PSI - Issue 68

E. Ezgi Aytimur et al. / Procedia Structural Integrity 68 (2025) 540–546 E. Ezgi Aytimur / Structural Integrity Procedia 00 (2024) 000–000

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Fig. 2. Deformation distribution of all material models

Fig. 3. Equivalent (von Mises) distribution of all material models

accurate results under extreme impact conditions. The Elastic model, being the simplest among the three, assumes linear elastic behavior without considering any rate-dependent e ff ects or material softening mechanisms. As such, it inherently underestimates the total deformation experienced by the material during dynamic loading scenarios, resulting in the highest total deformation value among the models considered in this study. The equivalent stress values for the Johnson-Cook, Cowper-Symonds, and Elastic material models were found to be 394.4, 368, and 180.6 MPa, respectively. As can be seen from these results shown in Figure 3, the Johnson-Cook model gives the highest equivalent stress value, while the Elastic model gives the lowest value. The Cowper-Symonds model gives a value in between the two. These di ff erences are due to the fact that each model uses di ff erent assumptions and approaches. The main di ff erences between them lies in how they incorporate the e ff ects of strain rate. The Johnson-Cook model is a more sophisticated model that takes into account complex e ff ects of material behavior such as plastic deformation, strain hardening and temperature e ff ects. The Cowper-Symonds model is simpler and only considers plastic deformation and the relationship between yield stress and strain rate (Sˇ krlec and Klemenc (2016), Zhang et al. (2023)). Therefore, the actual equivalent stress value occurring in the target material varies depending on the model used. To determine which model gives the most accurate result, the mechanical properties of the material and the impact test conditions should be taken into account. In this study, the Johnson-Cook model gave the highest equivalent stress value because its better accounts for the complex e ff ects of material behavior. Although the Cowper-Symonds model is a simpler model, it gives more accurate results than the Elastic model. The elastic model gives the lowest value because it only takes into account the elastic behavior of the material. The results can be supported by the study of Liu and Guedes Soares (2019). The study, which numerically supports quasi-static and low-velocity impact tests, has shown that the strain rate e ff ect improves the accuracy of numerical studies involving dynamic and high plastic deformation.