How can I calculate this in Inventor
I dont know if its possible to calculate the thread stress on two pipes that are connected to eachother with thread. See picture.
Can someone share some light here.
Your question would be better posted at http://www.engineersedge.com/. Doing a bit of homework on that site, you might even find a set of equations that would be appropriate.
That said someone with access to FEA could certainly help identify the stress on the threads.