Model Used

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Upright CAD model version 9.2.

Loading

Relevant loading notes: For the forces in the Y and Z directions, both vectors are resolved into 1 resultant vector (using trig/pythagoras) and applied this way in the simulation. This is more representative of what is happening in reality and helps to potentially expose stress concentrations not apparent when the Y and Z forces are applied separately. Forces in the positive X direction are applied to a circular split face the same diameter of the spindle head (not the entire recessed face).

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Resultant force vector from combining the Y and Z forces.

Fixtures and Connections

2 sets of 6 bolted connections are used to fix the upright to the upper and lower bearing caps. In the simulation, the head diameters of the nuts and bolts are both 12.5mm, which is representative of the diameter of a M6 washer that would likely be used here (not the actual diameter of the bolt head and nut). This had the effect of reducing stresses around the bolt holes in the simulation. The bolts also have a preload of 14.59 N.m and a friction factor of 0.14 based on the specifications for a class 10.9 high strength M6 bolt listed in the table below.

Component contact interactions are used between the upright and the two bearing caps to prevent interference. To simulate the presence of the bearing, advanced fixtures and virtual walls are used. Cylindrical advanced fixtures are used in the bearing housing of the upright to restrict movement in the radial direction. Virtual walls are used on the flat surface of the bearing housing to restrict movement in the axial direction. Virtual walls are also used on the body of the upright to mimic the presence of the steering arm mounting points. Lastly, the bearing caps are fixed in space in all directions, acting like a test fixture (since we are only interested in simulating the behavior of the upright).

Mesh Convergence

Notes:

• Using blended curvature-based mesh, node size is max node size.

• Material yield strength: 505 MPa (7075-T6 aluminum).

• Simulated stresses near bolt holes are often higher than they are in reality.

• Maximum and minimum stresses are plotted for the upright only (the bearing caps are dummy parts).

• Local contact interactions break this simulation, not sure why. Used component interactions instead.

Loading Case 1

Loading Case 2

Loading Case 3

Loading Case 4

Loading Case 5

Results

Loading Case 1: Results are converging. Stress decreases as the mesh is refined. Max stress is not concerning. Lowest safety factor: 2.6.

Loading Case 2: Results are generally converging. Stress increases as global mesh is refined but decreases when mesh refinement is applied to high stress areas. Highest stress level still not a cause of concern. Lowest safety factor: 1.6.

Loading Case 3: Results are converging. Stress decreases as the mesh is refined. Max stress is not concerning. Lowest safety factor: 2.6.

Loading Case 4: Stress increases as mesh is refined to a 5mm global size, but decreases once local mesh refinement is applied. Max stress is still not concerning though. Lowest safety factor: 1.3.

Loading Case 5: Results are converging. Stress increases as the mesh is refined. Max stress not concerning. Lowest safety factor: 2.5.

Recommendations and Next Steps

• Apply more local mesh refinements in the model and in all simulation iterations.

• Remove rotation lock on bearing cap fixtures.

• Run a topology study.

• Work on designing a lighter prototype.