As shown in the diagram, four different stress locations were selected for analysis:

1. Where the fillet between the big end and the base end
2. Where the end of the web is filleted
3. At the surface before the web of the "I-beam" section rounds out
4. The ring where the connecting rod connects to the wrist pin
   
   For the purposes of stress analysis, point 1 could straightforwardly be treated as a bar with a shoulder fillet and point 4 as an infinite plate with a round hole; the latter assumption holds up surprisingly well despite not being entirely accurate. Point two was a little more complicated; it could be treated as another bar with a shoulder fillet, but that doesn't take into account the flanges. I eventually discovered the best simplification was indeed as a bar with a shoulder fillet and computing the stresses at the center of the rod, with the caveat that the stress had to be multiplied by the percentage of the web area out of the total cross-sectional area. Point 3 was the most interesting as I attempted to model it as a combined plate with hole and a solid cross section, with a stress concentration. However, I found that not introducing a stress concentration gave more accurate results.

Having derived the stress equations, I was able to leverage python to perform all the kinematic, pressure, and stress calculations at 200 crankshaft angles over the compression and power stroke of the piston. This enabled quick iteration over the design parameters including fillet radii, the width and thickness of the web, the width and length of the main connecting rod body and the size of both the big end and the ring of the small end.

Design parameters were selected based on what minimized the loading stresses at all four points and a fatigue analysis of the design was performed under cyclic loading conditions using the Soderberg criterion. These parameters were used to create a parametric model in Fusion 360 so that the geometry could be imported into ANSYS for structural finite element analysis.