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.