Finite Element Analysis of Soft-Pad Moldless Stamping of Bistable Circular Micro Shells

Area of Science:

• Materials Science and Engineering
• Mechanical Engineering
• Nanotechnology

Background:

• Bistable microstructures are crucial for microelectromechanical systems (MEMS) due to their multi-state stability and sensitivity.
• Fabricating non-planar, two-dimensional bistable structures like micro shells presents significant challenges compared to one-dimensional designs.
• A novel moldless stamping technique has shown promise for creating initially curved micro plates.

Purpose of the Study:

• To develop a systematic modeling approach for the moldless stamping process of bistable micro shells.
• To understand the influence of process parameters and material properties on shell geometry and residual stresses.
• To provide a tool for optimizing the design and manufacturing of micro shell structures.

Main Methods:

• A finite element (FE) based methodology was developed to model the stamping process.
• The model incorporates elasto-plastic material behavior for the plate and nonlinear behavior for the stamp material.
• Contact interactions between the plate and stamp were explicitly included in the simulation.

Main Results:

• Stamping pressure and plate material properties were identified as critical factors determining residual shell curvature and shape.
• The fabrication process was shown to partially relieve pre-existing stresses, resulting in a unique residual stress distribution.
• The FE model successfully simulated the formation of an aluminum (Al) micro shell with realistic geometry.

Conclusions:

• The developed FE methodology offers a robust approach for modeling and optimizing the fabrication of bistable micro shells.
• Understanding the interplay between process parameters and material properties is essential for controlling micro shell geometry and performance.
• This work provides valuable insights for the design and manufacturing of MEMS devices incorporating micro shell elements.