PSI - Issue 63

Petr Lehner et al. / Procedia Structural Integrity 63 (2024) 43–50

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3.3. Results Three FEM models were prepared with the same geometry and the same boundary conditions but with different 3D printed element materials. The results of the numerical analysis are presented in Figure 4 and Figure 5. Figure 5 shows the deformations in the section plane in the middle of the structure so that the separation of the wood and polycarbonate parts can be evaluated. In all cases, this was done. As expected, the tensile part of the wood diagonal transmits the deformations only through the bolts and moves away uniformly. This induces large tensile deformations on the top of the 3D printed joint, and at that moment the first differences between the models can be observed due to the different values of the elastic modulus. The biggest difference is in model PC03, where the joint has higher stiffness, thus producing a larger deformation in the horizontal element. Models PC01 and PC02 deform more and therefore the horizontal wood element deforms less. Figure 6 shows the von-Mises stresses on the 3D printed part only (wooden members are ignored in the plot) for all three models. Large differences can be seen in the stress distributions as well as in the maximum values. The colour scale and legend for these results are set so that values exceeding 80 MPa are in red. The extreme peak of stress for model PC01 is 807 MPa, for model PC02 is 670 MPa, and for model PC03 is 1248 MPa. For all models, extreme values are concentrated around the bolt holes, which is expected. In a real structure, there will be an indentation or a dangerous failure. Furthermore, for the PC03 model, extreme values are observed in the area between the horizontal and oblique parts of the joint. Again, this is due to the higher stiffness of the material, which comes at the expense of toughness.