Erik Kostson
Ansys Employee

the cumulative mass fraction for mode ÔÇ£nÔÇØ is the the addition/sum of individual Effective Mass Fractions for modes 1 through to the number of modes we requested and got.

So say in the Y-direction for the first mode the effective mass is 48 kg and the total effective mass in Y is ~ 68 kg then the Cumulative Effective Mass Fraction is 0.7 as shown in the image below.
As we add more and more modes the effective mass fractions from modes are added together.
So in the example below for the 2nd mode it is small and we can neglect say here (so I do not have to write this out), for the 3rd mode it is 14kg and the Effective Mass Fraction for that mode is then ~ 0.22 (14.8/67.9), so add that (0.22) to 0.7 from the first mode (we accumulate) we get 0.92 as shown below (3rd row), and so on so forth.