Vibrations of strings and strips: How tension affects the propagation of waves - Maxime Lanoy (LAUM, Le Mans)

When we sing or tune our guitars, we adjust the tension of a string or a strip to control the speed of a transverse mechanical wave. In this seminar, I will revisit this phenomenon through simple experiments. Starting from the case of a single strip subjected to a periodic excitation, I will introduce the broad family of elastic waves that propagate and contribute to the resulting dynamics. I will show how original dispersive effects emerge when the strip becomes sufficiently soft. An interesting feature of soft structures is their ability to undergo significant deformations. Therefore, in the second part, I will examine the effect of a static stretching on the propagation. We will see that certain waves, such as the familiar transverse wave, are strongly altered while some others remain entirely unaffected. Finally, we will navigate uncharted waters, investigating a situation where the external stretching is applied in a dynamic manner. We will specifically consider two different configurations: a sudden loading and a periodic modulation. Here again, I will show that surprising responses emerge when the structure is soft.

Contact: Emmanuel Siéfert