Enhanced Formability in Sheet Metals Produced by Cladding a High Strain Rate Sensitive Layer

Abstract

The necking behavior of cladding sheets with a ratesensitive layer cladding on a rateinsensitive core material has been studied. A nonlinear longwavelength analysis, similar to the one proposed by Hutchinson and Neale (1977, “Influence of StrainRate Sensitivity on Necking Under Uniaxial Tension,â€‌ Acta Metal., 25, pp. 839–846) for monolithic ratesensitive materials, is developed to identify the onset of necking in a ratesensitive clad sheet. This relatively simple analysis is validated by comparing its numerical results with those based on more complicated finite element analysis. It is demonstrated that for monolithic ratesensitive materials the proposed nonlinear analysis reduces to the one developed by Hutchinson and Neale (1977). For cladding sheets, it is found that the necking strain increases monotonically by increasing the strainrate sensitivity of the clad layer if the volume fraction of cladding is fixed. It is also revealed that, for fixed strainrate sensitivity of the clad layer, necking localization is retarded by increasing the volume fraction of the cladding layer.