Parallel processing simulations of the propagation of ultrasonic waves through material interfaces

Computer simulations of the propagation of ultrasonic pulses in multilayers require a specific physical model both for the material layers and for the interfaces. In the Local Interaction Simulation Approach (LISA) a “spring model” can be conveniently adopted for this purpose. In the spring model, the propagation medium is replaced by an analog set of tensorial springs. The springs within the layers are assumed to simulate the propagation inside the laminates, while the springs representing the interface (“internal springs”) are assumed to predict the interface effect on the wave propagation due to its physical condition. The latter depends on a six component “contact quality tensor”, Q_ij, for each discretization node along the interfaces. When all Q-components are equal to one, the bond at the corresponding node is considered “perfect”. A smaller or zero value for any component of Q _ij indicates and characterizes possible interface flaws, which is useful for NDE applications. Due to the flexible nature of the model, many other physical features affecting the wave propagation, such as attenuation, nonlinearity, hysteretic behavior and plasticity can be easily incorporated and the treatment extended to general 3-D heterogeneous and anisotropic media