PSI - Issue 66

Mohammad Jameel Ziedan et al. / Procedia Structural Integrity 66 (2024) 229–246 Author name / Structural Integrity Procedia 00 (2024) 000–000

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Fig. 4. Left) Cranial fracture; right) prosthesis (Bagudanch et al., 2018).

1.7. Heating Methods Heating methods in SPIF can enhance material formability and reduce springback. heating the workpiece uniformly reduces yield strength, increasing ductility. Heating parameters like temperature, heating rate, and duration must be controlled for effective heating and to avoid thermal damage (Clavijo-Chaparro et al., 2018a; Davarpanah et al., 2015). (Conte et al., 2017) investigated the use of SPIF for shaping PMMA sheets. As PMMA has a high glass transition temperature, external heating was necessary for successful forming. It was found that a combination of moderate initial heating (controlled by an electric heater) and low spindle speed (which affects frictional heating) yielded the best results, preventing cracking and spring back while maintaining good surface finish. The "downward heating" strategy, where the temperature is gradually decreased as the forming depth increases, resulted in more homogeneous heating and reduced defects compared to a constant heating approach and formed GFRP cones with wall angles up to 55 degrees. Internal cracks and voids started to appear when reaching the wall angle of 50°. The trajectory, created by interpolating neighbouring contour lines, effectively decreased twist and wrinkle formation. A thermal-assisted incremental forming setup was devised to improve polymer sheet formability and decrease fracture possibility; see Fig. 5.

Fig. 5. Thermal assisted single point incremental forming (Yang & Chen, 2020).