FEA-ROLLCAGE

In Accordance with the rules for 2015 HPVC, two static cases were analyzed of the roll cage loading with SolidWorks simulation. The first case study is 2670 Newton vertical load acting downward at the top of the roll cage at a 12-degree from the vertical. A maximum of 5.1 cm of deflection is required for the roll cage to be considered safe and achieve the maximum score.

The second case study is 1330 Newton applied horizontally to the roll cage. The location of applied load is approximately at the rider’s shoulder height, which stimulates the vehicle in a side crash. A maximum of 3.8 cm of deflection is required for the roll cage to be considered safe and achieve maximum score.

As instructed by HPVC rules, the vertical load is reacted by fixed constraints of where the vehicle seat would be attached to the frame. These two cases are considered as shell  analysis. For both case studies, a safety factor of 2 will be applied to compensate for human errors such as calculation or manufacturing errors. Like stated before, the yield stress for carbon fiber is 450 MPa. Taking the safety factor into consideration, the maximum allowable stress for both case study is 225 MPa.  

 Since the vertical load is at an angle, the load was applied to the model using the components of the load as shown in Figure 7.

 

 

 

 

 

 

 

 

 

 

 

 

The corners of the roll cage was the area for local refinements and the results are tabulated in Table 2. It is hard to tell just from looking at the table if the mesh converges or not. A plot is necessary to determine the convergence and the results plotted as shown in Figure 8. This results can be considered converged because there is 1 MPa change over 2000 nodes.  

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Once mesh convergence is obtained, the displacement figure can be examined. The displacement results of this analysis can be seen in the Figure 9 below.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

As shown in Figure 9, the maximum deflection is approximately 16 mm (1.6 cm). This deflection is very low compare to the required deflection that ASME reports safe for the rider. Although the deflection is very low, it is an area of concern. This study does not take into consideration the affects the external load would have on the frame. More studying will be done in upcoming weeks to ensure that there is no additional reflection caused by the frame when the load is applied.

Figure 10 shows the boundary condition, which is same as in previous case study but the difference is the location of the load. 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

This results were plotted as shown in Figure 11. The graphs shows a better mesh convergence than study 1. The results have converged to 34 MPa, which again is relatively low compare to the yield strength of carbon fiber.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

After obtaining the convergence plot, the maximum deflection for the side load is approximately 4.6 mm (0.46 cm). This deflection is relatively low compared to the displacement allowed by ASME for maximum score. But the same concern arises with this case study as it did for case study 1.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Mesh convergence was one way of validating the SolidWorks results. Another way is looking at the displacement results and determine if the results are displacing as they are expected. From Figure 9 and Figure 12, it can be determine that the displacements are accurate and the boundary conditions reflect the physical situation. In the upcoming weeks, another study would take place where the fix geometry will be replaced by a spring with a high spring constant because in physical world, there would a deflection caused by the loads on the frame.