Mechanics of Materials: Cross Sectional Area Problem

[Yeeeezyy]

<Moderator's[/PLAIN] note: thread moved from a technical forum, so homework template missing.>

https://www.physicsforums.com/threads/mechanics-of-materials-homework.855915/

This is a link to a problem which I am trying to solve. The only problem I am having is visualizing this in 3D and obtaining the cross sectional area at "a" and "b" where it shears.

Would you guys be willing and able to help out with this?

Thank You.

 

[billy_joule]

Can you draw a diagram looking down the axis? Both areas are cylindrical surfaces, with different radii and depth..