Development of a methodology for the assessment of the fatigue life of hot forging dies based on advanced material models
Mechanical Properties of Metallic Materials and their Microstructural Origins
Final Report Abstract
Hot forging dies are subject to high thermo-mechanical loads which can lead to damage and consequently to failure of the dies. The tools’ loads can be calculated by means of the FE method. For this purpose, appropriate material models are necessary for description of the mechanical material behaviour. In this project, a visoplastic material model was further developed based on an extended experimental database, particularly to describe TMF of the tool steel 1.2367, so that the thermal and cyclic softening of the material can be described for TMF. For this purpose, a method for determining material properties from the experimental database with experiments with three heat treatment conditions was developed. Additionally, a mechanism-based lifetime model was formulated to calculate the number of cycles to failure of the hot forging tool. The lifetime prediction model is based on a fatigue crack growth law and utilizes fracture mechanics estimates for the elastic-viscoplastic cyclic crack tip opening displacement. With the material parameters dependent on thermal and cyclic softening, a uniform description of the different heat treatment conditions and the changing mechanical material properties is possible. The material and lifetime model were implemented numerically and integrated into the simulation program Simufact Forming v16.0. With a method called "cycleskipping", the softening behaviour of the tool steel can also be considered in the lifetime assessment of tools in FE calculations. To evaluate and validate the models, a hot forging process was set up practical and numerical. The tool analysis was conducted thermomechanically using coupled FE calculations. Practical forging experiments were performed to validate the numerical results. Furthermore, the cycles to failure were recorded.
Publications
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Achtung heiß: Das neue Werkstoffmodell für Warmumformwerkzeuge, Forschung im Fokus, Hochschule Offenburg, S. 39-41, 2022
M. Schlayer & T. Seifert
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Numerical Investigations on Stresses and Temperature Development of Tool Dies during Hot Forging. Key Engineering Materials, 926, 559-568.
Behrens, Bernd-Arno; Rosenbusch, Daniel; Wester, Hendrik & Siring, Janina
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A Temperature-Dependent Viscoplasticity Model for the Hot Work Steel X38CrMoV5-3, Including Thermal and Cyclic Softening under Thermomechanical Fatigue Loading. Materials, 16(3), 994.
Schlayer, Markus; Warwas, Marc & Seifert, Thomas
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Simulation of Hot-Forging Processes with a Temperature−Dependent Viscoplasticity Model. Lecture Notes in Production Engineering, 81-90.
Siring, J.; Schlayer, M.; Wester, H.; Seifert, T.; Rosenbusch, D. & Behrens, B.-A.
