Skip over navigation

 

Combined Constrained Crystal Plasticity Finite Element Modeling of Single Crystal Niobium

Aboozar Mapar (Michigan State University), Farhang Pourboghrat (Michigan State University), Thomas Bieler (Michigan State University), Christopher Compton (National Superconducting Cyclotron Lab)

Instability in Solids and Structures

Mon 4:20 - 5:40

Barus-Holley 190

Niobium is a superconductor and the material of choice for particle accelerators. Fine grain Nb sheets are deep drawn into bowl shapes and then welded together to make particle accelerator cavities. Large grain Nb sheets have a better superconductive performance and are cheaper; however, anisotropy is more pronounced in them. To use large Nb sheets, one needs to redesign the manufacturing process. However, unreasonably high price of Nb as well as its anisotropic behavior is the hindrance. A more cost-effect approach is to use computational techniques to model the deformation behavior of Nb during its complex forming history. In this study a crystal plasticity model based on the constrained optimization method is used to predict the deformation behavior of single crystal Nb. The goal is to model a large grain sheet, assuming each sheet consists of a number of grains with different crystal orientations. Although the model predicts reasonable results for some crystal orientations, it is unstable for some others. This instability is more prevalent in softer orientations. To deal with this issue the classical hardening rule is revised and a dynamic hardening rule is proposed. Using a weighted combination of these hardening rules dramatically increases the accuracy and stability of the model.