phisical meaning of equivalent von misses stress

huangyhg

phisical meaning of equivalent von misses stress
  i wonder that the phisical meaning of the equivalent von misses stress.e.g
  when i have designed some mechanical part in fem, i found the equ.von misses stress as 143 mpa and s11 as 60 mpa.yield strength of material is 350 mpa.am i compare the equ.von misses with the yield strength or not???
the answer is yes. the von mises stress, or stress intensity, is comparable with the yield strength of the material. for design purposes though it is normal to compare this stress intensity with some factor of yield stress. the von tresca calculated stress intensity is a more conservative value but is also used for the yield criteria by some codes. mises has been shown to be more reliable for steel.     
i do accept this. von mises stresses are mulitplied with some safety factors and compared with yield strength of the
material ( particularly for steel)
  in my fem program there is a term named as 'equivalent von mises stress' but the result of that is different from 'von mises stress'.what is the differance between them.