After my long search and contacting companies, i FINALLY found some FREE FEA and stress analysis software that will work with OBJ and STL files. I have tested it out and it does indeed work.
The first one is intact design. The free account allows you to have 10 simulations saved on your account, unless you have a .edu email, its unlimited. It is a web based engine and works very well. Just make sure your parts are solids. If you do not have a .edu email address, you are allowed to have 10 saved simulations on your account. If you need to do another sim, you have to delete one of the 10
The other is a software you download. it is called welsim. It has a 7 day trial, but i contacted the creators and as long as its for personal use, you can request the trial key every 7 days. They are very fast at responding to emails. within an hour for me.
there are youtube videos specifically on welsim.
hope this helps others out