Hi,
First, many thanks Tater for help and link.
For ramming, I have decovered that the file submarine.zon is needed.
In these files, the last amor level must be at "-1".
In this case :
- soundness is the same,
- durring depthcharging lights inside the sub flicking more.
In addition with the NSM mod, I have noticed that ramming work properly, but not for all submarine.
Later, I noticed that the same sub took damages only in some cases (depending of cfgdate) and I have decovered that the folder concerned was "Objects".
After many tests I have found that the *.sim files (in the folder object) for PORPOISE and S-type was corrupted and I repaired them.
My last tests showed that the *.dat in association with *.sim, *.zon and *.val files (in folder objects) are corrupted and concerned :
GATO conning01 conning02 conning03 conning04
ramming....OK........OK..........NO............NO
SALMON conning01 conning02 conning03
ramming......OK..........OK...........NO
SARGO conning01 conning02 conning03
ramming OK............ OK .........NO
TAMBOR conning01 conning02 conning03
ramming ......OK ..........NO ........NO
BALAO and GAR, ramming never work.
So I need better modder than me to find by comparison the good parametre and repare ramming. 
the link :
http://mpgtext.net/subshare/910ramming.7z
Many thanks for helping
best regards,
Jean