LAUSR

Abstract It is highly appreciated the using reinforced layers in supporting metallic parts due to increased performance and formability of the sheets. Firstly, the effect of reinforcing layer will be investigated on the expanding of rings as a benchmark stability problem and then considered when the composite panels undergo the axial and biaxial stretches near instability threshold. In the ring expanding case; process will be explored by the wavelength and wave number changes through the linear perturbation analysis. The linear perturbation or linear stability is established on the elastic-visco-plastic fragmentation of the rings that includes the effect of significant deformation, geometric softening and hydrostatic pressure. Alternately, the vertex model will be used in prediction of localized necking instability that, considers the discontinuity of stress and strain rates inside the neck band. Here, the DYC-angle and quadratic Hill yield criterion help us to predict the localized necking band and consider the anisotropy effect, respectively. Also, the forming limit diagrams will be used for presenting the vertex analysis results. In the vertex theory, the non-linear reinforced layer will be considered among the neo-Hookean materials. Results will be validated with the other theoretical and experimental data available in the literature.