Ultrasonic welding is a very promising technique for joining thermoplastic composite (TpC) components in aircraft primary structures [1, 2]. The potential introduction of new lightweight structures in civil aviation has been driving the change towards condition-based maintenance (CBM) as an alternative to the regular inspection interval approach [3]. In turn, CBM has been pushing forward the de...

Probing material degradation and properties change to anticipate stages of damage can be achieved using advanced in-situ and hybrid non-contact remote ultrasonic sensing including laser generation and air-coupled detection arrangements. The sensing technology is based on application of guided waves such as plate (Lamb waves) or surface waves (Rayleigh waves) for direct material interrogation th...

Previous studies on elastic wave propagation in fractured media have demonstrated that a single planar fracture supports fracture interface waves and that two plane parallel fractures support fracture channel waves. Here, the results are presented for plane wave propagation through an infinite number of plane parallel fractures with equal fracture spacing and fracture stiffnesses. Analysis of t...

The modeling of the interaction between piezoelectric wafer active sensors (PWAS) and structural waves and vibration is addressed. Three main issues are discussed: (a) modeling of pitch-catch ultrasonic waves between a PWAS transmitter and a PWAS receiver by comparison between exact Lamb wave solutions and various finite element method (FEM) results; (b) analytical modeling of the power and ene...

We developed a novel fiber-optic acoustic emission (AE) monitoring system and applied this to gas-leak detection. The system is a Mach-Zehnder, homodyne-type optical fiber laser interferometer with a phase compensation feedback circuit. The phase compensation was given by a piezo-actuator, which can maintain the system at being quadurature condition. The system was demonstrated to measure the i...

High Quality Factor Lamb Wave Resonators by Jie Zou Master of Science in Electrical Engineering and Computer Sciences University of California, Berkeley Professor Albert P. Pisano, Chair The small-in-size and CMOS compatible micro-electromechanical system (MEMS) resonators are likely to be the driving core of a new generation of devices such as radio frequency (RF) filters and timing references...

Use of smart sensor technology along with intelligent signal processing plays a crucial role in the implementation and working of ultrasonic wave based damage detection system. In this work, the interaction of A0 Lamb mode with damages like crack and delamination are studied. Piezoelectric Wafer Active Sensors (PWAS) are used for generation of Lamb waves to detect damages in metal and composite...