Si informa che Venerdì 31 maggio, alle 15:00, presso il Dipartimento di Ingegneria, Università degli Studi Roma Tre (Aula Dir-01, edificio ex-OMI), il professore Timothy Healey terra’ il seminario
Wrinkling of Highly Stretched Sheets: Modeling and Analysis
Transverse wrinkles often develop when a finely thin, rectangular, elastic sheet is highly stretched in the longer direction – think of a sheet of sandwich wrap. Much like the famous Euler buckling of a compressed thin rod, this can be analyzed as a bifurcation problem: The flat, unwrinkled state bifurcates to the wrinkled state as the applied macroscopic stretch is slowly increased. This idea is well known, and the problem has been widely popularized in recent years. In this talk we present some new phenomena for this problem:
– We propose a new class of models incorporating finite nonlinear elasticity for the membrane behavior, accompanied by small, non-zero bending stiffness.
– We analyze our model via numerical bifurcation/path-following techniques in multiple parameters to uncover realistic wrinkling behavior. In particular, we show that elastic wrinkling occurs for a specific range of aspect ratios only; within that range, the wrinkles first initiate, develop to a small maximum amplitude, and subsequently diminish and then disappear as the macroscopic strain is steadily increased.
– We discuss recent experimental results of Sipos & Feher, where the following striking phenomena was observed for certain polyurethane sheets: No wrinkles were observed upon first loading, while wrinkling occurred upon unloading and during all subsequent loading cycles. We present a pseudo-elastic model that accurately predicts such phenomena.
Si veda anche l’allegato.