Currently, usually, tensor data is calculated and written at integration points as it'll be accurate. But, for the calculation of Safety Factor, we usually consider ONLY surface nodes as crack initiation happens only on surfaces and also to reduce new field output calculation.

But, there is no API to access the stress results at nodes which are written at integration point.
We can output the such stresses at nodes in a report file (using writeFieldReport), but that does not give access to the data directly. 
If we can access the stresses at nodes, then we can apply many other APIs to manipulate it. And
that is very beneficial when calculating a new field output. Is there a other way?

Also, considering data can be asked to write at nodes (from .inp input file) is not so good as we want to consider the general cases.
Version: Abaqus/CAE/Viewer 2018