## 3 Results and Discussions
### Design Analysis and Finite Elements  
The automotive suspension control arm components are subjected to loading forces applied in three directions as shown in Figure 4. Longitudinal force can be calculated by the combination of the rolling resistance force and the traction force. Rolling resistance force can be calculated by multiplying the coefficient of rolling friction '\(\ell\)' with vehicle vertical load. While traction force can be calculated by multiplying the instantaneous value, the friction coefficient '\(\mu\)' with the vertical load. The equation can be written as follows:  
\[\text{F}\_(\text{long.})=(\mu-\text{f})^{*}\text{F}\_\text{v} \tag{2}\]  
According to the understanding of applied forces on suspension mechanical structure, finite elements using Abaqus software was applied on the designs proposed in this study by SolidWorks software. Four designs were selected according to the applied forces, as well as specific design parameters that possessed excellent performance. Figure 6 shows the proposed designs in this study, which are mainly defined as follows: design 1 (inclined web with reinforcement ribs), design 2 (Planar thin web), design 3 (Hollow design) and design 4 (Trussed design). Figure 6: Modified design proposed for automotive mechanical suspension control arm structure. The first design, inclined web with reinforcement ribs, followed the inclined Z-shaped web instead of the conventional straight design. Web inclination was set to 7\({}^{\circ}\), relative to the normal of the plane parallel to the upper flange, as shown in Figure 6a, to compensate the 5\({}^{\circ}\) inclination of the ball socket. The angle of inclination was selected, after multiple trial and errors, using a different angle each time and carrying out FEA simulation. The structure was reinforced by means of a small rib at the lower part of the control arm to limit excess deformation under load. The total mass of the part was found to be 1198 g, which is nearly similar to that of the conventional design (1200 g). The result of the finite elements analysis of the inclined web design is shown in Figure 7. The maximum von Mises stress is found to be 213 MPa, observed near the lower bushing of the control arm. A maximum stress concentration factor (SCF) of 8 is observed near the lower bushing region. The maximum deformation at the location of the ball joint is 1.45 mm under the 5500 N force. A homogenous stress distribution in the lower flange is observed, as shown in Figure 7b, as a result of the inclined web that compensated the inclination of the ball joint socket. The inclination of the web instead of the ball socket leads to the presence of homogenous stress in the lower flange and the absence of any stress raiser regions. The second design relating to thin web design is the most basic design in the critical thinking of manufacturing of the part (due to its simple design). The design eliminates the use of any reinforcement ribs and increases thickness of the upper and lower flanges in critical stress regions. The middle web has a thickness of 4 mm, as shown in Figure 6b, which decreases the total mass of the control arm to 1141 g (by 59 g less than the conventional design). The decrease of weight is not considered enough for performance improvement; thus, elimination of more material is required. The results of the planar thin web design, shown in Figure 8, shows a maximum von Mises stress of 199 MPa. A maximum SCF of 9.95 is also observed near the lower bushing of the control arm in the location of maximum stress. The planar thin web design has nearly similar maximum deformation to the first design of 1.46 mm. The stress distribution in the lower flange is not homogeneous as the previous design due to the straight middle web. A SCF of 3.725 is also observed at the location of the arrow shown in Figure 8c. The design is observed to have high SCF values, despite the lower maximum von Mises stress.