## 5 Results
### Final Swingarm Design  
Considering the forces applied on the different loading scenarios, we mostly depend on results obtained for the worst-case scenario which is under emergency braking conditions. A swingarm redesign and material replacement is decided, targeting lower weight and production cost. It is clear that stress and displacements will be raised, but the objective is a safety factor close to \(N=2\) and at the same time to keep displacements as low as possible. A topology optimization procedure was used at first, so as to assist on redesign of the swingarm and obtain valuable results regarding specific areas of material removal (Figure 11). Modelling and simulation were conducted based on parameters referred in Section 4.4. The finite element model was solved using the second (worst) loadcase scenario for various topology optimization parameters and the new form obtained was again validated (solved) in a static analysis. In this way it was possible to fine tune certain parameters such as the percentage of mass removed from the swingarm, which was finally set to 40% reduction compared to the original mass. It must be noted that we also experimented with higher reduction percentages, but the results indicated: a) even more complex swingarm forms, which were difficult to manufacture with our production capabilities (CNC machining) and b) similar stresses and displacements. For these reasons, the specific percentage of mass reduction (40%) was chosen. As seen in Figure 11, material was mostly removed on the front part of the swingarm as well as in the middle, indicating that hollow parts should exist at these points. Most of the features of the form obtained through this procedure were incorporated in the new design.  
Various designs were considered and evaluated and two new alternatives are shown in Figure 12a,b. Their analysis was based on loads of the first loading scenario and the material used was aluminum 7075-T6. The results obtained are presented in Figure 12c,d, respectively.  
Figure 11: Topology optimization results for the swingarm.  
The first alternative design showed a weight reduction of 13% (4.94 kg), while the second alternative provided even higher weight reduction of 18.5% (4.62 kg). Considering the results of analysis, the first one presented higher maximum stress (37.2 MPa--first, 25.63 MPa--second) while both had almost the same displacements (0.38 mm--first, 0.37 mm--second). It is evident that the second design alternative was the type of design we should focus on for the final version. The final form was slightly changed, mostly affected by our production capabilities, where CNC machining manufacturing was chosen. According to the redesign procedure followed, the final swingarm design is presented in Figure 13.  
Figure 12: Different swingarm versions and results: (**a**) 1 st alternative swingarm design; (**b**) 2 nd alternative swingarm design; (**c**) results of stresses and displacements for 1 st alternative swingarm; (**d**) results of stresses and displacements for 2 nd alternative swingarm.  
Figure 13: The final redesigned single-sided front swingarm.  
As mentioned, low stress distribution and a high safety factor of the initial design gave us the flexibility to choose a new aluminum alloy (5083-H116) for the swingarm, targeting lower production cost. The modelling of the isotropic material properties used for the new swingarm assembly can be found in Table 5. Four different materials are used: (a) Aluminum 5083-H116 (swingarm and link), (b) Stainless steel 304 (suspension), (c) Stainless steel S-A4-80 (swingarm axle), (d) Steel AISI4130 (bearings). The required properties used by the pre-processor are: (a) Elastic modulus, (b) Poisson ratio, (c) Shear modulus, (d) Density and (e) Yield strength.