## 2 Backgrounds and Manufacture Requirements  
Static structural analysis was performed using the ANSYS Workbench(r) computer program to examine the behavior of the proposed upper limb prosthesis design. Similarly, the weight was estimated, in five different materials, including the original, and through its density the lightest material and their machinability were determined. The prosthesis model proposed by the authors is shown in Figure 1. It was manufactured in ABS [22]. The design of the arm prosthesis with 7 DOF distributes its movements as follows: 3 DOF in the shoulder, 1 DOF in the elbow, and 3 DOF in the wrist. As a result, the functional design of an upper limb prosthesis was conceived. The model's weight is 0.96 kg considering the arm, forearm, and wrist, while the shoulder mechanism and the motors are 0.96 kg. Therefore, the total weight is 1.92 kg, unlike an actual upper limb as it is lighter [22]. The SolidWorks(r) software was used to determine the physical properties of the model. The property of most significant interest was the volume since each material has its own density. With this data obtained, an estimate of the model's mass was made. Concerning materials, it should be emphasized that researchers seek to satisfy the most significant number of demands of the prosthetic industry by selecting stronger, lighter, and more durable materials [23]. In Table 1 four materials are shown, compared with the original, using their properties of interest such as the density (\(\rho\), kg/m\({}^{3}\)), the coefficient of Poisson (\(\
u\)), and the modulus of elasticity (E, GPa) together with specific solicitation parameters to be evaluated such as the cost of mass production and the machinability of the material [24]. In addition, the ABS model's properties were considered for comparison with the original model. Each material density exposed in Table 1 and the volume of the prototype obtained in SolidWorks(r) were required to estimate the mass of each material's assembly. Although the prosthesis mass was reported around 1.92 kg, the actuators' weight and components are neglected. Therefore, the starting mass is 0.630 kg for ABS. An adaptive mesh of 83,405 elements and nodes 137,630 was proposed. The parties made the model verify the contact areas established manually (Figure 2). Once the discretized model was obtained, the movement restrictions were established (Figure 3). \begin{table}
\begin{tabular}{l c c c c c c c} \hline \hline
**Material** & \(\rho\) & \(\
u\) & E & \(\mathbf{\xi}\) & **Machinability** & \
\begin{tabular}{c} **Density** \\ **(kg/m3)** \\ \end{tabular} &
\begin{tabular}{c} **Mass** \\ **(kg)** \\ \end{tabular} \\ \hline Aluminum 7075-O & 2800 & 0.36 & 72 & 19 & Perfect & 2810 & 1.686 \\ Stainless Steel SAE 304 & 8000 & 0.29 & 193 & 12.5 & Regular & 8000 & 4.8 \\ Titanium Ti-6 Al-4V & 4430 & 0.34 & 114 & 118 & Bad & 4430 & 2.658 \\ Steel AISI & 7850 & 0.29 & 200 & 4.20 & Good & 7850 & 4.71 \\
1040-Normalized & 1060 & 0.33 & 2.30 & 5.18 & N/A & 1060 & 0.630 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Materials to manufacture. Figure 1: Arm of [PERSON]. (**a**) Front view. (**b**) Side view. (**c**) Weight of the hand attached to the arm. Figure 2: Discretized model. A load of 5 N was applied to the palm component \"X\", whereas the model was in a completely rigid position of 180\({}^{\circ}\). Therefore, it was considered the most critical arm position (Figure 4) to obtain the reaction forces on each of the joints of the links that set the mechanism. Naturally, area containing the ball handler's shoulder is expected to be the most critical. Therefore, the theory used was the maximum shear stress (TRESCA) because this criterion of static resistance is applied to ductile materials. After all, it has a greater inclination for safety. Since the selected material was aluminum 7075-O, Figures 5-7 show the maximum displacement, shear stress, and strain. Figure 4: Application of the average load to the “X” axis. Figure 5: The total displacement, material aluminum 7075-O.