Normal/Shear stress & Von Mises analysis

[TheStebes]

Hello all,

I am working on a design project (school work, nothing too important) and I'm trying to wrap my head around how to analyze potential failure in a shaft with an applied tensile load at one end and a torque near the midpoint. (The beam is fixed at the other end.) The tensile force is an axial load. http://imgur.com/BeA0e.png"

Looking at the Von Mises equation, things simplify down to a single normal stress in the axial direction and a singe shear stress.

What I'm not sure about is the portion of the beam beyond the point where the torque is applied. I understand that the shaft does not continue to twist beyond this point, but is there still a shear stress in this portion of the shaft? If the answer is no, as I suspect it might be, the effective stress given by the von mises equation simplifies to the single normal stress in the x-direction.

Thanks for the help, sorry if this should have been posted in the mech. eng. section.
Scott

 

[TheStebes]

I guess I'll reword my most basic question.

Let's say you have a shaft fixed at one end, free at the other. If you apply a torque at the midpoint, will there be a shear stress anywhere between where the torque is applied and the free end of the beam?

In this problem, if there isn't a shear stress in that portion of the shaft, both the Von Mises equation and the Principal Stress equation simplify down to the single normal stress (due to the axial load).

 

[Mapes]

Your intuition is right; there is no shear stress between points B and C, only normal stress.