PSI - Issue 61

Toros Arda Akşen et al. / Procedia Structural Integrity 61 (2024) 268 – 276 8 Toros Arda Akşen, Bora Şener, Emre Esener, Ümit Kocabıçak, Mehmet Fırat / Structural Integrity Procedia 00 (2019) 000 – 000 Finally, the fracture loci are constructed (Fig. 5a) and FLCs were produced (Fig. 5b) regarding the computed parameters. 275

b

a

Fig. 6. (a) Two-dimensional fracture loci and the (b) FLCs predicted by VGM (c 1 =1.7, c 2 =4.1) and MMC (b 1 =0.02, b 2 =219, b 3 =1.01) criteria.

According to Fig 5a, the MMC criterion estimated the region covering from plane strain (η=0.577) to pure shear path accurately (η= 0), whereas the VGM only estimated the region extended from plane strain to uniaxial tension (η=0.33) path. Similarly, the estimation zones of VGM and MMC remained identical, taking the FLCs into account. Both criteria agreed better with the experimental outcomes from the plane strain to uniaxial tension conditions. 6. Conclusions The current study evaluates the FLC prediction capabilities of VGM and MMC fracture criteria in conjunction with the HomPol4 anisotropic yield criterion. To this end, the analyses of the uniaxial tensile tests of different notch shapes were performed through Marc FE software coupled with a user-defined material subroutine called Hypela2. The HomPol4 criterion was adopted in the FE approach of the tensile tests to consider the anisotropic effect exhibited by the AA6016-T4 sheet. It was seen that the HomPol4 criterion described the anisotropic behavior of the AA6016-T4 alloy precisely. Regarding the performances of the ductile fracture models, MMC produced an accurate fracture locus and FLC in a broad spectrum, while the prediction capability of the VGM was restricted to the region remaining between the uniaxial tension and plane strain loading paths. These results point out that the MMC criterion is suitable owing to its Lode parameter and triaxiality-based identification for different metal forming processes. Nevertheless, many essential process parameters, such as temperature and velocity effects, may influence the FE simulation performance. The prediction performance of MMC should also be further assessed in the metal forming processes where the process parameters play crucial roles. Recently, eco-friendly processes such as flow forming have become prominent to meet the requirements of aerospace, defense, and automotive industries. Tubular forms can be produced through the flow forming technique, thereby ensuring the desired wall thickness is achieved (Erdogan et al. (2022), Vural et al. (2022)). Recently, Erdogan et al. (2023) conducted research on failure prediction in the flow forming process of AA6016-T6 aluminum alloy. They adopted the Cockcroft-Latham, Johnson-Cook, and MMC criteria and examined the impact of the roller’s axial and rotational velocities on damage evolution. Although the Cockcroft Latham criterion is more basic than the MMC, the results of the Cockcroft-Latham model showed plausible agreements with the experimental findings. Moreover, temperature dependency is included in the FE simulations for the Cockcroft-Latham criterion, and this effect was found to be essential in this work.