I have been trying to generate a solution to the below theoretical shaft loading in solidworks 2015. The goal is for minimum shaft radius where allowable stress is 25 MPA. Modelling as a beam I have perfect agreement with the hand calcs solution in terms of support reactions and bending moment shape and values. The equation below predicts that a diameter of 29.4 mm will provide a maximum shear stress of 25 MPA assuming that the maximum stress occurs at C. My simulation results confirm the same maximum stress location but that a diameter of 29.4 mm will withstand exactly double the expected stress; 50 MPA.
I modelled A as an immovable support and B allows translation along the beam axis. I don't think material choice should come into play - permissions issues with the way solidworks was installed by the university prevents me from creating custom materials, so I am using 6063-O (yield 50 MPA) and extruded the shaft profile for each beam sections.
Can anyone see where I have gone wrong or explain why I should accept/rationalise the higher result? I have attached my part file, and grateful for any responses.
Message was edited by: Ross Maclachlan - fixed image diaply and attached screenshots to make viewing easier.