Prediction of Strain Gradient Hardening During Microextrusion

Abstract

A new formulation is presented to predict the strain distribution through the thickness of the workpiece during forward extrusion. By using shear components, a new model is established to estimate the geometrically necessary dislocation density, which is found to increase with a decrease in the initial and final specimen diameters and an increase in the die angle. Also, strain gradient hardening during forward microextrusion is predicted according to the calculated geometrically necessary dislocation (GND) density. It is found that to experience a significant amount of strain gradient hardening, the diameter of the material should be on the order of 400 µm or less.

Keywords:

• Analytical model
• Extrusion
• Microforming
• Strain gradient hardening

ACKNOWLEDGMENT

Funding from the U.S. National Science Foundation (CMMI-0644705) is gratefully acknowledged.