PSI - Issue 80

Pavel Šandera et al. / Procedia Structural Integrity 80 (2026) 169–176 Šandera / Structural Integrity Procedia 00 (2025) 000 – 000

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points from the mean (reference) plane for both porosities are similar, unlike the global mean deflection of the tortuous fracture surface from the projection plane described by parameters R L and S dr .

Fig. 5. The dependences of the roughness parameter S a on the plastic zone size R pz for both porosities.

4. Summary The first version of the model simulating the fatigue crack path in metallic materials with variable porosity is presented to help interpret fatigue tests results of titanium scaffolds and their porous filaments. The roughness parameters S a , S dr and R L of fracture surfaces created by the model for two different porosities of fibers (compact and porous) were determined as functions of the crack-tip plastic zone size R pz and can be compared to roughness parameters measured on real fracture surfaces. The main results can be summarized as follows: (i) The S dr -values for the porous material were found to be distinctly higher than those for the compact material, which means higher shielding effects indicating a higher fatigue life of porous filaments when compared to the compact ones. As also expected, the S dr -values increase with the increasing R pz -values, i. e., with an increasing fatigue loading and a decreasing number of cycles to failure. (ii) The mean S dr -values previously measured on several scaffold filaments fractured under cyclic compression tests correspond well to those predicted by the model (iii) The R L -values predicted for the porous material are also significantly higher than those for the compact material and increase with increasing R pz . (iv) Calculated values of R L and S dr nearly follow the well-known approximative formula connecting these parameters. It seems that already this first version of the model could be used to interpret results of fatigue tests of scaffolds and their filaments and to provide a reasonable prediction of the general dependence of the scaffold fatigue resistance on microporosity. Acknowledgements This work was supported by the Ministry of Education, Research, Development and Youth of the Slovak Republic under the project VEGA 1/0080/24, by the Czech Science Foundation under the project number 23-07879S and by the Brno University of Technology under Specific Research Project FSI-S-23-8324.