PSI - Issue 51

Maja Dundović et al. / Procedia Structural Integrity 51 (2023) 192 – 198 M. Dundovi ć et al. / Structural Integrity Procedia 00 (2019) 000–000

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Fig. 5. The last cycle snapshots of Sample B under dynamic loading.

Fig. 6. The residual stress fringe pattern in (a) The samples 14 mm thick; (b) Samples 7 mm thick.

4. Conclusion Plastic materials are often used in AM technologies and due to their favorable flexibility to strength ratio are well suited for compliant mechanism applications. However, their main drawback is low fatigue strength and complex material behavior modeling. In this paper we have investigated application of the photoelasticity methods for estimation of the 3D printed material properties. Furthermore, we have assessed the fatigue strength of the corner filleted flexure hinges manufactured from transparent acrylic based photopolymer using a DLP AM technology. Three-point flexural experiments have been conducted on the rectangular beam samples with standardized dimensions printed in vertical and horizontal orientation. The obtained results show high anisotropic behavior: the calculated flexural moduli are 1570 MPa and 950 MPa for vertically and horizontally printed samples, respectively. Furthermore, the horizontally printed samples exhibited brittle behavior, while the vertically printed samples yielded. Corner-filleted flexure hinges printed in vertical orientation have been subjected to dynamic cantilever beam bending tests at relatively high stress amplitudes. We have concluded that such materials are adequate for application in low dynamic compliant mechanisms applications, since they have failed after 2500 dynamic cycles. Furthermore, the performed qualitative photoelastic observations have shown that the photoelasticity is applicable in dynamic experiments and will be used in our future studies for stress concentration and residual stress determination. Acknowledgements This work has been supported by Croatian Science Foundation under the project number IP-2019-04-3607 and by University of Rijeka under projects number uniri-tehnic-18-34 and uniri-pr-tehnic-19-21. References Aben, H., Anton, J., Errapart, A., 2008. Modern Photoelasticity for Residual Stress Measurement in Glass. Strain 44(1), 40-48. Ajovalasit, A., Petrucci, G., Scafidi, M., 2015. Review of RGB photoelasticity. Optics and Lasers in Engineering 68, 58-73. Baragetti, S., Božić, Ž., Arcieri, E. V., 2020. Stress and fracture surface analysis of uncoated and coated 7075-T6 specimens under the rotating bending fatigue loading. Engineering Failure Analysis 112, 104512.