A Generalized Stress State and Temperature Dependent Damage Indicator Framework for Ductile Failure Prediction in...

Area of Science:

• Materials Science
• Mechanical Engineering
• Manufacturing Processes

Background:

• Heat-assisted forming is crucial for automotive body-in-white applications.
• Non-isothermal conditions complicate the assessment of forming limits using traditional methods like Forming Limit Curves (FLCs).

Purpose of the Study:

• To develop and investigate a temperature-dependent extension of the Generalized Incremental Stress State Dependent Damage Model (GISSMO).
• To predict forming failures in sheet metal under non-isothermal conditions by integrating multiple isothermal FLCs into a temperature-dependent forming limit surface.

Main Methods:

• A temperature-extended GISSMO fracture indicator framework was developed.
• The model was tested using coupled thermo-mechanical Finite Element Analysis (FEA).
• Simulations focused on the warm forming of an AA5182-O sheet metal cross-die cup.

Main Results:

• The temperature-extended GISSMO model accurately predicts forming limits under non-isothermal conditions.
• The model showed improved prediction accuracy, achieving up to 20% greater drawing depths than established methods.
• Failure risk and location were visualized directly on the part geometry via contour plots.

Conclusions:

• The developed GISSMO model offers a robust approach for evaluating forming limits in heat-assisted processes.
• It enables fuller exploitation of sheet metal forming potential and lightweight design.
• The model accurately predicts material behavior beyond necking, up to ductile fracture, even at low triaxialities.