Design of a shaft subject to torsion/bending/fatigue

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The discussion revolves around a design task involving a shaft subjected to torsion, bending, and fatigue. The user has created a free body diagram and calculated reaction forces at bearings, deducing a torque force of 1.1 kN and reaction forces of 5.877 kN at bearing B and 6.023 kN at bearing A. They have also drawn shear force, bending moment, and torque diagrams but are uncertain about calculating the shaft diameter using equivalent bending moments and torque values. Key questions include whether the maximum bending moment (Mmax) is derived from the highest value on the bending moment diagram and which torque force to use. The user seeks clarification on these calculations to proceed with the design task effectively.
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I have attached the design task I have been given and I am unsure as to what to do next! I will explain that which I have done so far and if anyone can point me in the appropriate direction that would be greatly appreciated!
1. I have created a Free body diagram (FBD), and drawn in the unknown two reaction forces at bearings and the torques where known.
2. For the unknown torque force 'F' I have assumed there is no net torque for the system, and stating my positive Z direction and using T=(f2-f1)xr, have deduced that F=1.1KN
3.I have then gone back to my FBD and drawn in the newly calculated force, and by considering moments throught the first bearing support A and deduced the reaction force at B is 5.877KN. Using the sum of Y forces = 0, I could then calculate for at A=6.023KN.
4. I then drew my shear force diagram, followed by my bending moment and torque diagrams!

Now I am stuck!
I am lead to believe that I must use the relevant equivalent bending moment and torque diagrams, and tau, sigma and twist rate values calulate a suitable diameter for the shaft.
Where:
Me= 0.5[ Mmax +[Mmax^2+T^2]^0.5 ]
Te=[Mmax^2+T^2]^0.5
Is my Mmax value simply deduced from my highest value on my BM diagram, and what T force do use?
I'm not sure if these questions are rather elementary, apologies if that is the case!
Many thanks
Dan
 
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