Vibration measurement methods for solid rocket motors
1 Subject content and application scope
This standard specifies the composition, technical requirements, operating procedures, and data processing methods of the vibration acceleration measurement (hereinafter referred to as vibration measurement) system for solid rocket motors during ground testing.
This standard is applicable to vibration measurement of various parts of solid rocket motors. The upper limit frequency of the measured signal is 10kHz, and the acceleration is less than or equal to 1,000m/s2 (about 100g).
2 Terms and symbols
2.1 Terms
2.1.1
charge sensitivity
amount of charge output by a piezoelectric accelerometer under unit acceleration, pC/g
2.1.2
output
peak voltage output by charge amplifier when piezoelectric accelerometer bears unit acceleration, V·s2/m(V/g)
2.1.3
stationary random vibration
a random vibration in which the mean and root mean square values of its amplitude do not significantly change over time within a certain time interval. or, in other words, a random vibration in which the power spectral density and spectral shape of each sub segment are roughly the same when the signal is divided into several sub segments according to statistical accuracy and resolution requirements
2.1.4
locally stationary random vibration
It has the following two characteristics:
a. The power spectrum patterns of each sub-segment are similar, but their magnitude is quite different;
b. Short duration; five frames cannot be taken and averaged to form power spectral density estimates.
2.1.5
transient vibration
an unsteady random vibration that exists temporarily and cannot be locally stationary in its duration
2.1.6
sampling
process of converting continuous analog signals into digital sequences
2.1.7
frame
equally long sub-intervals by dividing the entire data sampling interval used for a single Fourier transform operation when using the fast Fourier method for spectral analysis, with each sub-interval along with its transformation result
2.1.8
residual shock spectrum
relationship between the maximum response of the system and the natural frequency of the system after the shock pulse stops
2.2 Symbols
fs——the data sampling rate, Hz;
fmax——the maximum frequency of analysis, Hz;
f0——the starting frequency of analysis, Hz;
fc——the filter cut-off frequency, Hz;
tl——the length of time for a frame of samples, s;
tt——the total length of samples required, s;
Δt——the sampling interval, s;
Δf——the frequency resolution, Hz;
N——the total number of data per frame;
M——the number of frames used to form the power spectral density estimate;
1 Subject content and application scope
2 Terms and symbols
3 Composition and uncertainty requirements of systems
4 Measurement instruments and equipment and their requirements
5 Preparation before commissioning
6 Commissioning
7 Work after commissioning
8 Record sheet filling
9 Data processing
Annex A Vibration measurement record
