During execution of the adams command, the following warning and error messages may be output:

WARNING: There are 'N' elements in substructure Z1, but only 'M'
   -=> mass matrices have been processed from the results file. 
   -=> Carefully review this discrepancy before proceeding.

Explanation: If the number of mass matrices read is zero, verify that there is an *ELEMENT MATRIX OUTPUT, MASS=YES option in the *FREQUENCY step that preceded the *SUBSTRUCTURE GENERATE step.

If m is nonzero but less than n, the model may be correct. Some Abaqus elements, such as dashpots, do not have mass matrices. The mass of other elements may be neglected if they are not significant in representing the mass of the substructure. Elements with negligible mass are not required in the element set whose mass is written to the results file.

WARNING: No fixed-interface normal modes.
   -=> The results file did not contain any modes from 
   -=> a *FREQUENCY step. Typically, this step contains:
   -=> *NODE FILE
   -=> U,

Explanation: Vibration mode shapes were missing in the results file. A *FREQUENCY step must precede the *SUBSTRUCTURE GENERATE step. Vibration mode shapes from the *FREQUENCY step are written to the results file using the commands:

*NODE FILE
U,

Typically, all the mode shapes will be written. However, if a subset of the computed modes is retained in the *SUBSTRUCTURE GENERATE step (using the *SELECT EIGENMODES option), the *FREQUENCY step must write only those modes.

ERROR: Missing element mass matrices.
   -=> No element mass matrices were found in the results file. 
   -=> The input file must contain an entry similar to:
   -=> *ELEMENT MATRIX OUTPUT, MASS=YES, ELSET=elset_name
   -=> This entry must be in the *FREQUENCY step preceding 
   -=> the *SUBSTRUCTURE GENERATE step.

Explanation: The *FREQUENCY step must write element mass matrices to the results file using the syntax given in the error message.

ERROR: Missing generalized stiffness and mass matrices.
   -=> Verify that the input file defines this substructure 
   -=> and contains the following option:
   -=> *SUBSTRUCTURE MATRIX OUTPUT, STIFFNESS=YES, MASS=YES, 
   -=> RECOVERY MATRIX=YES [, SLOAD=YES]

Explanation: The *SUBSTRUCTURE GENERATE step must write the generalized (reduced) mass and stiffness matrices, as well as the recovery matrices, to the results file. The substructure load vector may also be written using SLOAD=YES.