NAVIGATION INSTRUMENTS
THERMOELASTIC LOSSES IN STRUCTURAL MATERIALS
OF WAVE SOLID-STATE GYROSCOPE RESONATORS
B.S. Lunin
,
A.V. Yurin
,
M.A. Basarab
,
V.A. Matveev
,
E.A. Chumankin
Bauman Moscow State Technical University, Moscow, Russian Federation
e-mail:
bmic@mail.ruOne of the key features of the resonators of wave solid-state gyros is their quality
factor defining in many respects the instrument’s systematic and random errors. To
enhance the resonator quality, it is necessary to take into consideration peculiar
properties of different dissipative processes in design process. The contribution of
these processes depends on the resonator material behaviour, its design, its surface
processing quality, vacuum level in the instrument. Thermoelastic internal friction is
a fundamental dissipative process. The influence of internal thermoelastic friction on
the characteristics of resonators made of various materials is revealed by means of a
thermoelastic processes model and finite-element simulation. It is shown that internal
thermoelastic friction in quartz glass is very small as compared to other structural
materials. It permits to recommend quartz glass as a main structural material for
wave solid-state gyroscope resonators.
Keywords
:
wave solid-state gyroscope, resonator quality factor, thermoelastic losses,
finite-element simulation.
In the last decade, vibratory giroscopes have become widespread, their
operation based on Сoriolis effect. The centerpieces of these instruments are
mechanical resonators of various design — frame, ring, hemispherical, etc.
[1, 2]. One of the main features of these resonators is their quality factor,
which to a large degree determines the instrument’s systematic and random
errors [2]. To enhance the quality factor, materials with small thermoelastic
internal friction are usually selected as structural materials: quartz glass,
silicon, metals, synthetic sapphire, etc. To achieve the best results in the
resonator design, one should take into consideration specific features of all
dissipative processes. It will be recalled that the internal friction in a solid
body is the whole set of all irreversible thermodynamic processes resulting
in energy dissipation of resonator’s elastic vibrations. The value of internal
friction is proportional to the ratio of energy dissipated for one period of
vibrations (
Δ
W
), to the total resonator’s energy (
W
):
ς
= Δ
W/
(2
πW
)
,
(1)
here the resonator’s quality factor is
Q
=
ς
−
1
.
As the internal friction in the resonator is determined with the sum of
all dissipative processes, then
ς
=
ς
T
+
ς
V
+
ς
S
+
ς
G
+
. . . ,
(2)
28
ISSN 0236-3933. HERALD of the BMSTU. Series Instrument Engineering. 2015. No. 2