PSI - Issue 66

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

material's side wall. The findings indicated that spindle speed and sheet thickness significantly impacted formability and surface roughness. Additionally, a smaller tool diameter resulted in better surface quality; see Table 2. The increasing of the step size and applying heat after forming led to reduction in spring back. The types of failure in polymers differ from those in metals. While polymers more likely to resemble a tear, unlike metals, which primarily crack. Therefore, it is clear that the methods used in forming composite materials differ from those in metals. The results indicated that υ and ( ω × Φ ) significantly influence the forming performance of PVC sheet material, υ is the main influencing factor on SPIF performance of PVC sheet. Excessive ω can lead to material wear-out. (Bagudanch, Centeno, et al., 2017) revisited the formability and failure of different polymers PVC, polycarbonate (PC), polypropylene (PP), polycaprolactone (PCL), and ultrahigh molecular weight polyethylene (UHMWPE) during deformation using SPIF, see Table 3. Traditionally, spindle speed is a crucial parameter affecting forming temperature and material formability limits as well as failure mode. Table 3. The results of maximum depth, maximum angle and failure occurrence and mode of failure for the different SPIF tests (Bagudanch, Centeno, et al., 2017). Test Materials Spindle speed, S (rpm) Maximum depth (mm) Maximum angle (º) Failure? 1 PVC Free 42.5 89.5 YES 2 2000 43 90 Twisting without fracture 3 PC Free 29 79.8 YES 4 2000 32.5 82.5 YES 5 PCL Free 43 90 Small cracks and twisting 6 2000 43 90 Small cracks 7 PP Free 43 90 NO 8 2000 43 90 NO 9 UHMWPE Free 43 90 NO 10 2000 43 90 NO 1.3. SPIF of Hole-Flanges SPIF of hole-flanges requires careful consideration of process parameters such as tool size, step size, feed rate, spindle speed, and material properties to achieve the desired formability, dimensional accuracy, and surface finish. But the formability is limited by fracture, unlike conventional press working where necking precedes fracture, see Table 4. SPIF also resulted in cracks forming around the circumference of the flange wall, while press working led to cracks along the hole edge, see Fig. 2. Table 4. Summary of the results obtained in hole-flanging of conventional PW and SPIF. The dark grey cells correspond to failure fracture (Cristino et al., 2015). D o (mm) Conventional press working SPIF Drawing angle of the intermediate stages � � º � 65 70 75 80 85 90

127 121 115 102

95 73 52

The feasibility of using SPIF to create hole-flanges in polymer sheets was investigated (Centeno et al., 2014). Therefore, it was found that the polyethylene terephthalate (PET) is suited for this process due to its ability to withstand significant deformation at room temperature. The research shown that PET sheets could be formed into hole-flanges