Effect of Rate Sensitivity on Necking Behavior of a Laminated Tube Under Dynamic Loading

An elastic-viscoplastic based finite element model has been developed to study the necking behavior of tube expansion for rate independent materials, rate dependent monolithic materials, and laminated materials during dynamic loading. A numerical study shows that for rate independent materials, the dynamic loading will not delay diffused necking but localized necking; for rate dependent materials, high strain rate sensitivity can significantly delay the onset of localized necking for both monolithic and laminated sheets and affect the multiple-neck formation in high-speed dynamic loading. The model also shows that a higher volume fraction of a clad layer with positive rate sensitivity material in a laminated sheet improves the sheet ductility.