You won't be able to use DMAP alters to output stress results to the op4 file. Op4 files may only contain MATRIX data, and the alters in the reference are outputting displacement vectors (i.e. matrix data in columns). Stress data is generated in TABLE format, and tables cannot be output to op4. Both tables and matrices may be output to op2 files, but op2 files are only available in either binary or neutral formats, and the neutral format, although it uses ASCII characters, is not human readable (well most humans anyway). In addition, unless you use native format op2, the data is truncated to 32 bit precision, which takes you back to your 6 or 7 if you are lucky decimal places you already have in the f06 file.

Your best bet is to use the HDF5 output file (define MDLPRM,HDF5,1 in the bulk data). Your STRESS output request data will be written to an HDF5 file (.h5 extension). This file is an open source format defined by the hdf5 group (hdf5.org). On their website you can download a utility called hdf5viewer. This tool will allow you to open and view the .h5 file. Locate the stress output and then export it to a text file (use right click on the dataset). You could also write a tool in Python to read the .h5 file (use pytables to do this).

DG