Stage-oriented monitoring of industrial hot die forging using non-invasive methods and FEM simulations

Abstract This study investigates stage-oriented monitoring and validation of industrial hot die forging processes using a coordinated combination of non-invasive experimental techniques and finite element–based numerical simulations. Hot die forging consists of a sequence of technologically distinct operations—such as billet cutting, heating, preforming, final forging, and trimming—each governed by different physical phenomena and associated quality risks. Effective process control therefore requires operation-specific monitoring strategies rather than isolated analysis of the final forging stage. The proposed framework systematically integrates thermographic measurements, contactless geometric inspection, and FEM simulations across successive stages of the forging route. In addition, additive manufacturing (3D printing) of selected preforms and tool components was employed to support FEM-based verification during technology prototyping, allowing efficient assessment of geometric modifications and material flow prior to full-scale industrial implementation. Instead of focusing on a single component, individual industrial forging cases are intentionally selected to represent key technological operations, including carbon steel and stainless steel forgings. This approach enables assessment of the transferability and universality of non-invasive monitoring strategies across different materials, geometries, and process conditions. Numerical simulations are employed to reconstruct material flow, temperature evolution, and strain histories, while non-invasive measurements provide quantitative validation under real industrial conditions without interfering with ongoing production. When applied in isolation, these techniques are well established; however, their coordinated, stage-consistent integration within a unified process framework constitutes the key novelty of this work. This synergistic application transforms established methods into an advanced, non-invasive diagnostic approach enabling continuous monitoring of critical forging stages and early identification of process deviations or tool-related risks. Microstructural observations are used as secondary validation of reconstructed thermomechanical histories, supporting assessment of process stability and material quality. The results demonstrate that the proposed methodology enables reliable, stage-specific evaluation of hot die forging operations and provides a practical, industrially applicable basis for improved process monitoring, defect prevention, and production reliability.