gap of von mises stress between Ansys and Abqus

Hello ,

 I am doing the correlation between Ansys and Abaqud for a shroud of cooling module (solid 92-C3D10) .I find the coorelation is perfect in frequency , but when i do the powerspectral density analysis, i noticed a gap of 10-20% on the peak value of nodal von mises stress ,  i'd like to know the reason of the diffrence .

Thank You .