Abstract

Deformable coated materials hold promises for various applications such as polymer coated sheet metal for stamping and thin film coated polymer for flexible electronics. The major challenges in forming coated materials into useful products are in keeping the coating form tooling contact damage and in maintaining the adhesive bond in the deformation process. To develop successful processes and products, it is critical to understand the behavior of the coatings and substrates under plastic deformation.

In this talk, two recent studies in coating adhesion during large deformation are presented. To evaluate the performance of pre-coated sheet metal in stamping, a new testing methodology that combines the key attributes of various experimental techniques is proposed.

Experiments were conducted and the results showed that the methodology can be successfully used to characterize the strength and weakness of two different types of PVDF coated materials. To analyze adhesion loss, the concept of adhesion potential is proposed, and the result in uniaxial deformation mode is presented.

Motivated by the needs of improving corrosion resistance, extrusion of polymer coated metal rods was investigated in the second study. Analytical models based on upper bound method were developed to evaluate axisymmetric conical die extrusion of pre-coated metals. The rigid plastic boundaries were optimized to obtain minimum extrusion power and to predict coating failure. From the models, the critical extrusion die angle can be derived. The analytical results agreed well with the results from finite element simulation. The developed models can be used for extrusion die design and process analysis.