Flutter instability in a non-associative elastic-plastic layer: analytical versus finite element results

This paper provides an assessment of flutter instability predictions in non-associative elastic-plastic solids based on “linearized stability analyses” that use only the constitutive moduli of the loading regime. Analytical and numerical predictions of flutter, based on such linearized dynamic stability analyses, are confronted with the results of finite element non-linear dynamic analyses, where both loading and unloading regimes are taken into consideration. A layer that is in a homogeneous stress state on the yield surface is considered in all these analyses. The numerical results show that the non-linear dynamic behavior of the layer is quite different in the cases of constant or variable applied loads. Only in the second case, some correlation is found between the predictions of the above linearized analyses and the existence of growing non-linear dynamic solutions. The dynamic behavior of the layer in the neighborhood of a quasi-static trajectory in strict plastic loading is studied, for decreasing non-null applied load rates, and taking into account the time scales involved in the dynamic response and in the loading process.