PSI - Issue 41

Mohammad Reza Khosravani et al. / Procedia Structural Integrity 41 (2022) 664–669 Mohammad Reza Khosravani et al. / Procedia Structural Integrity 00 (2022) 000–000

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di ff erent sides of the hole. In our experimental investigations, the crack initiated from one edge of the hole at the yielding point and then propagated throughout the specimen. Here, all specimens with two di ff erent hole diameters showed acceptable failure modes. Ultimate tensile strength of the open hole plate can be calculated based on the following equation: F OHTu x = P max A (1) where F OHTu x is ultimate open-hole (notched) tensile strength in the test direction (MPa), and P max is maximum force carried by test specimen prior to failure (N). Moreover, A is gross cross-sectional area (disregarding hole). Based on the conducted experiments, we documented ultimate tensile strength of 36.9 MPa and 29.7 MPa for the specimens with hole diameter of 6 mm and 12 mm, respectively. The experimental results indicate that the ultimate open-hole tensile strength reduces by an increase in the hole diameter.

4. Numerical simulations

In the present study, we used Abaqus to simulate the fracture of 3D-printed parts under tensile load. Fig. 4 shows the results of the numerical simulation of the plate with hole diameter of 12 mm. In addition, force-displacement curves of experiments and numerical simulations are illustrated in Fig. 4. The numerical simulation show that the large stresses around the hole where the first visible damage occurs. In numerical simulation, failure occurs at the hole which is similar to the experimental practice and according to the standard it is an acceptable failure mode.

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Hole diameter: 6 mm (experiment) Hole diameter: 12 mm (experiment) Hole diameter: 6 mm (simulation) Hole diameter: 12 mm (simulation)

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Displacement (mm)

Fig. 4. A finite element model with hole diameter of 12 mm (left), and force-displacement curves (right).

The numerical simulation indicates that the distribution of stresses is symmetric with respect to both the principal directions x and y . By drawing a comparison between the experimental results and numerical simulation findings, the reduce of fracture load with an increase of hole diameter is confirmed.

5. Concluding remarks

Considering applications of 3D-printed parts as functional end-use product, investigation on the strength of these components is a necessity. In the current study, we designed and printed open hole plates using PLA material and FDM technique. The fabricated plates are subjected to the tensile load and their mechanical strengths are determined. As ratio of the specimen width to the hole diameter ( w / D ) has e ff ect on the strength of the part, we have printed specimens with di ff erent hole diameters. Moreover, finite element models were built to numerically investigate the mechanical strength of 3D-printed open hole plates. Based on the experimental practices and numerical observation, the specimens with small hole ( w / D = 6) show higher tensile strength. Indeed, the mean strength value increases by a reduction in the hole diameter.