# Structural Optimization of MicroMED Dust Analyzer
## 3 Results
### Optimizations Findings Discussion  
The numerical results showed that the first natural frequency of the current OB was about 407 Hz. As depicted in Figure 6, the corresponding mode shape included an alternate bending of the OB produced by the heavy OH lumped mass on its footprint. The motion slightly involved the MPG and LG subassemblies as well. Moreover, the quasi-static analyses pointed out that the worst loading case was the one encompassing the 1000 m/s\({}^{2}\) acceleration along the \(Y\)-axis. This was attributed to the larger mechanical compliance of the OB in the latter direction with respect to the others. Finally, the cold case and the hot case analyses suggested that for both the foreseen temperature ranges fully compliant stress values were achieved, and negligible thermal deformations as well.  
With the Model A proposal, the TO guaranteed a mass budget of 64.63 g. The mass saving was approximately 55% of the mass allocated to the ribs grid (i.e., 3.18 g against about 7 g of the current OB), corresponding to approximately 6% of the overall component mass. The modal analyses highlighted that the Model A first natural frequency was at about 412 Hz, i.e., a value comparable with the current OB one. Moreover, comparing Figure 6 with Figure 10, a change in the mode shape can be noticed: the first natural frequency mode shape involved mainly the LG, a favorable condition considering the motion is displaced from the OH footprint, i.e., the most sensible region of MicroMED to preserve the alignment of the instrument. In addition, all the quasi-static and thermoelastic analyses provided positive safety margins, proving the effectiveness and robustness of the proposed design.  
Similarly, the numerical results achieved with the Model B were promising. Indeed, the modal analysis showed that the optimal component natural frequencies were taking place at values larger than the current OB ones. In particular, the first natural frequency was at about 607 Hz, corresponding to an increase of approximately 50% with respect to the current OB one while maintaining a comparable mass budget. Likewise, the Model A, the mode shape was slightly shifted towards the LG footprint (Figure 14). Moreover, the quasi-static analyses and the thermoelastic analyses provided a decrease of the Von Mises stresses magnitude for the former and a slight increase for the latter. The result was explained considering that Model B has larger mechanical stiffness with respect to the current OB, therefore providing increased structural robustness of the component and reduced thermal compliance.  
Finally, both Model A and B highlighted negligible thermal deformations for the investigated case study, showing that the proposed designs are not sensible to the temperature environment foreseen by the mission.  
Indeed, among the proposed designs, both providing interesting improvements with respect to the current configuration, Model A was considered the most promising one for MicroMED mechanical hardware future development and was selected for further experimental investigation.  
Figure 15: Overview of MicroMED Model B assembly relative thermal deformations for the cold case (**a**) and displacements at the defined probes (**b**).