Slow acoustic surface modes through the use of hidden geometry

The acoustic surface modes supported by a partly covered periodic meander groove structure formed in an assumed perfectly rigid plate are investigated. This allows one to create a slower acoustic surface wave than can be achieved with the same uncovered meander structure. By changing the size of the uncovered section the phase and group speeds can be tuned. When the uncovered section of the meander structure is centred along the grooves then the distance along the grooves between neighbouring holes is the same on both sides of the structure so no band gap is observed at the first Brillouin zone boundary due to glide symmetry. This then gives quite linear dispersion. As the uncovered section’s position is moved away from the centre of the meander structure a band gap opens at the Brillouin zone boundary.

Particles bed morphology under an oscillating stiff and flexible plates

We analyse the different morphologies induced by an oscillating plate above an erodible bed. We present some data describing how the shape and the stiffness of the plate affects the main features of the generated heap. We investigate several configurations with different geometries, frequencies and the amplitudes. Some preliminary results are available, in which the role of the flexibility of the plate is taken in account. Unlike the rigid plate in which a proper oscillation induces the formation of one heap, the morphology of the bed is now characterized by more than one heap due to a different pressure profile induced by a flexible plate.

Influence of friction in a case of impact simulation

This paper presents an analysis of two cases, simulating the impact of a cylindical projectile on a perfectly rigid plate. One case is run without friction, the second one is run taking into account a friction coeficient between the plate and the projectile. The authors used for the projectile the same material constitutive model for both cases, based on experimental data and model developed by Johnson and Cook. Here, the comparing criteria were the maximum value of von Mises stress, the velocity and acceleration of the central point on the opposite face to the contact face of the projectile. Introducing friction, the simulation is more realistic. Taking into account friction, the projectile is less deformed and there was no edge breakage, at the same time moment.