Satellite Structural Design - Finite Element Analysis for Satellite Structures - page 53

Table 3.1 Mechanical properties of semi-finished work pieces made of alloys AMg6 and VT-16

Material Semi

finished
workpieces

Material
condition

Density
(kg/m 3 )

Ultimate
tensile
Strength r u
(MPa)

Yield
Strength
r y

Modulus of
Elasticity E

Elongation
d (%)

AMg6 Plate Annealed 2,630

72 9 10 3 12-25 mm 310 150 11

72 9 10 3

25-50 mm 300 140 6

72 9 10 3 50-80 mm 280 130 4

Sheet
0.5-0.6 mm 71 9 10 3

320 160 15

110 9 10 3 VT-16 Bar 20 mm Annealed 4,430 923 903 10

It is supposed to use a wide range of nonmetal materials in the satellite units
and subassemblies, such as rubber and plastic-metal parts, metal and varnish
coatings, and solid lubricants and lubricant grease. Materials used for the manu-
facture of the satellite should not generate (in operation conditions) aggressive or
conductive media that can result in structural failure or electric breakdowns, and
also should not sublimate at a high rate.

3.3.2 Developing Structural Modules

The next consideration in the design process is developing the structural modules
and mass properties of the satellite. The optimal structural design chosen for Small
Sat is a combination of milled plates and modified isogrid frame structures. This
technique uses an array of milled cutouts to improve the structural performance of
a flat metal plate. Ideally, machining milled plates and modified isogrid frame
structures reduce the mass of the original plate by approximately 75 %, and reduce
the strength of the plate by approximately 25 %. This procedure may produce a
200 % increase in structural efficiency compared to the original flat plate. Another
advantage of machining an array of milled cutouts is that the plate remains iso-
tropic. Therefore, it exhibits similar strength in all directions, and minimizes
locations of stress concentrations. Finally, milled integral constructions are usually
easier and cheeper to manufacture than skin stringer structures.

3.3.3 Iterative Process of Design Development

The design development process consists of several steps. The first step ensures
that all subsystems will fit into the satellite. The second step uses Mechanical
Desktop package ''MDT'' and finite element analysis by ANSYS package to