In this paper, a vibration testing and health monitoring system based on an impulse response excited by laser-induced
breakdown is proposed to detect damage on membrane structure. A health monitoring apparatus is developed with this
vibration testing system and damage detecting algorithm which only requires the vibration mode shape of the damaged
membrane. The vibration mode shapes of the membrane structure are analyzed by using 2-D continuous wavelet
transform, and applying boundary treatment and the concept of iso-surface. The effectiveness of the present approach is
verified by finite element analysis and experimental results, demonstrating the ability of the method to detect and
identify the location of damages.
In this paper, the authors propose a finite element model of a simple single bolt joint that undergoes loosening in order to
verify characteristic changes due to bolt loosening and develop a loose-bolt detection system. The model is created using
3D solid elements and surface-to-surface contact elements between head/nut and flange interfaces. Pretension effects and
contact behavior between flanges to be joined are also taken into account. In order to validate the finite element model
by experiment, vibration testing method based on non-contact impulse excitation by high-power YAG pulse laser which
can produce an ideal impulse is conducted. The characteristic changes due to the bolt loosening in high frequency region
can be extracted by the present laser excitation system. Finally, an approach of loose bolt detection is demonstrated by
applying statistical evaluation of Recognition-Taguchi (RT) method to a six bolt cantilever which has loose bolt.
This paper proposes a vibration testing and health monitoring system based on an impulse response excited by a laser
ablation. High power YAG pulse laser is used for producing an ideal impulse force on structural surface. It is possible to
measure high frequency vibration responses in this system. A health monitoring system is constructed by this vibration
testing system and a damage detecting algorithm. A microscopic damage of structures can be extracted by detecting
fluctuations of high frequency vibration response with the present health monitoring system. In this study, loosening of
bolt tightening torques is defined as the damage of the system. The damage is detected and identified by statistical
evaluations with Recognition-Taguchi method.
Laser supported propulsion of a micro-airplane with water-covered ablator is demonstrated. The repetitive use of overlay structure is experimentally demonstrated with specially-designed water supply. The various transparent overlay is investigated by the CIP-based hydrodynamic code and experiments by pendulum and semi-conductor load cell. The momentum coupling efficiency of 5000 N-sec/MJ has been achieved by ORION experiments that agree with the simulation code. With the maximum efficiency approximately 10<SUP>5</SUP> N- sec/MJ predicted by the simulation, 30 pulses of MJ laser can give the sound speed to 10tons airplane. The concept can also be used for driving a micro-ship inside human body and a robot under the accidental circumstance of nuclear power reactor in which large amount of neutron source makes electronic device useless.