Strength Analysis - Finite Element Analysis for Satellite Structures - page 157

Table 4.19 Cumulative
fatigue damage values for
each critical point due to
mechanical dynamic
vibrations

Structural module Critical points Cumulative fatigue damage

Base plate 1 9.25E - 06

2 1.01E - 04

3 1.27E 2 04

4 9.17E - 05

5 7.38E - 07

Mounting plate 6 1.46E - 04

7 1.49E - 04

8 5.94E - 05

9 1.64E - 09

10 1.65E 2 04

Basis plate 11 4.41E - 03

12 2.68E 2 01

13 1.68E - 02

Basis walls 14 8.24E - 07

15 1.09E - 03

16 9.74E - 02

17 3.85E 2 01

18 4.01E - 06

Upper frame 19 5.77E 2 02

20 2.16E - 02

21 2.55E - 05

22 2.34E - 04

23 2.80E - 04

Lower frame 24 3.45E - 02

25 3.55E - 02

26 2.08E - 05

27 2.31E - 02

28 4.19E 2 02

29 2.46E - 04

It clarifies that point 17 located at the basis walls module is the most affected point
in the whole satellite structure by mechanical dynamic vibrations as it has the
maximum value of cumulative fatigue damage index (0.385). Tables 4.20 , 4.21 ,
4.22 , 4.23 , 4.24 and 4.25 explain the dynamic fatigue damage calculation for only
the most critical point located in each structural module. They list the fatigue
calculations criterion and the cumulative damage index for points 3, 10, 12, 17, 19,
and 28 located on the base, mounting, basis plate, basis walls, upper, and lower
frame module, respectively.
After performing the fatigue damage analysis for the entire satellite structure
and determining the most critical points affected by dynamic vibrations in several
loading phases, the main question is how are the first 15 sorted natural frequencies
of the satellite structure sufficient to give accurate fatigue calculations or not? To
answer this question, the fatigue damage is summed up for each natural frequency
in all dynamic loading phases. Figures 4.53 , 4.54 , 4.55 , 4.56 , 4.57 , 4.58 , 4.59 , 4.60
and 4.61 show the total accumulated fatigue damage for the most critical points