Recently, the interest about wind energy
was increased by the demand of clean energy in the world and many researches were actively performed for applying
SHM technology to wind turbine systems. Piezoelectric sensor is one kind of sensor which is widely used for SHM
system to assess damage creation. In this paper, the small scale wind turbine blade was fabricated and health monitoring
of the blade was performed using the piezoelectric sensor. The
quasi-static bending test of the blade was carried out and
the PVDF (Polyvinylidene fluoride) sensors, which are polymer type piezoelectric materials, were used for health
monitoring. Two-cycle test was performed; the load was applied during 350 sec and removed at the first cycle, and load
was applied again until the blade was broken completely at the second cycle. The voltage of PVDF sensors were
measured during the quasi-static bending test in order to find out the moment when the damage occurrence started. The
voltage of the sensor critically changed at the moment of damage occurred.
Recently structural health monitoring (SHM) systems are being focused because they make it possible to assess the
health of structures at real-time in many application fields such as aircraft, aerospace, civil and so on. Piezoelectric
materials are widely used for sensors of SHM system to monitor damage of critical parts such as bolted joints. Bolted
joints could be loosened by vibration, thermal cycling, shock, corrosion, and they cause serious mechanical failures. In
this paper, impedance-based method using piezoelectric sensors was applied for real-time SHM. A steel beam specimen
fastened by bolts was tested, and polymer type piezoelectric materials, PVDFs were used for sensors to monitor the
condition of bolted joint connections. When structure has some damage, for example loose bolts, the impedance of
PVDF sensors showed different tendency with normal structure which has no loose bolts. In the case of loose bolts,
impedance values are decreased and admittance values are increased.
The interactions between the inflatable structure and shape memory alloy (SMA) strip actuators are investigated using finite element simulation. The numerical algorithm of the 3-D SMA thermomechanical constitutive equations based on Lagoudas model is implemented to analyze the unique characteristics of SMA strip. For the numerical results presented in this paper, the ABAQUS finite element program has been utilized with an appropriate user supplied subroutine (UMAT) for the modeling SMA strip. In this model of SMA strip, the shape memory effect is restricted to one-way applications. The geometrically nonlinear, updated Lagrangian equilibrium formulation implemented in ABAQUS is used for the numerical model of inflated membrane structures.
Many piezo actuators can be used without increasing costs and weights of corresponding control system with common control command. Piezo actuator configurations which maximizes degrees of controllability are obtained using genetic algorithms, general optimizers. Optimal placement of piezo actuators is determined for a cantilevered plate, and it is observed that actuator pattern is closely related to the phase of modal control force of each actuator.
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