## 2 Material and Methods
### Analysis from the Mechanical Engineering Standpoint
#### 2.2.3 Application of Contacts  
For an accurate simulation using FEM, it is imperative to establish the existing contacts between the elements constituting the assembly. Autodesk Inventor Professional 2024 facilitates the automatic establishment of these contacts, offering significant advantages for assemblies comprising a large number of components. The manual establishment of contacts in such cases would be excessively time-consuming due to the high number of contacts involved. The existing contacts in the software are briefly elucidated below:  
* Fixed contact: This type of contact assumes that the contacting parts are fixed to each other and cannot move or deform relative to other parts. It is used to model rigid connections, such as bolts or welds.
* Sliding contact: This type of contact allows relative movement between the contacting parts only in a specific direction. It is useful for modeling situations where slippage is expected, such as in guides or rails.
* No penetration contact: This type of contact allows contact between the parts but prevents penetration between them. It is helpful for modeling situations where parts are in contact but cannot pass through each other, such as in nested assemblies or joints.
* Interference contact: This type of contact is used in situations where the contacting parts are allowed to penetrate each other.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Material**} & **Young’s** & **Poisson** & \multirow{2}{*}{**Density (Kg/m3)**} & **Yield Strength** \\  & **Modulus (MPa)** & **Coefficient** & & **(MPa)** \\ \hline Aluminum 6061 & 68,900 & 0.330 & 2700 & 275.00 \\ Brass & 109,600 & 0.331 & 8470 & 103.40 \\ Cast Bronze & 109,600 & 0.335 & 8870 & 128.00 \\ Cast Iron & 120,500 & 0.300 & 7150 & 758.00 \\ Mild Steel & 220,000 & 0.280 & 7850 & 207.00 \\ Nylon & 2930.00 & 0.350 & 1130 & 82.75 \\ Stainless Steel & 193,000 & 0.300 & 8000 & 350.00 \\ \hline \hline \end{tabular}
\end{table}
Table 1: Properties of each material used in the analysis.  
Figure 4: Isometric view of the simplified assembly: front view (**left**) and rear view (**right**).  
* Bonded contact: This type of contact assumes that the parts in contact are joined together as if they were glued. It is useful for modeling situations where parts are joined, such as with adhesives or welded joints.
* Pressure contact: This type of contact is for the contact between surfaces under a certain pressure but without friction. It is used to analyze situations where the pressure between the parts is relevant, such as gaskets or seals.
* Separation contact: This type of contact is for situations where the contacting parts can separate during analysis, that is, a gap is allowed to exist between the contacting surfaces. When a separation contact is used, the parts are allowed to move apart from each other if the forces applied exceed a certain threshold. This is useful for modeling situations where parts are expected to separate, such as the opening of a crack or the separation of components.  
Within each contact type, the choice between symmetrical or asymmetrical contact is available. In symmetric penetration, the nodes of one mesh cannot penetrate the nodes of an adjacent mesh; in the asymmetric type, such penetration is permitted.  
An inherent drawback associated with automatic contact generation is that the software exclusively creates them as bonded-type contacts. Consequently, the behavior of this model may not accurately reflect that of the real model, as there exist different types of contacts within the assembly.  
To address this issue, we can choose between two options: enter all the contacts manually, which is not recommended given the complexity and number of elements of the assembly, or enter all the automatic contacts of a single type (of which it is thought that there are more, in this case the \"bonded\" type) and later change those that are not for the correct type of contact.