A method for determining equivalent hardening responses to approximate sheet metal viscoplasticity

Area of Science:

• Materials Science
• Mechanical Engineering
• Manufacturing Processes

Background:

• Elevated temperature metal forming offers improved formability and reduced springback compared to cold forming.
• The complex viscoplastic behavior of alloys at high temperatures hinders industrial design and adoption of these advanced processes.
• Existing methods for modeling high-temperature alloy behavior are complex, creating a barrier for designers.

Purpose of the Study:

• To develop a simplified method for determining equivalent strain hardening responses for alloys under elevated temperature conditions.
• To approximate the viscoplastic behavior of sheet metals using single material hardening curves and hardening exponents.
• To facilitate the creation of early-stage design guidelines for elevated temperature metal forming processes.

Main Methods:

• Proposed a novel method to derive simpler, equivalent strain hardening responses from the complex viscoplastic behavior of alloys at elevated temperatures.
• Expressed equivalent hardening responses using single material hardening curves, with hardening exponents approximating sheet metal viscoplasticity.
• Applied the method to two viscoplastic alloys under hot stamping conditions to determine equivalent hardening responses.

Main Results:

• Successfully determined equivalent hardening responses for two viscoplastic alloys under hot stamping conditions.
• Finite element simulations using the determined equivalent material models showed consistent thinning distributions compared to viscoplastic models.
• Validated the method's feasibility across a range of component designs by comparing simulation results.

Conclusions:

• The proposed method provides simpler, equivalent material models derived directly from experimental stress-strain data, outperforming existing viscoplastic models.
• Equivalent hardening exponents enable straightforward comparison of cold and hot stamping capabilities, facilitating rapid material and process selection.
• The developed design guidelines are crucial for promoting elevated temperature metal forming technologies, supporting lightweighting and environmental efficiency.