What is the fea stress output file name
Please refer to this KB Solution:
Solution ID: S-019472 - SOLIDWORKS Simulation Database files description
[SOLIDWORKS MODEL NAME]-[STUDY NAME].CWR is the compound database file containing al the results of the study.
More precisely, the file containing the stresses has the .STE extension for static studies.
The .cwr file is the one that contains all the results. From memory it's <study name>.cwr in the same folder as the SW geometry.